How to Calculate Vibration from Generators and Transformers?

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Discussion Overview

The discussion revolves around calculating vibration from generators and transformers in relation to building structures. It includes considerations of mechanical equipment vibration, resonant frequencies, and the effects of induction motors on vibration levels.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant seeks guidance on calculating vibration from generators and transformers affecting the building structure.
  • Another participant suggests that the term "striation" may be incorrect and proposes that the resonant frequency of the building may interact with the mechanical equipment's vibration.
  • A question is posed regarding the operational speed of the equipment, specifically referencing 1800 RPM.
  • It is noted that induction motors operate at speeds influenced by load and typically have a slip of about 5%, leading to expected vibration within a frequency band around the motor's design speed.
  • Discussion includes that vibration from motors is linked to motor RPM frequency and that load imbalance can affect vibration frequencies based on pulley diameter ratios.
  • Magnetostriction in transformers is mentioned as a source of vibration, generating a frequency at twice the fundamental frequency of the supply, with specific frequencies given for 50Hz and 60Hz supplies.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and propose different aspects of the problem, indicating that multiple competing views remain without a consensus on the best approach to calculate the vibrations.

Contextual Notes

There are assumptions regarding the definitions of terms used, such as "striation," and the specifics of equipment operation, which may not be fully resolved. The discussion also highlights the dependence on various factors like load, slip, and pulley ratios that could influence vibration calculations.

TonyTS
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Hi, I am training to be a Building services engineer. I have come across a problem where I have to calculate the vibration from the generator and the transformer to the striation of the building.. how should I do it?
 
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Maybe you mean "structure" of the building rather than "striation" of the building.
The resonant frequency of parts of the building may be sympathetic with the mechanical equipment vibration.
The equipment should be based on vibration isolating mounts.
 
1800 rpms?
 
Induction motors run at (synchronous – slip) speeds determined by load. They are usually specified with about 5% slip. Unbalance vibration from the motor can be expected in a band +/–5% of the motor design speed. That will be 0.95 * supply_frequency / poles, where the number of poles is usually 2 or 4 but can also be 6 or 8.

While the vibration from motors is at motor RPM frequency, where the driven load is coupled through V-belts, load imbalance vibration will be centred on frequencies determined by the ratio of pulley diameters.

Magnetostriction in transformers will generate a buzz at twice the fundamental frequency. For 50Hz supplies that will be 100Hz, while for 60Hz supplies it will be 120Hz.
 

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