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

[William Pechter]

In article <n9quvs$l1l$1 at Iltempo.Update.UU.SE>,
Johnny Billquist  <bqt at softjar.se> wrote:
>On 2016-02-14 23:10, Scott Dorsey wrote:
>> Johnny Billquist  <bqt at softjar.se> wrote:
>>> On 2016-02-14 14:31, Scott Dorsey wrote:
>>>> Johnny Billquist  <bqt at softjar.se> wrote:
>>>>> However, no hard drive uses a 3-phase AC motor to drive the disk. Anyone
>>>>> with half a brain should realize this. 3 phase AC motors always follows
>>>>> the phases of the supply like slaves. There is no spinup time. You go
>>>> >from standstill to full speed immediately, always. That is not how you
>>>>> want to spin up a disk drive.
>>>>
>>>> If the motor is designed to have some slip, you can bring it up to speed
>>>> without too much trouble.  Synchronous motors in general always follow
>>>> the supply like slaves, no matter how many phases they have.
>>>
>>> "Slip"? An AC motor cannot have slip. It is controlled by the phases of
>>> power. It has to follow the phases.
>>
>> Look at the nameplate on a typical induction motor, you will see that it
>> is probably rated for around 2% slip.  A fan motor will have much higher.
>> A synchronous motor won't have any.
>>
>> Because of that, a synchronous motor has an additional winding (or set
>> of windings) in order to get it up to speed, or else it needs to be
>> spun up by a second motor or a hand crank.
>>
>> If you watch Cinema Paradiso, for instance, the projectionist is using
>> a Prevost projector with a synchronous motor and no start winding.  On
>> the first film cue, he pushes in a crank, spins the motor up, turns the
>> motor on so it can lock in on speed, then waits for the second film cue
>> which is spaced long enough for the motor to be at speed and hits the
>> douser to change over to the projector.
>
>So we are down to a separate starter motor? Fair enough, if you have 
>that then yes, you can definitely do different tricks. But then you no 
>longer have that simple AC motor.
>
>And I can tell you that the RP06 have no such thing. There is just one 
>electric motor, and it's a DC one.
>
>	Johnny
>
>-- 
>Johnny Billquist                  || "I'm on a bus
>                                   ||  on a psychedelic trip
>email: bqt at softjar.se             ||  Reading murder books
>pdp is alive!                     ||  tryin' to stay hip" - B. Idol


What the.  IIRC, RP06's have the same 220 AC motor that I remember changing.
IIRC the same motor's in either my washing machine (20 years old or so)
or my electric clothes drier... Big heavy and 220 volt. 

No way that's a DC motor.  Two phase -- yes.  

Bill
-- 
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Digital had it then.  Don't you wish you could buy it now!
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