Evaluation of Control Schemes for Thyristor-Controlled DC Motors

Phase-angle control (PAC) is commonly used in the solid-state control of dc motor drives. This paper investigates other control schemes, such as symmetrical-angle control (SAC), extinction-angle control (EAC), current-limit control (CLC), and time-ratio control (TRC). The drive system with the control schemes is simulated on a digital computer and an efficient time-saving method is used for computation. The performance characteristics, such as torque speed, input power factor, fundamental power factor, harmonic content, and peak motor current are obtained and compared for the different control schemes. Each control scheme has certain advantages over the others. The control schemes are implemented on an experimental setup to demonstrate the basic principles of operation.