Who's rewired their house for this hobby?

Johnny Billquist bqt at update.uu.se
Mon Nov 24 14:28:27 CST 2014

On 2014-11-24 10:12, Jon Elson wrote:
> On 11/23/2014 03:15 PM, Holm Tiffe wrote:
>> but sine you already have 240V outlets, it should be possible to
>> change the distribution slowly to 3 phase power.. it's a matter of
>> time and the only needed thing for compatibility are the transformers
>> with modified secondaries. I don't think that this would ever happen
>> since the US is the biggest US of the world and other people are just
>> dumb aliens, aren't they? :-) But with that stone age power system you
>> are stumbling over your own feet all the time.. Regards, Holm
> Well, we only have single phase 7200 V running down our street. This
> 7200 V run goes a LONG way,
> so an entire region that may be about a mile square is running off a
> single phase HV line, that
> branches over and over again into the neighborhood.  Many of these feeds
> that go back
> into subdivisions are buried, and have pad-mount transformers placed
> every few homes.
> Our house has a pole-mount 50 KVA transformer that supplies just our one
> house, although
> that is kind of an accident of the layout.  We are on the corner lot,
> and otherwise probably
> would have shared that transformer with a neighbor.  Our LV drop is buried.
> So, what I'm saying here is there is a lot of high-cost infrastructure
> that would have to be
> ripped up (literally out of the ground) to go to 3 phase into the
> homes.  Not to mention
> all the meters, service entry gear and breaker panels.
> I have a small machine shop in my basement, and some years ago it seemed
> like 3-phase
> would be real nice for that.  Now that VFDs can run 3-phase motors so
> nicely off single
> phase power, it is no longer of much interest.
> Unless you desire to run a Cray 1 in your home (yeah, keep dreaming)
> there really isn't
> that much need for 3-phase power.  Most machines that "require" 3-phase
> can actually
> be rewired internally to run off single-phase.  One I can think of that
> won't is the
> KL-10B, which had a totally insane power system starting with a 3-phase
> transformer
> and rectifier.  A mid-scale 370 like the 145 had a motor-generator set,
> which could be
> run off a large VFD.  Or, replace the stupid MG and 415 Hz power
> supplies with
> off-the-shelf large power supplies running off single-phase 240 V.

Stuff I know need 3-phase:
VAX 86x0 machines. They have 3-phase motors for the fans. (Don't wire 
things up backwards, or your airflow will run backwards, which is not good.)
RP06 disk drives. They use 2 phases for their motors.

I wasn't aware that the KL needs 3-phase, but it might just be that the 
power supplies are large enough, and complicated enough, that you can't 
just rewire them.


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