The influence of capacitor voltage fluctuation on energy efficient C-dump converter

Abstract

Positive torque of a Switched Reluctance Motor (SRM) can be developed by energizing the stator winding during the positive slope of the phase inductance. Due to the inductive nature of the circuit, demagnetizing process can not make the phase current turn off instantly so negative torque is also generated. To minimize the negative torque, negative voltage can be applied during demagnetizing process of the phase winding to reduce the current faster. A capacitor is commonly used to realize it in C-dump converter topologies. A C-dump converter without inductor utilizes a capacitor voltage to turn off the active phase winding and then returns the stored energy into the next phase winding, therefore it is more efficient. This paper describes the influence of the capacitor voltage of a C-dump converter on the phase current reduction under demagnetizing mode. A simple control strategy is also proposed to keep the capacitor voltage in the specific level without a voltage detector. To verify the analysis, finally simulation works were done. The results show that a C-dump converter with smaller capacitance has greater voltage fluctuation therefore it is capable to minimize the negative torque developed by the motor.