Devices for generating three-phase PWM waveforms for control of induction motors.

摘要

Programmed digital equipment is utilized in a device (10) to generate three-phase pulse width modulated (PWM) waveforms that are used in controlling an induction motor. A microprocessor (12) is programmed to initialize conditions in the system (10), to perform a main task including the storage of a converted analog signal, the checking of limits of motor motion and information fed back from the motor concerning its position, and the ramping of frequencies to change the position of the motor. A memory is provided for the programming, which memory also contains tables that correspond to 90 DEG of each desired waveform. A simple 90 DEG segment of each waveform is needed to generate all parts of each of the three phases. An analog to digital converter (44) is utilized to convert analog information concerning gain, set point, deadband and feedback signal into digital signals which are stored and processed by the microprocessor (12). Programmable timers (16, 18) are connected to the microrocessor (12) for generating the waveforms and for supplying master timing and interrupt signals indicative of an undesirable condition in the motor control.