DESIGN AND CONSTRUCTION OF AUTOMATIC STAR-DELTA STARTER

Abstract

The star delta starter of induction motor is designed to reduce high starting current and torque. The star delta starter is designed by three magneticcontactors, an overload relay, timer relay and circuit breaker. For Starter, a motor must be connected in delta mode position during a normal run. When induction motor is start in direct online .The motor winding flow a large amount of current .The starting high currentcan be reached in 8-10 times of the rated. So there is need to control high starting current before starting the motorTherefore, in a star connected system line current is equal to phase current but line voltage is equal to the root three times of phase voltage. For this reasons at first motor is connected to the star system and it reduce the high starting current. In delta connection, line voltage is equal to phase voltage and line current is equal to √3 times phase current.In run mode the motor connect in delta system so that the full voltage applied to the motor. The Starter is made by three magnetic contactors, timer relay, and a thermal overload relay or circuit breaker.