rotor bar

When your rotor bar is broken, that’s a serious sign of trouble. You could be putting yourself and your motor in serious danger.

You may not notice any immediate repercussions of a bar that’s damaged. But, it slowly causes the other components to deteriorate, leaving your machinery a safety hazard.

There are several ways one would be able to detect a broken bar. Some your repair team can try, while others should be carried out by a professional repair shop.

Don’t take any foolish risks when it comes to your large machinery. Read on to learn about 5 ways you can detect a broken rotor bar.

1. Single Phase Rotor

The single phase rotor test is looking to see if there is any alternation in AMP draw. A broken rotor bar will cause the stator current to increase or decrease.

The best way to perform this test is to apply single phase power to your motor. Only use low voltage over the course of several amps.

2. Vibration Spectrum

This is a good test to conduct if the motor is running under load. When your motor is running, its vibration will adjust to the frequency of the poles.

A broken rotor bar is usually unable to produce a frequency because they wouldn’t have a current. When there isn’t a current, there aren’t any magnetic forces to pass through.

3. High Current Rotor

As the name suggests, in this test, you’ll want to create a high current to the shaft of the rotor. If your bar is broken, this current will produce short laminations on the rotor.

You would need to thermally scan the motor to detect a lamination. To do this, you’ll need infrared or thermoscan technology. So, for this one, it’s likely you’d need to visit a repair shop.

4. Current Spectrum

For this test, your motor needs to be at 50%-100% load. This will produce a current around the supply line frequency.

This current is a direct reflection of the slip frequency and number of poles within the motor. For that reason, this test is the most precise way to measure a broken bar.

The sideband amplitude will tell you if and how severe the breaks are. Check the stator windings within the motor.

5. Growler

The last method we’d recommend is to again check the current flow being produced by the rotor. However, in this test, you’d need to remove the rotor from the stator.

Find a laminated core that is wrapped by wire and place it close to the rotor. Since the bar is magnetized, it should pull the core closer to it. If it does not, you know there is a disturbance in the rotor.

Get Assistance With Your Rotor Bar and Other Parts

Your rotor is obviously an absolute essential. You need to ensure it’s kept in the best shape and if it’s broken, don’t wait to get it fixed.

That’s where we come in. We’re Electrical Apparatus and we have the solutions for your AC rotor needs.

Since 1974, our team has helped customers like you — check for yourself!

If you like what you see, contact us here and let’s get started!