Abstract
Capacitors are prone to two major types of energizing transient phenomenon: transient overvoltage and inrush current (charging current). Capacitor switching transients are harmful to the capacitor and the switching device. For reducing these transient phenomena, this paper proposes a capacitor energizing transient limiter (CETL). The
proposed CETL can automatically provide high impedance at the instant of capacitor energizing, thus, the switching transients can be effectively suppressed. The operating condition of the proposed circuit can be divided into two states: the charging suppressive mode and the steady state with its initial transient. During the charging suppressive mode, a pair of diode strings conducts automatically and then the DC reactor provides high impedance at the instant of switching on in order to suppress the capacitor energizing transients. During the steady state with its initial transient, all diodes of the bridge rectifier conduct simultaneously and the limiter freewheels; therefore the limiter acts as a short circuit and has no effect. Thus, it is not necessary to increase the capacitor-rated voltage when the CETL is used. Related components are depicted. Finally, the simulation results obtained using different methods of capacitor switching verify the feasibility and performance of the proposed CETL