3UA series thermal relay is suitable for using in power system with AC 50HZ, rated operation voltage up to 660V and 1000V, in main circuit, current form 0. 1A to 630A. It is used to protect 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 characteristics. The products also can be supplied with protecting case to ensure safety. The products can be plugged in the contactor and installed independently or mounted by rail.