The Star / Delta starter is generally manufactured from three contactors; And an electromechanical timer and thermal overload for the operation of a three-phase motor at 440 volts at 50 Hz AC power. The interlocking arrangement of all the coils of the contactor is traditionally wired at 440 volts AC.
This project uses a system to start a three phase motor at 440 volts AC 50 Hz with a set of 12 volt DC relays in star mode first and then to delta mode with an electronically adjustable timer. A set of relays is used to change the motor connections from star to delta with a time delay.
The project is supplied with six lamps instead of a 3-phase motor, ie two lamps representing each phase winding of the motor. The interlocking arrangement of the relay coils and the electronic timer are connected to 12 volt low voltage DCs powered from a built-in DC power source for safe starter handling during the study. It still retains its application for a 3 phase motor that starts with single phase prevention as well.
During star operation, the lamps would light up dark indicating that the supply voltage across the coils is 440 / (3) root. In the delta condition after the timer works the lamps would shine with full intensity indicating the full source voltage of 440volts. The timer comprises a 555 in monostable mode whose output is fed to a relay to change the three-phase star-to-triangle power supply.
The project also has a single phase protection, as the 3-phase motors are burned if a phase is missing during operation. The output to the lamps must be completely cut off in case of phase failure.
In addition, the project can be improved by using a thyristor on the principle of trigger angle control for soft startup of the induction motor that would overcome all the drawbacks of star star delta.