3UA series thermal relay is suitable fro using in power system with AC 50Hz, rated operation voltage up to 660V and 1000V, in main circuit, current from 0. 1A to 630A. It is used to pretect AC three-phase asynchronous motor against overload and open-phase. The relays have the test push-button for breaking NC contacts and the operating indication and free trip characterstics. The products also can be supplied with protecting case to ensure safety. The products can plug in the contactors and install independently or mount by rail.