Evaluation of DC-link Capacitor RMS Current in Switched Reluctance Motor Drive

In this paper a method to evaluate the DC-link capacitor RMS current of a switched reluctance machine (SRM) drive under different operating conditions is presented. Square current reference is considered. Methods are developed for both soft chopping and hard chopping method of current control. A newly proposed simplified flux linkage model is used to evaluate converter switching functions and phase currents which are then used to evaluate the capacitor current stress. The capacitor current is found to be lower for soft chopping than for hard chopping. While the capacitor current is maximum at lowest operating speed with hard chopping, the maximum occurs at an intermediate speed for soft chopping for a given magnitude of current reference. The proposed method is useful to size the DC-link capacitor during the design of SRM drive.