DESIGN SIMULATION & IMPLEMENTATION OF FOUR QUADRANT OPERATION OF DC DRIVE

Abstract

Use of microcontroller based system has given flexibility for implementation of closed loop operation, to get variable speed of DC motor irrespective of supply fluctuation and load variation by incrementing or decrementing firing angle for dual convertor. In dual converters with non circulating current, only one converter operates at a time and another converter is temporarily blocked from conducting by withdrawing firing pulses to the Thyristors. Since only one converter operates at a time no reactors are required between the converters. The paper includes details on design of zero crossing detectors to detect zero crossing instant of A.C. input to converters to determine firing angle, control circuit is designed to read some input parameters like 8-bit digitized set speed and actual speed from taco generator, use of two double pole switch to read direction and acceleration. Current limiting circuit using Hall effect IC to detect threshold voltage level corresponding to desire current limit to provide over load protection. Software development in assembly language for 89s51 microcontroller to provide real time control.