"Karl Townsend" wrote in message
...
I haven't built a phase converter sence Fitch was a regular here. Now
I'm building one for "The Kid". He has his eye on a Haas VF2 with a 20
hp. spindle.

So, we've found a 5 hp. and a 20 hp. idler motors. The plan is to
start a 5, delay a few seconds then start a 20. I've done this with a
10 and a 15 for years, works great. I plan to pretty much copy the
Fitch designed unit but with different motors and circuit breakers
instead of fuses.

If you check the actual hp of the spindle motor, you will likely find you
will *never* need the 20 hp idler.
Even if the motor were 20 hp, you'd have to be doing some big-time hoging to
warrant more idlers.
I run a Haas GR510 AND a Fadal 3016 off one 5 hp rpc, no pro'lengs, lite
work.
If some real work is brewing, I'll stage in another 5 hp.
I have over 30 hp in staged idlers, and can't remember switching in the
others, except to show off my switching/relay/cap circuitry.

It would be far more economical NOT to run that gonzo idler, but rather
stage 2, 3, 5 hp motors, switch them in as is needed.
Much more economical, and likely much better overall regulation.

I have my idlers started by motor starters, and breaker the wild legs
separately, ultimately feeding into the "main" generated leg supply.

Running big honking idler motors is like having a really big dick --
impressive in the locker room, but almost all women complain.
In the rpc case, your electric bill will complain. Esp. when yer doin 1/4
hp worth of drilling/tapping.....


My questions
1. what size circuit breaker for a 220 VAC 3phase 5 hp motor

2. what size circuit breaker for a 220 VAC 3phase 20 hp motor
2b. what wire size for above motor

3. How much start caps for the 5 hp motor?

4. about how much run caps for the 25 hp system? I know we'll need to
tune it. Fitch got my other unit within 10 volts.

At what load?
I've gotten mine and a buddy's within 1 volt, no load, a few volts at about
a 1-2 hp load -- different caps switched in, of course.

You should have two idenditcal banks of switchable caps, from 5 to 100 uF.
You can switch them in/out to L1-L3, L2-L3 as needed, whether for starting
or running, for a variety of load conditions..
Don't, however, switch caps in/out to electronic circuits while the circuits
are energized. Best to test with resistive loads. If you test with other 3
ph motors, THOSE 3 ph motors contribute to the generated-leg system, as
well, if they aren't directly loaded themselves.

I had a chance to
check it the other day, max volts was 252 L2-L3, lowest was 244 L1-L2,
don't remember the L1-L3 but it was in between. Now, I do wish I
remembered how he did it.

Trial and error, with the above.
--
EA




Karl