Humming noise

[patweldon]

I would like to know if
you or your members might be able to help me one more time.
I am the Manager of a large Data Center electrical infrastructure, we
are in the process of installing a new UPS system. As a temporary feed
to the data center we are using a Cutler- Hammer 800A molded case switch
in a motor control center configuration. Since we cut over to this
switch I have noticed a vibration and hum very similar to a 60 cycle
transformer, coming from this switch and enclosure. We have contacted
the vendor and have taken infrared pictures and vibration analysis, to
no avail. The load is evenly balanced across all three phases at about
300 amps. We have current harmonics averaging 20% and voltage harmonics
averaging 6% across the phases. I wondered if you or any of your readers
have ever experienced this.

Thank You
Pat Weldon

 

[bennie]

Re: Humming noise

Remove the cover, tighten the interior fasteners.

 

[catchtwentytwo]

Re: Humming noise

We had a buzzing noise on an I-Line Breaker(also in a major Data Center). In our case, Square D determined that it was related to the internal solid state electronics of the breaker and not an issue.

Does the Cutler-Hammer model have any internal electronic circuitry such as a trip unit? Can you get Cutler-Hammer to do an inspection?

 

[charlie tuna]

Re: Humming noise

300 amps per phase is enough current to cause vibration in items like the ark suppressors. noise is caused by movement of marterials. the most important test you performed was the infrared scan. if the breaker looked normal with even heat distributed(no hot spots inside) i wouldn't worry about it. we have had a few breakers that had internal contact problems buzz, but the contact problem showed up in the infrared scan. remember the added load of your equipment has added load to the entire motor control center and it's making some of this noise also.

 

[brian john]

Re: Humming noise

If this is a circuit breaker (not a switch as you state) and the over current protection is a thermal magnetic, it is possible that the long time (thermal) may be close to the pick up range (though the IR scan should rule this out) Was this circuit breaker primary injected tested prior to being installed as a temporary CB?

If this is a switch as you state then the IR should have resolved the issue and the most likely cause is as stated by others, componet virbration.

 

[Neelesh]

Re: Humming noise

One of the dominant frequency of harmonic spectrum may resonate with the basic material frequency of the CB or its parts that may lead to vibrations.