Time ratio control (TRC) scheme for a DC series motor Part I: Performance

This paper is concerned with the detailed study of time-ratio-control (TRC) scheme for a solid state dc series motor drive. The performance characteristics such as torque-speed, supply power factor, supply harmonic content, peak armature current variations are obtained and compared with those obtainable with the commonly used phase angle control (PAC) scheme under identical operating conditions. The comparative study has revealed that certain performances are improved in the TRC scheme. The drive systems with PAC and TRC schemes are simulated on a digital computer and an efficient time-saving method is employed for computation. Oscillograms obtained from the experimental setup using a 3 HP dc series motor are presented to demonstrate the feasibility of the schemes and to verify the basic principles of operation.