noisy transformer

[cj]

i had my transformer in my heil furnace replaced last winter and the new one hums rather loudly...is that a sign of a problem?also, does that mean that the transformer is using electricity even if the furnace is not running?

thanks, cj

[windcrest]

Some things you can try:

If its mounted on a steel J box try rotating the transformer 90 degrees.

Is there anything else on that branch circuit like a refrigerator that could be inducing interference onto the powerline? This can cause a transformer to hum more. Your furnace should be on a dedicated breaker. Some applicances can also leak a little DC on the powerline, wreaking havoc with transformers.

It could simply be a cheapo transformer. Good transformers are wound tightly, the laminations use high quality glue and they are potted in epoxy. Cheap transformers may not even be potted and will always hum more.

Check for a simple mechanical looseness somewhere on the J box.

If all else fails, get a high quality transformer, they are simple to replace. I suspect its just a cheap unpotted transformer or loose lamination on the core.

Yes, it is pulling a small amount of current all the time, but that current varies with the load on the secondary.

[windcrest]

There are a couple of other reasons a transformer will hum besides DC/ interference on the line or loose laminations/windings.

If a transformer was designed for 50Hz and you are using it in the US at 60Hz it will hum, maybe the guy put on the wrong transformer.

If the transformer is underrated for the load it will hum more (and also heat up and fail early) in this case up the rating of the transformer. Maybe he was cutting corners by using a transformer that was rated under or just at the load level, the cost of a transformer is proportional to its current rating with all other factors the same.

If your mains voltage is too high the transformer will hum more, you cant do anything about this, but a high quality transformer will handle it better.

A poorly designed transformer with high magnetic field levels will hum more, again this is probably your problem, a cheap-ass transformer.

[jeff_wisnia]

See if you can dribble, pour or squirt some quick setting epoxy onto/into it. (With the power to it off of course).

That's worked for me more than once.

Jeff

[stan]

I recall once hitting a transformer with a hammer to bang the laminations together and also IIRC correctly, squeezing one in a vise. To also tighten the laminations. Another idea might be to loosen (yes loosen) the bolts holding it down to whatever is amplifying the sound and/or slipping some bits of rubber under the edges!

[windcrest]

You got lucky. The laminations are in the core iron, and the windings completely wrap the core, laminating core iron gives a transformer a much higher saturation point than a solid iron core (the laminations are glued). Hitting with a hammer is more likely to just short the winding by chipping the enamel off the wire someplace because the coil wire will get hit and core untouched.

[Don Klipstein]

In , windcrest wrote in part:

Actually, transformers designed for 50 Hz work better at 60 Hz than at

1. But if this transformer was made for 120 volts, I give low chances it was designed for 50 Hz, since line voltage is 230 volts where the line frequency is 50 Hz (such as Europe and Australia).

60 Hz transformers used at 50 Hz with full rated voltage, on the other hand, will have their cores pushed closer to or more into saturation than intended, and will get hotter than intended and usually hum in the process.

- Don Klipstein ( [e-mail])

[The Daring Dufas]

Like the capacitors, it probably came from China.

TDD

[clare]

Likely Chinese - or possibly Mexican manufacture - most definitely "cheap" even if not low cost. ALL transformers hum a little bit - and all use SOME current even with no load, but the better ones hum less and use less power.