What Causes Unusual Vibration Patterns in AC Induction Motors?

In summary, there is a conversation about measuring the spectrum of an AC induction motor, including points at non-drive end and drive end in both radial and axial directions. The conversation also discusses measuring velocity and acceleration in the horizontal direction and two questions regarding potential electrical issues causing peaks in the spectrum at high RPMs. It is suggested that the issue may not be a bearing failure, but an electrical problem, and it is recommended to record details about the bearings, such as size, manufacturer, and rotation rate, to further analyze the issue. The speaker also asks if the vibrations are new or if they have been present in previous measurements and if the motor drives a gearbox and how many slots are in the stator.
  • #1
shaiab
1
0
Hello!
I want to ask about spectrum of Ac induction motor, first of all, we measure points at non drive end + drive end - radial+axial direction.

At horizontal direction we measure not only velocity but also acceleration. Two questions:

1. I see a peak around 65000 rpm with sidebands at running speed (1500 rpm) , I suspect it not a bearings failure but as electrical problem.

2. Here, too, I guess it electrical problem – suddenly the g' of the motor jumping and characterized by high peak around the 160000 – 200000 rpm, also with sidebands but at line frequency relative to motor running speed. For example, motor running speed is 1490 rpm the sidebands will be close to 6000 rpm. Even in case the motor has VFD (motor 3000 rpm 50-60Hz) and the running speed is close to 3600 so the sidebands will be 7200 rpm . Sometimes, it supported at the velocity spectrum by high harmonics at line frequency (6000 rpm).

I hope you're familiar to these problems and can tell me ''recommended action'' to prevent or reair it.
 
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  • #2
Welcome to PF.
shaiab said:
I suspect it not a bearings failure but as electrical problem.
Why do you suspect electrical?
Is the vibration in phase with the motor rotation or the supply voltage? Induction motor slip will help discriminate between vibration of bearing/rotor/load and electrical/supply.

Are these new vibrations? or were they there last time you measured the motor?
Does the motor drive a gearbox?
How many slots are there in the stator?

A damaged ball or a track imperfection can be analysed by knowing bearing details. Record bearing size and manufacturer, number of balls in the bearing, ball rotation rate and frequency of balls passing a track imperfection.
 
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Likes bigaggie and Greg Bernhardt

Related to What Causes Unusual Vibration Patterns in AC Induction Motors?

1. What is vibration spectrum analysis?

Vibration spectrum analysis is a method used to measure and analyze the vibrations of a system or structure. It involves measuring the amplitude and frequency of vibrations and using this data to determine the underlying causes of the vibrations.

2. Why is vibration spectrum analysis important?

Vibration spectrum analysis is important because it helps identify potential issues and failures in a system or structure before they occur. It can also be used to monitor the health and performance of equipment, allowing for timely maintenance and repairs to be made.

3. How is vibration spectrum analysis performed?

Vibration spectrum analysis involves using specialized equipment such as accelerometers and data acquisition systems to measure the vibrations of a system. The data is then analyzed using software to create a spectrum plot that shows the amplitude and frequency of vibrations.

4. What are some common applications of vibration spectrum analysis?

Vibration spectrum analysis is commonly used in various industries such as manufacturing, aerospace, automotive, and power generation. It can be used to diagnose issues with rotating machinery, engines, pumps, and other equipment, as well as to monitor the vibrations of bridges, buildings, and other structures.

5. How can vibration spectrum analysis data be interpreted?

Vibration spectrum analysis data can be interpreted by comparing it to known vibration patterns and frequencies for specific equipment or structures. Any deviations from these patterns can indicate potential issues or failures. Additionally, the data can be analyzed to determine the root cause of the vibrations, such as imbalanced components or misalignment.

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