Which type of reduced voltage starter provides the greatest amount of starting torque?

The type of reduced voltage starter that provides the greatest amount of starting torque is the auto transformer starter. This method utilizes an autotransformer to reduce the voltage applied to the motor during startup. By doing so, it allows for a higher starting torque than other reduced voltage methods.

The operation of an auto transformer starter involves adjusting the voltage down to start the motor, and as the motor reaches a certain speed, the voltage can be increased. This means that while you initially reduce the voltage, you still provide a significant amount of starting torque, as the motor can still receive a voltage enough to generate high starting currents.

In contrast, a star-delta starter reduces the starting torque because it initially connects the motor windings in a star configuration, resulting in a lower voltage and therefore lower starting torque. Once the motor reaches a certain speed, it switches to delta configuration, which provides higher torque, but the initial kick is less than that achieved with an auto transformer.

Soft starters gradually ramp up voltage and current, contributing to lower starting torque and gentle acceleration, which works for applications where reducing mechanical stress is essential but does not maximize starting torque.

Direct-on-line starters connect the motor directly to the supply voltage, providing full torque from the start, but since the question