How To Test A Single Phase Motor With A Multimeter

How To Test A Single Phase Motor With A Multimeter. There could be various reasons why a single-phase motor fails to start, develops hot, trips its overcurrent device, or runs intermittently.

The primary issue could sometimes be found in the power supply, such as the motor controller or the branch circuit wire. Another scenario is that a driven load has been stuck.

How To Test A Single Phase Motor With A Multimeter

how to test a single phase motor with a multimeter

A burnt wire or winding failures, such as a deteriorated bearing or insulation degeneration, could cause your single-phase motor.

You can use various diagnostic equipment to figure out the actual reason for these symptoms, but a multimeter is considered the best.

As a result, we’ll go over how to use a multimeter to test a single-phase motor in this post.

Process of testing a single-phase motor with a multimeter

Once you’ve completed the necessary steps, evaluating the condition of your single-phase motor is pretty simple.

The primary purpose of testing an AC motor is to see how healthy it is. Here are the main steps to consider while determining the health of your motor:

1. Testing electrical motor impulse

Checking an electric motor One of the essential aspects of electrical motor maintenance is impulse. When it comes to motor testing, there are a few factors you should keep in mind:

  • Examine the insulation to see whether it has degraded or the impulse testing is defective.
  • Can you use a DC resistance, Megger, Inductance, or a HiPot to diagnose your motor’s poor insulation?
  • After failing an impulse test, check if your motor still works properly.
  • Examine whether your motor can perform as expected despite a turn-turn short.

2. Testing earth continuity and resistance

Check the resistance across the motor frame and the earth using your multimeter. A decent motor should have values of less than 0.5 Ohms. Otherwise, any value greater than 0.5 Ohms indicates a defective motor.

3. Testing power supply

A single-phase motor’s predicted voltage levels are 230V or 208V. This level varies depending on utilizing an American or a UK voltage system. You should always check to see if the motor receives the proper voltage supply.

4. Testing winding resistance in the single motor phase

Use your multimeter to verify for winding resistance or the Ohms reading from your motor, use your multimeter. Because single-phase engines have three terminals (S, C, and R), this is how you should evaluate winding resistance.

Measure the resistance of the windings from C to S, C to R, and S to R. C to S + C to R should be equal to S to R measured values. Single-phase motors are subject to the following rules:

  • The motor’s maximum resistance reading should be the Ohms reading halfway between S and R.
  • The motor’s lowest resistance reading should be the Ohms reading between C and R.
  • The C and S Ohms readings provide intermediate values between S to R and C to R.

5. Testing insulation resistance

Insulation resistance failure in a motor is one of the most telling symptoms that your engine is broken. Insulation resistance is often measured using a megohmmeter or an insulation tester between the motor winding and the earth.

Set your insulation resistance tester to 500V and examine the motor winding’s connection to the ground. Examine the C to E, S to E, and R to E scales. 1M is usually the minimum test value for an electric motor in good working order.

6. Testing the running amperage

Check the maximum load amps with an appropriate meter while running, then compare it to the motor nameplate FLA. Any divergence from the plate name FLA indicates that the engine under test is defective.


How To Test A Single Phase Motor With A Multimeter. As we come to a close, we hope that this article has assisted you in resolving all of your single-phase electric motor’s defective symptoms.

However, you’ll need to gather and evaluate a lot of data while putting it all into perspective. The electricity will not be required at any stage throughout the testing of your single-phase motor.

As a result, make sure the engine is disconnected from the power supply before starting your test.

How to test a single-phase motor?

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