The three wires of the brushless DC motor are equivalent to the U, V and W three-phase wires of the AC motor, which are connected with the three-phase wires of the drive respectively; If the motor current is very large, vibration, abnormal rotation after connection, the wiring sequence of the three wires is changed successively until the motor runs normally; One of the switching states makes the motor rotate clockwise, the other makes the motor rotate counterclockwise, and the other states the motor cannot operate normally