Three phase variable frequency constant torque controllers for high torque servo positioners

摘要

A controller (10) for a three phase induction motor (14) used as a servo positioner (12) comprises a position control module (32) including a microprocessor with memory for generating a plurality of pulse width modulated waveforms. The module (32) includes an analog to digital converter for converting one of four analog signals into digital signals readable by the microprocessor. The analog signals correspond to a gain signal, a feedback signal, a set point signal and a dead band signal. The module (32) also receives digital signals for programming purposes. The microprocessor is programmed to initialize conditions and convert the analog signals. The controller (10) includes drivers (34, 36, 38) connected to the module (32) for receiving the waveforms and generating corresponding AC inputs to the motor (14). An overcurrent detector (66) is provided for sensing overcur- rents in the AC signals and for generating an interrupt signal which is applied to the module (32) for interrupting the function thereof. The module (32), according to its programming, can be placed in one of three modes for interface with a broad spectrum of automatic control systems. The modes include automatic-analog, automatic-pulse, and closed- contact controls.