Closed loop, microcomputer controlled pulse width modulated inverter-induction machine drive system

A microcomputer-controlled pulse width modulated inverter-induction machine drive system comprising:

• (a) a potential source;
• (b) an n phase induction machine where n is an integer greater than zero;
• (c) an inverter configured of n pairs of solid state switch devices, the switching devices of each of said pairs coupled in series-aiding fashion across said potential source and adapted for coupling at the junction between solid state switching devices to a respective one of said n induction machine phases, each of said solid state switching devices of each of said n pairs being alternately rendered conductive in sequence for intervals of varying duration to supply said n-phase induction machine with an alternating current potential;
• and
• (d) control means having
• (1) sensor circuit means coupled to said inverter for generating, from inverter output current and output voltage, an n-phase output signal which varies in accordance with actual flux magnitude;
• and
• (2) processor means coupled to said sensor circuit and said inverter, said processor means comprised of a first and second microcomputer, said first microcomputer generating an n-phase reference signal representative of the desired induction machine flux magnitude and varying in amplitude and frequency in accordance with the magnitude of an externally-varied amplitude value and frequency value, respectively, and generating a periodic interrupt signal, said second microcomputer coupled to said first microcomputer and generating, in response to said first microcomputer periodic interrupt signal, an n-phase control which is supplied to said inverter to vary the conduction intervals of each of said n pairs of inverter solid state switches, said second microcomputer n-phase control signal varying in accordance with a prescribed relationship between the deviation in magnitude of said sensor circuit output signal from said first microcomputer reference signal and the deviation in magnitude of said sensor circuit output signal from a preset value.