GeoLane at PTD dot NET wrote in message
...
I'll be picking up my Bridgeport 2 HP 2J in a couple of weeks, so
it's time to start working on a rotary phase converter. I know that
my ideal size is 3 HP for the converter. There's a possibility of
getting two 2 HP motors incredibly cheap. Can you gang them together,
or is there a disadvantage to doing that?

I"m early in my search, so I don't know if there are any reasonably
priced 3 HP motors out there in our rural area at the present time.

As Ig stated, there are numerous advantages, which hopefully he'll elaborate
on.

I see the advantages as lower start up cost, lower running cost, greater
flexibility (run as many as you need), easier start up (won't brown out the
neighborhood), AND, I suspect, overall better power regulation, and, all
things being equal, quieter operation. Also less heat buildup.

I have an arsenal of about 6 idlers.

In fact, I see no advantages to one big idler over numerous small ones,
except one: simpler wiring.
Others may disagree, however.

Best to separate start up caps from run caps, and even better to have a bank
of switchable caps for best load/voltage matching.

With a bank of switchable caps (to both L1-L3 and L2-L3, (L1-L2=line)), you
can use the caps you need to start up, then switch those out, switch in the
run caps predetermined for the idlers chosen, *and* the anticipated load.
Stage the idlers in, one by one, as needed. Only need start up caps for the
first idler started.

Get 3 cheap digital multimeters from HF (also 3 of their dert cheap clamp-on
multimeters) to let you observe voltage and current in all three legs
simultaneously. Really helps in the tuning process.

Another poss. superior alternative for your BP is a VFD, esp. if the head is
belt, and not variable speed. This way, you won't need an rpc, at least not
for this machine.

--
DT






RWL