🚀 go-pugleaf

In article <15DEC199216354453@almach.caltech.edu> 
shoppa@almach.caltech.edu (TIM SHOPPA) writes:
>The sort of transformer I need is 120VAC to around 20 VAC
>center-tapped, at a few V-A's. As I understand, Toroid transformers can have a
>much smaller radiated EM field than usual transformers. 
>	There are several manufacturers of toroidal power transformers,
>but they all seem to want an arm and a leg ($50+) for even the smallest
>transformers.  Does anyone know of a more inexpensive source for these?
>Alternatively, is winding my own toroidal transformer out of the question?
>I have wound several RF toroidal transformers, but I imagine that a totally
>different core material would be used in a 60 Hz transformer, and saturation
>of the core would be a big concern.  Do any toroidal core manufacturers
>give information on using their cores in 60 Hz transformers?  I'm looking
>for the sort of information Amidon gives on their cores - sort of a cookbook
>procedure on how to make your own transformer.

A quick and dirty approach would be to get a toroidal variable transformer
(Powerstat, Variac, etc.) and wind the appropriate secondary on it.  Our
lab chemists routinely destroy small Variacs used to power mantles and heating
tape. [It is nearly impossible to teach them to use the correct fuse size! ;-) ]
I have quite often repaired these units for home use and used them as the
primary for custom transformers.  Count the turns on the original transformer
to get the turns per volt rating and wind your secondary to your needs.  I use
glass cloth tape the insulate the original Variac.  Watch out to not exceed
the VA rating of the transformer. [Most of our lab units are 1 KVA.]  Also
be very careful of your insulation ratings.  You do NOT want a primary to
secondary short!
					Barry
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|  ___  ________  |    Dr. Barry L. Ornitz          WA4VZQ
| |  / /        | |    Eastman Chemical Company
| | / /         | |    ECC Research Laboratories, Engineering Research Div.
| |< < K O D A K| |    Process Instrumentation Research Laboratory
| | \ \         | |    P. O. Box 1972, Building 167B
| |__\ \________| |    Kingsport, TN  37662  (615/229-4904, FAX 615/229-4558)
|                 |    INTERNET:   ornitz@kodak.com
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