RE: Three Phase Generation and transformer

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hi Dave,

That seems reasonable. I am thinking a counterpoise for RF since this is
mobile 12" and a required ground rod to power sources. You are suggesting
that if I clamp a current probe I should have no measureable current flowing
to the ground rod?

Odd, the neutral on the HV transformer input is combined with what appears
to be the center tap of the 208v primary. What do you make of that?
The transformer core is grounded.

Neutral on the genhead is grounded.

I guess it is reasonable to put my 3 phase fused disconnect at the
generator, yes? Is it normal code to ground the neutral on the step down
transformer to the case and earth? I believe I read somewhere that is code
on the generator.

The HV transformer may need further investigation.

Thanks,
Jim Mora

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Monday, February 19, 2007 3:39 PM
To: tesla@xxxxxxxxxx
Subject: Re: Three Phase Generation and transformer

Original poster: <davep@xxxxxxxx>


 > I am nearing completion of my 3 phase 20KVA Diesel powered generator.
 > Yup, Portable power! The generator is currently wired 277/480V Wye. I
 > have a 480v delta to wye step down transformer which would then be
 > 208/120 (with neutral). My HV supply wants to see 208v 3 phase and a
 > neutral which in turn supplies 28KVDC.
 >
 >     * is it ok to connect the generator 480v wye (sans neutral) to
 > the Delta Primary of the step down transformer?
 >     * If so, how should the wye generator, delta-wye step down
 > transformer, and wye HV step up transformer be grounded?
      Its been a Long time, so if anyone knows better, speak up.

      I would tie the three neutrals together:
       alternator,
       Transformer &
       HVDC supply

      and ground the lot.  If one is available, a
      current transfromer in the 'ground bus', would be
      instructive, should read zero  If not zero, find out
      why.

      I'm thinking earth ground ~should~ be nearest the HVDC
      supply, but not real critical?

      'coil' rf ground' to be 'seperate'.

      As i say, other views welcome.

      best
       dwp