How to Test Single-Phase Motor Windings

In this episode, Keith walks us through how to test and check motor windings on a single phase motor. If you suspect your motor is starting to fail, it could be a symptom of broken windings. Keith will also show us how to check the insulation resistance of a motor.
00:00 Introduction
00:59 Why test motor windings and insulation?
01:13 How to Test Three Phase Motor Windings
01:25 How to Test Windings on a Single Phase Motor
01:52 Motor Winding Resistance Test
02:24 How to Check Insulation Resistance of a Motor
02:48 When to Test Motor Windings With a Megger
Our step by step guide to test your single phase motor windings:
✅ Disconnect the motor power supply.
✅ Next, you’ll test your capacitors. Check out other video for the step by step guide to test the capacitor: • How to Replace a Motor...
✅ Remove the end bell off and do a visual inspection of the motor windings. You’re looking for burns, melting, or breaks in the motor windings. If you do see burns, your motor’s likely been overloaded and will need to be repaired or replaced.
✅ Next, we’ll check the resistance of your motor windings to make sure the start and run are not shorted together and they are not grounded.
✅ Make sure your multimeter is set to measure in OHMS and place the meter across the isolated winding leads.
✅ If your insulation is good, your multimeter will ready OL. If the windings are shorted, the multimeter will read 0.
✅ Use your multimeter to see if there is continuity or low resistance between any of the motor leads to the terminal and the housing or chassis. Repeat with all the leads. There should be high resistance between all the leads and the motor chassis. If any of these tests indicate a low resistance, your insulation may be damaged.
✅ If your resistance is low but not zero, you could also test with a megohmmeter to get a more accurate reading. Instead of a true short circuit, you may be dealing with a direct short, insulation breakdown, or dielectric breakdown. The megohmmeter (sometimes called a 'megger') applies a high voltage, so you should be cautious when using this device.
Need help replacing a single phase or three phase motor? Contact our team now: www.emotorsdirect.ca/contact-us

[@sambathbunkh]

Very good video and explanation

[@emotorsdirect]

Glad it was helpful!

[@rafepittenger7484]

I have a single phase 1/3 hp electric motor with a start windings that are thin diameter and a run windings that are thicker. The whole motor does not have capacitors to begin with. Its a furnance belt driven blower motor. Everything on you tube has single phase motors with explanations on how do deal, diagnose and repair but none on ones with no capacitors. My understanding is that the primary starting winding for a non capacitor electric motor is 45 degrees out of phase with the run windings. Both windings get their voltage from 24v transformers to provide the kick. I believe the non capacitor electric motor I have has a centrifugal switch to cut the start windings open once the motor reaches speed. Where do I find information on how to test single phase motors without capacitors?

[@emotorsdirect]

Hi Rafe, I haven't created any content specifically on single phase motors without capacitors and I don't deal with those often.
Are you trying to diagnose an induction start induction run motor with a centrifugal switch? The only replaceable part would be the switch. Just based on the information shared, that's where I'd start with the troubleshooting.

[@linossinkala7840]

Thankyou so much

[@emotorsdirect]

To answer your earlier question, the other answer is correct. To switch the direction, T5 to T8 for most single phase motors, however this is not possible for all motors. Some won't expose sufficient connections to reverse and others will have a physical switch for reversal.

[@engraita5059]

Hello sir.. It is glad to see this.. Today I have got multimeter reading of two single phase motor that.. One of them is OL and the other is 11.4 ohms.. What does the second readings mean? Is it good or bad? Thank you.

[@emotorsdirect]

0L generally indicates no connection between two points. if a motor winding is reading 0L the motor is dead.

[@andilehlophe4778]

Which winding have a great resistance between auxiliary and main winding in the motor?

[@emotorsdirect]

Are you asking whether the main or auxiliary winding has higher resistance? If that's the case, the answer is the auxiliary winding due to the higher wire gauge (smaller diameter wire).