02GF74
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| posted on 31/1/16 at 10:35 AM |
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transformer mounting, fishing for ideas
I have a pcb transformer i wish to mount on a flat steel panel without using a pcb. There are four 3 mm hokes. Ideally id like to use nylon bolts but
they would need to be 40 mm long, not sure they are avaikable.
Not sure but steel bolts make be ok but will they short out the laminations? probably not and even if they did, it shoudont impair operation as there
is a bead of weld each side to hold them together. (Need to remind myself about transformer design). This would be best as it keepssoace required to
a minimum.
So far im thinking of bolting al sheet then use cable ties through the holes, unless there are other suggestions.
Photo below.
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Slimy38
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| posted on 31/1/16 at 10:42 AM |
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Nylon sleeves and washers then slightly thinner steel bolts through the middle?
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r1_pete
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| posted on 31/1/16 at 10:45 AM |
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The 'standard' method is to cut a square hole in the sheet for the plastic insulator and contacts to drop through, then 4 steel screws.
The laminates make up the 'core' it not part of the circuit so no worries about shorting.
 
trans in amp
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02GF74
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| posted on 31/1/16 at 10:53 AM |
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Not electrical shorting but magnetic. This is going back many years but from memory to reduce losses from eddy cuurents, the core is made from slices
of iron insulated from each other, im guessing the 'shorting' depends on the contact area.... this is the bit i need to research.
Btw ive found two ebay sellers doing 40 or 42 mm m3 screws so problem is possibly solved, depends on how sturdy they are, steel would be preferred
choice. I guess i could try it and see how hot it gets 
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Dingz
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| posted on 31/1/16 at 11:28 AM |
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Brass screws?
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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02GF74
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| posted on 31/1/16 at 12:23 PM |
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quote:
Originally posted by Dingz
Brass screws?
I believe we have a winner.
As I suspected, a magnetic bolt e.g. steel would short out the laminations increasing losses (as heat) but the transformer is so designed so the bolt
holes pass through the laminations where there is least magnetic flux - explains the weld bead.
In conclusion, steel bolts could be used, stainless steel (less magnetic) are better but brass is better still. Nylon bolts will creep.
Thanks to all replies - I think we're done on this one.
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MikeRJ
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| posted on 31/1/16 at 09:13 PM |
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You won't get any magnetic 'shorting' by mounting this on a steel panel with steel bolts/spacers and nuts. This only occurs when
you form a shorted turn which passes though the magnetic circuit, e.g. through the center of a toroidal transformer. This is quite difficult to
achieve accidently on a transformer with E/I type laminations.
FWIW this is exactly how many valve amps mount the transformers on a chassis.
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