JR29 series thermal overload relay is mainly suitable for A.C.electric power system with voltage up to 660V, current up to 500A, 50/60Hz. It is generally used for the protection of overload and phase-tacking in circuits with three-phase induce motors and is often made up electromagnetic starters with B series A.C. contactors. The product conforms to GB14048.4, IEC60947-4 standard.