The first method: Now adjust the multimeter to the AC range (if it is divided, adjust it to a range greater than 220VAC), and connect the black test lead directly to the ground (you can connect it to the hole in the middle of the three-phase socket, if not, you can directly connect it to the ground or wall), the red test leads are connected to the neutral wire and live wire socket holes respectively. The larger number is the live wire.

Ordinary three-phase squirrel cage motors have two speeds: one is the synchronous speed N1. The so-called synchronous speed is the speed of the motor's rotating magnetic field. This speed has a strict relationship with the number of magnetic pole pairs of the motor, that is, n1 - synchronous speed, rotation speed. /point;

J--frequency of current, cycles/second;

P--The number of magnetic pole pairs of the motor.

The rotational speed of the rotating magnetic field is slightly lower, but the difference is almost the same. For example, for a pair of magnetic pole motors, the speed of the motor wheel is 2950 rpm, for a two-pole motor, it is 1430 rpm, and for a three-pole motor, it is 920 rpm. Based on the above principle, a multimeter can be used to determine the number of magnetic poles of the motor, and then determine the speed of the motor;