A Simple Transistorized Controlled Four-quadrant Chopper DC Drive

摘要

A transistorized controlled four-quadrant chopper DC drive system has been implemented in laboratory. A simple circuit using the dedicated integrated circuit TCA 780 (Icotron-Siemens) has been developed for IGBT firing angle control. A DC control voltage, Vcc, (0→10 [V]), connected to pin 11 of each of the TCA's 780 makes possible to modify the cycle-ratio (α), so that when á varies in the range from 0 to 0.5 pu, corresponding to Vcc varying between 0 and 5 [V], gives speed in one direction. However if á is between 0.5 to 1 pu, corresponding to Vcc between 5 and 10 [V], the speed will be in the other direction. The firing circuit consists of three stages. The first one is the pulse generator, made from the dedicated integrated circuit TCA 780. The second one is a delay circuit for transistors in the same leg. The last one is the optocoupler isolation and transistor amplification pulses for the IGBT's. There are two PI regulators, one for speed and another for current, connected in cascade. The DC control voltage, Vcc, (pin 11), is the current regulator output. The inner proportional-integral (PI) regulator makes possible to limit the motor current, and both PI speed and current regulators act when a load disturbance torque occurs. Presently, digital PI regulators are being implemented to compare the results of the dynamic behavior of controlled system.