Repetitive Impulse Withstand Performance of Metal–Oxide Varistors

This study focuses on the relationship between test current waveforms and impulse withstand capability of metal- oxide varistors (MOVs) (withstand energy, current density, and the number of withstand shots) in repetitive impulse application and discusses the mechanical and electrical failure mechanisms. The performance and relationship of withstand energy and withstand shots for conventional 2-ms rectangular waveform, 4/10-μs, and newly introduced 10/350-μs impulses are investigated. Notably, the 10/350-μs waveform has aspects of both steep rise impulse and long duration impulse. In addition, the varistor voltage change after repetitive impulse applications for 10/350-μs and 4/10-μs waveforms is investigated. There is no direct relationship between varistor voltage drop and repetitive withstand shots. However, VI
_{m A}
and V
_{0.01 m A}
changes indicate the degree of MOV damage caused by the impulses and are important factors to monitor progressive damage. Based on these findings, optimal MOV design is discussed.