Use of microprocessors in invertors

Microprocessors were first used in inverters to create novel methods of waveform generation in pulsewidth modulated voltage source invertors. It was recognised that the microprocessor could offer the user significant advantages in terms of parameter repeatability and protection, and advanced diagnostics. The PWM inverter has the advantage of lower unit cost, better efficiency, powerfactor and low speed performance. It is also less sensitive to interruptions on the mains supply. On the other hand, the current fed invertor is naturally current limited, has natural regeneration and has active output voltage control, i.e. the output voltage is controlled independently of input voltage. It would be an advantage to have all these features in one unit, but to do this on a PWM invertor requires intelligence in both the control and waveform generation. The author describes such a unit consisting of a waveform generator and a control processor