Subcyclic Switching and Symmetrical Chopper with Tap Changing

Abstract

Dual-Tap Chopping Stabilizer is an AC voltage regulator with dual tap changer. AC regulators based on tap changers are implemented with SCR’s and TRIACs are widely used for their robustness. With thyristor soft switching, commutation losses are reduced to nearly zero, but it allows only supercyclic commutation, i.e, only one commutation per cycle is possible. By replacing thyristors with high power transistors and gate turn off thyristors, it is possible to achieve several tap changes in one half cycle ,i.e, subcyclic commutation. In this paper an AC chopper is designed with MOSFET switches to achieve subcyclic commutation. Thus subcyclic switching is achieved. A freewheeling circuit is added in the load side. The freewheeling circuit has the following advantages.