reduction in voltage will result in an increase in current and therefore constant power. Whilst this is true for certain fixed-power loads, most sites have a diversity of loads that will benefit to a greater or lesser extent with energy savings aggregating across a site as a whole. The benefit to typical equipment at three phase sites is discussed below. Three phase motors Three phase induction motors are probably the most common type of three phase load and are used in a variety of equipment including refrigeration, pumps, air conditioning, conveyor drives as well as their more obvious applications. The de-rating effects of overvoltage and three phase imbalance on AC motors are well known. Excessive overvoltage results in saturation of the iron core, wasting energy through eddy currents and increased hysteresis losses. Drawing excessive current results in excess heat output due to copper losses. The additional stress of overvoltage on motors will decrease motor lifetime. Avoiding overvoltage high enough to cause saturation does not reduce efficiency so substantial energy savings can be made through reducing iron and copper losses. However, motors designed for the nominal voltage (e.g. 400 V) should be able to cope with normal variation in voltage within the supply limits(+/-10%) without saturation, so this is unlikely to be a significant problem. Reducing voltage to an induction motor will slightly affect the motor speed as slip will increase, but speed is mainly a function of the supply frequency and the number of poles. Motor efficiency is optimum at reasonable load (typically 75%) and at the designed voltage, and will fall off slightly with small variations either side of this voltage. Larger variations affect efficiency more. Very lightly loaded motors (<25%) and small motors benefit most from reducing voltage. For the case of motors driven by Variable Speed Drives, when the input voltage is reduced, there will be a proportionate reduction of the output voltage from the VSD and the motor will draw less current and eventually consume less power. However, if the motor is running on high load (>80%), the reduction in voltage will result in reduced torque and motor will end up drawing more current and power. Lighting When lighting loads are in use for a high proportion of the time, energy savings on lighting equipment are extremely valuable. When voltage is reduced, incandescent lighting will see a large decrease in power drawn, a large decrease in