In the star-delta starting method, the electric motor starts in a star configuration, which provides a lower voltage in the coils, thus reducing the starting current. By means of this method, the engine will make a smoother start, reducing its current by approximately 1/3 that of direct starting. With the reduction of the starting current, leeson 113019.00 there is a significant loss of torque at the start. Thus, this method is applicable for starting of unladen or empty engines, or with loads having low and nearly constant resistant torque.
The load resisting torque can not be greater than the starter torque of the motor, nor can the current at the star-to-triangle switching point be unacceptable. In addition, the system determines that the motor has at least six terminals available and that the rated voltage (utility voltage) is equal to the motor voltage triangle. In the power circuit, when energized, the motor is in the starting mode, receiving in each coil group approximately 58% of the mains voltage. With the reduction in the applied voltage value, the current and the torque are also reduced to the same ratio.