Implementation in Automatic Star Delta Starter with Protection Scheme

The project is designed to provide low voltage start to induction motor. This is achieved by using star to delta conversion. The star delta starter is generally obtained from three contractors, electromechanical timer and a thermal overload for operating a 3 phase motor at 440 volt at ac mains supply 50Hz.A set of relays are used to shift the motor connections from star to delta with a time delay. Since in star connection current is same in different phases while line voltage is root three times the phase voltage. So the voltage is reduced if motor is started as star. And also in delta connection the voltage is same as that of phase voltage so full voltage is applied if we run the motor as delta connection. The interlocking arrangement of all the contactor coils is traditionally wired in 440volt AC. If any of the phase goes off the single phasing circuit comes into action which disconnect the motor and save it from overloading.