[Info-vax] OT: the Daily WTF for today is a VAX/VMS story

[Kerry Main]

> -----Original Message-----
> From: Info-vax [mailto:info-vax-bounces at info-vax.com] On Behalf Of
> already5chosen--- via Info-vax
> Sent: 14-Feb-16 4:49 AM
> To: info-vax at info-vax.com
> Cc: already5chosen at yahoo.com
> Subject: Re: [New Info-vax] OT: the Daily WTF for today is a VAX/VMS
> story
> 
> On Wednesday, February 10, 2016 at 10:03:18 PM UTC+2,
> rdpi... at gmail.com wrote:
> > See
> >
> > http://thedailywtf.com/articles/overpowered
> >
> > for a nostalgic trip down memory lane.
> >
> > RDP
> 
> There is one technical detail that I didn't understand: how did hard drives
> get their three-phase AC power when operating from battery ?
> 
> Also something sounds wrong with rpm. 3000 rpm is a correct AC
> frequency in the most of the world, but this particular story happened in
> USA, right? Isn't it 3600 rpm there?
> 
> More I think about it, more the story of VAX hard drive with three-phase
> AC motor (in early 90s, non-the-less) appears apocryphal.

Without knowing much other than the story presented here, I do know
from my first job (nuke plant control systems tech), that when you 
commissioned a new 3P motor, one of the first things you did with no 
load was to turn on the juice and make sure the drive shaft turned the 
right way. If not, you locked the power off (we had our own locks for 
safety) and then reversed 2 of the input motor leads. You then removed 
your lock from the breaker, re-applied power, and then made sure the 
drive shaft now turned the right way.

Let's not forget that DC battery power is applied via an inverter to create
3P power which in turn is applied to the target devices. This may have 
had some impact, but I'm not sure - perhaps someone with more specific 
knowledge of DC batteries, inverters and 3p power could comment?

Regards,

Kerry Main
Kerry dot main at starkgaming dot com