Phase Converter Causing loud humming noises from CNC transformer

[MsBisMuth]

Hello all! I am helping troubleshoot an issue that kind of has our service department stumped and am looking for more knowledge on how these two systems work together.


Basically, a gentleman has a CNC machine with a transformer, which from his usage, has been getting louder and louder over the past year or so. Its being fed power by a phase converter; 3 phase 240V out. We suspect something within the phase converter, but was wondering; what exactly causes transformers to hum like that? Google makes it seem like it degradation over time, I suspect it could be harmonics to some degree, but what do you think? Im happy to answer any questions regarding this setup, and once again; just trying to learn what causes transformers to hum loudly/louder (over time) when getting power from a phase converter. Any help is appreciated!

 

[jim dungar]

The phase converter likely has little to do with the noise. Your transformer core laminations are vibrating, look up magnetostriction. This can be caused by rust or broken core clamps.

 

[Jraef]

The phase converter likely has little to do with the noise. Your transformer core laminations are vibrating, look up magnetostriction. This can be caused by rust or broken core clamps.

Or… age. In some transformers (especially cheap ones often used by OEMs), the laminations are poorly held together and over time, they become less tight. When that happens, the vibration caused by the magnetostriction is amplified.

 

[kwired]

Is this transformer a single phase control transformer within the equipment?

If so at least try to keep it off the "derived third phase" and connected directly to the main source 240 volt leads. The "derived" phase won't be as steady or clean of a voltage as the main source leads.

 

[synchro]

Does the transformer feed a rectifier? If so, a blown diode could result in DC current flowing in a winding and that causes the core to saturate during a portion of the AC cycle. This could cause a buzzing noise to occur.

 

[hillbilly1]

Maybe some of the caps failing in the converter? Though it would look like the machine would harder to start.