Design of automatic star-delta starter by adjustable electronic timer and relays for induction motor

This paper reports the design an automatic star-delta starter using electrical relays and an electronic timer by feeding the motor with 1⁄√3(58%) of the full load current to limit the starting current surges by starting the motor at reduced voltage and then have full supply voltage reconnected when they run up to near rotated speed. This method is commonly referred to as “Soft Starting” the motor. Traditionally, in many regions there is a requirement that all motor connections be fitted with a reduced voltage starter for motors greater than 4 KW5HP. This is necessary to curb the high inrush of starting currents associated with starting induction motors. In this paper, a low cost-based circuit that can be used to control the operation of an induction motor is designed and a delta-star starter is used in controlling the turning on of the motor with low power loss and electrical relays deployed for conversion of star to delta. This design reduces the high starting current of induction motor and along these lines forestall the motor from overheating.