How To Test Motor Winding With Multimeter? It Is Quite Easy

The motor is the heart of the machine. It can fail to start for many reasons. Learn how to test motor winding with multimeter and troubleshoot with this guide.

When your motor fails, it can be caused by several reasons. Sometimes we can’t find out just by looking at it. Therefore, a few simple checks with a multimeter will help you solve the problem. Read this article to learn how to test motor winding with multimeter.

Why Should You Test Motor Winding?

The winding of an electric motor is a wire placed in a coil, usually wound around a flexible, coated iron magnetic core to form a magnetic pole when amplified by an electric current.

As we all know, the winding of a motor is essential to its mechanics. Afterward, they will wear and tear, so you need to check them regularly and replace them if necessary.

It’s always critical to know the cause of motor winding failure before replacing a new one. Motor windings are damage varies in appearance. Therefore, it is very important to remove the wire from the motor and identify the problem that needs replacing.

A multimeter

How To Check Single Phase Motor Winding With A Multimeter?

Structure Of Single Phase Motor Winding

In general, a single-phase motor consists of two main parts: a rotor is a rotating part, and a stator winding is a part. An AC induction motor has two parts: one main winding and one auxiliary winding.

An AC motor is commonly found in households, such as domestic appliances or electric tools. Most of these devices do not need too much power and must be easy to use.

Check The Winding Resistance For Short-To-Ground Connections

We should check the earth continuity windings in the circuit and any open or shorted windings. To test the motor for a short circuit, you must set the multimeter to a resistor and disconnect the motor from the controller. Then test each wire and look for infinite readings.

Similarly, to check windings for open or short circuits, you should check motor terminals T1-T2, T2-T3, and finally T1-T3. In this case, you must utilize a 0.3 – 2 Ohm reading. If the reading ends at zero, you need to run the test again to see if it returns zero again. Conversely, a value of 0 means a phase shift.

In addition, deficiency means that the wire is shorted to the ground, usually breaking the wire. If the value is greater than 2, the coil can be opened. And, an open winding simply refers to an open motor wire.

Check Winding Resistance In The Motor

You can use your multimeter to test for winding resistance or check the Ohms reading from your motor. Then estimate the resistance of coil C to S, C to R, and S to R.

The value measured from S to R must be equal to C to S and add C to R. The following rules apply to single-phase motors: The resistance reading of the motor should be a resistance value between S and R.

Otherwise, the minimum value of the motor’s resistance should be in ohms between C and R. C and S ohm readings offer some intermediate values between S to R and C to R.

Examine The Motor’s Insulation

Insulation resistance can be measured with an ohmmeter or insulation tester between the motor windings and the ground.

Motor insulation may occur near installed cables, appliances, power distribution subsystems, and any type of electrical device or wiring. Therefore, people should strictly follow the correct setup, connection procedures, timing, and precautions to prevent deadly electrical shock.

When the motor is under test, you should turn it off and disconnect it from all unnecessary equipment and wiring. Such external equipment will not only invalidate the test but can also be broken due to the applied voltage.

Unsuspecting people can also be exposed to dangerous high voltages. Therefore, you should set the insulation tester to 500V and check the grounding beforehand.

Generally, one milliohm is the minimum test value for a  good engine.

A Motor Winding

How To Check three-phase Motor Winding With a Multimeter?

So how to test motor winding with multimeter if your motor is a three-phase model? Read on to find out.

Three-Phase Motor Winding Structure

Like other induction motors, a three-phase induction motor consists of two main parts: a rotor and a stator.

The rotors of the 3-phase motor are further classified as:

  • squirrel-cage
  • slip ring
  • wound rotor
  • phase wound rotor.

Check Wind Resistance For Short Trips To The Ground

People use an Ohm meter to calculate the motor windings. Connect the positive end of the multimeter to the red end of the Bill motor. And, in the same way, connect the negative end of the multimeter to the black end of the motor. It will display the motor winding readings on the multimeter’s screen.

Similar to a single-phase motor, you can simply isolate the motor by disconnecting all the wires from the motor controller. Besides invalidating the test, the applied voltage could damage such extraneous equipment. Additionally, unsuspecting individuals could be exposed to hazardous high voltages.

Check The Winding Resistance In The Motor

You can check the electric motor winding resistance by using a Winding Resistance Meter or Multimeter. What to look forward to is the same electrical resistance reading between all three windings.

Check The Motor Insulation

Improper insulation often signals a failure of your motor. Insulation resistance is usually measured between the motor winding or phase and the motor frame.

In this test, set your multimeter to the suitable voltage setting. If your motor has a rated voltage of 500V, set the multimeter to 500V. For motors with a higher voltage, you would want a 1000 to 2500V multimeter.

After that, perform a phase to phase test then a phase to motor frame test. If the result is less than one, the motor insulation is having a problem.

Make sure the insulation is working

Conclusion

The method to measure in single-phase and three-phase motors do not differ. We need to check the “short-to-ground”, the winding resistance, and the motor insulation.

Obviously, a quick test with a multimeter can help determine the root cause of the problem and save money on repairs. We hope this article helps you know how to test motor winding with multimeter.

If you have any concerns, feel free to reach out and let us know.

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