Constrained layer damping tape on toroidal transformer?

@ketchup

I would like to know why you say not to use a stainless nut, though. I build a lot of stainless parts for race cars and for food and beverage and try not to use stainless nuts on stainless bolts due to galling, but that’s only if they have a decent amount of torque applied to them. For lightly tightened things like a transformer, though, there usually isn’t a galling problem. So, why not use a stainless nut? You could always use a little bit of anti-seize if you’re worried about galling.

Anti-galling compound should work fine...  I'm just nervous about it perishing and being a problem years down the road.

Just for fun, if you have one of those lazer temperature sensing gadgets, its easy enough to see that a ferrous bolt runs considerably hotter than the transformer itself. Its also easy to see that the latter runs cooler once the bolt is replaced.

Getting rid of DC on the AC line with a DC blocker is the best option. Even a slight amount (less than 1/2 volt) can cause many toroid transformers to become noisy. DC blockers are not expensive.

Most damping materials are also insulators. Transformers need to get rid of heat which can damage their windings. So damping materials can be risky.

Here's a little tip which might help though! The idea of a toroid transformer is less radiated magnetic field which toroids do quite well but they are not perfect. As a result, the bolt that holds the transformer in place should be a non-magnetic material such as non-magnetic stainless. A regular steel mounting bolt is often a magnetic short to the transformer and so its common for the mounting bolt to run considerably hotter than the transformer itself as a result! So replacing the bolt with a stainless bolt can reduce the load on the primary, and can help to silence the transformer.  As a further tip, **do not** use a stainless nut to secure the bolt or you will have to break the bolt to remove the nut. Use a self-locking regular steel nut.


We found this fact out about 30 years ago- but I've yet to run into a toroid transformer vendor that knows it.