SOFT STARTER FOR ELECTRIC MOTOR

PROBLEM TO BE SOLVED: To provide a compact, semiconductor type motor starter that is manufactured easily. SOLUTION: The semiconductor type motor starter (10) includes: semiconductor power switches (46, 48) clamped between a pair of buses (32, 42); an electromagnetic relay (50) fitted in an opposite direction between an input end (36) and an output end (44); a radiator (64); and a cooling fan (66) installed between the electromagnetic relay (50) and the radiator (64). A pair of magnetic pins (124) for converging magnetic flux at a current sensing region and a Hall effect sensor for sensing a current at the current sensing region are provided at the current sensing region of the buses (32). In a motor operation mode, current is shunted from the semiconductor power switches (46, 48), thus forming a current path essentially in a straight line via the electromagnetic relay (50), reducing power loss, and minimizing an increase in heat. COPYRIGHT: (C)2009,JPO&INPIT