To stack toroidal transformers, or not?

[falcott]

A question, if I may, as I'm at the design/layout stage:

Is it permissible to stack 3 toroidal transformers on top of each other, and running a single bolt through their centres? I'm guessing that the shorted turn phenomenon shouldn't be a problem, but what about magnetic interference (or whatever) of one affecting the performance of the other? Should they be spaced apart with, say, a 10 plywood spacer?

Thanks for your thoughts.

 

[Jocko Homo]

Worked on a 5-channel amp a while back that stacked all 5. They were laid on their "sides", and had a "semi-circular" plate on top. Bolts ran from the plate downward to the chassis bottom. The bolts served as spacers between them.

Jocko

 

[rcavictim]

The magnetic fields in torroidal transformers are well contained compared to other traditional core types but I wouldn't stack a power xfmer toroid in the same stack as the two output transformer toroids. You'd be asking for hum in the speakers. You should be fine stacking power torroids together. You could stack L&R channel o/p toroids but I think it wouldn't hurt from a channel separation point of view to use a plywood disc as you suggested between them. Say 1/2-3/4"?

 

[falcott]

Thanks guys.

All 3 of the transformers to which I refered are to power amps and valve/tube filaments, so it should all be good.

(I just noticed that I missed out the "mm" after "10" in my last post, but I'm glad to see that it didn't throw you too much!)

Cheers!

 

[AndrewT]

Hi,
both your toroids will generate heat.
Try leaving an air gap either through the cores or between the toroids so that the top once does not get excessively hot.
Normally they would radiate heat out through edges & top face.
regards Andrew T.

 

[falcott]

Hi Andrew, yeah, I never thought of that.

These torroids, as supplied, are normally mounted sitting on the chassis, with a circular plate clamped on the top, effectively cutting off all airflow from the centre of the transformer anyway.

Maybe I can get some convection going if I drill holes in the top mounting plate, and allow some air between the transformers.
I just need to work out a way of doing that, without creating localised pressure on some of the windings...