# Abnormal noise of electro motor

Dear all

I am facing to 100 kw (3000 rpm)electro motor with abnormal noise . This noise heard at both coupled and free run test in workshop.by increasing noise, vibration either growing form 3mm/s up to 7m/s.

Dominant peak is 150HZ.amplitude of this peak go up by increasing the noise.

Best regards.

Original Post

"150 Hz is 4x Line Frequency (50 Hz LF), isn't it?"

No, 4 x 50 = 200 Hz!

Normal electrical magnetostriction produced vibration and radiated sound occurs at harmonics of 2x line frequency or 100, 200, 300 Hz. 150 Hz is unusual (3x 50-Hz), so it may be the result of looseness in stator or motor frame and possibly amplified by resonant structure. Inspect for looseness and test for natural frequency near 150-Hz.

Walt

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Walt Strong posted:

"150 Hz is 4x Line Frequency (50 Hz LF), isn't it?"

No, 4 x 50 = 200 Hz!

Walt

Thanks Walt.

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Is there a way to "edit" a post after it is posted?

Did not see anyway to edit a post, so I just deleted my erroneous one.

Thanks,

Ralph

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Walt Strong posted:

"150 Hz is 4x Line Frequency (50 Hz LF), isn't it?"

No, 4 x 50 = 200 Hz!

Normal electrical magnetostriction produced vibration and radiated sound occurs at harmonics of 2x line frequency or 100, 200, 300 Hz. 150 Hz is unusual (3x 50-Hz), so it may be the result of looseness in stator or motor frame and possibly amplified by resonant structure. Inspect for looseness and test for natural frequency near 150-Hz.

Walt

Dear walt.

If this frequency related to electrical source ,it should be disappeared after the motor power off. We test it but 2line frequency dont disappeared .

Of course we had 3 times stator burned during ten years.it is unusuall.

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Yes, electrically induced vibration/sound should disappear when power is turned off.  Considering 3 stator failures, you might test electrical power quality. You have not indicated what the motor is driving and the type of coupling, and the service conditions. More information can lead to better diagnosis!

Walt

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Hi,

did you try to get the enveloping data or TWF? did you try to get the starting current? i had an experience same with your problem which i encounter an unbalance voltage of motor due to unbalance system voltage.

regards,

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Ralph Stewart posted:

Is there a way to "edit" a post after it is posted?

Did not see anyway to edit a post, so I just deleted my erroneous one.

Thanks,

Ralph

Click on "Take Action" at the lower right corner of the specific post.  One of the choices is Edit but I think you can only do an edit once.

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Have you checked the rotor for any cracked bars or end rings? There are certain stator/rotor slot combinations that produce noise, vibrations and other torque issues. If you can post the no. of stator and rotor slots, I can check it for you.

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edisonindia posted:

Have you checked the rotor for any cracked bars or end rings? There are certain stator/rotor slot combinations that produce noise, vibrations and other torque issues. If you can post the no. of stator and rotor slots, I can check it for you.

Thanks . I try to find them. But you mean that is maybe related to design problem of motor?can you explain more about certain stator/rotor slot combination?

Best regards

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