Determining number of motor poles without a motor data sheet:

1. Use a lab power supply and make sure the current limit is set to less than the motor rated current. Do not turn on the supply
2. Connect V+ of the supply to phase A and V- of the supply to phase B of the motor. Any 2 of the 3 phases can be chosen at random if they are not labeled
3. Turn on supply The rotor settles at one position with the injecting current.
4. Manually rotate the rotor until rotor snaps to another settle position. The rotor has several settle-down positions around one mechanical cycle
5. Count the number of settle-down positions for one fully mechanical cycle, which is the number of pole pairs. Multiplying by two calculates the number of poles.

Be careful of gearing systems within a motor. The gearing ratio determines how many rotor revolutions correlate to the shaft’s mechanical revolution.