15 Jul
2021
15 Jul
'21
1:19 p.m.
From: Paul Koning <paulkoning at comcast.net>
To: Chris Zach <cz at alembic.crystel.com>, "cctalk at classiccmp.org"
<cctalk at classiccmp.org>
Subject: Re: Looking for VAX6000 items
A number of the large disk drives use 3 phase motors; RP04/5/6 are
examples as well.
Three phase motors won't run on single phase power without help from run
capacitors. (There is no such thing as "two phase power" -- 220 volts is
single phase, balanced.)
paul
The RP06 uses 220VAC single phase motors for the spindle and blower.
I converted an RP06 from three-phase to single-phase to use with PDP-10
KS10 at home. Instructions are here:
https://sites.google.com/site/mthompsonorg/Home/pdp-10/rm03-and-rp06-inform…
--
Michael Thompson
15 Jul
15 Jul
1:22 p.m.
On Jul 15, 2021, at 4:19 PM, Michael Thompson via
cctech <cctech at classiccmp.org> wrote:
Interesting. I distinctly remember a disk drive installation manual that warned about
phase order. Perhaps that was for the RP04 and not the RP05/6 ?
paul
From: Paul Koning <paulkoning at comcast.net>
To: Chris Zach <cz at alembic.crystel.com>, "cctalk at classiccmp.org"
<cctalk at classiccmp.org>
Subject: Re: Looking for VAX6000 items
A number of the large disk drives use 3 phase motors; RP04/5/6 are
examples as well.
Three phase motors won't run on single phase power without help from run
capacitors. (There is no such thing as "two phase power" -- 220 volts is
single phase, balanced.)
paul
The RP06 uses 220VAC single phase motors for the spindle and blower.
1:33 p.m.
The power cord is three-phase, and actually daisy-chains to a second and
third drive. The phases on the AC output connector are rotated to balance
the load on all three phases when three drives are daisy-chained. If you
look at the power wiring diagram on page 3-120 of the Memorex 677-01 manual
you will see only two of the phases going to the power transformer.
On Thu, Jul 15, 2021 at 4:22 PM Paul Koning <paulkoning at comcast.net> wrote:
Interesting. I distinctly remember a disk drive installation manual that
warned about phase order. Perhaps that was for the RP04 and not the RP05/6
?
paul
--
Michael Thompson
On Jul 15, 2021, at 4:19 PM, Michael Thompson via
cctech <
cctech at classiccmp.org> wrote:
>
> From: Paul Koning <paulkoning at comcast.net>
> To: Chris Zach <cz at alembic.crystel.com>, "cctalk at
classiccmp.org"
> <cctalk at classiccmp.org>
> Subject: Re: Looking for VAX6000 items
>
> A number of the large disk drives use 3 phase motors; RP04/5/6 are
> examples as well.
>
> Three phase motors won't run on single phase power without help from run
> capacitors. (There is no such thing as "two phase power" -- 220 volts
is
single
phase, balanced.)
paul
The RP06 uses 220VAC single phase motors for the spindle and blower.
2:13 p.m.
On Jul 15, 2021, at 4:33 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
The power cord is three-phase, and actually daisy-chains to a second and third drive. The
phases on the AC output connector are rotated to balance the load on all three phases when
three drives are daisy-chained. If you look at the power wiring diagram on page 3-120 of
the Memorex 677-01 manual you will see only two of the phases going to the power
transformer.
Ok. I just looked up the RP04 maintenance manual. It isn't all that explicit but it
does say that the spindle motor is a 3-phase induction motor.
paul
2:50 p.m.
I believe that the CDC built RP04 has a three-phase spindle motor.
On Jul 15, 2021, at 5:13 PM, Paul Koning
<paulkoning at comcast.net> wrote:
On Jul 15, 2021, at 4:33 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
The power cord is three-phase, and actually daisy-chains to a second and third drive. The
phases on the AC output connector are rotated to balance the load on all three phases when
three drives are daisy-chained. If you look at the power wiring diagram on page 3-120 of
the Memorex 677-01 manual you will see only two of the phases going to the power
transformer.
Ok. I just looked up the RP04 maintenance manual. It isn't all that explicit but it
does say that the spindle motor is a 3-phase induction motor.
paul
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