Re: [CAD_CAM_EDM_DRO] twin transformer ?

Sounds like the unit with two seperate sets of coils is a CV (constant
voltage) transformer. (There should also be a set of 'magnetic-shunt'
lamination stacks separating the two coils). They're commonly used in
'brown-out' susceptable areas, where high reliability is necessary. They
usually construct the CV to be able to output rated voltage when the input
sags as much as 20 percent! Draws current like hell, though, under those
conditions... noisy, too!
The other trx may just be to feed the power circuits the unit was developed
for. With no rating nameplates, it's hard to guess their actual use. If
you give me the dimensions of the core (height, width) and depth of the
laminatiion stack, I can calculate about how much power you could handle
with the regular transformer (but not the CV unit). Then, if you could
calculate the turns for me, I could probably tell you the approximate
voltage the unit was designed for. Wrap, say, ten turns of insulated wire
around the coil, connect those ten turns in series with another coil
(making sure they 'add') and apply 1 volt across the ten turns. The number
of turns on the 'test-coil' should fit the ratio of 10 turns per volt = 10X
turns per volt of the test coil. eg 1 volt : 20 volts is 10 turns : 200
turns. (Here is where a Variac comes in handy!) I'll go off-line, if need
be, but other DIY's may gain some insight here.

RayHex

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> From: dave_ace_me <davemucha@...>
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] twin transformer ?
> Date: Wednesday, April 03, 2002 8:34 PM
>
> Hi,
>
> I was lucky enough to get a junk yard transformer/cap/set of diodes
> from what I think was some sort of telecommunications unit. It is
> marked ROLM Corporation on the enclosure and is dated 1983.
>
> There are two large transformers, some model or part numbers, but
> unfortunately no manufacturer name.
>
> One transformer has a 7" x 8" steel square frame and it has two sets
> of coils inside. One is a little over 5 inches in diameter and one
> and a half inches long, the other is also about 5 in dia and about
> 3.5 inches long.
>
> The main power is on the small coil and the output is on the larger
> one. The output goes to 4 diodes to get DC, and to a 68,000 uf / 75
> volt cap and above the cap is a label 48 Volts RMS. There is also a
> 100 ohm 55 watt resistor across the cap.
>
> The smaller coil has 5 leads, 2 are connected to input power and the
> large coil had 4 leads. 2 go to a set of diodes, I am sure to
> rectify the AC to DC. the other 2 leads on the large coil go to a
> small cap, 20uF 440 VAC. There is no connection between the two
> coils so one must feed the other thru the frame.
>
> Can anybody shed light on this thing ?
> Obviously, my first question is how much power would such a large
> transformer have ?
> and my second question is can I use it to drive a herd of Gecko's ?
> (a gaggle of Geckos?, flock...pack...)
>
> Then why the 100 ohm across the cap ?
>
> The other transformer is just a large unit, 5" x 6" on the frame and
> 4 inches dia on the coil and th coil is about 3.5 inches long. I
> think I should be able to figure this one out. Just keep adding load
> until it gets hot (?) 8 wires so I will have some fun figuring the
> combinations out.
>
> If anyone would like to see a pic, I could post some or e-mail.
>
> Dave