🚀 go-pugleaf

In article <845@gt-stratus.UUCP>, chen@gt-stratus.UUCP (Ray Chen) writes:
> A friend of mine found me what seems to be a 2500 watt isolation
> transformer.
> 
> It's black, *heavy*, and made by Freed Transformers of Brooklyn, NY.
> Dimensions are 10" long X 6" wide X 7" high (or so).  The thing weighs
> a ton.  We managed to put it inside an industrial strength milk crate.
> So now 2 people can lift it and not get hernias if they're careful.
> There are 2 sides with terminals.  One side says "Input 115 V/50 60 Hz".
> The other side says "Output 25KVA".  We think that's a misprint that
> should read "Output 2.5KVA" as the concept of a 1 cubic foot
> 25,000 watt transformer boggles the mind.
> 
> There are some numbers on the top that read "5950-856-1800" and
> "37076".

	The "5950-856-1800" is a universal military stock number, indicating
that this was built for the government.  I don't have any NSN directories,
so I can't offer any help. 
	The "37076" is probably a date code of sorts, since normal Freed
part numbers for transformers are all alphanumeric.  An example Freed
p/n for an isolation transformer is IT4, and for a ferroresonant transformer
is MCV61000LC.
	According to a Freed catalog, they don't manufacture isolation
transformers greater than 500 va, and they don't manufacture ferroresonant
transformers greater than 1.0 kva.
	Since this is a military transformer, Freed could have made almost
anything under these circumstances.  Bear in mind that ferroresonant
transformers ALL require capacitors; if this is a ferroresonant device then
you are either going to find a removable plate which will reveal capacitors,
or you will find additional terminals for external capcitors (military
ferroresonant transformers made by Freed all have external capacitors,
according to their catalog).
	I have a funny feeling that this is NEITHER an isolation transformer
NOR a ferroresonant transformer.  I don't know what it is - it may even be
a high-voltage transformer which puts out 25 kilovolts.
	My advice is to forget it, since you don't know what you are
getting into.  If you are bound and determined to power it up, use extreme
CAUTION in case it is 25 kilovolts on the secondary!


> 	Output	    Xformer	Wall
> 	+ ---------- +|+ -------- +
> 	GND --        |        -- GND
> 	- ---------- -|- -------- -
> 
> Is this the right way to do it?

	That's a conventional method of connection, but the +/- business
bothers me.  Turns direction on AC transformers are usually designated by
a "dot" on the "start" of winding, or by "S" and "F" to indicate start and
finish terminals.

> Third, anyone got any idea on how much E&M (RFI, whatever) this
> thing will put out?

	Plain 'ole transformers generate no RFI, but do generate a weak
magnetic field.  I certainly wouldn't be concerned about anything at least
2 feet away.  Ferroresonant transformers do generate some RFI, but it
is rather low frequency, and limited to powerline harmonics (<< 1 KHz).

> Fourth, any ideas on heat output?

	A very rough guess is a 5% energy loss to heat on a conventional
transformers.  UNloaded ferroresonant transformers can get quite warm.

> Sixth (just for fun), how bad do you think the noise might be?

	Probably less noise than the fans on your PC, unless the transformer
is a real pig with loose laminations.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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