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Re: 10KV RMS -at- 300MA for less than $100



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Tesla List wrote:
> 
> Subject: 10KV RMS -at- 300MA for less than $100
> Date: Mon, 10 Mar 1997 12:41:18 -0500
> From: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
> To: <tesla-at-pupman-dot-com>
> 
> Fellow Coilers,
> Yes, 10KV RMS -at- 300ma for less than $100 delivered in the USA.
> 
> I have run across a transformer that is just about perfect for Tesla Coil
> work, and I want to let you all in on it.
> 
> Herbach and Rademan have 100 of these transformers in stock. They are rated
> at 5,000 volts RMS, 300 ma continuous duty. These are *open-frame*
> transformers, absolutely NO tar or anything else to give you problems. Mine
> came with power factor correction capacitors included.
> 
> There are current shunts installed... which is actually a *plus*, because
> it means you do not need any reactance added to the primary! If you insist
> on removing the shunts, it is very easy to do so, since it is all open
> frame construction!
> 
> The secondary is entirely isolated from the core!
> 
> I bought two of these and wired the  primaries in anti-parallel. This makes
> the phase of the two secondaries *opposite*. That allows me to take the
> inner wires of each secondary and wire them together so that the two
> *outer* wires of the secondaries are oppositely phased. In other words, the
> total series output is now 10,000 volts AC RMS (14KV Peak!) at 300 ma. If
> desired, the inner wires of the secondaries can be connected to AC ground,
> so that the electrical stresses are reduced. But if you want to, you can
> also leave them floating. Both ways work.
> 
> By two for $39.50 each, throw in about $15 for shipping, and you are under
> $100 for an almost perfect 10KV RMS 300ma *open frame* NO TAR transformer
> for your Tesla coil.
> 
> The really daring among you can figure out other combinations of these
> transformers, I am sure.
> 
> Part Number TM92XFR2019  5KV 300ma Transformer  $39.50 each
> 
> Herbach and Rademan
> 18 Canal St.
> P.O. Box 122
> Bristol, PA  19007-0122
> 
> Orders 1-800-848-8001
> Fax 215-788-9577
> Business hours Mon-Fri 8 am - 5pm EST
> 
> Ask to be placed on their mailing list!
> 
> Hope that this is something useful for all of you. This is not exactly a
> pole pig, but two of these will deliver 3,000 VA at continuous duty. Not
> bad!
> 
> Fr. Tom McGahee

Tom,

If these are the transformers I think they are, the capacitors are not
for power factor correction, but are for the ferroresonant coil that is
positioned between the primary and secondary, which, I have been told is
to keep the current and voltage constant. The original use was for
copiers. Some types of these transformers also have a .050 to .060" gap
between the top core piece and the 3 legs of the main core to further
limit current.  I bought several of these transformers a couple years
ago to use with my vacuum tube coil, and although I only paid $8.00 each
for them at my local surplus place, it turned out that they were no
bargain. They performed dismally on my tube coil compared with a
standard plate transformer. 

I still have one of these in my basement shop that has been modified by
removing the ferroresonant coil and eliminating the built in gap in the
core. I just went down to the shop and powered up this unit and measured
2600 volts on the high side with 120 volts in on the low side. Having
just acquired a voltage probe capable of measuring high voltage AC, I
never had measured the output of these transformers before, but it
appears that in order to put out the rated 5000 volts, the ferroresonant
coil and capacitor must be in place as originally designed. Maybe some
of the EEs out there could explain these puppies a little better than I
can!

I would be wary of buying these for disruptive coil work. Especially at
$39.50 each! If I am wrong about the type of transformers these are,
forgive me. The units I have are GE 9T68Y5021G10 and the ones that H&R
has are GE 9T68Y5022G10, one digit difference.

BTW H&R has moved. Their new address is:

Herbach and Rademan Co.
16 Roland Avenue
Mt.Laurel, N.J.  08054

Order phone is still the same: 1-800-848-8001, Office/info 609-802-0422,
Fax 609-802-0465

Ed Wingate






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