----- Original Message -----
From: "Anders Hogrelius" <ahs@hogrelius.nu>
To: "Gunther Schadow" <gunther@aurora.regenstrief.org>
Cc: "Sridhar Ayengar" <sridhar@ikickass.org>; <port-vax@netbsd.org>
Sent: Saturday, April 21, 2001 2:31 AM
Subject: Re: Three Phase


> Take a look at this page. It has some info on converting a VAX from 3
> phase to single. There are also some bits on the possible pitfalls.
The
> problems described might or might not apply to the VAX 6000 as well.
>
> http://vaxarchive.org/swdoc/bsd/vaxine/section6.html

Okay, seen this page before, unfortunately, not until AFTER I had done
my conversion(s).
This is similar to my method, except I connected the 240vac between one
of the actives and neutral (return)
This gives a little over 300v, but it has been fine on my first attempt
for over 5 years.  I don't know if they are
actually regulating the 300v rail or not.  Considering all it does is
feed some switchmode PSU's that produce
all the voltages used by the system, I don't really see any point, as
long as it's within reasonable tolerances.
The problem you guys in North America have is this 110v single phase
business.  I'm starting to think that
a ~1KVA 110v to 220v transformer may be the solution, though I'm
buggered if I know where you'd find
something like that.


            ____________________    +300V
            |    |    |
            -__  -__  -__  thyristors
            ^    ^    ^
            |    |    |
  L1  ------*    |    |
  L2  -----------*    |
  L3  ----------------*
            |    |    |
            -    -    -    diodes
            ^    ^    ^
            |    |    |
            --------------------- Return

I'll pull one of my 300v supplies down over the weekend (it's Fri
evening here now) and see if it looks like this.  I seem to recall that
there are several variants of the supply, and that they have somewhat
different input circuitry, but basically do the same thing, slightly
different ways.
(I've made 3 of them work on 240vac single phase - that's easy, but the
110v looks to be more complex.
2 phase using the differential should work, that would give you around
the 220v you are looking for, you will just need to
convince the mains input box there are 3 phases there, not two,
shouldn't be too hard, it's trivial to make it single phase,
you'd just need to bridge one of the actives across to the non existant
phase, the only place they get used other than the 300v
supply is in the switching, which is fairly straightforward.  The main
switching is done by a contactor (3 phase relay for want of a better
description).

Can someone confirm that you also have available 220v single phase in
some form?
Or is the 'dryer circuit' I keep hearing about 2 or 3 phase?  I've seen
conflicting information.

Cheers

Geoff in Oz