Subject: Re: Converting 3-pahse VAX Power.
To: None <port-vax@NetBSD.ORG>
From: None <>
List: port-vax
Date: 03/29/1996 08:22:50
> Ja, ja. Just a little common sense and a bit of electronics 
> background is all you need. Put in single phase fans and the mod will 
> work. Exactly where/how to do it on a 86X0 (or a 88X0 for 
> that matter) I have no idea , I'm not very familiar with 
> those machines. Goodness knows what line current one of those ECL 
> machines will draw using single phase power , I would make sure the 
> cables are ADEQUATELY rated ! This of course is the REAL reason for 
> using a multiple phase supply on such a machine (not just to run the 
> fans and make your life difficult). It reduces considerably the line 
> current , and in doing so allows cables of reasonable cross section 
> to be used , obviating problems with voltage drops over long cables , 
> etc. Also , the ripple at the output of the 3-phase rectifier of 
> higher frequency than that obtainable with a single phase rectifier 
> (you have 3 voltage (or current) cycles per 360 degrees) , so you can 
> get away with smaller smoothing caps also.

The 86x0 require huge amounts of electricity, 30 A a phase if I 
recall myself right (The powerconnector on my machine is about 3.5cm 
in diameter that would be about 1.3") And changing the fans would be 
a horrible project since they are kind of mounted in the bottom of 
the machine, wich means that you have to strip it all down (You dont 
turn a 86x0 upside down... ;-)
 But i guess thats all hypothetical since anybody with enough 
airconditioned space to house probably got a three phase connector 
aswell (or can afford to install one)..