Analysis of three-phase zero-voltage switching with synchronous start

The analysis of three-phase zero-voltage switching circuits (star-connected load without neutral connection as well as line-controlled delta-connected load) with resistive load is presented. The system is started in the same way as a single-phase system with zero-voltage synchronous switching, and after 90° the system reverts to three-phase. Results show that, although there is a small DC component in the load voltages, their amplitudes decrease as the number of cycles in the time base is increased. It is also shown that the configurations discussed have approximately the same characteristics as the one-phase integral zero-voltage switching scheme for larger values of the time base. Experimental results obtained with a prototype unit are given to verify the analysis