Re: FREE TO A GOOD HOME

From: Eric Smith (eric-no-spam-for-me_at_brouhaha.com)
Date: 05/26/03

  • Next message: JF Mezei: "Re: FREE TO A GOOD HOME" 
    Date: 25 May 2003 17:28:39 -0700

    Chris Olive <nospam@raytheon.com> writes:
    > Huh... could have sworn a 750 ran on 3-phase... 8-/

    moroney@world.std.spaamtrap.com (Michael Moroney) writes:
    > Not the 750 itself, but some old disk drives of that era apparently did.
    > A long-time Deccie was telling me just today about these drives with
    > three phase drive motors.. wouldn't even spin on single phase.

    The common DEC drives that used large packs, such as the RP02 through
    RP06, and the RMxx drives did not use three-phase motors. I'm not sure
    about the RP07, but it seems unlikely that it would have had a three-
    phase motor either. Perhaps the RP20 might have, but I've never seen
    one. It was a rare beast with two separate spindles and an IBM channel
    interface; it needed a DX20 to attach it to the Massbus.

    Of course, the drives that took small packs (RK02-07, RL01-02, RC25)
    didn't need three-phase for the motors or otherwise.

    The RP05, RP06 and similar drives came wired for 120/208V three-phase
    wye, but they simply wired the single-phase drive motor between two
    phases, and the electronics between one of those phases and neutral.
    The manual for the drive says that the motor is rated for a fairly wide
    range of voltages, from under 208 to over 240. (I don't have it handy
    to check the exact numbers.) So it should be entirely possible to run
    an RP06 without three-phase power, if you have single-phase 240V. If
    your 240V receptacle doesn't have a neutral, you might have to use a
    step-down transformer to power the electronics.

    The only parts of any DEC machines that actually *required* three-phase,
    AFAIK, were the ECL power supply of the KL10 and the blower motors on
    some VAXen. The KL10's ECL supply ran the three-phase through three
    ferroresonant transformers with approximately 12V secondaries, and
    fed the secondaries into a three-phase full-wave bridge rectifier.
    This allowed them to reduce the amount of filter capacitance needed
    as compared to a single-phase design.

  • Next message: JF Mezei: "Re: FREE TO A GOOD HOME"

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