Re: Wiring two 15KV 240V/50Hz Transformers in Series for use with 110V (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sun, 17 Jun 2007 07:43:03 +0800
From: westland <westland@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Wiring two 15KV 240V/50Hz Transformers in Series for use with 110V
    (fwd)

As it turns out, the solution to my problem is right in front of me.  My 
variac has 0 to 230V output and either 110 or 220v input, so I can just 
use this as the step up transformer

Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Sat, 16 Jun 2007 11:22:29 -0400
> From: Marko Ruban <Marko@xxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Wiring two 15KV 240V/50Hz Transformers in Series for use with 110V
>     (fwd)
>
> What if you disconnect the middle tap in both NSTs, and then connect one
> output terminal of each to both cases, thus making a new "middle tap". 
> Just a thought.  I'm sure you'd need to select the right terminals, to
> keep the secondary windings in the same direction, otherwise they will
> cancel the potential.  Of course the old middle taps might arc to the
> casing if left uninsulated.
>
>
> Tesla list wrote:
>
> ---------- Forwarded message ----------
> Date: Sat, 16 Jun 2007 08:48:23 +0800
> From: westland <westland@xxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Wiring two 15KV 240V/50Hz Transformers in Series for use with 110V
>     (fwd)
>
> Gary:
>
> Thanks so much for the insight.  I would never have known this.  Is 
> there a particular reason for having a tap in the middle of the secondary?
>
> I suppose I could grab 230v off of the mains, but my setup is less than 
> 1KVA, so I probably will just buy a step up transformer here (they are 
> much cheaper here) and put it in with the transformers.  Or maybe just 
> buy some new transformers when I'm in the US
>
> Thanks again
>
> Chris
>
> Tesla list wrote:
>   
>
> ---------- Forwarded message ----------
> Date: Fri, 15 Jun 2007 09:42:34 -0400
> From: "Lau, Gary" <Gary.Lau@xxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: RE: Wiring two 15KV 240V/50Hz Transformers in Series for use with 110V
>     (fwd)
>
> Hi Chris:
>
> Sorry, but you can't do what you propose.  15kV NST's are made with the
> secondary midpoint connected to the case.  If you connect the
> secondaries in series, the two cases will have 15kV between them.  The
> primary-to-case insulation is not designed to sustain that and will
> fail.
>
> Most US households have 240V available in the breaker box to power
> electric stoves, dryers, and other large appliances.  You'll have to use
> the NST's at their rated input voltage.  If you're in an apartment that
> doesn't have 240V available, your only alternative is to get a 120/240
> step-up xfmr.
>
> Regards, Gary Lau
> MA, USA
>
>
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> Date: Fri, 15 Jun 2007 14:10:05 +0800
> From: westland <westland@xxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Wiring two 15KV 240V/50Hz Transformers in Series for use with
>     
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>
> 110V
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> I have an interesting variant on one of the questions that just came
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> up
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> about series wiring of transformers.  I'll be moving to Chicago in two
> months, and from 220V to 110V mains.  I currently have two 15KV
> 240V/50Hz/0.03A Transformers wired in parallel (for .060A) that power
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> my
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> TC.  I'm wondering if there is any problem switching leads around for
> 110V/60Hz ... running the secondary in series, and the primaries in
> parallel.  I figure since its a 50Hz transformer, it's already about
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> 20%
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> overengineered, and the secondaries takes 15KV at .03A, so I should
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> end
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> up with output of 15KV at .03A (rather than the 0.03A I get in Hong
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> Kong).
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> I'm looking for a sanity check on my logic, just to make sure that I
> don't bring them to the States only to burn them up.  Clearly, I can
> keep the current arrangement, and just precede them with a 110 to 220V
> stepup transformer.
>
> Chris Westland
>
> --
>
> ___________________________________________________
>
> J. Christopher Westland, PhD CPA
> Professor, ISMT, University of Science & Technology, HK Clearwater
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> Bay,Kowloon,
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> Hong Kong
> Tel: 852 2358 7643
> Fax: 852 2358 2421
> Mob: 852 9528 1745
> URL: ihome.ust.hk/~westland
> Mobile e-mail: chris.westland@xxxxxxxxxxxx
>
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-- 
____________________________________________________

J. Christopher Westland, PhD CPA
Professor, ISMT, University of Science & Technology, HK Clearwater Bay,Kowloon, Hong Kong
Tel: 852 2358 7643
Fax: 852 2358 2421
Mob: 852 9528 1745
URL: ihome.ust.hk/~westland
Mobile e-mail: chris.westland@xxxxxxxxxxxx