> On Jul 13, 2021, at 11:34 PM, Chris Zach via cctalk <[email protected]>
> wrote:
>
>> When we got an 8530 at work in the early 90s (needed a machine with a
>> Nautilus bus for specific hardware testing), it was definitely a
>> 3-phase machine and since we were in an industrial setting, I just
>> tapped into our panel at the back of the warehouse and wired up a
>> 3-phase outlet for it. It never sat on our datacenter floor as a
>> result, but it really only ever had one purpose and that wasn't a
>> daily driver. Too much power, too much heat for so few employees (at
>> that stage of the company).
>
> Interesting. Were the power supplies 3 phase input? Like you I have noticed
> that most pdp and vax gear just pull 120 volt legs off the 3 phase to balance
> power loads. So you can run them on a couple of 120 circuits. Outside of say
> the RP07 (which is a real 3 phase motor)
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.)
If the issue is motors, a "variable frequency converter" will do the job
easily. I have suggested in the past that three phase power supplies could run
from those, but others have pointed out I overlooked some issues. So that's
probably not a good idea.
If you need three phase power to feed power supplies or other non-motor power
consumers, the best answer is probably a "rotary converter". You can find
those in machine tool supply catalogs. Basically they are a three phase motor
equipped with run capacitors so they can be fed single phase power; the three
phase power needed is then taken off the three motor terminals. You can think
of these as rotary transformers -- dynamotors in a sense, for those of you who
remember electronics that old. :-)
Don't look at "static converters" -- those are only for motors, it seems they
aren't much more than run capacitors in a box. They won't help you for
anything other than a motor, and even for motors they aren't very good.
paul
