Two or more contactors can be used to provide an effective and lower voltage when starting the motor. Using an autotransformer or series inductor can apply a lower voltage to the terminal when the motor is started, thereby reducing the impact of starting torque and current. When the engine speed reaches a certain percentage of the rated speed, the starter automatically switches the motor terminals to normal input voltage. Since the autotransformer and series inductance only have a large inrush current when starting, the time may only be a few seconds, but their rated power is lower than the same current, so the rated current will be lower in continuous use.