Electrical check on a motor.?

Question

Is there an electrical check for testing the windings on single and 3 phase motors?

Answer 1

you can do it with a ohm meter, but this will only detect a clean break or short. Many times the problem doesn't surface until a load or heat is generated to create the problem. Look for a shop that checks motors. They place a load on them and can tell you everything.

Answer 2

The correct way to check motor windings is to use a megger. Make sure the motor is disconnected from the mains and has no other connection to it

Check the three terminals to earth, on lead of the megger on the earth, the other on the going on to the terminal. For this reading there should be infinite resistance.

You then need to check the windings resistance to each other. One lead of the megger on terminal A, the other lead checking terminals B and C. The resistance being equal on each winding.

On either test of the megger shows 0 resistance then its either a dead short to earth or a shorted winding

You can repeat the test on single phase motors just disconnect the capacitors and the centrifugal switch if you can get to it.

You should always use a megger rather than a mutilmeter, as the a meter isn't powerful enough to check correctly.

The easiest way of checking a blown motor is if main fuses blow when the machine starts is bust.

Answer 3

If you are just wanting to check continuity (no breaks in the wire) use an ohmmeter to make sure the phase of the single phase motor has finite resistance.

For a three phase motor, there are two different options based on the connection type of the motor. For Y connected motors, measure the resistance from A phase to neutral, B phase to neutral and C phase to neutral. They should each be finite and nearly equal. For delta connected motors, measure the resistance from A phase to the B phase, B phase to C phase and C phase to A phase. Again, they should each be finite and nearly equal.

In addition to testing the continuity, you could check the phase inductances, mutual inductances, and flux linkage due to the permanent magnet (if one exists). But these tests would depend on the type of motor being tested.

Answer 4

as stated by others:

2 tests to carry out:
1. phase resistance/continuity

2. insulation resistance

1. phase resistance.
check the resistance of your test probes: record this value
disconnect all connections on motor (record where they were)
measure the resistance of each winding, they should all be of similar value. if one is very different you have a problem.

2. insulation resistance.
measure resistance between each winding and each other winding and earth, at 500v (as per stuart B's answer)

Answer 5

For single phase - With multi meter set on ohms, place probes on phase and neutral terminals to the winding (power disconnected!) a resistance reading should indicate all is well. An infinity reading means the winding is blown and a zero reading means it has short circuited. Dunno about three phase as that has three live conductors and one neutral!

Answer 6

You could use a multimeter and switch it to resistance. If coil is not open circuit, you should get 0 to very low reading. Then check same coils to earth and you want open circuit.