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Re: DC Supply



At 04:16 24/09/98 -0600, Greg Leyh wrote:

...Snip...

>Remember, with center-tap grounded secondaries, the windings 
>cannot be connected directly together in either delta or wye,
>since now you will have *six* phases to worry about (2 per
>CT'ed secondary).
>Each secondary HT terminal must go to its own full-wave 
>rectifier set (consisting of 2 stacks), and the DC outputs 
>of the rectifier sets can then be bussed together. 
>
> ---------------------- +
>             |_
>             D^
>             |
>    HT ------o
>(6 places)   |_
>             D^
>             |
> ---------------------- -
>
>The resultant DC voltage will be symmetrical around ground.

Greg, Jim, Bert H, Malcolm & Others,

I don't get this.  Surely the two NST secondaries, centre-tapped are
*in-phase* with each other.  There can only be 3 phases, to have 6 would
imply phase shifting by the transformer ????

Imagine using paired MOTs on each of the 3 phases, running the secondaries
in series ....... why would they be out-of-phase ?

The real question is "what to do with the centre taps".   Jim Lux, who
started this question, thinks I should still ground them.

To my simple medical mind.  The only effect grounding the centre-tap should
have is to reference the rails to +/- 7.5 kV, as opposed to "15 kV floating
in the breeze".

Following Greg's diagram above.  Surely this would give me 7.5 kV rectified
at double the amps, cf. 15 kVAC ??

As stated, I am **WAY** out of my depth here .......

Some other EE or experienced coiler care to comment ...... PLEASE !

thanks ......


Mark

http://www.cobweb-dot-com.au/~dkfinnis