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

["Tesla list" <tesla@xxxxxxxxxx>]

---------- 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


  
    

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
    
      

110V
  
    

I have an interesting variant on one of the questions that just came
    
      

up
  
    

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
    
      

my
  
    

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
    
      

20%
  
    

overengineered, and the secondaries takes 15KV at .03A, so I should
    
      

end
  
    

up with output of 15KV at .03A (rather than the 0.03A I get in Hong
    
      

Kong).
  
    

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
    
      

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