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.

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

Comments?

Thanks,

Adam Smith
Midland, ON

"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

NO! You should not drive the 25 hp motor through a Lovejoy. You need
to drive the 25 hp using a belt drive that is adjustable. The reason
is that if you drive it with a Lovejoy, you may or may not be actually
driving it. Say the RPC with no motor driving it turns at 1740 rpm and
your 10 hp motor runs at 1725. Then the RPC will be driving the 10 hp
motor.

If you do connect the RPC and a 10 hp motor with an adjustable drive,
you can measure the current going into the 10 hp motor and adjust the
drive so that the current is at or somewhat below the rated nameplate
current. It will then be driving the RPC slightly faster than the RPC
would turn at on its own. And life will be good 8-).

Dan


Adam Smith wrote:
So: I'm asking myself if I should balance the RPC (and if so, to which
load?). Or if I should just get one 10 hp single phase motor, drive the 25
hp through a lovejoy, and make true 3 phase. Which would probably make any
future 3 phase equipment happier, (ie CNC stuff, welders or plasma, anything
that is fussy about its power).

Comments?

Thanks,

Adam Smith
Midland, ON

I don't understand how the motor could be driven by the generator, I'm
afraid. Wouldn't there need to be some kind of loop for that to happen? I'm
contemplating a situation were the generator would not have any electric
feed lines, would simply be mechanically driven. I would have guessed the
effect of driving the 1740 generator at 1725 would be to produce 59.48 hz
power, but I may (probably) be missing something.

I'm not at all determined on this, my current situation is not very broken.
If you and Bob come back and say I'm crazy to think of this, I'll just
balance to the vertical mill, and let the horizontal and shaper be
under-balanced.

Thanks,

Adam

wrote in message
oups.com...
NO! You should not drive the 25 hp motor through a Lovejoy. You need
to drive the 25 hp using a belt drive that is adjustable. The reason
is that if you drive it with a Lovejoy, you may or may not be actually
driving it. Say the RPC with no motor driving it turns at 1740 rpm and
your 10 hp motor runs at 1725. Then the RPC will be driving the 10 hp
motor.

If you do connect the RPC and a 10 hp motor with an adjustable drive,
you can measure the current going into the 10 hp motor and adjust the
drive so that the current is at or somewhat below the rated nameplate
current. It will then be driving the RPC slightly faster than the RPC
would turn at on its own. And life will be good 8-).

Dan


Adam Smith wrote:
So: I'm asking myself if I should balance the RPC (and if so, to which
load?). Or if I should just get one 10 hp single phase motor, drive the
25
hp through a lovejoy, and make true 3 phase. Which would probably make
any
future 3 phase equipment happier, (ie CNC stuff, welders or plasma,
anything
that is fussy about its power).

Comments?

Thanks,

Adam Smith
Midland, ON

"Adam Smith" wrote in message
...
I don't understand how the motor could be driven by the generator, I'm
afraid. Wouldn't there need to be some kind of loop for that to happen? I'm
contemplating a situation were the generator would not have any electric
feed lines, would simply be mechanically driven. I would have guessed the
effect of driving the 1740 generator at 1725 would be to produce 59.48 hz
power, but I may (probably) be missing something.

I'm not at all determined on this, my current situation is not very
broken. If you and Bob come back and say I'm crazy to think of this, I'll
just balance to the vertical mill, and let the horizontal and shaper be
under-balanced.

Thanks,

Adam

Adam, your concerns are with respect to the afore mentioned induction
generator. Speeds such as 1740 and 1725 are not
absolute. Induction motor speeds vary slightly with loading and are stated
on a motor's nameplate with respect to the rated HP. Check into induction
generator theory before making any such speed / voltage calculations.

Bob Swinney




wrote in message
oups.com...
NO! You should not drive the 25 hp motor through a Lovejoy. You need
to drive the 25 hp using a belt drive that is adjustable. The reason
is that if you drive it with a Lovejoy, you may or may not be actually
driving it. Say the RPC with no motor driving it turns at 1740 rpm and
your 10 hp motor runs at 1725. Then the RPC will be driving the 10 hp
motor.

If you do connect the RPC and a 10 hp motor with an adjustable drive,
you can measure the current going into the 10 hp motor and adjust the
drive so that the current is at or somewhat below the rated nameplate
current. It will then be driving the RPC slightly faster than the RPC
would turn at on its own. And life will be good 8-).

Dan


Adam Smith wrote:
So: I'm asking myself if I should balance the RPC (and if so, to which
load?). Or if I should just get one 10 hp single phase motor, drive the
25
hp through a lovejoy, and make true 3 phase. Which would probably make
any
future 3 phase equipment happier, (ie CNC stuff, welders or plasma,
anything
that is fussy about its power).

Comments?

Thanks,

Adam Smith
Midland, ON

Sorry, I misunderstood what you were thinking. If I were doing this, I
would not simply drive the generator with no electric feed lines.
Induction generators do not work well when not connected to the power
grid. But they do work well if they are connected to the power grid.
So if you leave your RPC connected as is and change the pony motor to
a ten hp motor driving the RPC through a belt drive, it will work very
well. By leaving the RPC connected to electric power, you will not
have to generate that phase. You could probably get by with less than
a 10 hp motor.

About 25 years ago I made someone a three phase source using a 7.5 hp
three phase motor and a two hp single phase motor. It powered a
centerless sander that had a 5 hp three phase motor as I remember. It
worked well for some twenty years until the business was sold and the
sander was moved to a location with three phase power.


Dan

Asdan said, " Induction generators do not work well when not connected to
the power
grid. But they do work well if they are connected to the power grid."

And therein lies part of the problem. If you've got a mechanically driven
induction generator connected to the "grid" for excitation purposes and if
you mechanically drive it faster than slip speed you will, in fact, generate
AC. If this were done, you'd see your watt/hour meter running in reverse
compared to its usu. direction of rotation. This would indicate power was
being supplied to the grid rather than consumed from the grid.

In the more general case of a "line excited" induction generator there would
have to be some way of supplying excitation to the generator rather than it
being directly connected to the grid as is done in the motor's case. Don't
confuse RPC's with induction generators - they are quite different animals.

Bob Swinney

wrote in message
oups.com...
Sorry, I misunderstood what you were thinking. If I were doing this, I
would not simply drive the generator with no electric feed lines.
So if you leave your RPC connected as is and change the pony motor to
a ten hp motor driving the RPC through a belt drive, it will work very
well. By leaving the RPC connected to electric power, you will not
have to generate that phase. You could probably get by with less than
a 10 hp motor.

About 25 years ago I made someone a three phase source using a 7.5 hp
three phase motor and a two hp single phase motor. It powered a
centerless sander that had a 5 hp three phase motor as I remember. It
worked well for some twenty years until the business was sold and the
sander was moved to a location with three phase power.


Dan

You learn something every day.

Thanks once again, Bob and Dan.

I'll stick to running the motor as an RPC for the foreseeable future. If I
want to get into experimentation for its own sake, I might do that sometime,
but I won't plan on running the shop from the experiment.

Regards,

Adam Smith
Midland ON


"Robert Swinney" wrote in message
. ..
Asdan said, " Induction generators do not work well when not connected to
the power
grid. But they do work well if they are connected to the power grid."

And therein lies part of the problem. If you've got a mechanically driven
induction generator connected to the "grid" for excitation purposes and if
you mechanically drive it faster than slip speed you will, in fact,
generate AC. If this were done, you'd see your watt/hour meter running in
reverse compared to its usu. direction of rotation. This would indicate
power was being supplied to the grid rather than consumed from the grid.

In the more general case of a "line excited" induction generator there
would have to be some way of supplying excitation to the generator rather
than it being directly connected to the grid as is done in the motor's
case. Don't confuse RPC's with induction generators - they are quite
different animals.

Bob Swinney

wrote in message
oups.com...
Sorry, I misunderstood what you were thinking. If I were doing this, I
would not simply drive the generator with no electric feed lines.
So if you leave your RPC connected as is and change the pony motor to
a ten hp motor driving the RPC through a belt drive, it will work very
well. By leaving the RPC connected to electric power, you will not
have to generate that phase. You could probably get by with less than
a 10 hp motor.

About 25 years ago I made someone a three phase source using a 7.5 hp
three phase motor and a two hp single phase motor. It powered a
centerless sander that had a 5 hp three phase motor as I remember. It
worked well for some twenty years until the business was sold and the
sander was moved to a location with three phase power.


Dan

However if the mechanical drive to an induction generator is an
electric motor, then the power meter will not run backwards as any
power generated by the induction generator comes from the electric
motor.

As far as I know most induction generators are directly connected to
the power grid. And while you think that induction generators and
RPC's are quiet different animals, I think of the usual RPC as being an
induction generator with the drive being a three phase motor run on
single phase. It may not work for you, but it seems to explain exactly
how a RPC works for me. To me a three phase motor connected to single
phase power can supply mechanical power or can be supplied mechanical
power and the in between point with no power being supplied or being
supplied is exactly what most RPC's are.

Dan

Robert Swinney wrote:
As dan said, " Induction generators do not work well when not connected to
the power
grid. But they do work well if they are connected to the power grid."

And therein lies part of the problem. If you've got a mechanically driven
induction generator connected to the "grid" for excitation purposes and if
you mechanically drive it faster than slip speed you will, in fact, generate
AC. If this were done, you'd see your watt/hour meter running in reverse
compared to its usu. direction of rotation. This would indicate power was
being supplied to the grid rather than consumed from the grid.

In the more general case of a "line excited" induction generator there would
have to be some way of supplying excitation to the generator rather than it
being directly connected to the grid as is done in the motor's case. Don't
confuse RPC's with induction generators - they are quite different animals.

Bob Swinney

wrote in message
oups.com...
Sorry, I misunderstood what you were thinking. If I were doing this, I
would not simply drive the generator with no electric feed lines.
So if you leave your RPC connected as is and change the pony motor to
a ten hp motor driving the RPC through a belt drive, it will work very
well. By leaving the RPC connected to electric power, you will not
have to generate that phase. You could probably get by with less than
a 10 hp motor.

About 25 years ago I made someone a three phase source using a 7.5 hp
three phase motor and a two hp single phase motor. It powered a
centerless sander that had a 5 hp three phase motor as I remember. It
worked well for some twenty years until the business was sold and the
sander was moved to a location with three phase power.


Dan