SPEED CONTROL OF SEPERATELY EXCITED DC MOTOR USING THYRISTOR CHOPPERS

Abstract

This dissertation describes the analysis and the experimental studies of a seperately excited do motor fed by a thyrietor chopper as a variable speed drive motor. A critical review of the various convent io'-nal. schemes of adjustable speed drives is given in the introduction. The reasons for the accelerated trend in the use of thyrietor control for variable speed drives in general and thyrietor choppers. in particular. are mentioned. Chapter 1 consists of a study of chopper action, triggering and commutation circuits. The working of the two circuits are described in detail. The steady state operation of a chopper is analysed in chapter 2. Further, the general expressions for the current torque and speed of the motor are derived. The starting and braking methods of the motor with chopper circuits are described in chapter 3, The commutation and loss problems in a motor operated on rectified power supply are also given. The methods of improving the motor performance are suggested.