How must the motor windings be connected to utilize a wye-delta starter?

In a wye-delta starter configuration, the motor windings are connected in a wye arrangement during the starting phase and switched to a delta arrangement once the motor has reached a sufficient speed for normal operation. This approach is applied to reduce the starting current and the starting torque, making it particularly beneficial for larger induction motors.

When the motor is in wye configuration, the voltage across each winding is reduced to approximately 58% of the line voltage, which significantly decreases the starting current. This is crucial because high starting currents can lead to electrical stress and can affect the lifespan and reliability of both the motor and the electrical supply system. After the motor reaches approximately 70-80% of its full speed, the starter switches the windings to delta configuration, enabling the motor to operate efficiently at higher torque and power levels suited for normal running conditions.

This transitioning from wye to delta maximizes the efficiency and performance of the motor while minimizing the initial electrical impact, which is why the method of connecting the motor windings in this manner is essential in industrial applications.