A New Microcomputer Controlled Modulator for PWM Inverters

The design of a new microcomputer controlled modulator for a pulsewidth modulated (PWM) inverter supplying a three-phase induction machine is presented. The requirements for the control of variable speed drives in general are discussed. The specifications for the PWM modulator are set out and explained. Analog and digital techniques are used in the design. All the control parameters of the modulator are under microcomputer control, and a few different PWM switching strategies may be implemented. The system is thus very flexible. The modulator has a very high frequency resolution. Some experimental results are also included.