On Mon, 3 May 2004, Patrick Finnegan wrote:
> On Monday 03 May 2004 22:14, Tony Duell wrote:
> > > 208 is really a 240 volt 3 phase system measured in a star
> >
> > Is it? I'd assumed it was 120V neutral-phase, which is then 208V
> > phase-phase.
>
> Tony is right here. At least in Indiana, Illinois, and the Code Book,
> 208 three-phase is a "Y" setup with 120V from each phase to neutral,
> and 208V from phase to phase. 240V three-phase is a delta setup, with
> the neutral half-tapped between two phases, giving 240V phase-to-phase,
Wait a minute! By definition, a delta configuration can have no
neutral. Else it is no longer delta.
- don
> 120V phase-to-neutral on two of the phases, and 208V phase-to-neutral
> on the third one. It's important to realize when wiring a system like
> this that the third phase is NOT 120V to neutral like the other two,
> I've heard of some people (idiots) ignoring that, and having issues
> when they tried to turn on their 120V lamps they just wired. : )
>
> > > I have not looked at any 3 phase power supplies for computers, but
> > > I would bet they are 240 volt 4 wire and don't bother with the
> > > neutral at all, just 3 phases and a ground.
> >
> > Not at all. A very few PSUs are genuinely 3-phase, and some large
> > disk drives have 3 phase motors. But in the case of DEC machines at
> > least, the individual PSUs are single-phase units run between a phase
> > and neutral (star connected). Of ocurse the load is approximately
> > balanced between the 3 phases (or it is if the machine is configured
> > properly).
>
> Agreed.
>
> Pat
> --
> Purdue University ITAP/RCS --- http://www.itap.purdue.edu/rcs/
> The Computer Refuge --- http://computer-refuge.org
>
Received on Mon May 03 2004 - 23:14:04 BST