Re: DC Supply

To: tesla-at-pupman-dot-com
Subject: Re: DC Supply
From: Jim Lux <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Fri, 25 Sep 1998 17:41:18 -0600
Approved: terryf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: Greg Leyh <lod-at-pacbell-dot-net>
> 
> > Original Poster: Mark Finnis <mefinnis-at-medicine.adelaide.edu.au>

> Sure!  Transformers make fine phase shifters, and if you compare
> the two HT secondaries (with respect to the case) on any NST,
> you will see that they are 180deg out of phase.  This is required,
> since if they were in phase, there would be no net voltage difference
> between their HT terminals.
> 
> Consider 3 NST's, with their 3 primaries connected in 'wye' to a
> 3-phase feeder with neutral.  Each primary is referenced to the
> neutral, and is shifted 120deg from its neighbors.
> The center-tap/case of each NST is attached to ground.

But what if the primaries were fed in Delta?  120/208Y is quite common
in light industrial/office areas, because you get the 120V to run
everything. However, in heavier industrial, you see more 240 delta, with
no neutral. Sometimes they ground the centertap of one of the feeder
transformers, so that two of the legs are 120V relative to ground.

Then, you could connect the secondaries of the NST's in delta, with no
problem, but I am not sure about the centertap (having been too busy to
calculate it or try it)

Then you'd have a 6 pulse rectifier....
>