METAL OXIDE DEVICES IN MICROPROCESSOR INVERTERS

Imad  A. KASSAS

An investigation into the use of metal oxide devices in time-shared microprocessor controller inverters for improved power delivery, origins of losses and improvements to means of assessment.

An extensive investigation into the use of the power  MOSFET as a switch is  undertaken.  Incidental  dissipation and  switching  transients  caused  by  different  types  of load are simulated.

A special technique for measuring incidental dissipation in power devices during switching is then developed. Results of tests made on the system for different conditions and devices are given and discussed.

The design and implementation of a microprocessor controlled, variable voltage variable frequency three‑phase, PWM inverter, using power MOSFETs  as switches is presented.

The MC68020 microprocessor is used to calculate the pulse widths, which are, generated in real time by a programmable timer module the MC68B40. Drive circuit for power MOSFET devices and protection are examined. Shoot‑Through is avoided by the use of an appropriate circuit. The performances of  the  inverter  when  supplying a  resistance  load,  inductive  load and  induction  motor are  analyzed . Harmonic content  and  distortion   factor are investigated.

The effect of the injection of certain amount of third harmonic into the PWM waveform is inspected. It is shown practically and by simulation that the fundamental component can be increased by introducing an appropriate amount of third harmonic.

The microprocessor performance is evaluated. The time‑sharing of a single processor by different. Tasks are demonstrated practically. The harmonic spectra under such condition are considered.