There are several methods for step-down starting of three-phase AC motor.

First, Y-delta starting is suitable for large-capacity motor with triangular connection during normal operation.

The second is the step-down starting of resistance or reactor, which is usually applied to high-voltage motors.

Three, autotransformer starting, autotransformer generally has several taps, can control the starting voltage to 60%, 65%, 80% of the original voltage.

Four, Yanbian triangle starting, each phase winding of this motor has an extension section, which is only connected when starting.

Five, frequency-sensitive rheostat starting, is a kind of contactless electromagnetic element, its equivalent impedance decreases with the decrease of rotor current frequency, and it is short-circuited after successful starting.