Karl Townsend wrote:

On Thu, 20 Jun 2013 18:38:34 -0500, Ignoramus4976
wrote:

On 2013-06-20, Karl Townsend wrote:
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.

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

FLA

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

FLA -- but how are you going to run them on two separate circuits,
when one starts another?

2b. what wire size for above motor

See FLA and AWG table

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

Try 100 uF, it differs from motor to motor as to how much will start it

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. 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.

I can find out how much is in my 17.5 HP phase converter (same
principle), it balances voltages great.

I googled FLA and found 20 amp and 60 amp breakers, sounds about
right. Never knew the term FLA before.

Don't see why you think a breaker for each motor is a problem, its
just there for a failure. I will be using an entire three phase load
center panel so he can breaker all his machines.

The idlers end up wired in parallel anyway, if each is on it's own three
phase breaker in a three phase panel they're still in parallel. The only
oddity is that the main breaker into the panel (or main lugs) only has
two hot legs connected. You could even wire some run/balance caps in on
2 pole breakers and put a few meters on the panel cover so you can
dynamically adjust the balance.