Analytical model of AC contactors for studying response mechanism to multi-dimensional voltage sag characteristics and its novel applications

The sensitivity of AC contactor (ACC) to voltage sag leads to unnecessary tripping of the motors, resulting in huge economic losses to users. The purpose of this study is to reveal the response mechanism of ACC's behaviour to multi-dimensional voltage sag characteristics theoretically, based on the analytical model proposed here, and some suggestions are provided to reduce the impact of unnecessary tripping events. First, an analytical model of ACC to sag has proposed and its effectiveness is proven by the laboratory test results. Based on the proposed model, the response mechanism of ACC to voltage sags has been investigated analytically considering the characteristics of voltage sag, including duration, voltage magnitude, point on wave, and phase angle jump. The impact of fault criterion, the practical way to a quick evaluation of the sag immunity of ACC, and the immunity improvement schemes to reduce the unnecessary tripping events by the offline and online way is also discussed here.