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VK3ABK > TECH 30.11.05 01:01l 30 Lines 1311 Bytes #999 (0) @ WW
BID : 12597_VK3BBS
Read: GUEST DL1LCA OE7FMI
Subj: Re: Microwave Xfmr (ZS1CS)
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<DK0WUE<7M3TJZ<F6KMO<KP4IG<LA2MV<N2BQF<
VK3FIS<VK3BBS
Sent: 051129/0839Z @:VK3BBS.#MEL.VIC.AUS.OC #:12597 XFBB7.04h Bid:12597_VK3BBS
From: VK3ABK@VK3BBS.#MEL.VIC.AUS.OC
To : TECH@WW
Hello Clyde.
You wrote...
"Can anyone please tell me why the Laminations of a Microwave oven's
transformer are welded together??? This is against all theory regarding
eddy currents I was taught many years ago. 73 Clyde ZS1CS"
It's true that most AC inductors and transformers have laminated iron cores,
and this is to limit eddy currents that would react with the magnetic field.
The laminations are 'insulated' by the scale that forms on the hot rolled
steel, and years ago, brass or steel rods, nut and screwed, and passing
through the laminated cores, and insulated from them by fibre washers, were
used to clamp the laminations tightly.
But there was always a small amount of vibration, and consequently noise
that could be annoying. This, and the main reason today, cost, has seen a
quick and cheap 'fix'; the welded strip across the laminations. This has
only a small effect on the eddy currents, and microwave ovens are a prime
case for welding. Cost, and noise in domestic kitchen, being the reasons.
If we had microwave transformers 60 years ago when 'big rigs' were the go,
many kilowatts of Ham RF would have been causing the dreaded 'climate change'.
A few thousand volts didn't do much harm and kept you on your toes. :-)
73. Dick. VK3ABK.
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