Understanding Transformer Noise: Causes and Solutions

[the Physic freak]

If a transformer has loose parts, then a hum is heard while there is current flowing through the primary coil. how do you explain this noise?

 

[chroot]

Sounds like a homework problem. What are your thoughts?

- Warren

 

[the Physic freak]

could it be because the coil vibrates?

 

[chroot]

Well, the loose part -- whatever it is -- is pulled back and forth by the changing magnetic field, right?

- Warren

 

[the Physic freak]

oh ic, thanks a lot ^^

 

[Averagesupernova]

Well, the loose part -- whatever it is -- is pulled back and forth by the changing magnetic field, right?

- Warren

I envision the following inserted in the answer space of a homework question: The loose part -- whatever it is -- is pulled back and forth by the changing magnetic field.

 

[chroot]

Yeah, well, you can't win 'em all.

- Warren

 

[the Physic freak]

what do you mean averagesupernova?

 

[fawk3s]

whats the loose part? and how can you be sure its metal :P?

 

[vk6kro]

Hint:

Go to Wikipedia and look for Laminated Steel Cores under Transformers.
http://en.wikipedia.org/wiki/Transformer

 

[vk6kro]

Just to wrap this one up a bit...

The laminations in a transfromer all get the same magnetic polarity induced in them by the changing current in the coil, so they tend to repel each other. If they are not adequately clamped, they can tend to hum or even rattle a bit.

Likewise, the coil interacts with this changing magnetic field and it can experience forces, too. So you can get coil movement and corresponding sounds.

 

[Bob S]

There are three possible sources of hum:
Loose lamination(s)
Loose coil or coil windings
Magnetostriction of iron

 

[negitron]

Four, if you count loose mounting hardware as part of the transformer.

 

[b.shahvir]

The hum is due to property of 'magnetostriction' exhibited by ferromagnetic materials. It is due to the elongation and contraction of the core laminations at 100 times/sec (for 50Hz supply) and causes noise due to vibrations. Go to wikipedia and search for 'magnetostriction', you will get the detailed theory for the same.

The hum is also due to the magnetic forces of attraction and repulsion between the primary and secondary windings as well as between identical windings when the transformer is considerably loaded.


Shahvir