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

[Johnny Billquist]

On 2016-02-14 21:28, JF Mezei wrote:
> On 2016-02-14 04:48, already5chosen at yahoo.com wrote:
>
>> 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.
>
>
> RA82 drive motors were 1/3 horsepower motors. They were not 3 phase, but
> required 3 wires in. There was one used to start the motor in the right
> direction as I recall.  There was some capacitor that would discharge to
> get motor going. I don't recall the exact details.

RA81/RA82 do not, as far as I can recall, have any large capacitors to 
get them running. And they draw a hell of a lot of power when spinning 
up, which is why you have the power sequence cable on them, so that they 
do not all try to spin up at the same time, as that would blow fuses. 
Once they are getting up to speed, the power requirement is much lower.

I can't remember how many wires went into the motor, but I think you are 
right in that there was some trick to ensure that it would start 
rotating in the right direction. The manuals are probably online if 
someone wants to read up on the details.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
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