Re: Power Supplies (paralleling transformers)

To: tesla-at-pupman-dot-com
Subject: Re: Power Supplies (paralleling transformers)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Sun, 28 Sep 1997 08:01:15 -0600 (MDT)
Approved: mod1-at-poodle.pupman-dot-com


---------- Forwarded message ----------
Date: Sat, 27 Sep 1997 10:39:38 -0700
From: Jim Lux <jimlux-at-earthlink-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Power Supplies (paralleling transformers)

First, make sure that they are all the same mfr and model.  If they aren't,
you are doomed to trouble because the series impedance of the transformer
will be different and the current won't share evenly.  There are techniques
to get around this particular problem.

Assuming they are all the same model and mfr, the polarity should be
identical for the same connectors, so you just hook identical terminals
together.

Now, if they aren't identical, you have a challenge in front of you.  Here
is one way: Assume that one transformer has two HV outputs: H1A and H2A. 
The other has outputs H1B and H2B.  (Label them arbitrarily).  Connect H2A
and H2B together. Hook an AC milliammeter between the remaining high
voltage outputs: H1A and H1B.  Connect the primaries in parallel in one
configuration of the two possible.  With the primaries fed from a variac,
or a big series resistor (a 40W light bulb will work nicely), measure the
current.  If the transformers are identical, and phased correctly, there
will be no (or minimal) current flow.  

Now, reverse one of the primaries, leaving the HV secondaries connected the
same.  Apply power. Now, you should see some current flow (essentially, you
have two shorted secondary windings in series with the current limited by
the leakage inductance).  

Ask if you have questions.

----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Power Supplies
> Date: Friday, September 26, 1997 8:49 PM
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Sat, 27 Sep 1997 13:10:44 +1000
> From: The Meyer Family <meyer-at-webfront-dot-net.au>
> To: tesla-at-pupman-dot-com
> Subject: Power Supplies
> 
> Hello,
> 	My name is Andrew Meyer, I am 16 years old and enjoy experimenting with
> high voltage devices especially Tesla Coils. I am writing to see whether
> anyone can help me. My original coil (6" diameter) has been powered by
one
> 12kv Neon Sign Xfmr at 30mA. I have recently obtained five more NST's to
> hook into the coil. I am writing to ask how you determine the polarity of
> the transformer so you can hook up all of the -ves and +ves together?
> 
> Thanks :->
> 
> meyer-at-webfront-dot-net.au
>