Electrical equipment manufactured for the EU is designed to operate with an incoming supply of between 207V and 253V, which means electrical equipment has to accept a range of input voltages about its nominal design centre. But if the actual supply is higher than the necessary minimum the equipment will often consume excess power. For example, a resistive load subjected to a 5% overvoltage will consume 10.25% more power than necessary. This excess consumption reduces equipment lifespan and increases ownership costs.
Voltage optimisation technology helps mitigate this issue. Acting as a middleman between the national grid and equipment, it adjusts the output voltage so that equipment only receives the power necessary to operate, delivering energy savings of up to 25%.
Which loads show the greatest savings?
Voltage optimisation affects electrical equipment in a variety of ways, as different loads respond differently to reduced voltages.
- In terms of commercial lighting, fluorescent luminaires with magnetic ballasts offer the greatest savings. Voltage optimisation is generally a better option than replacing magnetic ballasts or luminaires with more efficient types.
- Other forms of lighting such as low pressure sodium, high pressure sodium and high bay installations all offer opportunities for energy savings with voltage optimisation, and will also see extended lifetimes.
- Variable speed drives show no energy savings with voltage optimisation since they are constant power devices. They will operate well within the operating voltage range, but the current drawn will increase proportionally as the voltage is reduced.
- Heating pumps, ventilation and air conditioning systems all offer opportunities for energy savings when they are driven by non-optimised induction motors.
As the nature of a site’s connected load determines what energy savings can be achieved, a comprehensive analysis of the power conditions is necessary to assess whether voltage optimisation is a viable option. A standard site survey includes an equipment assessment, a power supply analysis and three phase electrical logging to identify energy saving potential.
Equipment Selection – Reduction vs. Regulation
The correct technology then maximises this energy saving potential. There is more than one type of equipment that bills itself as ‘voltage optimisation’ technology, but in most cases this is a misnomer.
Fixed-tap energy saving transformers
Most products on the market are simply voltage reduction devices, although they are often called ‘voltage optimisers’, ‘energy saving transformers’, or ‘voltage reducing transformers’. These devices are essentially fixed-ratio or fixed-tap transformers that reduce the supply voltage by a fixed percentage. They can achieve useful levels of savings if the site’s voltage is stable and the phases are always balanced, but for the vast majority of sites this is not the case, and equipment often ends up receiving higher voltage than necessary, which results in excessive power consumption.
These devices feature a series of taps that each adjust the voltage to a different output level. Once the incoming supply is detected to be at a specific threshold, the device changes to a different tap that more closely reflects the power conditions at that point in time.
This technology provides an added degree of flexibility over fixed-tap transformers for sites that experience supply fluctuations but still presents risks if there are frequent variations in supply quality or if phases are unbalanced. Because there is a sudden step change in output voltage when the taps are changed, there can be a corresponding change in equipment performance. The effects of this include flickering lights or a momentary loss of synchronisation on computer or video screens.
Energy saving regulators and stabilisers
Most sites require true, dynamic voltage optimisation to maximise energy savings. This technology has a ‘regulator’ or ‘stabiliser’ function that continuously and automatically adjusts the amount by which the voltage is reduced rather than relying on changing taps. Regulator technology facilitates a controlled environment similar to that achieved with air conditioning or a compressed air system, ensuring that electrical equipment never receives more or less than the required minimum voltage for correct operation. It also constantly balances the three output voltages, providing better operation of three phase loads. With this technology, savings are greater than with a simple fixed-ratio or tap-changing transformer, and electrical equipment lifetimes are maximised, giving a truly controlled and optimised supply.