An electronic method of controlling multiple reignition switching transients in vacuum contactors

An electronic method is described for controlling the contact tip opening of a vacuum contactor in such a way that the probability of transient overvoltages caused by multiple reignitions during load switching is minimized. The multiple reignition transient problem is described, and the electronic hardware utilized to control the vacuum contactor is discussed. Tests of the effectiveness of the system were performed. The test procedure and results of the tests are described. The tests confirmed that control of the tip-opening point on the load current waveform will prevent vacuum contactors from producing multiple reignition transients even under severe conditions such as jogging duty. By varying the tip-opening angle of the contactors under test, a range of arc angles was found in which multiple reignitions did not occur. The test procedure also proved that the electronic control can maintain contactor tip opening in the target band consistently. Other functions that the microprocessor-based electronic control can provide are also discussed