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Old 13th July 2011, 04:50 AM   #1
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Default Toroid Transformer mounting question

I have a question about the mininum space that a toroidal transformer can be mounted to the enclosure side wall/heatsinks? I have a project that I want to build, but I am worried about the space between the sides of the enclosure and the toroid. I have a total of 4.5mm to 5mm on either side of the toroid.

Is there any mechanical problems that will be a deal breaker? Insulation between the heatsink and toroid is no problem just curious if it will humm, buzz, etc.

I will try to shoot a pic later,

Thanks for any input

Steve
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Old 13th July 2011, 06:17 AM   #2
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Quote:
humm, buzz
That's usually due to the design of the toroid and/or due to DC on mains. So far I haven't had any issues with noise due to close mounting to metallic parts (noise due to proximity to the pcb I know however very well).

Hannes
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Old 13th July 2011, 06:26 AM   #3
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Here is what I am working with. This is a 15.75inch long Aluminum I beam. I want to cut out a notch and mount the toroid on the bottom along with both PSU PCB. I have a Antek 5415 toroid 4x15V 400VA to make a dual mono block Mini Aleph with.

I will then attach my heatsinks to the I beam, and the notch will provide the clearance i need to fit the toroid into the design. I can turn on its side and cut out extra material, however, That would remove material and effect heat transfer from from to back, and the amp PCB would not be shielded from the power supply.

I am hopeful that this will be possible. The bowl lid is the same size of toroid, here you can see how close it really is!


pic attached:
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Old 13th July 2011, 09:45 AM   #4
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Quote:
and the amp PCB would not be shielded from the power supply.
Alu does not provide any shielding as also iron does not. Count only on mu-metal for significant shielding.

Keep the pcb at least 10cm away from the toroid (certainly more is better), otherwise you've great chances to get nice humm. (depends on wether its only the output stage board or there is some voltage amplification as well going on)

Hannes

Last edited by h_a; 13th July 2011 at 09:47 AM.
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Old 13th July 2011, 12:15 PM   #5
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go ahead, but don't expect any magnetic attenuation.

Ferrous materials will modify the magnetic fields around the toroid transformer.

buzz due to winding or lamination vibrations are best reduced by vac vac varnish impregnation.

buzz or hum or grumble due to non symmetrical AC mains waveform is best reduced by a DC blocker in the primary circuit. Research this thoroughly. There are very severe risks if done incorrectly.
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Old 13th July 2011, 01:57 PM   #6
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I am glad to find out that the small mounting area should not cause any problems. I can proceed with building the case now. I have had the amps running for some time now with no humm, buzz, or any other problems. I know that alot of things come into play, and that when I started to case this amp up I might run into something.

Thank you for the information and now its time to drill.

I will update soon.

Steve
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Old 14th July 2011, 12:05 PM   #7
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Quote:
I will update soon.
Don't forget: we want to see pictures

Hannes
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Old 14th July 2011, 12:41 PM   #8
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In my experience,the most important things to consider are; avoid mounting active circuits or pc boards too close to the transformer to aviod hum from magnetic field leakage as was already mentioned, especially along the mounting bolt axis where the field has the most strength; don't mount the transformer to the chassis so that the mounting bolt creates a shorted turn, bolt and mounting hardware should contact chassis at only one point; and be sure transformer has adequate air exposure for cooling.

Mike
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Old 14th July 2011, 11:48 PM   #9
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UPDATE:

Day one: Notch I-Beam to clear the toroid. I think this came out pretty well. This is a tight fit.
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File Type: jpg 004.JPG (746.5 KB, 670 views)
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Old 3rd September 2011, 07:05 AM   #10
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Here are some pics.

All fab work is about done. I will finish the back panel AC input, XLR, Power switch tonight, and then run all the wires also.

Then tear it all down and clean, prep, and finish it up.

This thing is a TANK!
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