"Adam Smith" wrote in message
...
I currently have the following equipment running off 3 phase 220v:

Cincinnati 24" shaper (7 1/2 hp)
Excello 602 vertical mill (1 1/2 hp)
B&S #2 surface grinder (1 hp)
Cincinnati #2 horizontal mill (5 hp, I think)

I have serveral other pieces of equipment not currently under power that
it would be very convenient to run on 3 phase. (It is either that, or buy
a bunch of single phase motors, which seems silly).

What I'm using for an RPC is a 25 hp motor, fired up by a pony. No
balancing caps, no nothing. Been meaning to balance it and do a proper
install for ages, so far it hasn't got to the top of the project list.


Comments?

Thanks,

Adam Smith
Midland, ON
You didn't say what "3-phase" voltages you are getting from the 25HP idler,
nor how much of the total 15 HP load is running at the same time. I would
be surprised if there is much of a voltage imbalance, even at full 15 HP
load. I wouldn't consider adding any "balancing" capacitance unless there
is a significant amount of imbalance, say, 10% from phase to phase.

You said, "So: I'm asking myself if I should balance the RAP (and if so, to
which
load?). Or if I should just get one 10 hp single phase motor, drive the 25
hp through a love, and make true 3 phase. Which would probably make any
future 3 phase equipment happier, (i.e. CONC. stuff, welders or plasma,
anything that is fussy about its power)."

This seems like you are considering driving the 25HP idler motor with a 10
HP single-phase motor through a flexible coupling to make a sort of
"motor-generator set". That is not a good idea. Gen sets are not made that
way - doing so would simply leave a starting (pony) motor permanently
connected to the idler motor. Perhaps you are thinking about making an
induction generator. In order for an ordinary motor to be used as an
induction generator it must be driven faster than its normal operating
speed; there are other problems concerning excitation and regulation. Check
into a good Electrical Engineering handbook and I think you will be
discouraged re. an induction generator.

Check your phase voltages. Unless they are seriously unbalanced now, I
would leave them alone. Voltage balancing must be done for a single load
value - be that total load or the load of any single machine. Individual
balancing of each machine (separately) would not be effective unless and
until all machines were on line. Essentially, you can only balance for 1
load.

Bob Swinney