Transformer Hum

[Javier Perez]

Why does ballast transformer hum? what is actually moving inside it to make
it hum? I wonder

 

[Art]

Electro-Magnetic Resonance. The magnetic materials [transformer core pieces,
etc] within the ballast are reacting to the frequencies of the applied
current source and vibrating. The noise will vary with the load, ambient
operating temperature, and length of time in operation. The hum you hear is
the result of these items actually vibrating within the ballast assembly.

 

[Asimov]

"Javier Perez" bravely wrote to "All" (06 Jul 04 04:11:48)
--- on the heady topic of "Transformer Hum"

JP> From: "Javier Perez" <[email protected]>

JP> Why does ballast transformer hum? what is actually moving inside it to
JP> make it hum? I wonder

It is an effect called magnetostriction. Every time the magnetic field
reverses the atoms in the metal vibrate away from each other and then
closer again. On a long piece of metal as in a transformer this may
only be a difference of 1 micron but at 120Hz it is easily heard. The
cure is to mount the transformer on rubber isolators and screw all the
laminations down tight. There will always be residual hum.

A*s*i*m*o*v

.... 'Keep the smoke inside.' -- 1st Rule of Electronics.

 

[Now and then]

because it does not know the words

 

[Cougercat]

Ballast hum is usually due to loose iron laminations in the transformer.

 

[Jerry G.]

I see that in the other replies you received some very factual reasons why
the transformer can make a buzzing or humming noise. As these ballasts
transformers age, they will get louder, because the laminations and windings
will loosen up a bit. This is a more simplified reason for the hum you are
hearing. They all hum to some extent, but the level of this noise will
increase of a period of time. The fix is to replace it.

--

Jerry G. GLG Technologies GLG
==========================


Electro-Magnetic Resonance. The magnetic materials [transformer core pieces,
etc] within the ballast are reacting to the frequencies of the applied
current source and vibrating. The noise will vary with the load, ambient
operating temperature, and length of time in operation. The hum you hear is
the result of these items actually vibrating within the ballast assembly.