Letter to the Editor: Contactors Immunity to Voltage Sags

Abstract Voltage sags are among the most important power quality events due to their economic effect on all types of customers, especially industrial users. Normal contactors would open when a voltage sag of given depth, duration, phase-jump, and starting angle takes place. Results given here were obtained from a series of experimental tests carried out on six contactors with dissimilar characteristics and manufacturers. The traditional immunity curves (or time/voltage characteristics) were obtained. The tested contactors show similar behavior, with very small variations. A few tests were conducted to analyze the increase in contact voltage drop due to voltage sag presence in order to investigate the contacts welding under rated-current conditions.