On Sep 27, 7:56*am, Brian Lawson wrote:
Hey Vernon,

Comments on Rotary Phase Converter (RPC). *
Is there anything "better"? *Yes. *
Anything cheaper? Probably no. *Anything easier? *Probably yes, but
not a whole lot. *
Anything that even a less than fully equipped shop can not do? *No, it
can be REALLY simple. *
Smallest foot-print? *No, by far the biggest, but it can be at some
distance, and easily "tucked out of the way".
Anything sophisticated? *Not necessarily.
Easy to find parts locally? *Probably, but depends on where you are
located and considering "locally" to be within an hours drive.

Probably a bunch more questions too, but my "first" RPC was just
another 3Phase motor the same size as the one I wanted to drive, and
coupled directly to a 1/2 HP 1750RPM 120volt single phase from a
furnace fan that I had laying around. *The direct coupling in my case
meant V-belt and pulleys. *There are certainly a few more
sophisticated options, but this method does away with all the
"electronics". *The smaller motor is first turned on and allowed to
get the larger 3phase *up to speed, and then the 220 is applied to the
RPC generator motor, and voila...3 phase is available. *Kinda crappy
3phase, but good enough to drive your mill. *To me, one, if not the
only, non-replaceable feature of 3phase is the instant reversibility
of the mill or lathe spindle.

I note (after I started to type this) that another poster replied with
a webpage for an RPC circuit. *That's the "sophisticated" stuff, and
has to do with self-starting, versus my suggestion of "manual
starting". *Nothing wrong with that at all if you have the
skill/talent and time and inclination. *It IS what I have now of
course, but I first wanted to see mine run!

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXX

On Fri, 26 Sep 2008 21:22:43 -0700 (PDT), Vernon
wrote:



At an internet auction a few days ago I bought a KBC bench mill. *The
model is Grip-16.

The pictures neglected to show a view of the mill that is clearly
stamped "3 phase". * I thought the motor was single phase because the
auction listed it as "230v". *Until today, apparently in error, I
thought that 3 phase motors were 208V.

However, the KBC tools web site for this mill almost leads me to
believe that the motor can be wired for single or 3 phase.

Will somebody help me out here? *A motor is either single or 3 phase
but can't be changed. *Yes?

I already understand that a 3 phase machine can be operated from
single phase with a phase converter. *And I may have to go in that
direction unless I can get a single phase replacement motor.

This mill was built in 1989. *Since even when new it wasn't a high end
precision machine would it be prudent to check the accuracy of the X Y
table? *As we get deeper into machining I'm sure I will join the quest
for split hair precision. *But for now, we just wanna play.

On Monday I will call KBC and look into my options. *But meanwhile,
any advice on how to logically approach the aftermath of a possibly
illogical purchase will be appreciated.

Regards and thanks,

Vernon- Hide quoted text -

- Show quoted text -

To everybody who answered. Thanks! Upon reflection a rotary phase
converter will suit us to a tee. I have already started googling and
quickly found some "how to" instructions. About a year ago, when I
went to pick up an auction item I bought, the auctioneer gave me a
huge plenum box that sat atop a multi-story commercial building. It
was the cooler / blower for the entire building! It is a large, well
insulated box, containing a large blower driven by a 3 phase motor. I
don't know the horse power of the motor. But I'm guessing about 15
HP.

I also don't know the voltage. But I will find out tomorrow when we
go to our farm. For purposes of discussion and assuming that it IS a
15 HP, 240V 3 phase motor, would this be overkill as an idler motor?
I actually have a couple of other 3 phase tools I've had forever that
I haven't been able to use for the same reason. One of these is a
very large band saw!

It sounds like with a properly designed and built unit I can power all
of this stuff simultaneously. These a a 48" bandsaw, a Delta
Unisaw, and the newly acquired mill. The band saw probably has the
biggest motor. But I'm pretty sure all of these motors are smaller
than the motor in the air conditioner blower box.

Tomorrow I will get the technical specs off the motor data plate.

Thanks to all.

Vernon