Gluing Ferrite Cores

Gluing Ferrite Cores  -  John Dunn, Consultant, Ambertec, P.E., P.C.

Audible vibration can be troublesome with ferrite core transformers. There is no set of "do this and do that" instructions that can be guaranteed to stop the noise, but there is one thing that can be suggested as a start.

When a ferrite core is made up two pieces that are mechanically joined just with mounting hardware, the two core halves may need to be epoxied to each other as the core shown just below was epoxied.

Mounting hardware alone may not be sufficient to suppress audible vibration between the core halves and trying to suppress that noise by tightening the hardware too much can crack the ferrite.

This core, which was dissected out of a now defunct SMPS unit, has its core halves bonded with an epoxy which is so strong that it must have been mixed together by Superman's daddy, Jor-El, on the planet Krypton.

I've tried to separate these two core halves from each other just as you see them here with no mechanical restraint other than the epoxy itself and I just can't do it. I've tried to cut into the epoxy with a blade and I can't do that either.

There were several such magnetics assemblies in the working units from which there was no acoustic noise at all.