JRS8 (3RU) series thermal overload relays are suitable for using in the power system with AC50/60Hz, rated operation voltage up to 690V, rated operation current from 0.1A to100A. They are used to protect AC 3phase asynchronous motors against overload and phase failure. They also have the functions of temperature compensation and trip indication. The products can be fixed with 3RT series contactors, or be independently fixed. The items conform to IEC60947-4-1.