Sensitivity of AC coil contactors to voltage sags, short interruptions, and undervoltage transients

This paper discusses the sensitivity of ac coil contactors to voltage sags, short interruptions, and undervoltage transients on the basis of extensive test results. Existing standards and previously published work are reviewed, and a detailed description of the testing procedure used is presented. The following tests were performed: sensitivity to rectangular voltage sags with ideal and nonideal supply voltage, testing with two-stage voltage sags, and voltage sags which occur during starting of large motors, as well as testing against measured voltage sag. The importance of voltage sag characteristics besides magnitude and duration was also investigated. Generic sensitivity curves are proposed.