Drives, motors and controls

  • Drives & controls - Energy efficiency – the holy grail

    Motor manufacturers have been challenged in today's low carbon environment to target one of  the holy grails of the motoring community, energy efficiency. Two significant approaches have found their way into mainstream motoring, automated stopping of the engine when idling at traffic lights, and conserving the energy generated in braking to optimise the fuel usage and reduce carbon emissions. In fact the second approach even found its way into Formula 1 as a way to get a performance boost. Jeff Whiting of Mitsubishi Electric looks at how inverter drive technology, in the form of the regenerative drive, answers real issues in industrial environments, and indeed demonstrates a number of other operational benefits

    Until a few years ago, when drivers stopped at traffic lights or a level crossing, they simply left their engines running. But now there are many campaigns to encourage switching off - in California it's already a legal requirement for commercial vehicles. But restarting an engine, even a warm one, requires an extra squirt of fuel, leading to extra CO2 and NOX, so regenerative technologies are being used to capture braking energy that was previously dissipated through hot brake discs and provide a carbon neutral kick start when the lights go green. A number of car manufacturers have automated this approach bringing clear energy reductions.

    Historically in industry, an electric motor was started and left running throughout the shift. There was often a good reason for this as starting motors usually took a huge energy inrush until it got moving and built up its own resistance. This power inrush could be up to 12 times the working current of the motor and therefore motors are usually rated with a number of direct starts allowed per hour. Leaving the motor running seemed quite a realistic approach. However, fitting a motor with an inverter offers a much softer starting regime, and is far less restricted in terms of available starts. This really opens up the opportunity to only run the motor during operational requirements, and to save significant energy by switching the motor on and off.

    A inverter drive offers even more energy ‘bang for its buck' by optimising energy used in the electric motor whatever the load, and also by running the process at lower speeds which can also save significant energy and therefore costs. The best savings can normally be made when running a fan or pump, as a slight reduction in speed can really impact the power consumption. Maybe this isn't a realistic goal of Formula 1, and wouldn't attract much of an audience, but it is well known that a smooth driver uses far less petrol than a boy racer. Uncharacteristically, Jeremy Clarkson and his Top Gear colleagues demonstrated this sometime ago by driving large cars from Paris to Liverpool on a single tank of petrol. By maintaining a steady, moderate speed, avoiding stop/start driving, rapid acceleration and hard braking, fuel consumption was kept in the optimum range and the total mileage proved to be way beyond what is normally achieved.

    The savings gained by using inverters in real terms are both financial, affecting a business' bottom line and ecological in the reduction of CO2 used. In fact it has been calculated that the CO2 savings made by the inverters sold in the UK each year relate to the CO2 used by 100,000 Business cars doing normal mileage.

    An inverter doesn't just save energy or allow a process to be optimised for changing loads and requirements. There are many types of industrial processes driven by motors. Some of these applications bring a number of other challenges which are easily addressed by today's high performance inverter drives. Typical of these is where energy in the process overhauls the power of the motor. To keep the process under control, this energy must be dealt with, and if possible used to power other parts of the production cycle. This was the principle of the Kinetic Energy Recovery System used for a short period of time in Formula 1 racing, but finding a far more appreciative audience in today's high efficiency and hybrid cars. Normally, under braking conditions, the weight of the car generates heat in the brake disks. With the latest technology, KERS uses this condition to capture the energy and release it during the driven part of the journey, thereby reducing fuel consumption.

    Consider an escalator at a deep London Underground station at rush hour. The ‘up' escalator will be working hard to lift maybe a hundred people over a considerable height. The ‘down' escalator will be carrying just as many people - and it will be creating energy as they descend. In power terms, the motor requires power to be fed into it to drive the loaded escalator upwards, whereas when descending, the motor has a load driving it, making the motor act as a generator. Under these conditions the power has to be controlled for the passengers need to descend in a safe manner. This is generally done by using an inverter to ensure safe control and a measured stopping function. Without this, an uncontrolled stop could have huge repercussion with people thrown every which way - mainly downwards into a big heap of limbs and bodies. People could be hurt and the legal repercussions last for years.

    To achieve this continuous control under all load situations, an inverter has to shed this extra energy somewhere. There are many mechanical ways to collect some of this energy - counterweights, winding sprints, etc - but most of them are fairly crude and only partially effective. As this generated energy is in the form of electricity, it is general to dissipate it in that form. In the past, vast banks of braking resistors were used to dissipate the electricity into heat. This could become a considerable fire risk anywhere, but doubly so in a dusty, hot underground machine room. However, a specially designed regenerative drive, such as Mitsubishi's Regenerative A701 drive, controls the load under all conditions and sheds the excess power by converting the kinetic energy into electricity and pumping it safely down the mains or even sharing it with other drives by connecting their power reservoirs together. The energy generated during the lowering stage can be dissipated and lost, or captured and reused. By contrast, a regenerative drive captures all of the energy and feeds it back into supply mains giving welcome savings in electricity bills.

    The basic requirements of a soft start-up and stop can be programmed into a regenerative drive quite easily. Throughout a normal day's operation of the escalator, the drive will still be minimising the energy used. As you can imagine, during rush hour the escalators are fully loaded with people rushing to get to and from work, yet for most of the day there will only be a trickle of people using them.

    A typical energy strategy would be to operate at full loading with optimum transfer speed to get the rush hour passengers through as quickly as possible, and then to slow the escalators slightly for the rest of the day where the speed requirements are not so prevalent. The use of a reduction in transfer speed will bring an immediate energy gain, which will be further enhanced by the inverter's innate capability to shed excess power when there are fewer people on the escalator. The next stage in the developing strategy takes its lead from the stop-start strategies beginning to appear in today's high efficiency vehicles. As previously stated, using an inverter means the motor can start and stop the escalator quickly and safely when required. Maximum savings will occur when there are no passenger requirements and the escalator can be stopped. Implementing controls which sense approaching passengers means the inverters can start the escalators and bring them up to speed before a passenger arrives to step onto it.

    Industrial electrical engineers have long known of the energy saving benefits of inverters, and although they might not be in a position to teach the likes of Button, Hamilton and Schumacher a thing or two about fast driving, regenerative drives show they know a lot about efficient recovery and use of kinetic energy in the real world.

  • Variable speed drives promote a revolution in wind power

    ABB has helped wind power generation experts quietrevolution ltd to develop an innovative wind turbine to capture wind power in areas never before exploited.

    Architects, developers and local councils are showing strong interest in the company's QR5, a vertical axis wind turbine designed to operate in urban areas, where wind speeds are lower and wind directions change frequently. Its helical design ensures it is robust and able to deal with even turbulent winds.

    The wind turbine turns an ABB permanent magnet motor which is linked to an ABB industrial drive acting in regenerative mode to provide the energy conversion and regenerate power back into the grid.



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  • ABB launches drives and motors swappage scheme

    ABB launches its drives and motors swappage scheme, allowing companies to trade in their old products from any manufacturer for new ABB drives and motors.

    The scheme offers at least 17.5% discount off published list prices for new drives from 0.12 kW to 400 kW and new motors from 0.75 kW to 710 kW when old equivalent products from any manufacturer are traded in.

    "The scheme is launched to coincide with the recent introduction of the government's CRC Energy Efficiency Scheme and aims to give organisations an additional incentive to meet their carbon dioxide reduction commitment," says Steve Ruddell, division manager for ABB's discrete automation and motion business.

    In order to get the correct drive or motor to match the needs of individual installations, ABB is offering a free, no obligation energy appraisal. A qualified engineer will come to site and carry out a full energy appraisal, giving an accurate picture of how energy is being used on the premises. The energy appraisal consists of an engineer assessing the installation; identifying areas that will yield the greatest return through upgrade; and determining the potential savings that can be achieved after new equipment is installed.

    ABB partners will also help organisations meet the cost of investment in new equipment by offering help and advice with interest-free loan applications and Enhanced Capital Allowances through the Carbon Trust.

    The scheme addresses a market for replacement drives that continues to grow. In 2010 it is expected 40% of all new drive purchases will be replacing existing drives.

    For more information on ABB's swappage scheme call 07000 DRIVES (374837) or
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  • Drives & Controls - High efficiency motors – the changes made simple

    A new harmonised European standard EN 60034-30:2009 is to replace the old  voluntary Eff classes. The first phase is now a year away so machine designers need to be conversant with the regulations now. The good news is the changes need not cost much more, and for the end user and the environment the results are entirely positive

    The new regulations apply to 3-phase asynchronous motors in a power range 0.75 to 375kW in 2,4 and 6 pole designs, basically the vast majority of motors and used in the construction of machinery. There are certain exceptions, for example 8 pole motors, motors that are an inseparable part of a machine and those with supply voltage over 1000V.

    However, the scope is predicted by the UK Government Department of the Environment to be sufficient to arrest the current increase in energy and used by electric motors. This is no mean feat bearing in mind the massive number of motors in service and the fact they consume nearly 40% of the nation's energy.

    Three new energy efficiency bands are defined:
    IE1    for motors of Standard Efficiency, equivalent toEff2
    IE2    for motors of High Efficiency, equivalent to Eff1
    IE3    for motors of Premium Efficiency, no previous equivalent

    Looking further ahead it is anticipated an ever higher level of efficiency IE4 will be introduced. The actual limits of these three efficiency bands vary according to motor power. As an example in round figures, the minimum efficiency for a 7.5kW motor is 85% at IE1, 88% at IE2 and 92% at IE3.

    There is a phased introduction of the new regulations beginning in 2011:

    16 June 2011 -  motors must meet the IE2 efficiency level as a minimum

    1 January 2015 -  motors from 7.5 to 375 kW must meet the higher IE3  efficiency level, or must be ‘equipped' with an inverter variable speed drive

    1 January 2017 -  the 2015 regulations are extended down to motors of 0.75kW

    The regulations are based around the concept of motors that are ‘placed on the market'. This means motors delivered from motor manufacturers and their subsidiaries, including replacements for existing motors. Old stock at independent distributors or at machine manufacturers can still be sold. Repairing and rewinding old motors is permissible.

    Thus any new machine or old machine requiring a replacement electric motor will require compliance with the new regulations. For the end user this is almost invariably a benefit. Over the lifetime of an electric motor, energy costs amount to about 97% of the total costs of ownership. Therefore a 2-3% gain in efficiency can achieve big savings in the long term. Based on 8000 hours per year, stepping up an efficiency level can give payback times on the extra investment of about 2 years. As a simple guide, if a motor is used for 2000 hours a year or more, an advice is to buy premium efficiency or high efficiency with inverter drive now.

    There are strict requirements for labelling of the motor rating plate. From June 2011 the following information must be shown on the rating plate and the motor documentation: lowest efficiency at 100%, 75% and 50% rated load, the efficiency level (IE2 or IE3) and the year of manufacture.

    As stated above, from 2015 IE2 motors equipped with a frequency inverter can be used instead of IE3 premium efficiency motors. This is an attractive alternative and the IE2 + inverter combination will generally yield greater savings compared to IE3 if variable speed is required. There is no expectation the inverter will be integrated into the motor, although that is possible, and it is expected many customers will purchase motors and inverters from different sources. Documentation requirements are not yet defined, but it would seem likely a degree of self-certification will apply. 

    As the efficiency levels of motors increase, so does the cost as a result of increased material and manufacturing costs. The increase in costs does depend on frame size. Changing from IE1 to IE2 currently brings in a price premium of 20-30%, less on larger frame sizes, but as production volumes increase this is likely to fall to 10 to 20%. The premium to step up to IE3 is likely to be a little less. However, adding more copper to meet higher efficiency levels can also result in changing dimensions. Often the motor length will increase. In a minority of cases the motor frame size may increase, for example from IEC90 to IEC100. In turn this may cause problems on existing machine designs with replacement motors.

    Many people would say the new regulations and efficiency bands are long overdue.  We are playing catch-up with countries like the USA and Australia. With the first phase a year away, we have time to take the necessary steps for the changes. Increases in costs are modest compared with the lifetime costs for motors. The big winners are the end users with lower energy costs and the environment as a whole.

    Lenze is well positioned to offer high efficiency products and packages. Right now, as well as IE2 motors there is a range of IE2 geared motors available up to 45kW. As a manufacturer of frequency inverters, Lenze can offer packages of motor/geared motor and inverter that are IE3 equivalent. Other products, such as the MF motor range, can deliver better than IE2 efficiency and 30%  savings at part loads, also regenerative braking units that can return excess energy to the mains.

  • Versatile tiny drives launched

    Additional EMC filtering options, configurable analogue inputs and enhanced fieldbus  connectivity are among the many new features that have been added to the latest M-MAX variable speed drives from Eaton's Electrical Sector, which are available with ratings up to 7.5kW.

    Featuring compact book-style construction and very competitively priced, M-MAX drives can be configured by the user for either V/f or sensorless vector control. This makes them an ideal and cost-effective choice for energy-saving fan and pump applications, and also for general industrial applications where accurate speed control is needed.

    A large built-in display and operating unit makes it easy to configure the drives and to monitor their performance, while an electronic setpoint potentiometer facilitates accurate speed setting. Support is now also provided for users to set up and store two separate parameter sets, with switching between the two sets controlled by a signal to one of the drive's digital inputs.

    The versatility of these easy-to-use drives is further enhanced by their 1.5x short-term overload capacity, flying-start feature, PID functionality and, on larger units, an integrated brake chopper.
    As standard, M-MAX drives feature a built-in EMC filter that provides compliance with Categories C2 and C3 of IEC/EN 61800-3. Now, however, they can also be supplied in filter-less versions for use with external filters to cater for special applications, such as those where C1 compliance is needed or where earth leakage must be minimised.

    Six digital inputs, which can be set by the user for positive or negative logic, are provided, together with one transistor and two relay digital outputs, two analogue inputs configurable for voltage or current operation, and one analogue output. These extensive I/O facilities mean that, in many applications, the M-MAX drive can provide all of the control logic required, eliminating the need to use a separate programmable controller or intelligent relay.

    To facilitate integration with modern networked control systems, M-MAX drives have an RS485/Modbus interface. Options are now available, however, to extend their connectivity so that they can interface directly with other types of fieldbus system, including CANopen, PROFIBUS DP and DeviceNet.

    The M-MAX range of compact variable speed drives from Eaton's Power Sector includes single-phase 230V models with ratings from 0.18 to 2.2kW, three-phase 230V models with ratings from 0.25 to 2.2 kW and three-phase 480V models with ratings from 0.37 to 7.5kW. All models carry CE, UL, cUL and cTick approvals, allowing them to be used in virtually every country of the world.

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  • ABB to supply drives for major North West water project

    ABB has won a contract to supply two medium voltage drives to a water project that will form a vital part of the water supply system for the North West of England.

    The drives will control pumping for the £125m West East Link Main, being built by J Murphy and Sons for United Utilities between Merseyside and Greater Manchester. The 55km 1.2 metre diameter pipeline will connect the two areas, allowing United Utilities to move water around the region and balance supplies from the Lake District and North Wales.

    The pipeline is bidirectional. From east to west, the water will flow downhill, but from west to east it needs to be pumped along the pipe. To meet this need, ABB will supply two ACS1000i medium voltage drives and two AMA500L6A AC machines, both rated at 1790 kW. They will be installed at United Utilities' Prescot Works.

    Paul Foden, projects manager for Nomenca, mechanical and electrical sub-contractor for the project, says: "We chose ABB because it could supply the best package. The integral transformer in the drives allows us to step-down the site voltage to the drive minimising space requirements. The drives are also 24-pulse, ensuring they produce minimum harmonic interference to neighbouring properties, which was very important to United Utilities. Additionally due to the technology it was not necessary to de-rate the motor output".

    When completed, the West East Link Main will allow United Utilities to take other major pipelines out of service temporarily for cleaning, without any disruption to supply.

  • Demand drives manufacturing to full capacity

    Responding to a growing demand for Kevlar brand products, DuPont Protection Technologies has restored all Kevlar manufacturing facilities to operate at full capacity.

    In addition, construction of a new Kevlar plant at DuPont's Cooper River site in South Carolina continues to move forward and will enable the company to produce higher performing, next-generation fibres.

    "We are seeing greater demand for current and more advanced products across markets including automotive, aerospace, personal protection and many industrial applications," said Dale Outhous, DuPont Protection Technologies. "As a result, all Kevlar manufacturing facilities are again producing at full capacity, and construction of the new plant at Cooper River is progressing rapidly."


    The new Kevlar facility, an investment exceeding $500 million, is expected to be fully operational by the beginning of 2012. It will incorporate the latest fibre production technology and enable the business to deliver higher performing products industrial applications and ballistic protection.

    Demand has driven other investment as well. This includes increased research and development spending for additional technical personnel; state-of-the-art testing, modelling and simulation equipment and new laboratories in Brazil and India.

    "While these investments are crucial to speed innovation and provide additional services for customers and development partners, the business also must retain its financial health for continued growth," Outhous said. This week DuPont Protection Technologies communicated to its customers that effective 1 Oct, or as contracts permit, the business will increase pricing for DuPont Kevlar products by an average 5% globally.

  • Drives & controls - Energy savings - the torque of the town

    With plastics extruders and injection moulding companies looking to reduce energy usage, minimise maintenance costs and boost productivity, the role of the direct drive torque motor is coming to the fore. Andy Parker-Bates, of Parker SSD Drives Division, explains how the technology differs from conventional motors, and explores the benefits it can bring

    They’re known by many names – torque motors, direct drive motors, frameless motors – and often they are thought of as a new technology that needs to be more proven before it becomes a mainstay of industrial automation. So just what are torque motors?

    First off, it’s worth making the point this is not an unproven technology. It is a new take on existing brushless servomotor technology that has been around for decades, and is amongst the most reliable technologies available. In short, a torque motor is a rotary brushless servomotor optimised for low speed operation, typically in the order of 50-500rpm. It is a direct drive solution, so there is no need for mechanical transmission elements such as gearboxes.

    There are two different kinds of torque motors. There is the more traditional looking motor with frame, cooling system, terminal box and feedback sensor, and then there is a frameless motor made up of two independent elements (rotor and stator) intended to be tightly integrated into the mechanics of the application.

    Typical applications for the frameless version include semiconductor manufacture and machine tools, while the framed version meets the needs of applications such as paper machines, crushers, extruders and injection moulding machines. It’s certainly not a panacea for all applications, and indeed below about 30kW it’s questionable whether there are any gains to be had over a conventional motor/gearbox combination at all. But above this, in specific applications such as plastics extruders and injection moulding machines, at a time when end users are looking to reduce operating costs, through better energy utilisation and lower maintenance requirements, torque motors can offer significant advantages.

    For starters, a direct drive solution is inherently more energy efficient than a motor/gearbox combination. Modern motors can of course offer high efficiencies and gearbox design has also developed significantly leading to more efficient products. But gearbox efficiency is dependent on the load, the reduction ratio, and the number of stages. Optimum gearbox efficiency is obtained at maximum load, but efficiency decreases dramatically at light loads – down to as little as 20% in worst-case situations. And even in its most efficient load ratings a gearbox will still lose around 2% efficiency per gearing stage.

    Further, the motor and gearbox need to be closely matched in order to maximise energy efficiency, and even a good motor/gearbox combination may be only 80% efficient. Additionally, traditional motor/gearbox solutions will also often require belts and pulleys as part of the drive train, further reducing efficiency.

    Torque motors, by contrast, improve in efficiency at lighter loads. Thus the direct drive torque motor can easily be between 5% and 12% more efficient than a motor/gearbox combination. If we assume a typical 7% improvement, with an energy cost of €0.10 per kWh, then in 7200 hours operation per year on a 100kW extruder, €5040 will be saved in energy costs alone by switching to torque motors.

    Replacing a hydraulic motor to drive the screw on an injection moulding machine, the torque motor could easily offer energy savings in excess of 20%, and deliver higher productivity and clean operation, without the need for fluid changes or the risk of fluid leakage.

    We can look at maintenance costs, too. In a typical 110kW DC motor with a gearbox, maintenance can represent a cost of more than €3000 per year. How do we come to that figure? A typical year’s maintenance on a 110kW extruder, maintenance on the DC motor could account for €300 in motor revision, €150 in carbon control/change and €150 in filter maintenance. Gearbox maintenance could contribute €50 in oil draining and €250 in seals replacement, with the potential of €2500 or more in gearbox repairs. And that’s before we’ve considered the cost of downtime in terms of lost productivity.

    Use of a torque motor slashes these costs, firstly because it is an inherently low maintenance technology and also because there are no additional drive train components to wear.

    Also, without the need for all of these ancillary components, torque motor systems are much quicker and easier to install: having to install and align multiple motors, gearboxes, belts and pulleys on something like a plastics extruder is a process that can take days. By contrast, installing the corresponding number of torque motors can be achieved in just a few hours.
    A typical plastics extrusion machine could be using multiple motors, so the savings from not having additional power transmission components quickly add up to something very significant. In a co-extrusion machine, for example, there could be up to nine motors installed in a single machine.

    Torque motors also help to address specific machine requirements on co-extruders in the way that conventional motors are unable to match. For example, the screw extraction mechanism may be required from the front of the motor in some instances, but from the back of the mechanism in others. This is readily achievable with some torque motors. At the same time, torque motors with hollow motor shafts can provide extruder screw cooling through the motor, – especially important for big screws.

    Torque motors are a low noise, low vibration option. The European Noise Directive 2003/10/CE sets the maximum recommended noise level exposure limits for operators in order to protect against health and safety risks, and sets a maximum noise exposure limit of 87dBA. Above 80dBA, special protective measures must be taken. In a conventional motor/gearbox set-up, just the gearbox alone can often be producing above 90dBA. The torque motor, in contrast, is an inherently quiet technology, producing below 80dBA in most cases, and therefore can play a key role in minimising overall equipment noise levels. Similarly, it is a very low vibration technology. This again contributes to reduced noise levels, but it also has reduced physical impact on the rest of the machinery – ensuring greater reliability – as well as helping to ensure a more uniform product quality.

    We also have to look at the costs of downtime in the event of a power transmission failure. Plastics extruders represent some of the most demanding motor applications. Once production has started, the one thing you don’t want to be doing is halting production. The extruder is typically located at the beginning of the production line, so stopping it will call a halt to all production. Because it has to be heated, there are long ramp up times before production can begin. And when there are defects in the output, products cannot simply be recycled and disposal costs are high.

    Reliability is therefore paramount. With fewer components in the power train, the direct drive solution is inherently more reliable than a typical motor/gearbox combination, and certainly much easier to replace in the event of a fault, allowing production to be restarted much more quickly.

    From the machine builder’s point of view, the torque motor solution is generally much more compact than the motor/gearbox combination. The motor can also offer built-in advantages for specialist extruder manufacturers. An integrated thrust bearing can be added to support back pressure from the screw. This is a nice added feature on injection moulding machines, but is a mandatory feature on plastics extruders. Also, a screw extraction mechanism can be readily built in, making it easy to remove the screw from the extruder for routine maintenance or to allow a new production batch to be set up. And, as discussed, the screw can be cooled by water through the motor, which can be an extremely useful feature on large extruders.

    Typical torque motors cover torque ranges from 1200Nm to 22,100Nm, and speeds from 50 to 500rpm depending on size. Water cooling is standard on many designs, but natural ventilation is possible with suitable derating.

    With all these advantages, torque motors are steadily making inroads into the plastics extrusion and injection moulding markets. The upfront cost may be slightly higher, but the energy savings, elimination of ancillary components, reduced maintenance costs and improved productivity – not to mention the reduced noise levels – quickly allow users to recoup the premium on the purchase cost. In addition, the more compact design can lead to smaller machines, which frees up valuable floor space, potentially driving opportunities for even higher productivity.

  • Drives save £20,000 HVAC energy costs

    Operators of an office building in Reigate, Surrey, are saving £20,000 a year on energy costs for the building's HVAC system following the installation of ABB standard drives for HVAC.

    The Omnibus building was completed in 2001. Based on a disused bus garage in the centre of the town, the building is a multi-tenant facility offering over 65,000 sq ft of office space.

    Building manager Martin Dalgarno of NB Entrust said: "We were approached by Econowise Drives and Controls with a proposal to investigate our HVAC system and look at the scope for using variable speed drives (VSDs) to cut its running costs. We were keen to make energy savings and were attracted to Econowise as they could offer local manufacturer backed support."

    Econowise Drives and Controls, based in Redhill, specialises in supplying and installing VSDs for HVAC applications, as well as motors and other equipment for buildings in London and the Home Counties. After getting the go ahead from NB Entrust, Econowise conducted an energy appraisal of the existing system. Dave Lapsley, owner and director of Econowise, says: "The energy appraisal revealed that the motors driving the system pumps were all running at full speed, with flow control achieved by mechanical throttling. We calculated that putting VSDs on the application could save around £20,000 per annum in energy costs."

    Econowise installed twelve ABB standard drives for HVAC, six on the chiller pumps rated at 15 kW, four on the LPHW secondary heating pumps rated at 15 kW and two on the LPHW Primary pumps rated at 7.5 kW. Econowise opened all the valves and set the drives to maximum speed, reducing the speed until the water flow rate met the exact requirements of the building as detailed in the original commissioning information provided by Dalgarno.

    The building also had two existing VSDs operating an air handling unit but these were not running in a speed control mode. Econowise reprogrammed the PID controller on the exhaust fan drive to accept signals from a CO2 detector and drive it at an appropriate speed to remove the CO2. The two drives were connected so that the supply fan was driven at a speed to match the speed of the exhaust fan, hence maintaining design pressures at all times.

    Lapsley added: "Martin Dalgarno was very open to what we had to offer to help improve the efficiency of the building services, all too often people in Dalgarno's position are very sceptical of what can be achieved with the correct implementation of this technology, as a consequence of his foresight he and most importantly his clients have reaped the rewards of these very significant savings."

    Martin Dalgarno added: "The predicted savings of £20,000 a year have proven correct. With an investment of around £14,000, this gave us a payback of under nine months. We have also gained other benefits such as reduced wear and tear on the motors and have had no problems with maintenance since the drives were installed in September 2009."

  • Drives far greener than many think

    These past few years have seen inverters promoted, quite rightly, as one of the very best energy saving technologies, playing a key role in combating global warming. But Mitsubishi Electric's Jeff Whiting says controlling the power consumption of motors is only the first of their many environmental credentials

    We've heard the figures many times: motors account for 65% of all industrial power consumption, and yet only 25% of motors are fitted with variable speed drives. But use a variable speed drive to control a motor with an appropriate speed profile for the task in hand, and you can slash that motor's energy usage. Last year the government woke up to the fact that use of variable speed drives represents one of the best ways to reduce the UK's carbon footprint, bettered only by a wholesale switch to LED lighting and thermal insulation in commercial buildings.

    But, as the world economy recovers from its battering of the last couple of years, a more sophisticated definition of green manufacturing is emerging. And this time it makes even better business sense, because while measures such as the Climate Change Levy and the CRC Energy Efficiency Scheme effectively penalise companies financially for not reducing their energy consumption, in our more sophisticated picture of green manufacturing, best practice environmental measures can actually boost productivity. As ever, it is variable speed drives that can really make the difference.

    Consider, for example, the stopping of large machines, or indeed any shaft driving a load that needs to be brought to a controlled stop. Traditionally, this would be achieved with some sort of mechanical brake. But these work by clamping the shaft and using friction to bring it to a stop - an inherent by-product of which is of course heat, or wasted energy. But a key feature of many modern variable speed drives is regenerative braking, which converts braking energy back into electrical energy. This energy can then be fed back into the main supply or shared with other drives by connecting their power reserves together.

    Not only does this save energy in its own right, but the regeneration function also makes it possible to achieve smaller, less expensive drive systems and simpler, more compact switchgear layouts.

    It seems obvious, but better control of a motor on any machine or process, optimising speed and torque, means better controllability. When you apply that tighter control to the whole production line, what you immediately see is significantly increased useful output, with far fewer reject products, and a dramatically reduced need for any product rework. How many products, for example, are thrown away at the start of the production cycle as the machinery is tuned and optimised? How many more are rejected as processes drift out of tolerance? Variable speed drives can help in optimising machinery and processes from the minute they are turned on, and in keeping them at optimum efficiency throughout the production cycle.

    A reduction in reject parts and in the need for rework can significantly impact on a company's bottom line. If a process is making greater numbers of useful products for a higher proportion of time, that makes you more competitive and better able to meet customer requirements. But it also means that you're using less energy per finished product.

    We can apply the same thinking to the wider production cycle, which more and more today is characterised by frequent line changeovers that cater for short runs of many different products. The requirements of the customer and the need to optimise production efficiency can appear to be in conflict, since maximum efficiency is gained on the longest possible production run of a single product. But today's competitive global markets demand flexibility if a company is to thrive, or even to survive.

    In machinery and processes without inherent flexibility, there are significant costs in product changeovers, in terms of manpower and lost production. But once we have tighter control of those processes, changeovers from one product run to another become recipe based, with complete lines reset at the touch of a button. What would have required time-consuming retuning of motor speeds and profiles can now benefit from automatic adjustment. The recipes for each product to be made on the line will store all the relevant parameters and settings, and these can automatically reset the likes of variable speed drives as required.

    This optimisation of the production cycle can mean the difference between having to manufacture for stock and being able to manufacture to order - or at the very least to a more optimised inventory schedule. Because when we're simply manufacturing for stock, inevitably there will be over-production of some items which will then just sit on shelves losing value. Each of those products in the warehouse represents some degree of wasted energy in manufacturing.

    We can look at the wider plant environment, too, because every motor - regardless of its efficiency rating – generates heat. Outside of specific hazardous areas, it is unlikely that the heat produced represents much of a problem to the machine itself or to personnel. But when you consider the number of motors there are likely to be around a typical industrial site, then you can see that these motors will be contributing to a measurable temperature rise.

    In some controlled environments, that can be critical. In temperature sensitive environments such as cosmetics production, overall temperature has to be closely controlled within specific tolerances. If one process is generating excess heat, then another process has to be introduced to bring the temperature down - most likely some form of force air recirculation or air conditioning. And this, of course, is using energy.

    Much more efficient would be to reduce the heat signature of the motors themselves - or even capturing that energy - and here again variable speed drives come into their own. The variable speed drive more closely matches the motor to the load, and so the motor generates less heat. Not only is the motor being run more efficiently, less work has to be done to compensate for the heat generated.

    We can see then that variable speed drives have a hugely significant role to play in making industrial plants and processes more efficient. It may be the energy saving impact of not running a motor at fixed speed that grabs most of the headlines, but when we consider a more sophisticated picture of green manufacturing, it becomes clear that variable speed drives are making an even greater contribution to energy efficiency than might first be considered.

  • New high-power drives

    In the first of several planned extensions, Rockwell Automation has expanded the power range of its Allen-Bradley PowerFlex 755 AC drives to 450 kW/700 Hp, providing users with increased application flexibility. Featuring advanced diagnostics and a convenient roll-out design, the PowerFlex 755 AC drive is well-suited for motor control applications in a variety of heavy industries, including oil and gas, tire and rubber, refining, material handling, metals and mining.
    “Customer feedback about the desired attributes of a high-power drive gave us the information we needed to design our extended power range of PowerFlex 755 drives,” said Steve Perreault, drives product manager, Rockwell Automation. “They told us they needed excellent reliability, ease of maintenance, and common control options to help reduce inventory and spare parts. This drive delivers on all accounts, providing users with increased installation and application flexibility, along with the advanced diagnostics needed to minimise downtime and protect critical investments.”
    A key feature of the PowerFlex 755 extended power range drive is its roll-out capability, which allows easy access to the drive for fast installation and maintenance. The drive’s modular design helps simplify replacement of drive components, such as cooling fans, circuit boards and major subassemblies.
    This modularity also allows the drive’s converter and control pod to remain in the unit while the inverter is rolled out, so control wiring can remain connected. An additional advantage is the ability for the control pod in this drive to be mounted remotely for hassle-free access to low voltage control and diagnostics. 
    Advanced diagnostic capabilities include indication of blown fuses and blown surge protectors. Not only are these alarms reported to the main control to help ease troubleshooting, but they also provide essential protection inside the drive, helping to protect the customer’s investment. Monitoring and tracking of operating data on cooling fans, I/O relay cycles and motor run times also provides valuable data for preventative maintenance, helping to reduce unplanned downtime. 
    The PowerFlex 755 drive comes equipped with an embedded Ethernet port and five option slots that allow users to tailor the drive to best suit their application. Options include I/O, feedback, safety, additional communications, and auxiliary control power input.
    The PowerFlex 755 now supports Rockwell Automation Integrated Motion, allowing it to be configured and controlled using motion profiles and instruction sets in an Allen-Bradley ControlLogix controller with Rockwell Software RSLogix 5000 software. The ability to support variable frequency drives, motion drives, I/O, smart actuators and other EtherNet/IP-connected devices on a common network helps increase design flexibility, improve system performance and reduce engineering costs. 
    This power range extension expands the PowerFlex 755 AC drive offering from 0.75 kW (1 Hp) up to 450kW and 700Hp at 400/480 VAC input, providing robustness, ease of use, flexibility and performance in a single product family.

    Rockwell Automation

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