3UA thermal overload relays protection switch is suitable for using in power system with AC 50/60Hz, rated operation voltage up to 660v and 1000v current from 0.1A to 630A. It is used to protect AC three-phase asynchronous motor against overload and open phase. The current setting value can be regulated and the setting current values of many thermal elements are inter-crossing overlapping arrangement for easy selecting by the customers from -25°C - 55°C air temperature as the products have temperature compensating the relays have the test push button for breaking NC contacts the operating indication and free trip characteristics.