How can we test the three phase motor by multimeter on continuity and resistance test. What should be the value of the resistance in all three winding.
Should not be more than 0.5 ohms, greater than that results in insulation failure and would cause electric shock.
The value would be the sum of the resistance of individual windings if tested while connected.
But the best practice is to break the delta and star connections and read as between start and finish end of each winding. You don’t expect a standard value but certainly not zero. The values are supposed to be uniform for the 3 phases. The values depend on the size of the motor.
As for the insulation resistance test, a value of at least 1Mohm between phases and above 50Mohm between a phase and earth is acceptable. The value of Resistance of the windings depends on the size and the material used. The resistance of the windings should be balance. L1 and L2 = L2 and L3 = L3 and L1. The megohm readings should be at least 5meg ohms…L1 to ground L2 to ground L3 to ground. The shaft rotor should turn very smoothly at no load. But should be balance and equal in All three phases