Development of Closed Loop Control Schemes for Constant Speed Operation of a Thyristorized Commutatorless Series Motor Drive

This paper presents the development of closed loop control schemes for constant speed mode operation of a thyristorized commutatorless series motor (CLSM) drive. Constant speed mode of operation of electrical drives with closed loop control is commonly required to be realized in most practical industrial drive applications. Two control schemes, one using only a speed loop and the other using an outer speed loop and an inner current loop, as are generally done with standard drives, are separately studied for this unconventional machine. The strategies are tested for different controller settings after simulating the entire speed-controlled drive, utilizing the analytical model. The simulation results are presented. An analytical guideline has been proposed to provide a starting point for designing stable speed and current controllers. The discussed schemes are finally implemented in the laboratory on a small prototype and experimental results are presented.