Transformer noise

[BearB]

I have a Line Tamer CLT 5000 GTW Transformer with 120v in and 120 out feeding a Panel for several instrumentation devices. This unit is rated for 29 amps and is pulling 8 amps when measured, nothing on the load side has changed in over a year. It was noticed making a very loud humming noise that started several months ago and once kicked the breaker on the primary side. I can not find information on Line Tamer to see if the unit has capacitors, suspect that could be the source of the noise. I am asking if the above is enough information to consider changing this transformer. I believe it is but this site is great in discussing such question.

 

[jghrist]

What is the voltage measured on the high side? Did anything change that would have increased the voltage?

 

[alehman]

Can you measure the primary current with no load?

 

[BearB]

Thanks for the feedback. I plan to take readings tomorrow.

 

[BearB]

Primary side 114v 8amps, secondary 124v 4amps. Cannot remove load to read no load values because transformer is operating instrumentation that is in use.

 

[jghrist]

Primary side 114v 8amps, secondary 124v 4amps. Cannot remove load to read no load values because transformer is operating instrumentation that is in use.

Hmm! 912 VA in, 496 VA out. Explanation?

 

[waross]

Is this a constant voltage transformer? If so it will probably be working on the knee of the saturation curve. The magnetic forces will be close to maximum. It will be generating a lot of heat. If any looseness develops in the lamination stack you can expect noise.
These transformers are designed with quite a high resistance primary winding to limit the heat and avoid burnout due to core saturation.
How is your input voltage? A higher input voltage means more losses and more heat.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[BearB]

input voltage is 114v. As far as I know it is a constant voltage transformer. I cannot locate information for this device.
Waross if the lamination stack is the noise source, how about reliablity?

 

[waross]

That is very hard to say without being on site.
One of the reasons for this statement and something that you may want to check is the sounding board effect.
There is always some vibration in the core. Often some nearby object is excited by the normal transformer vibration and magnifies the noise greatly.
Your problem may be sympathetic vibrations of another object rather than direct noise from the transformer. It may be a damaged member inside the transformer that is contacting the core, it may be a resilient mount that has lost its resilience. The transformer mounting bracket may be transmitting vibrations to a nearby wall panel.
There may be a shipping bolt that was not removed.
Do a physical inspection. Push and pull things. Use a bar, use a hardwood stick. Make sure that you don't have sympathetic vibrations magnifying the sound level before changing out a transformer. Almost all transformers make some noise. Some are naturally louder than others.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[VibeAC]

It might be possible that a panel or some component of the assembly has come loose, and is now radiated more noise than it did previously. Over time bolts can come loose and change the acoustic radiation impedance of panels. These flexible panels can act like speakers, thus amplifying the noise.

 

[BearB]

We will open it up on a Shutdown and investigate, if nothing loose is found it will be replaced. Thanks.