Toroidal transformer hum

[Armadillo]

Simply put some damping material in contact with the thing..

Any material that is non-magnetic and non-flammable/melt-able at normal temperatures.
 so that the energy is used up in it.
Also, how the toroid is mounted would make a difference.

Don't even waste your time listening to it.      

[adauphin]

I wanted to update this issue as I heard the hum again a few times over the last few weeks. Each time I opened the sub panel breaker and the hum stopped.

Tonight it hummed lightly again so I shut down one breaker at a time in the sub panel. Last time I did this I don't remember anything happening, but this time it was different.

When I opened the breaker for the microwave, the humming stopped, was dead silent. The microwave was not in use, only the clock and the two incandescent surface lights.

I closed the breaker again and the humming was still gone.

What can be in the microwave that could possibly allow DC into the mains after a period of time?

Anything else come to mind?

[Richard Head]

Armadillo
Magnetising current is load independant.
But it is very much Volt.Second dependant.

[Armadillo]

Armadillo
Magnetising current is load independant.
But it is very much Volt.Second dependant.

Are you responding to me?
Nevertheless, from what you say, then forget about transformer VA rating.
Just apply enough V for enough S Not in the real world.

Edit: Thanks for pointing out. In my previous response, i should use load current instead of Im.