On 6/14/2018 10:55 PM, Bill wrote:

I was looking at a jointer with a 3HP 3-phase motor.Â* I'd like to run
this from my home which has 220v. Would I be able to run it on a 20A
(preferably) or 30A circuit?

Can you give me an example of a "phase converter" which would be up to
the task?Â* I saw one for $89, but I couldn't tell whether it would be up
to the task or not.Â* I imagine it might be wiser to avoid 3-phase and
keep looking, but I thought I would check with the experts here first.

Thanks!
Bill


3hp on 220V is (ideally) only about 10 amps. The reality it may peak a
little higher under a hard startup or if you bog down the motor.

A "good" rotary phase converter is the way to go if you think you will
run much 3 phase stuff. I don't recall the derating, but its something
like 30-40%. ie: Get a 5HP rotary for a 3HP motor. If all you wil ever
run is a motor directly you can probably go with a cheaper static phase
converter. Just remember that the derating is higher. Its best to see
if the MFG says "This converter will run a X-HP motor."

The easiest way for me (and most expensive) is I have dedicated variable
frequency drives on each 3 phase motor in my shop. When used 1ph in and
3ph out they have a 30% derating as well, but they give me infinite
variable speed control. Most are on CNC machines where a 0-10VDC analog
power signal controls frequency and rpm. Others I just use the controls
on the VFD. With most half decent 3phase motors you can run from half
speed (frequency) to double speed without them tearing themselves apart.
If they are inverter rated they may handle more. If you have one of
those fancy new washing machines you probably have a high speed 3 phase
motor controlled by a VFD already. You just didn't know it.

Anyway, even with the parasitic losses it will probably run just fine on
a 20 amp 220V circuit. Should be absolutely no issue at all on 30 amp.

I think 1HP is roughly 750 watts. I always figure 800 and then add a
fudge factor on top of that for safety.

3 X 800 = 2400 watts.
2400 / 220= 10.9 amps.

You will have some loss from your phase converter, heat, wire, etc.
Still with nearly double the fudge factor...

Odds are your 220V is really closer to 230-235 anyway.