Use the battery to identify the head and tail of the motor winding

As shown in the figure, connect two large dry batteries G in series with a manual switch SA, connect them to the head and tail ends of any winding, and put a multimeter (mA scale) across both ends of the other winding of the motor. When SA is turned on, the pointer swings to the side greater than zero. Then the terminal connected to the positive terminal of battery G is the same as the terminal connected to the positive terminal of the multimeter, which is the "head" of the winding. Then use this method to find all three "heads" of the three-phase winding.