> Date: Fri, 20 Apr 2001 15:31:36 +0000
> From: Gunther Schadow <gunther_at_aurora.regenstrief.org>
> To: Sridhar Ayengar <sridhar_at_ikickass.org>
> CC: port-vax_at_netbsd.org, classiccmp_at_classiccmp.org
> Subject: VAX 6000 3-phase conversion (was: Re: Three Phase)
>
>
> Let's look at the plan again:
>
>
> ____________________ +300V
> | | |
> -__ -__ -__ thyristors
> ^ ^ ^
> | | |
> L1 ------* | |
> L2 -----------* |
> L3 ----------------*
> | | |
> - - - diodes
> ^ ^ ^
> | | |
> --------------------- Return
>
>
> ---- FOR 220 V SINGLE PHASE -----------------------------------------
>
> With a 220 V single phase power supply (P and N coming out of your
> receptacle,) as in Europe, Australia, India (?), etc. all you would
> need to do is, e.g., put P on L1 and N on L2. That gives 220 V ~
> input and if this sqrt(2) rule is correct (which I'm still a little
> confused about) you get 220V * 1.414 = 311.8 DC, i.e., just right.
>
> ---- FOR US 2 x 110 V TWO PHASE -------------------------------------
>
> For the US I am thinking that may be the 2 phase 220 V dryer hookup
> is the best way to go. Not only is this line at a convenient location
> where you can store a big cabinet like this one, it is also well
> dimensioned to sustain a VAX or (and may be AND) your dryer. Otherwise,
> just dry your clothes on a line. But do not mistake the VAX's blower
> with your front-loading washer :-).
>
> Seriously, the two phases here, as I understand it, are:
>
> ------- P1
> ------- N
> ------- P2
>
> with U peek = 110 V and the phases of P1 and P2 being displaced by
> 180 degree. So, if you measure U between P1 and P2 you get 2 x 110 V
> = 220 V. So, I would then connect it like this:
This is really 220v single phase. And the 110 refers to the nominal
RMS voltage. Nearer to 120 these days. The peak voltage is, of course
about 1.4x the RMS.
>
> ____________________ +300V
> | | |
> -__ -__ -__ thyristors
> ^ ^ ^
> | | |
> P1 -L1 -----* | |
> (N)-L2 ----------* |
> P2 -L3 ---------------*
> | | |
> - - - diodes
> ^ ^ ^
> | | |
> --------------------- Return
>
> I am not sure whether to use N on L2 or leave N open (again, I
> notice how much I forgot about my high school physics.) This actally
> bugs me, because I don't know quite where to connect to the ground
> potential and how to deal with the protective ground here.
I would strongly advocate leaving one of the three inputs (L1, L2, L3)
open, and connect the other two to P1 and P2. This makes a full-wave
controlled bridge rectifier across the "220" line. The peak voltage
(hence the no-load DC output) would be 220 sqrt(2), about 340V.
The DC output is floating with respect to protective ground, but
will be isolated by the transformer in the switching supply that
runs from the nominal 300V.
carl (amateur electrician)
--
carl lowenstein marine physical lab u.c. san diego
{decvax|ucbvax} !ucsd!mpl!cdl cdl_at_mpl.ucsd.edu
clowenstein_at_ucsd.edu
Received on Fri Apr 20 2001 - 11:48:51 BST