• China drives electric

    China drives electric

    The 2004 Michelin Challenge for sustainable mobility was held last week in Shanghai. More than 150 vehicles took part with 70 of them electric-driven, of which 46 were built in China.

    The high number of battery electric, hybrid-electric and fuel cell-electric cars showed the access to advanced technology enjoyed by Chinese carmakers and academic institutions.

    North American, Japanese and European electric-drive entrants included Audi, Volkswagen, Peugeot, Ford, Toyota, Volvo, GM, DaimlerChrysler, Hyundai, and Nissan. Michelin, which founded and sponsors the annual event, entered its own EV’s, built in cooperation with Swiss-based PSI.

  • Make savings with long distance drives

    Make savings with long distance drives

    The networking of drives and controllers is an accepted practice these days. Numerous network protocols are routinely employed in industrial environments across the world. Among these, Ethernet TCP/IP, perhaps by virtue of its being more synonymous with office applications, is less familiar on the factory floor than might be expected, explains Mark Daniels of Rockwell Automation.

    Unlike decidedly blue-collar protocols like DeviceNet, ControlNet and ProfiBus, Ethernet TCP/IP was not conceived primarily as an industrial protocol. But while its apparent lack of industrial street-credibility might make the ubiquitous Ethernet seem a little too much of a ‘one-size-fits-all’ solution for industrial control applications, EtherNet/IP – the industrial ‘flavour’ of Ethernet – offers enough advantages over the native industrial protocols to make it a serious candidate worthy of consideration in industrial applications.
    Ethernet as a network has been around for a long time and over that time has evolved to become a very efficient way of making information widely and easily accessible across a variety of platforms. It is, after all, the technology that forms the bedrock of the internet. Its long history and broad usage has made it a cost-effective and reliable networking solution that is readily understood by non-specialist engineering support personnel. Ethernet’s ability to move information around networks and across network boundaries also makes it a powerful tool in the industrial environment.
    It’s 2am: are your drives still running? If they’re networked using EtherNet/IP, you could know the answer in seconds, no matter where you are. Production line problems invariably happen when it’s most inconvenient. The strength of EtherNet/IP networking is that it can effectively deliver drive information and control when and where it is required. What it lacks in robustness compared to ControlNet or scalability compared to DeviceNet, EtherNet/IP more than makes up for in connectivity. But connecting drives is just the start: Because of Ethernet’s plug-and-play connectivity with the wider network infrastructure, drives connected over an Ethernet IP network are able to deliver diagnostic information via a standard web browser, just like any website. If a drive triggered an alarm or became faulty, text messages to pagers or mobile phones can be delivered via the same medium.
    The ability for information – be it diagnostic data or commands – to flow effortlessly internally and externally across network boundaries is a great strength of Ethernet connectivity. But that’s not all. In purely practical terms, there is a significant labour and material cost saving from not having racks of I/O modules and wires running everywhere just to communicate with drives.
    Drives wired using discrete or point-to-point wiring require multiple discrete and analogue I/O modules, along with the associated wires snaking through panels and panel interconnects. Users also have to take the time to buzz out wiring during installation, or again if there are problems with I/O operations later on. All of this results in increased labour time that can be avoided with EtherNet/IP networking.
    With Ethernet, a single cable removes the need to run a multitude of wires through conduit and trunking. Dozens of drives can be networked over just one cable and, once the Ethernet connection is made, functionality testing is simply a matter of ‘pinging’ the required device from any Windows PC.
    Using readily available software tools, EtherNet/IP allows facility managers to have a virtual ‘window’ into the drive, providing complete access to metering data, diagnostic values, configuration parameters and fault information. Viewing this information gives staff time to correct production issues before they can impact the rest of the process. In addition, if a drive faults, the maintenance staff will have a significant amount of information available to enable them to troubleshoot the problem.
    In a situation where a drive or motor is beginning to operate outside of established parameters, users will know because the drive or controller software can be set to inform them directly. Drive configuration options are available that can e-mail or page someone with an alarm before a problem occurs, after a problem or faults occur and after an alarm or fault has been cleared. A hyperlink included in the e-mail message can be used to launch a web browser connected directly with the drive that sent out the message.
    Additional software tools can be launched from the browser to allow complete access to the drive’s information. Not only is this a very useful facility for front-line support, but EtherNet/IP also delivers a very cost effective way for OEM’s to troubleshoot when offering support contracts. Cost savings from being able to troubleshoot online are significant because often an engineer does not need to be dispatched over long distances to repair or adjust a system.
    Readily available wireless Ethernet technology makes life even easier by allowing maintenance personnel to roam freely to wherever a problem occurs. A wireless Ethernet card in a laptop or hand-held device and wireless access points on the factory floor are all that’s required to keep ‘connected’ to the network. The laptop becomes both the means of alerting that a problem has occurred and the tool to fix it. That makes it a very powerful tool indeed.

  • Drives & controls - Industry vulnerable to hidden power costs

    Drives & controls - Industry vulnerable to hidden power costs

    Power quality is an unfamiliar issue for many in UK industry, but it is likely to become very well known in the near future. Power quality covers a vast range of issues from voltage excursions, frequency variations, supply imbalance and harmonic distortion. Uncorrected power quality issues can bring a host of problems from unnecessary power losses which can disrupt production through to catastrophic equipment failure. Steve Barker, energy and power quality manager at Siemens Automation & Drives, outlines the extent of the power quality problem in the UK and offers some solutions for business...

    British industry of all sizes tends to take its electricity supply for granted. A simple flick of a switch and a plant or production facility has access to the supply network which will give a business as much electricity as it requires at any time of the day, no questions asked. A whole range of equipment from machinery and computers through to lighting and electric motors rely on the mains supply network with little thought given thereafter, other than paying the bill.
    However, the use of increasing levels of electronic equipment by business is causing a phenomenon called “harmonic distortion” on the UK electricity supply network. Harmonic distortion is caused by non-linear loads on the electricity supply system, such as personal computers, lighting systems, switch mode power supplies and variable speed drives.
    Regulation ER G5/4-1, published by the energy networks association (ENA) is the UK’s instrument to control this distortion and to assist compliance by business with the harmonised network standards such as the European EN50160 (it is important to note however that the UK measures are more severe than in the rest of Europe).
    ER G5/4-1 which was first published in 2001 and subsequently updated in November 2005, is the UK’s attempt to control harmonic distortion back onto the supply network and is the updated version of the earlier ER G5/3 which was originally published in 1976. Ironically, many of those businesses affected by power quality issues remain unaware of the original regulations let alone the updated version which are far more stringent.
    The updated regulation is far more onerous than previous regulations and specifies voltage and current limitation to which all industrial sites in the UK must comply in a three stage approach which takes into account different sizes of installation. Stage 1 applies mainly to small commercial installations supplied from the public low voltage network. Most industrial sites are typically assessed under Stage 2. Industrial sites of large users may fall under Stage 3 which applies for incoming supplies taken at 33kV and above.
    Excess harmonic distortion on a site can lead to two types of problem. Firstly, ER G5/4-1 compliance issues which can ultimately result in disconnection if remedial measures are not taken. More often than not, electricity users are not familiar with compliance issues and attempts by a company to achieve compliance with ER G5/4-1 can consume huge resources of time and money. I have personal experience of a number of installations where compliance issues have been tackled badly and the remedial measures have been more costly than early preventative considerations. One example involved a company foregoing a £50k investment in preventative measures that could have saved a small food and beverage company in the North of England around £1m – a figure which was later spent on mandatory remedial issues to correct the problem.
    Secondly there are a number of practical issues for end users involving power frequency harmonic distortion that can cause often hidden problems which can include:

  • Drives - Successful motor and drive combinations

    Drives - Successful motor and drive combinations

    Variable speed drives bring great advantages in controlling motors but care needs to be taken to match the characteristics of the drive to the motor to ensure the combination is a winning one. Geoff Brown, drive applications consultant for ABB investigates

    Of the approximately 10m motors installed in UK industry, only some 3% are controlled by variable speed drives. Despite the huge energy savings to be gained, often in excess of 50%, many companies are still not making use of variable speed drives to run their motors.
    Yet, process operators cannot simply connect a drive to any old motor and expect huge energy savings overnight or even a successful motor and drive match.
    To minimize the risk of selected motor failing, users need to understand the required operating and environmental characteristics of the application. Motors have to cope with all sorts of environments, from high ambient temperatures, to being immersed in sewage, to operating in dust or gas hazards.
    Special designs exist for all of these cases and the user must ensure he follows the motor manufacturer’s instructions. Getting all the help you can from motor and drive manufacturers is also a good idea in general; their experience with motors and drives will help find the most compatible motor and drive combination. Many will have local service representatives who can assist with setting up the drive. Users installing their own drives need to read up about the issues that exist when connecting AC motors and drives.
    Drives and their effects on motors
    Variable speed drives come in standard voltage ratings, which must be chosen to match your line voltage. In general, the lower the voltage, the easier it is on the motor.
    The high switching rates of inverter power devices can place a rain of high switching voltage pulses at the motor terminals, which will cause an electrical stress on the windings, which is partly dependent on the length of the cable connecting the inverter to the motor. The drive manufacturer will usually advise on the maximum practical cable lengths between 15m and 300m depending on the power rating. In some cases long cable runs may also require additional drive components such as du/dt filters. Long cable runs can also lead to EMC issues.
    Because a higher carrier frequency means more frequent pulses, a useful feature of the drive is an adjustable carrier frequency. Lower carrier frequencies place lower stress on the motor insulation system and reduce the incidence of damage due to bearing currents. However, higher carrier frequencies have a positive effect on reducing motor noise levels. Some switching strategies such as direct torque control have no fixed carrier frequency, which can also help, while ensuring a low noise spectrum.
    Frequency converters with non-sinusoidal current can also cause additional losses in the motor and an increase in motor losses of up to 15% was not uncommon in early PWM inverter designs, which translates into an overall reduction in motor efficiency of up to 1%.
    Modern inverter designs still increase motor losses, beyond those of a true sinusoidal supply, but in practice the effect is less than that caused by connecting to the supply network.
    Major factors causing an apparent reduction in output with modern drives is the fact that the output voltage is lower than the input voltage, due mainly to the presence of chokes and other components used to limit harmonics, and the improved switching patterns in the inverter. The reduction in voltage can often be compensated by using a low harmonic “active rectifier” drive solution.
    Choosing a motor for
    drive operation
    Given these points, how do you go about choosing a suitable drive for a motor? Firstly, always choose a good quality motor. High quality materials will extend the life of a motor, as well as improve efficiency. Look for thinner core plates giving lower iron losses, good slot fill giving improved stator performance, good bearings reducing rolling resistance. Reduced losses make for smaller fans, cutting noise and windage losses.
    Another important quality factor is the level of insulation of the windings. Voltage stress acting on microscopic air bubbles in the winding varnish can cause ionization flash-over, known as a partial discharge, breaking down the insulation. Different insulation materials can withstand different levels known as the partial discharge inception voltage (PDIV), so you need to make sure the insulation level is adequate. Standard motors commonly have a PDIV in the region of 1350 to 1600V. A higher withstand voltage is better in variable speed drive applications. Unfortunately as yet there is no common visible classification on a motor nameplate, the use of Class B, or F or H materials does not in itself confer a specific PDIV withstand level.
    Inverters also have common mode voltages in their outputs, which can give rise to induced voltages in the rotor, and if the path is not blocked can give rise to circulating currents, which can destroy bearings. This problem is solved by breaking the circuit by using insulated bearings.
    Choose the right combination for the environment
    A particular concern is the use of variable speed drives to power motors in hazardous areas. The main sources of risk are high surface temperature and sparks in either the winding or the bearings. This can result in increased temperature rises and higher voltage stresses on the motor insulation. These increase when self-cooled motors are used, as the speed of the cooling fan is reduced along with the motor speed.
    These factors can combine to create a source powerful enough to ignite an explosion. The best way to reduce this risk is to choose a combined Atex package, which gives end users the assurance that the motor and drive combination is optimised for their application.
    Note that the application of a drive with an existing, pre Atex motor is at the owners risk, and possible only in a Zone 2 area. In any case the product certification is the responsibility of the motor manufacturer.
    This practice of supplying matched drive and motor pairs is a growing trend and one that progressive vendors have adopted to help cut users’ workload to a minimum.
    Choose high efficiency
    The efficiency of the motor is always a major factor in the choice. Although a VSD will bring system efficiency gains, it will not compensate for a poor or inefficient motor. Always use the highest efficiency motor possible. Ideally, the motor should have a good efficiency across the load range.
    Motor power plays a major part because AC motors work at their peak efficiency over a limited range of their power output. Modern EFF1 electric motors usually produce peak efficiency at around 75 per cent of rated load. By contrast, older designs often have peak efficiency in a very narrow band around full load.
    This is important in energy saving installations because the object of a drive is to vary the speed of the load, especially with centrifugal fans or pumps. The time spent running at full load will therefore normally be limited to emergency situations, such as extracting smoke in the event of a fire.
    A new high efficiency EFF1 motor rated at 90kW with 95.2% efficiency, will cost around £5,900 and will use electricity costing around £37,250 per year, but will save nearly £9,000 compared to a standard efficiency EFF3 motor with 93% efficiency, over a 10-year service life. For companies operating large industrial complexes with many motor driven machines, such savings can mean tens of thousands of pounds, and tonnes of CO2 emissions annually.
    Although an existing motor already in place can usually be used with a drive, it may not be known how well the motor has been treated and higher efficiency may be gained by using a new motor.
    Choose the right speed profile
    It is important when designing a system to consider the motor as a source of torque. Torque equates both power and speed, and with variable speed it is the torque profile which is of importance.
    The two most common profiles are variable torque and constant torque. The first is used for centrifugal fans and pumps while the second is used for conveyors, extruders, positive displacement pumps, and similar loads.
    Variable torque loads are the easiest applications for motors and drives because load power is governed by the cube of the shaft rpm for centrifugal loads acting with little static head.
    It is also worth considering most load machinery is designed for sale in both 50 Hz locations such as Europe, and 60 Hz locations such as the US. Due to this the best efficiency is often between 50 Hz and 60 Hz nominal speeds, i.e. between 1500 and 1800 r/min. A variable speed drive allows this to be exploited. The freedom to select the output shaft speed can also be used to advantage to eliminate inefficiencies in belt drives.
    Constant torque can pose problems because in order to maintain a constant torque at low speeds, the motor needs to be supplied with a relatively constant current throughout its speed range. This mode of operation will continually produce more heat, which will need to be dissipated at low speeds.
    The current ratings of the inverter must also match the motor’s current requirements both at full load and during acceleration. The drive’s current rating and its suitability for the motor needs to be checked with the motor manufacturer, especially on motors operating below 30Hz and whenever acceleration torque is critical.

  • Drives - Energy management with Intelligent motor control solutions

    Drives - Energy management with Intelligent motor control solutions

    Rising energy prices are motivating industry to explore new methods – such as energy-efficient motor control solutions – for lowering operating costs. Engineers and consultants are tasked with selecting the most reliable motor control solution with the lowest total cost of ownership, which must take into consideration lifetime costs such as installation, operating efficiency, maintenance and energy use, explains Jonathan Smith, field business leader for power control at Rockwell Automation

    - Since over 80% of pump and fan applications require control methods to reduce flow to meet demand, those applications are crucial to savings. Process engineers commonly use fixed-speed controllers and throttling devices such as dampers and valves, but these are not very energy efficient.
    Variable-frequency drives (also known as adjustable speed drives) offer an alternative that will both vary the motor speed and greatly reduce energy losses. Advancements in drive topology, careful selection of the hardware and power system configuration and intelligent motor control strategies will produce better overall operating performance, control capability and energy savings.
    Things to consider when choosing a motor control solution include peak-demand charges, operating at optimised efficiency, power factor, isolation transformer cost and losses, regeneration capabilities, synchronous transfer options and specialised intelligent motor control energy-saving features.

    Beat peak-demand charges
    It’s important to be aware utility companies charge higher peak-demand electricity prices when companies exceed a preset limit or base load of electricity. Peak demand charges often occur when industrial motors draw large peaks of current when started across-the-line. Variable frequency drives (VFDs) help reduce the peaks by supplying the power needed by the specific application, and gradually ramping the motor up to speed to reduce the current drawn. The VFD also automatically controls the motor frequency (speed), enabling it to run at full horsepower only when necessary. Running at lower speeds and power levels during peak times contributes to a reduction in energy costs and increased operating efficiency.
    Kraftwerke Zervreila, a hydroelectric power generation plant in Switzerland, was causing a 20 percent under-voltage condition and line flicker on the electrical grid every time it started its 3.5 MW synchronous water pump motors that drew 1,600A in full-voltage starting conditions. In 2000, Zervreila retrofitted its 40-year-old motors with Allen-Bradley PowerFlex 7000 medium-voltage drives, which limited their starting current to 200A, greatly reducing its peak energy demand.

    Optimise power usage
    In addition to starting the motor, also consider how energy-efficiently the pump or motor operates. In applications where motors are unloaded or lightly loaded, VFDs can deliver additional energy savings and performance capabilities. Centrifugal loads, such as pumps and fans, offer the greatest potential for energy savings when applications require less than 100 percent flow or pressure. For example, significant energy savings can be gained by using VFDs to lower speed or flow by just 20%. If this reduction doesn’t impact the process, it can reduce energy use by up to 50%, which in many operations, can equate to substantial energy savings.
    Energy consumption in centrifugal fan and pump applications follows the affinity laws, which means flow is proportional to speed, pressure is proportional to the square of speed, and horsepower is proportional to the cube of speed. That means if an application only needs 80 percent flow, the fan or pump will typically run at 80 percent of rated speed. But at 80% speed, the application only requires 50% of rated power. In other words, reducing speed by 20% requires only 50% of the power needed at full speed. It’s this cubed relationship between flow and power that makes VFDs energy savers.
    Energy savings can also be realised by managing input power based on system demand. Vattenfall Europe Mining AG, in Germany, modernised the overburden conveyor systems of its open pit coal mine with 6.6kV Allen-Bradley PowerFlex 7000 medium voltage VFDs. The drive’s inherent regenerating capability allows fast, coordinated deceleration without the need of braking components and without wasting energy. The optimised conveyor loading (OCL) ensures system efficiency by using a material tracking system across an array of conveyors to continuously adjust speeds so that the conveyor belts are fully and uniformly loaded. A partly loaded conveyor wastes energy and causes unnecessary wear.
    Vattenfall’s biggest benefit is the reduced amount of installed drive power. Before modernisation, the conveyor required six fixed-speed controllers at 1.5MW each, totalling 9MW to start the motor. The conveyor with a variable speed solution now uses installed power of only three units at 2MW each, for a total of 6MW to generate a smooth start.

    Power factor makes a difference
    Power factor and how it affects displacement and harmonic distortion is an important consideration in drive selection. Drives that are near-unity true power factor translate to reduced energy use. Leading drives produce a 0.95 power factor or greater throughout a wide operating speed range. An example of the effect of power factor on energy cost compares two 4,000hp drives, one with a true power factor of .95 and one with a true power factor of .98. The annual operating cost for 8,760 hours of use at

  • New benchmark for large drives

    Silverteam will be using the Drives & Controls show to launch the high power versions, 160kW to 400kW, of the Hitachi SJ700 variable speed drive - small and medium sized version having been introduced in 2007.

    The SJ700 is a radical development of drives technology, it being the first off-the-shelf unit with integral easy sequence programmable functionality (EzSQ) as standard.

    Perhaps the first notable thing about the SJ700 is its compact size, an increasingly important issue as users and systems buiders seek to reduce control panel size. It also incorporates a patented power switching technology to reduce dVdT, with the IGBT (insulated gate bipolar transistor) stack at the heart of the drive. High dVdT is associated to motor insulation breakdown by the increased terminal voltage of motors when used with AC drives.

    The smaller drives caused a stir in the market when launched last year, and the new large drives are expected to be even better received.

    "Large drives tend to be installed and used for many years so can look very dated by the time they are replaced," explains Stuart Harvey of Silverteam, Hitachi's Drives and Automation Company in the UK. "The SJ700 resets the benchmark for small and medium sized drives, offering multipoint positioning and near servo performance from a standard induction motor. The 160kW-400kW SJ700 makes similar performance available right through the power range.

    The SJ700 is a sensorless vector drive, with 150% torque at zero speed and near total immunity to motor constants problems. It sets new levels of responsiveness and accuracy and includes enhanced autotuning for increased ease of set up. An optional feedback card can be used to close the vector loop for even finer control.

    "The built-in EzSQ functionality provides a very powerful controller that negates the need for an external unit such as a PLC in even the most demanding of applications," says Harvey. "Its communication with both the external system and the drive's internal circuitry is naturally very fast and very secure. This enhances operational performance all round."

    The large SJ700s should set new performance standards in water pumps, fans, hoists, lifts and many other applications. "With lifts, for example, we can offer very smooth floor transitions with adjustable S ramps and brake release confirmation signals, while the superior torque and speed control make it particularly suited in hoist applications like cranes or theatre flying systems."

    The SJ700 also offers notable benefits for applications where high performance is not critical. "There are savings because you don't have to buy a separate PLC, panel space savings, installation and commissioning time savings and an increase in reliability."

    Hitachi has designed the SJ700 for a working life of at least 10 years. As Harvey puts it: "Every detail has been looked at to design out possible failure modes. The patented switching is just one example of this.

    "We tested all the leading drives with many different makes of motor. Voltage spikes leading to insulation breakdown was always a potential problem particularly with cable runs over 50m, so we gave the designers the targets of reducing problems to negligible levels and for the drives to be usable with cables over 100m long without line reactors. To achieve this they could not refine existing techniques, so they had to develop next generation technologies."

    Other features of the SJ700 include brake transistors on sizes up to 22kW , integral EMI/RFI filters across the whole range, a full range of comms options, customisable display panel, intelligent energy saving, active frequency matching for restarting and flying load catching, regenerative braking under E-stop conditions and full RoHS compliance.

    Silverteam Limited

    Tel: +44 (0)1493 669879

    Fax: +44 (0)1493 669647

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  • Drives & Controls - Saving energy through drive system efficiency

    Many pump and fan systems are designed with safety margins which can make them grossly oversized. This in turn leads to inefficient use of energy, but the efficiency can be vastly improved with the use of variable speed drives

    Of all the resources used in modern manufacturing, energy is arguably the most fundamental. This resource has long been taken for granted, but rising energy prices and concerns over greenhouse gas emissions are increasingly leading users to critically assess their energy usage.

    In many technology areas, significant energy savings are difficult to achieve and gains of a couple of percent are then celebrated as breakthroughs.
    There are technologies, however, that can deliver very significant reductions in energy use. Foremost among these is the variable speed drive. It doesn't make much noise or develop extreme temperatures or go through complex motions. In fact it sits in a cabinet and usually doesn't even get a mention when the overall process is explained. However, it can deliver great cuts in energy consumption, frequently nearly halving the consumption, and if applied in all relevant plants worldwide, it can deliver energy savings that equate to the electrical consumption of a country such as Spain.

    The principle is simple: In the past, the motors that powered pumps were usually run at full power all the time, with the output controlled with valves. A drive regulates flow through direct control of the electrical power fed to the motor, so eliminating friction-based controls and the associated losses.

    The lack of system standards
    However, a lack of system standards for energy efficiency may result in up to 90 percent of pump installations being incorrectly sized, leading to energy waste.
    "We have standards for everything," you may argue. However, in the area of energy efficiency there are still important gaps. While there are standards for pump designs and many for the hydraulic data such as developed head, efficiency and net positive suction head, a search for standards providing guidance in system design is less likely to produce a result.

    To use an analogy, if somebody were to buy a three-ton truck for use on shopping trips, it would do the job, but would not be a demonstration of energy efficiency - even if the truck selected boasted the best efficiency figures for three-ton trucks. 

    When planning a system, there is a degree of uncertainty as to the shape of the system curves (friction, pipe cross section changes and the number of bends in the final pipe layout all take their toll). These factors all add to the risk that the expected operating conditions will not be met. There are three basic ways to address the changed operating conditions: 
    - If the changed condition is permanent, then the pump or fan size should be changed to match the load. 
    - This adds to the installation cost
    - The pump or the fan speed can be changed, or the impeller can be modified. 
    - A throttling device (such as a valve, damper or guide vane) can be added. 
    - Both of these options can waste energy. 

    The cost of energy is the all-dominating part of the lifecycle cost of a pump or a fan. Energy consumption is the best place for optimization to start.

    How systems get over-dimensioned
    Systems get oversized throughout the design process, but variable speed drives can be used to conserve energy.

    Despite careful analysis and design, many systems do not operate optimally. One reason is that many systems are simply sized too large to start with, resulting in higher operating and investment cost. To illustrate this, the case is considered of a system with a fan in a process plant.

    In this example, it is assumed that the ‘true' nominal condition for the application is 100 units of flow, requiring 4000 units of pressure. 
    In order to be on the safe side concerning the maximum flow, the figure for the fan communicated to the engineer is 110 units of flow. With the assumed system curve, this would require a fan with a higher capacity that can deliver 110 flow units and 5000 units of pressure. 

    When establishing the fan capacity, the engineer estimates the overall pressure drop that these 110 flow units will cause. The pressure drop value that is calculated is increased by a 10 % margin because is difficult to foresee whether the assumed number of bends in the duct will conform to that estimated (possibly the installation contractor will have to add bends to avoid other equipment). Also, the cross-section of the duct may be uncertain. A smaller cross section would lead to a higher pressure drop. This therefore means that a 10 percent margin is not unreasonable. 

    So what data are finally sent out in the requests for tender? Flow: 110 units at a pressure of 5500 units. Even if the original assumptions were correct, the fan is now grossly oversized. At 100 units flow the necessary additional pressure drops over the damper must be about 2800 units. This corresponds to 70% of the assumed correct total pressure. However, it is rare that 100% of the design flow will be needed other than for very short bursts. Assuming that most of the time, 80% of the flow rate will be required; the additional throttling needed across the damper will be about 6000 units. This corresponds to 150% of the assumed correct total pressure.

    The steps illustrated in this example are more common than they may seem. An additional factor is that, when it comes to the selection of a fan, this choice must be made from a standard range of fixed sizes. The next larger one will usually be chosen, with a motor sized to suit.

    The correctly sized fan for this example at point ‘g' should be 100 × 4000 = 400,000 power units, and the normal running at point "l" will require 80 x 2500 = 200,000. The case above produces a requirement for a fan of at least 110 x 5500 = 605,000 power units (150% of the optimum). Correcting this with damper control leads to high levels of wasted energy. The additional losses at the 80% flow point amount to 80 x (8100 - 2500) = 448,000 power units (120% of the full power of a correctly sized fan). These figures will in practice become worse, because the fan will not be working at its optimum efficiency throughout the operating range. With a speed controlled fan instead of damper control, nearly all of this energy can be saved.

    Old pumps given energy boost
    The Corus site at Port Talbot in Wales is one of the biggest steelmaking plants in the UK with an annual output of 5 million tonnes. Energy is Corus' second highest cost after raw materials. The costs and revenues of the business are fairly fixed, so high productivity is crucial to stay competitive.

    As part of a plant-wide energy saving programme, 24 ABB industrial drives, ranging from 140 to 400 kW, are being installed to control pumps on the hot strip and cold mills, plus three fans on the coke ovens. The pumps recirculate cooling water in the mills, while the fans are used for dust extraction at the coke ovens. The cost of the drives about £1m; the whole project including pumps, cabling etc. is around £2.5m.

    "The pump and fan motors were clearly oversized and running longer hours than necessary," says Guy Simms, leader of the energy optimisation team. "Much of the equipment on the site was installed during the sixties, seventies and early eighties. At the time, it was common practice to oversize the equipment by as much as 50%, to make sure it was sufficiently robust. In many ways this was a successful policy - after all, it has lasted all these years. But with the ABB drives we are now installing, we can fine-tune the applications to a degree that just wasn't possible in those days."

    The applications have varying demand but until now, the pumps and fans have been running continuously at full speed. Running to demand will not only reduce energy costs, a million pounds in annual energy savings is expected, but also save water and improve control, particularly of the cold mill, which could potentially result in better product quality.
    In any process where a restriction is used to control flow, energy can be saved, and in any process where volume can vary, energy can be saved.

    Picture top right: 24 ABB drives, controlling pumps on the hot strip and cold mills, plus fans on the coke ovens, will be saving a million pounds in energy annually at Corus Strip Products in Port Talbot

  • ABB introduces latest Drives & Motors Catalogue

    ABB's new Drives & Motors Catalogue provides technical details of ABB's range of low voltage AC drives from 0.18 to 2,800 kW and motors from 0.06 to 710 kW.  It also presents ABB's range of DC and medium voltage AC drives. Easy-to-use tables give ordering data, dimensions, options and electrical details for most products, together with prices for 2008. The brochure also lists all ABB Drives Alliance and Motor Service partners, so customers can easily locate their nearest ABB partner.

    The ABB Drives & Motors Catalogue 2008 is free on request from ABB's freephone Brochureline on 0800 783 7491 or from the website, www.abb.co.uk/energy.

    ABB Limited

    Tel: 01925 741 111;

    Fax: 01925 741 212;

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  • Drives & Controls - Delivering energy understanding to the top table

    Speak of deploying widespread AC inverter technology, or calculating cube law considerations for a plant's fans and pumps and the average finance director would keel over. However, as GAMBICA's variable speed drives group argues, until such topics are understood at the top table, industry will fail to maximise potential energy efficiencies

    In most developed countries, industry accounts for about half the electricity consumed. Of this industrial consumption, two thirds is typically used in powering electric motors. For this reason, the control of motors must be placed high on any energy efficiency agenda. Yet, because motor control involves highly technical issues, the overwhelming majority of boards of directors and senior business managers continue to focus energy efficiency attention on readily understood areas such as insulating building fabric and reducing lighting consumption.

    For many, energy measures revolve around the consideration of thermal issues in the building fabric with remedies such as insulation, glazing, and heat loss countermeasures. These are really only passive countermeasures that compensate for energy loss rather than the active control of the energy deployed.

    Under the Kyoto Protocol industrialised countries have agreed to reduce their collective emissions of greenhouse gases by 5.2% by 2008-2012 compared to the year 1990 (however, compared to the emissions levels expected by 2012 prior to the Protocol, this limitation represents a 29% cut). The target in Europe is an 8% reduction overall with a target for CO2 emissions to fall by 20% by 2020.

    The cost of an electric motor can be very deceptive; in particular, the annual energy cost to run the motor can be up to ten times its purchase price. Indeed, the running costs of a fully loaded motor operating at 50Hz can range from over £1,000 a year for a 2.2 kW motor to over £18,000 a year for a 37 kW one. Consider that, for example, a typical 11kW AC induction motor, that can be purchased these days for as little as £300, could cost as much as £30,000 in electricity consumed over a 10 year lifetime.

    Fit a variable speed drive and simply by slowing the motor by 20% the energy bill is halved. About 105TW of electricity is consumed by British industry each year. It is estimated that two thirds of that is consumed powering electric motors; and of those motors about three quarters of them power fans, pumps or compressors in continuous duty variable torque applications. It is these variable torque applications where the greatest savings can be made from VSDs.

    In other words, if every fan, pump and compressor motor was equipped with a VSD and had a 20% reduction in speed, the total consumption would fall by about 26TW per annum. Put another way, the savings would enable the closure of the UK's largest coal fired power station, saving 20 million tonnes of CO2 per annum. Even more dramatic to consider is that this figure effectively means that the CO2 emission attributable to  3.1 million homes would be negated. In other words, the whole of Greater Manchester and Birmingham would be rendered carbon neutral!

    If the targets of those nations compliant with the Kyoto Protocol are to be met, greater attention must be placed on broader energy efficiency regimes. These have to include motor speed control.

    Most of the bodies charged by government with communicating and effecting change in the approach to energy consumption are naturally focussed on conservation in the broadest public arena. For this reason, the public relations and other promotion has been almost exclusively targeted at the general public and on measures such as insulation, heating and lighting reduction. This is true even of the respected Carbon Trust and Energy Saving Trust in the UK. However, with ambitious national carbon reduction targets and current consumption trends failing to meet the rate of decrease needed indicates that the UK will fall drastically short within the 2020 deadline. Bodies such as Gambica, which represents most of the significant motor speed control manufacturers, know that more must be done.

    That government may impose further levies, legislation or penalties relating to energy use is speculation, but as the 2020 deadline looms, it remains a possibility. Against this backdrop, is the almost exponential rise in energy prices that are directly impacting on industry, commerce and consumers by its significant and proportionate affect on costs.
    In the simplest terms there are a number of things business can do: ignore energy issues completely and either pass on costs as increased prices or accept continuously reducing margins (rather than invest in energy efficiencies); take passive measures such as installing energy saving luminaires, improving insulation; take active energy initiatives and address all aspects of consumption.

    Hence, we return to the topic of motor control. This for industry, commerce and large commercial buildings represents low hanging fruit in terms of making substantial energy savings. In many respects fitting motor speed controls is like changing to energy saving light bulbs in the home - but with on-going automatic savings.

    First, a quick physics lesson
    Consider that billions of electric motors are in daily (often continuous use) every day. In most countries, fewer than 10% of the motors have any form of control. In continuous duty applications such as powering fans, pumps and compressors, it is possible to effect incredible savings by reducing the motor speed by a very small amount. This is because in such applications, the fundamental physical laws governing centrifugal fans and pumps also preside over the potential savings that can be achieved. In laws of physics, power is consumed as a cube of output. Indeed, affinity laws dictate that while motor torque varies with the speed squared, power varies with the speed cubed. Hence, the cube law impacts greatly the energy efficiency in such equipment.

    On loads of this type any speed reduction will save large amounts of energy (that is, a 20% speed reduction will result in a 50% power saving). Remember, torque varies with the speed squared, power with the speed cubed. This means that variable torque loads, such as fans and pumps offer the greatest potential for energy saving.
    Culture gaps inhibit industrial energy conservation
    Why there has not yet been a huge uptake of motor speed controls lies largely with ignorance of the technology and ambiguity within industry over who owns the task of implementing energy efficiency. To explain this statement more clearly, in a manufacturing plant for example, the plant engineers are often acutely aware of the energy efficiency benefits of installing variable speed drives (VSDs) to AC motors. In the boardroom, managers may be alert to the need to economise on energy for any number of reasons: escalating fuel bills; corporate social conscience; or even just because it's good marketing sense to be seen to be green. The problem is plant engineers are never measured on their ability to save energy; while directors and managers are unaware their plant engineers could do so. It is a simplistic view, but one borne out by evidence throughout manufacturing industries.
    Energy intensive industries such as metals manufacturing, glass and plastics processing and food and beverage production understand the need for energy management because their processes involve great amounts of heat. These businesses have traditionally sought ways to maximise their return on investment from the energy used in their primary processes. However, even these energy aware businesses often fail to realise how much more can be saved through building controls and a company wide energy policy.

    Of far greater significance overall is the use of variable speed drives in a broad range of processes.

    While in many countries industrial energy use has now been slightly outweighed by that consumed by commercial and residential buildings, it is a fact that industry consumes huge amounts of electrical power. About two thirds of that is typically consumed powering electric motors. Of these, an overwhelming majority can be made significantly more energy efficient by controlling their switching on and off or by controlling their speed.

    This is a relatively simple task of equipment retrofitting, yet it is clear that most manufacturing and process plants fail to take the step. The reason is often because those that control the costs of an industrial operation are not communicating with those charged with the management of the production processes.

    For example, if a painting plant uses hundreds of AC motors on fans, pumps and compressors (continuous duty applications) it could readily benefit from the use of variable speed drives. However, while the plant manager, as an engineer, understands this, he or she is invariable responsible only for improving productivity or output and not for the overhead costs. Higher management is concerned with paying the overheads but remains unaware that such a saving could be made because it is never on the agenda in engineering meetings.

    In industry, senior management and plant engineers must learn to talk if an holistic and comprehensive energy efficiency policy is to be achieved. In no other sector is the communication gap wider, than between those charged with making energy decisions and engineers in industry who know how energy can be saved.

  • Competitiveness boosted by maximising drives’ reliability

    ABB's three-tiered variable speed drives service programme is said to help users prevent downtime and production loss.

    The three levels of service - DrivesAdvantage, DrivesActive and DrivesActive+ - enable each customer to choose from a range of services that can be tailored to suit their needs and budget precisely.

    The portfolio ranges from the installation and commissioning of new drives, through maintenance and spares support during service, to replacing products as they reach the end of their working lives.

    A brochure describing DrivesActiveand DrivesActive+is available free from the BrochureLine, tel 0800 783 7491. Alternatively order online at www.abb.co.uk/energy.

  • Drives key for machine OEM

    An Indian manufacturer of biscuit production machinery is using ABB drives to ensure its customers can produce high quality, consistent biscuits.

    Located just outside Mumbai, Bake-O Nomic is one of India's leading OEMs of biscuit manufacturing lines, producing three fully automated biscuit production plants per year for sale mainly to Nigeria and other African markets.

    Because biscuit making is a continuous process, with a number of stages feeding into each other, it is important that each stage is controlled at its own appropriate speed. All the machines, such as biscuit cutting, forming, oven and cooling conveyors are linked to each other, accepting materials or part processed biscuits and passing them on to the next stage.

    As each type of biscuit has a different baking time, the company needs a reliable and energy efficient way to vary the speed of the different parts of the process.  An example is mixing, which is done in two stages. Shortenings and sugar are mixed at high speed and subsequently flour is added and mixed at a slow speed.

    One of the most reliable and energy efficient ways to control this sort of production line is through the use of low voltage AC drives.

    Praful Dattaram Kale, owner of Bake-O Nomic, says: "We chose ABB because of its reputation in the market. ABB is renowned as a reliable supplier with a broad product range. Also, as ABB is a global player, we can benefit from its extensive service network. Should any of our equipment need repairing or maintaining as a result of a drive malfunction, then it can be fixed locally and efficiently."

    The drives are used primarily on biscuit cutting and forming machines, mixers, ovens and conveyors. About 20 drives are used in a single biscuit making line, most of them below 5.5kW, although for mixers, drives as large as 30 kW can be used. Above 0.75kW, ABB standard drives are used, while below this power ABB machinery drives are used.

    Most are manually controlled individually, a method preferred by the company's customers, who need a fine speed variation depending on the requirements of the type of biscuits being produced.

    Bake-O Nomic has used AC drives for energy saving, both electricity and fuel, in some blower applications in its own biscuit making plant set up in Nashik.

  • Drives & controls - Making redundancy redundant

    Modern control systems are invariably designed with safety as a prime requirement. Often this can add significantly to the cost, particularly where high-power contactors have to be duplicated to provide redundant operation. Fortunately, there's now a better approach, as Moeller Electric's Steve Rickard explains

    Almost every control panel incorporates motor starters and there can be no doubt about it, when a safety relay operates or an emergency stop button is pressed, the motors controlled by those starters have to stop.

    It's easy enough, of course, to design the control circuits to behave in this way, but what happens if there is a component failure? In particular, what happens if a contactor has welded closed? The answer is that, unless further measures have been taken, the motor controlled by the welded contactor will continue to run.

    Clearly, this very dangerous state of affairs cannot be tolerated, particularly as welding is a relative common failure mode for contactors, especially those that have reached the end of their service lives.

    The usual solution is to incorporate two identical contactors in series in the starter circuit which meets the requirements of Safety Category 3 and 4. The risk of both contactors welding simultaneously is unlikely, so at least one of the contactors will always open when required to do so, and the motor will be safely stopped.

    While this approach of using redundant contactors is effective and widely used, it does have several drawbacks. The first is cost. While small contactors are relatively inexpensive, their larger counterparts certainly are not. So, with a 100kW drive, for example, using a second redundant contactor adds significantly to the overall cost of the control system. The next drawback is panel space. High current contactors take up a lot of panel space, and not only is panel space expensive, there is often insufficient room available on site to allow large panels to be accommodated. Finally, duplicated contactors increases the amount of heat generated within the panel, because of the losses from the coil and main contact circuits.

    To address these issues, Moeller Electric has pioneered the development and introduction of a new type of control component - the contactor monitoring relay, a device which is both compact and inexpensive.

    The principle of operation of this innovative device is easy to state. It simply compares the state of the main contacts of a contactor with the voltage that's being applied to the coil. If the coil is de-energised but the main contacts are still closed, the output relay of the contactor monitoring device operates, opening a set of contacts that can, for example, be used to trip an undervoltage release on the circuit breaker protecting the motor circuit. In this way, it's clear that, even if the contactor welds, the motor will still be brought to a stop safely. The need to use a duplicate contactor to ensure safe operation is, therefore, eliminated.

    While the principle of operation of the contactor monitoring device may be simple to state, however, designing a practical product is a little more challenging. For example, what is the best way to monitor the main contacts of the contactor?

    The solution adopted by Moeller Electric is for the monitoring device to look at the state of an auxiliary contact on the contactor. Not all auxiliaries are guaranteed to accurately reflect the state of the main contacts, however, especially when the contactor is faulty. The auxiliary used for this function must, therefore, meet the requirements for a mirror contact, as defined in the IEC EN 60947 Annex F.

    Essentially, these requirements state that a mirror contact on a contactor is a normally closed contact that can only ever close if all of the main contacts have opened. All N/C contacts on DILM and DILH contactors from Moeller Electric meet this requirement. That's not quite the end of the story, however, as we need to consider what happens if the auxiliary contact itself welds closed. This is very unlikely, but by no means impossible. The solution here is to compare the state of the N/C auxiliary with an N/O auxiliary in the same contact block. Provided that the contacts are positively driven - a condition once again met by the standard auxiliaries used with Moeller Electric contactors - they can never be closed at the same time unless a fault has occurred.

    By monitoring a positively driven N/O auxiliary as well as the N/C mirror contact, the contactor monitoring relay can, therefore, immediately detect problems with the mirror contact and generate an output to trip the drive.

    As this discussion shows, the characteristics of the contactor and of its auxiliary contacts have a critical bearing on the operation of the contact monitoring device. For this reason, Moeller Electric provides details of approved product combinations that will ensure the appropriate levels of safety are achieved.

    With these combinations, the operation of the contactor, the contactor monitoring device and the motor protective circuit breaker complies with the requirements of EN ISO 13849 for Performance Level e, provided the number of switching operations of the contactor does not exceed 350,400 per year, and that the number of switching operations of the protective device does not exceed 1,095 per year.

    In the calculation of the overall performance level for the control system, however, the safety components upstream of the motor starter also have to be taken into account. When this is done, the result is that, with the aid of the contactor monitoring device, control systems that overall meet the requirements for Performance Level d can be readily implemented.

    Small, easy to use and cost effective, contactor monitoring devices are a very attractive and convenient alternative to the adoption of redundant contactor designs in control systems. They save money and space, as well as reducing the amount of heat generated within the panel, all without compromising the level of safety achieved by the overall system.

    With contactor monitoring devices offering so many benefits, surely it has to be time to make redundant contactors redundant?

  • Drives & controls - Drive to reduce energy pays dividends for PET bottle producer

    Rockwell Automation has worked with Proplas International to help Europe's leading supplier of rigid plastic packaging to reduce its energy costs by £71,000 a year, with a payback period estimated at just 14 months

    ONE?OF Europe's leading suppliers of rigid plastic packaging is reaping the benefits of an energy saving retrofit on 13 injection-stretch-blow moulding machines. Engineering services provider Proplas International fitted 13 of the packaging specialist's PET bottle and jar moulding machines with Rockwell Automation's Allen-Bradley PowerFlex700 variable speed drives, helping to reduce energy consumption by over 27 percent.

    From its base in Burnley, Lancashire, Proplas International has built a reputation for helping industries to become more efficient - something which all companies will recognise as being vital in today's increasingly competitive market place. Amongst other areas, the company has become widely known for its energy saving projects, with a particular focus in injection moulding machines of all types where Proplas is a recognised leader in saving energy.
    In a recent project, Proplas fitted Allen-Bradley PowerFlex 700 drives to 13 injection-stretch-blow-moulding machines at Europe's leading supplier of rigid plastic packaging. The machines produce a range of bottles and wide-mouth jars in Polyethylene-Terephthalate (PET) for the food and drinks industry - containers that are used by a range of industry-leading manufacturers as well as by various supermarkets for their own-brand food and drink products.

    The injection-stretch-blow-moulding process is used because of its capability to produce high quality containers. In the process, molten polymer first flows into the injection cavity to produce the desired preform shape. A period of conditioning at a set temperature follows, after which the preform is ready for stretching and blowing into the finished shape. The preform is transferred to the blowmould area, and the mould closes. A stretch rod is introduced to stretch the preform lengthways, whilst differential air pressure is used to blow the preform out to the shape of the mould. Finally, after a set cooling time, the mould opens and the finished container is removed. In practice, the four stages are carried out concurrently with a revolving carousel of moulds.

    Proplas director Stephen Anderson comments: "The machines were being driven by hydraulic pumps, with their motors set at a constant speed that would cater for the maximum hydraulic demand - the periods in the process where the moulds are opening and closing. But this is an inefficient process, since the energy usage remains constant (and high) while the actual power demand varies."

    The Proplas solution was to fit variable speed drives to the pump motors, operating at two preset speeds - a higher speed during the maximum hydraulic demand when the moulds are opening and closing, and a lower speed during the periods of reduced demand.

    "We performed a number of tests with the company to demonstrate the potential, and convinced them that there could be major energy reductions and associated cost savings," said Anderson. "As a result, we were asked to retrofit a drives solution to 13 of the company's injection-stretch-blow-mould machines."

    The retrofit was built around 13 Allen-Bradley PowerFlex 700 drives, with each drive connected to an Allen-Bradley Pico micro PLC to provide the simple sequencing logic.

    "The available torque was a key issue in this application, because the profile is characterised by spikes in the torque demand that can cause many other drives to trip," says Anderson. "The PowerFlex drives delivered the same torque in the actual application that was promised on the datasheet, and in this case that capability allowed us to downsize to a lower power product without any fear of it tripping out or the motor stalling, helping deliver further energy savings for the customer."

    For the customer, all this has meant some substantial energy savings. The power usage of each machine before the modification was 40kW, but with the help of the drives retrofit this has been reduced by 11kW. With every kilowatt equating to around £500 in energy costs, the project is estimated to be saving the customer over £5000 on every machine, with an estimated payback period of just 14 months.

  • Customised drives now available online

    Danfoss Drives and its partners now offer online ordering of the VLT Micro Drive. Customers can order customised drives through a centralised platform and take delivery from their local distributor. The benefits include minimum processing time for orders, direct follow-up and the shortest possible delivery time.

    The new web site, at www.vltmicro.co.uk, allows users to customise the drive, select their local distributor and pay for the order using PayPal or major credit cards.

    "It's simple, easy and fast" says Anthony Pickering, senior sales director at Danfoss Drives. "We wanted a platform that allows the customer application to be up and running in the shortest possible time"

  • Drives and motors catalogue highlights new products

    The 2009 edition of ABB's drives and motors catalogue is now available for end-users, system integrators and Original Equipment Manufacturers (OEMs). The 48 page catalogue is free and can by downloaded directly from www.abb.co.uk/energy or a hard copy is available from freephone 0800 783 7491.
    The catalogue provides technical details of ABB's range of low voltage AC drives from 0.18 to 2,800 kW and motors from 0.06 to 710 kW. It also presents ABB's range of DC and medium voltage AC drives. Easy-to-use tables give ordering data, dimensions, options and electrical details for most products, together with prices for 2009.
    ABB Limited
    Tel: 01925 741 111

  • Drives & Controls - Could a basic energy audit prove the saviour of UK industry?

    As uncertainty surrounding the future of energy prices grows, and firms are pressured into attempting to reduce their carbon footprint, there has never been a better time for industry to consider the merits of variable speed drives and high efficiency motors. Manufacturer ABB has developed an energy audit that quickly and accurately pinpoints the potential savings in an industrial plant

    A variable  speed drive (VSD) and electric motor combination, when used to control the speed of pumps and fans, can reduce the energy bill of these applications by some 70% with a payback in less than 12 months.

    And yet a survey of British manufacturing managers with engineering roles has revealed that they do not regard VSDs as being the best way of cutting their companies' energy bills. The survey, conducted for ABB, reveals the 67 engineering managers surveyed placed VSDs at the bottom of a list of the ten most effective measures for cutting energy bills.

    Joint top of the list were negotiating better prices with their company's existing energy suppliers and fixing compressed air leaks. ABB had expected the survey to show significant differences in attitude between the financial and engineering managers, with the latter appreciating the role that high-efficiency technologies could play in cutting energy bills.
    The financial mangers believe that clamping down on visible waste, such as inefficient lighting and compressed air leaks, is important. Investing in equipment that makes industrial processes more efficient came at the bottom of their list.

    "This list is back to front," says Ruddell. "Making industrial processes more efficient can save much more than the other methods, but financial managers are simply unaware of the savings they can make. Most companies can save thousands of pounds worth of electricity and some can even save hundreds of thousands of pounds, often at comparatively low cost. Changing electricity suppliers is not going to make much difference at all in a market where prices rise across the board," he adds. "In addition, this does nothing to reduce the company's carbon footprint, which also ought to be a priority."

    ABB is in the vanguard of energy promotion, launching, in 2004, its award winning 6-step energy saving plan.

    6-step energy saving plan
    The plan documents six basic steps towards understanding and planning an energy saving campaign.
    Step 1. The facts:
    Gives an insight into the latest thinking on the Climate Change Levy and UK government actions to encourage greater energy savings.
    Step 2. The savings:
    In just half-a-day, an energy audit can help identify the applications that offer the best energy saving opportunities.
    Step 3. The finance:
    Offers information on how to finance a drive purchase while still benefiting from the government's Enhanced Capital Allowance.
    Step 4. The products:
    Guides the end-user through selecting the best motors and VSDs for specific applications.
    Step 5. The proof:
    Gives examples showing how industry has benefited from using VSDs and motors.
    Step 6. The action:
    Gives advice and further contact information at ABB and its extensive UK channel partner network.

    Energy saving audit
    At the heart of the 6-step plan is ABB's energy audit. On a typical industrial site with a £150,000 annual electricity bill, £100,000 will be spent on running motors. For example, are any motors or fans running on full power all the time when they could be driven by demand?
    The answer is a professional energy audit. Undertaken by a trained engineer, an energy audit will identify those applications that would most benefit from the introduction of VSDs. The results, based on measured data from the application, will help a user target their investment so that it produces the highest possible savings and gives the best return. ABB has devised a very simple and methodical energy audit that presents the customers with hard, compelling facts about the energy they can save.

    1. Outlining the scope of supply
    During an initial meeting the audit engineer takes a look at the inventory of motors contained within a plant.

    Energy surveys are most suitable for processes involving motors of 11kW or higher, used on large pumps and fans. This is where the savings from a VSD really start to look good compared to the investment cost. Often payback times of two years and below and sometimes under one year, can be achieved. ABB meets the end-user and outlines the benefits of the audit in detail, together with any assistance the end-user might need.

    2. Collecting the data
    The data collection phase is an active phase. It involves an on-site audit with selected fans and pumps, to determine operating parameters such as voltage, current and power factor and the energy being used. This stage will usually be performed over seven days to gain a complete picture of the plant's typical energy use. The end-users own staff may become involved at this stage although different auditors have different approaches.

    3. Analysing the data
    Following the collection of the data, the findings will be analysed and potential savings identified using dedicated software. The findings will be methodically presented - often tables or graphs will be created to help see where savings are likely to arise.

    4. Recommendations
    The action plan will then be prepared, usually comprising an Executive Summary and a detailed engineer's report, highlighting applications that can save the most. The figures will normally be translated into monthly savings, and there will be detailed recommendations for fitting particular VSDs or motors. The report should also clearly show the expected payback time on fitting new equipment.

    5. Implementation
    While not strictly part of the audit the aim is that the recommendations should be fully implemented. Once new equipment is fitted it is normal to track the actual savings against the predictions shown in the report. This will also help justify the investment in VSDs.

    6. Benefits
    An energy audit carried out by ABB or one of its channel partners brings the following benefits:
    - Clearly identified energy savings
    - Complete audit results and energy saving calculations 
    - History of other audits and associated energy savings
    - Proposed payback times 
    - Degree of customer training given as part of the process
    There are also other aspects to consider, for example whether financial options are available and if your supplier offers a replacement drive scheme.

    Carbon emissions calculator
    More recently, ABB has added another tool to its 6-step energy saving plan. As carbon emissions take a higher priority on company boardroom agenda's, ABB has developed a simple to use and understand carbon footprint calculator.

    The user enters a motor's rating, and the calculator shows the energy savings in kWh, as well as the monetary savings, the cost of a suitable drive, and the payback time.
    "Quantifying the carbon footprint helps organisations to manage their footprint and reduce emissions over time," says Ruddell. "But motor energy use is frequently overlooked, despite being the largest are of electricity use in industry.
    The carbon calculator can be accessed via www.abb.co.uk/energy

    Corus Strip Products
    It was just such an energy audit that produced spectacular benefits for a steel maker in Port Talbot South Wales, saving £1m on its annual energy bill.

    Corus is one of the biggest steel making companies in the UK with annual output of five million tones. Energy was Corus' second biggest cost after raw materials and with energy prices rising year on year it was important that energy expenditure was minimised.
    As part of a plant-wide energy saving programme, 24 ABB industrial drives, ranging from 140 to 400 kW, where installed to control pumps on the hot strip and cold mills, plus three fans on the coke ovens. The cost of the drives about £1m; the whole project including pumps, cabling etc. is around £2.5m.

    "The pump and fan motors were oversized and running longer hours than necessary," Says Guy Simms, leader of the Energy Optimisation team at Corus Strip Products. "But with the ABB drives we are now installing, we can fine-tune the applications reducing energy consumption."

    McKechnie Automotive and Engineered Plastics
    Following an energy audit at McKechnie, a manufacturer of engineered plastic assemblies ABB was able to reduce energy costs by over 30%.

    The plastics manufacturer based in Pickering brought in Halcyon Drives, an ABB Drives Alliance partner to improve the efficiency of their injection moulding machine. Typically most injection machines are hydraulically operated and often waste between 20 and 50 % of the electrical power they consume. By adding a variable speed drive it is possible to control the speed of the pump motor to deliver the precise amount of electricity needed for each sequence in the injection moulding cycle.

    "By introducing variable speed drives our energy cost has been significantly reduced" Says Rob Howlett senior process engineer for McKechnie.

  • Drives & Controls - VSD saves energy in hydraulic systems

    Hydraulic systems waste much of their energy as the fluid circulates at a constant  pressure, regardless of the amount of work carried out. Despite this, drives are not widely used in hydraulic installations, perhaps because the very impressive savings normally achievable in standard pump applications are not possible with the type of pump used in hydraulics. However, when Corus Colors on Deeside looked closely at the issue, the company found significant energy savings could be achieved

    When an ABB industrial drive was installed on a hydraulic pump, steel manufacturer Corus Colors on Deeside recorded a 70% energy saving.

    A trial was carried out by a graduate engineer at the company, Rob Chew, and Phil Tomkinson of Radway Control Systems. The aim of the study was to establish whether the drive would be a viable option for controlling energy consumption in hydraulic systems.
    The hydraulic system used during the trial is located on a production line used for retreating and inspecting strip material, driving actuators and web guiding systems in a 24-hour process.

    "As drives can be used to accurately control the speed of most motor driven machinery, hydraulic pumps should be no exception in this respect," says Chew. "Hydraulic systems waste much of the energy used, because fluid circulates continuously, although actuation is only required for very short periods of time."

    The energy used by the pump can be controlled by intelligently modulating the speed of the motor. The particular function used in this trial was the PID control, built into the ABB drive, which helps keep external values, like pressure, within certain limits. Pressure feedback is returned to the drive from a transducer. The drive automatically adjusts pump speed to maintain the system pressure.

    Pump design reduces saving potential
    Drives tend not to be used much on hydraulic systems, usually because the pressure is normally provided by a positive displacement pump, a type of pump that, theoretically, offers far less energy saving potential than the more common centrifugal pump.

    Unlike a centrifugal pump, which uses centrifugal force to throw fluid out through the discharge end of the pump, the positive displacement pump uses an internal mechanism that presses the fluid out. This means the output will be the same regardless of the resistance on the discharge side. The internal mechanism can be some type of gear or an arrangement with vanes. The installation at Corus Colors uses a positive displacement vane pump, driven by two 37 kW motors, one duty and one stand-by.

    Producing flow under pressure
    Positive displacement pumps are used in hydraulic systems because this type of pump can produce high pressure despite high system resistance. A centrifugal pump is far less effective working against a high system pressure. Its actual capacity can be anything from 0 to 100% of full capacity, depending on the resistance produced by the system pressure. Because the pressure in a hydraulic system is very high, a centrifugal pump would not be able to pump much at all against this resistance. A positive displacement pump, in contrast, only shows a very small change of flow when the pressure goes up or down.

    However, the energy consumption of the positive displacement pump is not reduced when the system resistance drops. For this reason, it does not offer the same energy saving potential as centrifugal pumps at reduced speed. While the centrifugal pump offers energy savings equal to the cube of the speed reduction, a change in flow by the positive displacement pump produces a linear change in power usage.

    But despite using a positive displacement pump, Corus Colors achieved significant energy savings by retrofitting the existing system with a drive. The pump speed was greatly reduced both when the system was in neutral and during actuation of the cylinders.

    Optimising speed
    Chew's trial aimed to establish whether system pressure could be maintained with reduced average motor speed, using a drive, with pressure data fed back to the PID control of the ABB drive from a pressure transducer. The installation was commissioned on a downshift as other maintenance was carried out on the production line.

    Vane pumps start losing their efficiency below 400 rpm, as the vanes are held in position by centrifugal force, so the pump efficiency had to be monitored throughout the trial as the optimum speed was sought. This was eventually established to be 450 rpm.

    Chew had concluded that leaving the drive just running in PID control would cause some unwanted side effects. The main issue was that a drop in pressure would be followed by an increase in motor speed in response to the pressure drop.

    The desired system pressure is 90 bar, while the maximum is 93 bar at full speed. As in many hydraulic systems, the on-load times are short. After actuation of the cylinders, the hydraulic system quickly settles back into neutral again. As the drive will have increased the motor speed rapidly to meet the drop in pressure, it is likely that it would overshoot the target of reaching a pressure of 90 bar, with the PID control having been set very high for a fast response.

    The system relief valve is activated at 93 bar so the system pressure will never get higher that this. As the drive only sees a small error in pressure of 3 bar, it may be slow to react. This means there will be a long transient time before the drive settles down to the required speed to maintain 90 bar in neutral and this will cause unnecessary waste of energy, sending excessive fluid back to the sump while the hydraulics are in neutral.

    Dual mode control
    The solution was to operate the drive in two modes, PID control and single-speed mode. The switching between the modes is controlled by the transistor output of the pressure transducer. When the hydraulic system is in neutral and the pressure is at the desired level, the drive runs at a single speed of 450 rpm, the optimum speed established through the trial.

    When the system is operated and the pressure drops, the transducer switches the drive into PID control. The desired pressure set in the PID is 93 bar, the maximum pressure for the system, and the proportional control is set very high to ensure a rapid response from the drive. Once the pressure increases to 90 bar, the transducer will switch the drive back to single speed mode. This will prevent any overshoot in speed and reduce energy waste.
    The drive's hysterisis control is used to stop rapid switching which could wear out components and pulse the motor excessively.

    Significant energy saving
    Once Chew had established the optimum speed, wired up the transducer and programmed the PID control, the installation was monitored for two days to compare the energy consumption between under drive control with direct-on-line operation. Energy consumption was measured before and after using an energy meter.

    When in neutral, power consumption was around 9 kW with direct-on-line operation. Under drive control, power consumption was reduced to 2 kW, a reduction of 77%. With the system under load, power consumption was reduced from 22 kW to 12 kW, a saving of 48%. As the on-load duty time for the system is 16%, the average energy saving over time was 70%.
    "The reduction in energy consumption under load initially surprised me, as it should take the same amount of energy to move a hydraulic cylinder a given distance regardless of whether a drive or direct-on-line operation is used," says Chew.

    Reduced peak power
    An experiment was set up to test the hydraulics on direct-on-line operation and under drive control with a single actuation on the largest cylinder. To record the readings, the drive's internal recorder was used with the DriveWindow software from ABB. This gave high sample rates over a short period of recording time. The drive was set up to run at a single speed of 1470 rpm to the mimic direct-on-line operation. The recording was then started and the cylinder actuated five times, once every five seconds. The procedure was then repeated with the drive in the dual mode setup with PID and single speed.

    The readings showed a similar performance between the two tests but a vast difference in energy consumption, the drive peaking at 20 kW while the system in direct-on-line mode peaked at 34 kW.

    "The test showed that the drive used a lower motor speed to achieve the required pressure," says Chew. "The flow rate will be lower, but the drive is still fully capable of matching the response times of a direct-on-line configuration."

    The reduced energy consumption will allow a payback time of just 18 months and reduce the company's carbon footprint by 33 tonnes of CO2 annually.

  • 20% discount on new IET Drives and Controls Handbook

    Commissioned by the Institution of Engineering and Technology (IET), the second edition of the Control Techniques Drives and Controls Handbook, edited by Professor Bill Drury, is to be launched on 6 July this year.  The handbook gives an insight into the technology and techniques of AC and DC motor control, from basic theory through to practical solutions.

    This book replaces the edition published in 2001 and according to Professor Drury, "Very little of the last edition has made it into the new one without at least some modification and there has also been a lot of entirely new subject material included."  This comprehensive and practical work runs over 750 pages and retails at £80. Electrical Review readers, however, can get 20% off when buying it through the IET by visiting www.driveshandbook.com.

    The handbook draws upon Control Techniques' engineering expertise in this field but encompasses all aspects of variable speed control applicable to all manufacturers' equipment, including AC/DC industrial motors, servo control, communications and system design.

    Recognising the handbook is used in a significant number of Universities as well as by industrial users, Professor Drury has added new sections covering basic electromagnetic and motor theory.  New developments in areas including power semiconductors, functional safety and control have also been included. 

    A detailed consideration is given to the ambient conditions which influence the specification of a drive and associated equipment through to the characteristic impacts of drives. Guidance on EMC, harmonics, thermal management, cabling and fusing have all been significantly updated, including changes to international regulations.

    The applications section has also been expanded, though given the breadth of this publication, it has been recognised that only core technologies and exemplars of use could be included.

    The structure of the Handbook has been radically redesigned into four parts to make it easier to access:
    -    Part A: drive types and core technology
    -    Part B: the drive in its environment
    -    Part C: practical applications
    -    Part D: appendices

    The index of the book has been revised to make it easier to find.

  • Energy University drives energy management awareness

    Schneider Electric has announced the launch of Energy University, a vendor-neutral, online educational community that provides the fundamentals needed to implement successful energy efficient solutions scaling various applications.

    The courses are designed to provide anyone involved in the decision-making, management, planning, design, or construction of a space impacted by energy, a level of expertise to address efficiency issues and apply safe, reliable and cost effective measures.

    "Schneider Electric believes there is a significant opportunity for sustainable energy savings that is unaddressed by industry and consumers today. Through Energy University, we expect to enable anyone to better understand and act on these opportunities, so they can do more with less," said Paul Hamilton, senior vice president, Energy and Solution University, Schneider Electric. "Energy University will reduce complexity and raise awareness by providing global users easy access to practical education on all aspects of energy management."

    Energy University courses are product-agnostic and focus on the critical concepts and best practices necessary to achieve a high degree of energy management.  Subject matter experts from all areas of the company assist in the development and creation of the courses. As the demand for new technologies and knowledge increases, Energy University will be incorporating additional courses to the programme.

    Currently, 11 foundational courses are offered- topics include:

    • Energy efficiency fundamentals

    • The economics of energy efficiency

    • Going green with leadership in energy and environmental design (LEED)

    • Trusted advisor program overview

    • Alternative power generation technologies

    • Data centre efficiency: Reducing electrical power consumption

    • Lighting basics for energy efficient applications

      Each course can typically be completed in less than one hour and an online platform makes learning convenient and accessible from any internet-ready computer. The self-paced learning experience is enhanced by an accompanying quiz for success measurement and preparation for the certification exam.  The certification verifies that a user has a comprehensive understanding of energy management and is able to independently handle situations related to energy awareness, problem solving and solutions design.

      Energy University is available on-demand via www.myenergyuniversity.com


  • Dedicated drives team for Schneider Electric

    Schneider Electric has announced the creation of a dedicated drives team within its industry business, headed up by the recently appointed national drives sales manager, Tony Pickering (pictured).

    Pickering joined Schneider Electric from Danfoss where he created a robust sales network across the European countries he was responsible for.

    Pickering explained: "The Schneider Electric business has always had a drives team within its organisation but this is currently being further strengthened via a tactical restructuring. The new organisation will support the company's regional sales activities and in addition will be split into industrial and HVAC dedicated teams.

    "We have decided to take this route as we have always had strong products in this arena and we want to make the team more visible in the marketplace, to showcase our world leading drive technologies" he continued.

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