The Sensata IEGS6661-1REG4-31957-50-V is a 3-phase, 50/60 Hz, 277V ac thermal overload relay. It features a Type 1 enclosure, a backplate mounting template, and self-powered sensing. It can protect three-phase induction motors from overload, short-circuits, and single-phasing. Additionally, the relay can be used to prevent the motor from starting when it is already too hot, and it will shut down the motor when there is an over temperature or under voltage condition.