A simple methodology for estimating the effect of voltage sags produced by induction motor starting cycles on sensitive equipment

Voltage sag produced by induction motor starting current is one of the main causes of sensitive equipment dropout. The use of a motor starter reduces the voltage sag depth but increases its duration. The subsequent connection to full voltage produces a new sag separated from the first one by a few seconds. A simple method is proposed, which allows to transform the information of starting current/time characteristics to voltage sag depth/time characteristics that are directly comparable with the sensitive equipment susceptibility curves (CBEMA and other curves). The methodology also allows to consider motor repetitive starts as well as different starting cycles.