Optimisation of losses in PWM inverters

PWM inverters are now widely used for a range of applications which include AC motor drives and uninterruptible power supplies. Design techniques for them are quite well established and they are relatively reliable and efficient pieces of equipment. The authors deal with the losses that are produced in an inverter. There are two main sources of loss, namely on-state losses and switching losses, and the latter can be further divided into device losses and snubber resistor losses. It is not a simple matter to write down expressions for these losses, even for ideal conditions. The on-state losses in the transistors and diodes of an inverter are given, together with mathematical results for switching losses. An example of the breakdown of losses in a 25 kVA inverter is given, together with some discussion of methods by which the losses could be minimised