Re: Test question

To: tesla-at-pupman-dot-com
Subject: Re: Test question
From: "Barton B. Anderson" <mopar-at-uswest-dot-net> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Fri, 25 Sep 1998 22:57:05 -0600
Approved: terryf-at-verinet-dot-com

Patti, af few comments,

Tesla List wrote:
> 
> Original Poster: "Patti" <asrai-at-palmnet-dot-net>
> 
> Greetings,
> 
> Last weekend was a dud for firing up my coil, and with the hurricane
> expected to throw rain up my way looks like not this weekend either.  So in
> the meantime, I engaged into some checking utilizing low voltages from my
> control cabinet and a couple of VOM's.  These were my results:
> 
> Test 1:
> 3.08 VAC on X1 and X2 (input) 120-0 leads
> 370 VAC on high voltage bushings (output)
> 120:1 ratio approxomatly
> Therefore: 240 VAC in, 28800 out
> 
> I know the output current would be reduced, but would the KVA rating be
> halved?  I'm thinking it would be since you are now using one set of
> windings on the primary.

First of all, putting 240 in a 120 designed winding cast
concerns. Output current would be halved, kva will
remain constant, but output voltage doubles it's design.
Possibly the output winding can handle this situation,
but you are pushing the design of both of these windings
and output current capabilities. Is it really necessary
to push it to twice it's rating? Think about the p-p
conditions = 56kv+ rms (tough to design or buy caps
capable of the instataneous voltages).

> Test 2:
> 3.00 VAC on X1 and X2 (input) 120-120 leads
> neutral being disconnected from output lug and connected together
> 180.0 VAC out
> 60:1 ratio (this is what I expected)
> Therefore: 240 VAC in, 14400 out
> 
> My question is, even though the skematic diagram on the nameplate shows that
> the two primary leads are connected together to form the X2, why is it that
> there is no output until the two leads are disconnected from the X2 and left
> connected together?

Well, if I understand your question correctly, unless
the two primary's are connected in series, you wouldn't
be putting voltage across the windings because in
reference to X2 and the input voltage of these two
windings, these input voltages would be 180 degrees out
of phase and the sum would always = zero.

Leaving the center input tap open simply provides the
series connection.

Bart

> Thanks!
> Patti