I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph
dust collector.

I connected them to a Phase-a-matic static phase converter; They
start and run ok, but they do seem to draw a bit more current
running on single phase than 3phase.

I figured that the big grinder would act like a rotary phase
converter for the dust collector, but I don't see any current
in the third leg with a clamp on ampmeter.

Input is L1 and L2. I measure
L1:L3 208V
L2:L3 224V

Should I experiement with some run caps or just leave it alone?

Another interesting fact is that the baldor grinder is rated
1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell
mill and that motor is rated 4.6 amps. Is baldor guiltly
of over rating like sears?

chuck

Is the rockwell mill three phase or single?

bob g.

Charles A. Sherwood wrote:

I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph
dust collector.

I connected them to a Phase-a-matic static phase converter; They
start and run ok, but they do seem to draw a bit more current
running on single phase than 3phase.

I figured that the big grinder would act like a rotary phase
converter for the dust collector, but I don't see any current
in the third leg with a clamp on ampmeter.

Input is L1 and L2. I measure
L1:L3 208V
L2:L3 224V

Should I experiement with some run caps or just leave it alone?

Another interesting fact is that the baldor grinder is rated
1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell
mill and that motor is rated 4.6 amps. Is baldor guiltly
of over rating like sears?

chuck

The Baldor is rated at 1.5 hp, but unless you are using it the motor
is not going to draw much current. The better the motor the less
current it will draw.
Dan



(Charles A. Sherwood) wrote in message ...
I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph
dust collector.

I connected them to a Phase-a-matic static phase converter; They
start and run ok, but they do seem to draw a bit more current
running on single phase than 3phase.

I figured that the big grinder would act like a rotary phase
converter for the dust collector, but I don't see any current
in the third leg with a clamp on ampmeter.

Input is L1 and L2. I measure
L1:L3 208V
L2:L3 224V

Should I experiement with some run caps or just leave it alone?

Another interesting fact is that the baldor grinder is rated
1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell
mill and that motor is rated 4.6 amps. Is baldor guiltly
of over rating like sears?

chuck

The Baldor is rated at 1.5 hp, but unless you are using it the motor
is not going to draw much current. The better the motor the less
current it will draw.

Well if you do the math 2.5amps @ 240V 3 ph is
2.5*240*1.7 = 1000 watts. No way is that 1.5HP.

"Charles A. Sherwood" wrote in message
...
I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph
dust collector.

I connected them to a Phase-a-matic static phase converter; They
start and run ok, but they do seem to draw a bit more current
running on single phase than 3phase.

I figured that the big grinder would act like a rotary phase
converter for the dust collector, but I don't see any current
in the third leg with a clamp on ampmeter.

Input is L1 and L2. I measure
L1:L3 208V
L2:L3 224V

Should I experiement with some run caps or just leave it alone?

Another interesting fact is that the baldor grinder is rated
1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell
mill and that motor is rated 4.6 amps. Is baldor guiltly
of over rating like sears?

chuck

With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase machine
on single phase current. The third leg is only intergized for starting.
After start-up the motor runs as a single phase machine with current through
2 of its 3 sets of windings.

Bob Swinney
"Charles A. Sherwood" wrote in message
...
I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph
dust collector.

I connected them to a Phase-a-matic static phase converter; They
start and run ok, but they do seem to draw a bit more current
running on single phase than 3phase.

I figured that the big grinder would act like a rotary phase
converter for the dust collector, but I don't see any current
in the third leg with a clamp on ampmeter.

Input is L1 and L2. I measure
L1:L3 208V
L2:L3 224V

Should I experiement with some run caps or just leave it alone?

Another interesting fact is that the baldor grinder is rated
1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell
mill and that motor is rated 4.6 amps. Is baldor guiltly
of over rating like sears?

chuck

With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase machine
on single phase current. The third leg is only intergized for starting.

But in this case I have two motors in parallel. The big 1.5HP grinder
motor and the little 1/2 HP blower. The big grinder motor is pretty
much unloaded and the the blower motor which is always loaded because
it is moving lots of air. I expected to see some current in the third
leg but I don't see any.

chuck

That's the way I understood your description in the first place and when
you said no current in the third leg, I figured I'd read it wrong. I
use a 2hp idler to run a 1/2 hp on an old lathe and there is current in
the third leg. If there were no current in the third leg, you couldn't
start a three phase motor off a rotary converter.
BTW, using the old rope start rotary converter, if you started the
converter in the wrong direction (who could be absent minded enough to
do that?) The load would also run in the wrong direction. The load
certainly found something to use in that third leg.

bob g.

Charles A. Sherwood wrote:

With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase machine
on single phase current. The third leg is only intergized for starting.


But in this case I have two motors in parallel. The big 1.5HP grinder
motor and the little 1/2 HP blower. The big grinder motor is pretty
much unloaded and the the blower motor which is always loaded because
it is moving lots of air. I expected to see some current in the third
leg but I don't see any.

chuck

Are the motors truly in parallel? As in; all three legs of one motor
connected to all three legs of the other motor? If so, you should see some
3rd leg current between the motors. Is there a separate switch on the 1/2
HP motor? If they are in parallel you should be able to switch on and start
the 1/2 HP motor *after* the 1.5 HP motor is up to speed. The larger motor
will be generating some unbalanced 3-phase power by transformer action. It
is acting like an idler motor in a rotary phase converter configuration.

Bob Swinney
"Charles A. Sherwood" wrote in message
...
With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase
machine
on single phase current. The third leg is only intergized for starting.

But in this case I have two motors in parallel. The big 1.5HP grinder
motor and the little 1/2 HP blower. The big grinder motor is pretty
much unloaded and the the blower motor which is always loaded because
it is moving lots of air. I expected to see some current in the third
leg but I don't see any.

chuck

Are the motors truly in parallel? As in; all three legs of one motor
connected to all three legs of the other motor? If so, you should see some

They are both on the same contactor and start at the same time.
However they are connected together before the overload controls.
One contactor suppling power to seperate "heaters" for each motor.
The third wire of the static converter connects to the third
wire of the motors through the heaters. Seems like the logical
way to wire it (at least to me).

I could connect the third legs together before the heaters, but
I really don't think that would make any difference.

I see no current in the third leg with a clamp on ampmeter after
the motors have started. The voltage in the third leg is 208 and 224
with respect to the other two legs. I guess there is no current because
the voltage is low.


3rd leg current between the motors. Is there a separate switch on the 1/2
HP motor? If they are in parallel you should be able to switch on and start
the 1/2 HP motor *after* the 1.5 HP motor is up to speed.

Probably could, but the motors are hard wired together.

In article ,
Charles A. Sherwood wrote:
Are the motors truly in parallel? As in; all three legs of one motor
connected to all three legs of the other motor? If so, you should see some

They are both on the same contactor and start at the same time.
However they are connected together before the overload controls.
One contactor suppling power to seperate "heaters" for each motor.
The third wire of the static converter connects to the third
wire of the motors through the heaters. Seems like the logical
way to wire it (at least to me).

I could connect the third legs together before the heaters, but
I really don't think that would make any difference.

I see no current in the third leg with a clamp on ampmeter after
the motors have started. The voltage in the third leg is 208 and 224
with respect to the other two legs. I guess there is no current because
the voltage is low.

Where are you applying the clamp-on ammeter? If between the
junction of the two motors' wires and the static converter, there
*should* be no current once the motors are started.

However, if you clamp around one or the other of the motors, you
should see some current at least. (Mostly the amount would be based on
the horsepower and the loading of the smaller motor.) Perhaps if both
motors are equally lightly loaded, they are each generating about the
same voltage for the third phase, and as a result, are generating very
little current between them. Put a serious load on one motor or the
other and see whether there is a visible upswing in the current.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 24 Aug 2004 19:25:25 GMT, (Charles A.
Sherwood) vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

PMFJI

Why is a rotary phase convert better than a 3-phase alternator driven
by a high-current single phase motor?

RPCs seem complex and prone to all sorts of vagaries (with SPC even
more so). Why not obtain high current 1 PH power, or several sources
of 1 PH power, and run a motor that runs a 3-phase alternator?
************************************************** ***
Marriage. Where two people decide to get together so
that neither of them can do what they want to because
of the other one.

"Old Nick" wrote in message
...
Why is a rotary phase convert better than a 3-phase alternator driven
by a high-current single phase motor?

First reason is complexity. Second is efficiency, I'd imagine, though I'm
not an expert.

RPCs seem complex and prone to all sorts of vagaries (with SPC even
more so). Why not obtain high current 1 PH power, or several sources
of 1 PH power, and run a motor that runs a 3-phase alternator?

You think this is simpler than an RPC? I built an RPC from plans on the 'net
a few weeks ago, and it was a *lot* simpler than I'd thought. I wouldn't
want to bother with a generator setup unless I really had no other choice.

Pete

Pete sez:

"You think this is simpler than an RPC? I built an RPC from plans on the
'net a few weeks ago, and it was a *lot* simpler than I thought. I wouldn't
want to bother with a generator setup unless I really had no other choice."

Right on, Pete! Also, it is a lot easier to find surplus 3-phase motors for
conversion to RPCs than it is to find alternators. Alternators should be
driven at a constant speed, regardless of load - not an easy thing.
Alternators need a separate source of direct current for magnetic
excitation - also adding to the complexity. Granted, alternators can be
"permanent magnet", eliminating the need for excitation power, but those
types, AFAIK, are not readily available or cost efficient in smaller sizes.
The only example I can think of might be a welding/AC supply "generator"
that outputs 3-phase 220v AC. Again, not nearly as economical as a RPC.
IMO, the only justification for an alternator would be if there was no
commercial power available.

Bob Swinney

"Pete Bergstrom" wrote in message
. ..

"Old Nick" wrote in message
...
Why is a rotary phase convert better than a 3-phase alternator driven
by a high-current single phase motor?

First reason is complexity. Second is efficiency, I'd imagine, though I'm
not an expert.

RPCs seem complex and prone to all sorts of vagaries (with SPC even
more so). Why not obtain high current 1 PH power, or several sources
of 1 PH power, and run a motor that runs a 3-phase alternator?


Pete

"Robert Swinney" wrote in message
...
Pete sez:

"You think this is simpler than an RPC? I built an RPC from plans on the
'net a few weeks ago, and it was a *lot* simpler than I thought. I
wouldn't
want to bother with a generator setup unless I really had no other
choice."

Right on, Pete! Also, it is a lot easier to find surplus 3-phase motors
for
conversion to RPCs than it is to find alternators. Alternators should be

In addition to the RPC plan I used
(http://www.frugalmachinist.com/rpc.html), I'll also recommend Bob's article
in Home Shop Machinist Nov-Dec 2001 "Induction Motors and Rotary Phase
Converters". I bought the back issue as part of my research.

I had originally planned to buy a VFD, but since my mill also has a coolant
pump I ended up building the RPC to power it.

conversion to RPCs than it is to find alternators. Alternators should be
driven at a constant speed, regardless of load - not an easy thing.

Not all the hard. There are governors on industrial engines that do
it well. Even the consumer quality generators do a pretty decent job
of it.

Alternators need a separate source of direct current for magnetic
excitation - also adding to the complexity.

Modern brushless alternators have the excitor built in and will
be self starting and self exciting. Some require an external
regulator which uses a tiny amount of generated AC to power the field.
For example the field on my 15KW unit is 30VDC at 1 amp. This
tiny control voltage is produced by the bassler regulator which
is powered by the alternator itself.

Source of 3 ph alternator and price?

bob g.

Charles A. Sherwood wrote:

conversion to RPCs than it is to find alternators. Alternators should be
driven at a constant speed, regardless of load - not an easy thing.


Not all the hard. There are governors on industrial engines that do
it well. Even the consumer quality generators do a pretty decent job
of it.


Alternators need a separate source of direct current for magnetic
excitation - also adding to the complexity.


Modern brushless alternators have the excitor built in and will
be self starting and self exciting. Some require an external
regulator which uses a tiny amount of generated AC to power the field.
For example the field on my 15KW unit is 30VDC at 1 amp. This
tiny control voltage is produced by the bassler regulator which
is powered by the alternator itself.

On 25 Aug 2004 19:18:36 GMT, (Charles A.
Sherwood) vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

Thanks for all the replies. I am interested because I see 3PH stuff
for peanuts, and single phase stuff is often limited in power.

conversion to RPCs than it is to find alternators. Alternators should be
driven at a constant speed, regardless of load - not an easy thing.

Not all the hard. There are governors on industrial engines that do
it well. Even the consumer quality generators do a pretty decent job
of it.

Alternators need a separate source of direct current for magnetic
excitation - also adding to the complexity.

Modern brushless alternators have the excitor built in and will
be self starting and self exciting. Some require an external
regulator which uses a tiny amount of generated AC to power the field.
For example the field on my 15KW unit is 30VDC at 1 amp. This
tiny control voltage is produced by the bassler regulator which
is powered by the alternator itself.

These were my thoughts, too. Alternators are available, and many have
themselves set up to generate power as bought. There certainly are
engines with governors that maintin a very good constant speed.

However, I have supply, but not 3PH. I was looking at using an
electric motor to drive the alternator to get 3PH.

The reason I see the alternator as better is that RPCs and VFDs seem
to have a rep for having trouble with load balance etc. The idea and
construction is simple, but they seem to be "picky". I have never used
one, but read a lot of stuff here about the problems getting them to
behave under various load conditions.

They also do not seem all that efficient, and seem to need a far
larger motor to act as the supply than the load.
************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

Why is a rotary phase convert better than a 3-phase alternator driven
by a high-current single phase motor?

Its cheaper, simpler, and smaller.
But I still think the alternator will generate more balanced 3ph power.

On 25 Aug 2004 19:07:03 GMT, (Charles A.
Sherwood) vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

Why is a rotary phase convert better than a 3-phase alternator driven
by a high-current single phase motor?

Its cheaper, simpler, and smaller.
But I still think the alternator will generate more balanced 3ph power.


AH. Thank you. That was my impression. See my other reply, posted
before I saw this one. Thanks.
************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

In article , Old Nick says...

RPCs seem complex and prone to all sorts of vagaries

You have to understand that most of the designs you
see are highly optimized. Using an oversized idler
motor that is started with a pony motor means you
don't need any power factor correction, no balancing,
and no starting circuitry.

It gets built for free, runs forever, and never
has to be thought about. Example is the patented
"jim's stone age converter" seen he

http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg

Your idea of using a large single phase motor to power an
excited field 3~ alternator is in principle the best way
to do this.

However because hardly anyone ever actually purchases a 3~ alternator
in the 5 hp range, and likewise 5 hp single phase motors, the
trouble is that those two things are incredibly expensive and never
available on the surplus market.

5 to 10 hp three phase motors on the other hand are literally
given away for scrap value on a regular basis. Likewise the small
1/4 hp pony motors to start the thing.

Folks build what they can afford, and what works. If you advocate
the more correct design, be prepared to put your wallet into the
breech to implement it. At the end of the day, nobody will be
able to tell the difference between the power on your wires, and
the power on my wires.

Your wires will wind up costing well over $1K. Mine are under
ten bucks.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Your idea of using a large single phase motor to power an
excited field 3~ alternator is in principle the best way
to do this.

However because hardly anyone ever actually purchases a 3~ alternator
in the 5 hp range, and likewise 5 hp single phase motors, the
trouble is that those two things are incredibly expensive and never
available on the surplus market.

5 to 10 hp three phase motors on the other hand are literally
given away for scrap value on a regular basis. Likewise the small
1/4 hp pony motors to start the thing.

Folks build what they can afford, and what works. If you advocate
the more correct design, be prepared to put your wallet into the
breech to implement it. At the end of the day, nobody will be
able to tell the difference between the power on your wires, and
the power on my wires.

Your wires will wind up costing well over $1K. Mine are under
ten bucks.


I assume you are refering to me because I proposed the motor
driving alternator design a while back. (but you quoted someone else)

I have looked for surplus motors to build a phase converter but
frankly I have not found the oasis where they are available for cheap.
The shipping costs are usually the killer.

One of the reasons I proposed building a motor alternator setup
is exactly what you quote above. I already have the alternator
and a 5HP motor to drive it. So to me it is cheap.

I started experimenting with a static phase converter because I
found a used one and a couple people here stated it would
be adequate for my needs. So far it seems to be working; but
running a 3ph motor on 2 windings rubs me the wrong way; Especially
when the run current in those two windings is higher than the
full load current spec of the motor.

Someday I will build that motor alternater setup and experiment
with it too. But for now, I got lots of projects ..

chuck

"Charles A. Sherwood" wrote in message
...

I have looked for surplus motors to build a phase converter but
frankly I have not found the oasis where they are available for cheap.
The shipping costs are usually the killer.

If you're in the Twin Cities (or nearby), Minnesota, I'll tell you where to
find a surplus motor. I got a 3HP GE motor for $30 (I countered a $50
original price, figuring that $10/hp was fair). It's running very nicely in
my garage.

The surplus store near my house (Axman) has 5HP motors for $200+, but
they're NOS rather than slightly used.

Pete

In article , Charles A. Sherwood says...

I assume you are refering to me because I proposed the motor
driving alternator design a while back. (but you quoted someone else)

My comments were specific to Nick who proposed an *electrically*
driven alternator to create a three phase supply, instead of
a rotary converter.

I have looked for surplus motors to build a phase converter but
frankly I have not found the oasis where they are available for cheap.
The shipping costs are usually the killer.

One of the reasons I proposed building a motor alternator setup
is exactly what you quote above. I already have the alternator
and a 5HP motor to drive it. So to me it is cheap.

Obviously in your case the 'works well and is cheap'
approach to life says you should use what you have
available. I would do the same thing if I had a prime
mover available, and no other easy way to get an idler
motor.

I started experimenting with a static phase converter because I
found a used one and a couple people here stated it would
be adequate for my needs. So far it seems to be working; but
running a 3ph motor on 2 windings rubs me the wrong way; Especially
when the run current in those two windings is higher than the
full load current spec of the motor.

Be aware that not all of that is 'real' power. Do see
how much it really is consuming, you need to check the
phase angle or have a true rms wattmeter available. It
might not be as much as you think from an ampclamp check.

Someday I will build that motor alternater setup and experiment
with it too. But for now, I got lots of projects ..

I understand that! I think I'm in the same boat as you on
this.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On 25 Aug 2004 15:01:18 -0700, jim rozen
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

In article , Charles A. Sherwood says...

I assume you are refering to me because I proposed the motor
driving alternator design a while back. (but you quoted someone else)

My comments were specific to Nick who proposed an *electrically*
driven alternator to create a three phase supply, instead of
a rotary converter.


I win! I win! GG

Obviously in your case the 'works well and is cheap'
approach to life says you should use what you have
available. I would do the same thing if I had a prime
mover available, and no other easy way to get an idler
motor.

AHereas I have to admit I do _not_ have the stuff available.

Someday I will build that motor alternater setup and experiment
with it too. But for now, I got lots of projects ..

I understand that! I think I'm in the same boat as you on
this.

Yes. My question also was not rhetorical, but is certainly theoretical
at present......some day...(sigh) :-
************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

Maybe my imagination but motors running under load on a static converter
seem to vibrate. My imagination? Anybody else?

bob g.

Charles A. Sherwood wrote:

Your idea of using a large single phase motor to power an
excited field 3~ alternator is in principle the best way
to do this.

However because hardly anyone ever actually purchases a 3~ alternator
in the 5 hp range, and likewise 5 hp single phase motors, the
trouble is that those two things are incredibly expensive and never
available on the surplus market.

5 to 10 hp three phase motors on the other hand are literally
given away for scrap value on a regular basis. Likewise the small
1/4 hp pony motors to start the thing.

Folks build what they can afford, and what works. If you advocate
the more correct design, be prepared to put your wallet into the
breech to implement it. At the end of the day, nobody will be
able to tell the difference between the power on your wires, and
the power on my wires.

Your wires will wind up costing well over $1K. Mine are under
ten bucks.



I assume you are refering to me because I proposed the motor
driving alternator design a while back. (but you quoted someone else)

I have looked for surplus motors to build a phase converter but
frankly I have not found the oasis where they are available for cheap.
The shipping costs are usually the killer.

One of the reasons I proposed building a motor alternator setup
is exactly what you quote above. I already have the alternator
and a 5HP motor to drive it. So to me it is cheap.

I started experimenting with a static phase converter because I
found a used one and a couple people here stated it would
be adequate for my needs. So far it seems to be working; but
running a 3ph motor on 2 windings rubs me the wrong way; Especially
when the run current in those two windings is higher than the
full load current spec of the motor.

Someday I will build that motor alternater setup and experiment
with it too. But for now, I got lots of projects ..

chuck

In article ,
Robert Galloway wrote:
Maybe my imagination but motors running under load on a static converter
seem to vibrate. My imagination? Anybody else?

Reasonable enough -- as you really running it purely from single
phase after it spins up to speed. The available torque goes through
zero twice per cycle (that is, at 1/120 of a second intervals in the
USA).

Real three phase -- or synthesized three phase from either a
rotary converter or a VFD does not, as when the torque from one phase is
approaching zero, another phase is approaching peak, and a third is just
past peak.

People who replace a three phase motor on a surface grinder with
a single phase motor notice a difference (degradation) in the resulting
finish.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 25 Aug 2004 21:45:26 GMT, (Charles A.
Sherwood) vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email


I assume you are refering to me because I proposed the motor
driving alternator design a while back. (but you quoted someone else)

Well if you're going to start fighting for glory...then so did I GG

Seriously, I did, and have experienced a lot of the same pricing
troubles and problems with the RPC idea that you have and so I still
want to keep looking at the motor-gen idea.


I have looked for surplus motors to build a phase converter but
frankly I have not found the oasis where they are available for cheap.
The shipping costs are usually the killer.


************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

If you can't find cheap three phase motors, you probably are not
looking in the right places. Try the scrap yards. I mean the yards
that supply steel scrap to steel mills. Not salvage yards.

As far as looking at a motor generator, have you considered using a
three phase induction generator?

Dan


Old Nick wrote in message

Seriously, I did, and have experienced a lot of the same pricing
troubles and problems with the RPC idea that you have and so I still
want to keep looking at the motor-gen idea.


I have looked for surplus motors to build a phase converter but
frankly I have not found the oasis where they are available for cheap.
The shipping costs are usually the killer.


************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

On 25 Aug 2004 13:18:31 -0700, jim rozen
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

In article , Old Nick says...

RPCs seem complex and prone to all sorts of vagaries

You have to understand that most of the designs you
see are highly optimized. Using an oversized idler
motor that is started with a pony motor means you
don't need any power factor correction, no balancing,
and no starting circuitry.

Ahah! OK. So simply throw grunt at the thing and avoid the fiddly
bits? That was something I had seen, but not understood (absorbed into
my soggy brain) the reason for, I think G

I agree about the lack of cheap/free 3PH alternators in the lower
ranges. They usually have a motor (fuel) attached. I did have the
opportunity yo buy one reasonably cheap. Did it work???? shrug. I
never went there, because I was not sure if my idea was the right way
to go.


It gets built for free, runs forever, and never
has to be thought about. Example is the patented
"jim's stone age converter" seen he
snip
Your wires will wind up costing well over $1K. Mine are under
ten bucks.

Jim

************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

On 25 Aug 2004 13:18:31 -0700, jim rozen
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

I did some reading. I remember now what my reservation was. While you
can throw plenty into the RPC, they are not good at allowing the
driven motor to produce full power. I am wondering what happens to
welders etc. Welding is one area where I see real bargains for very
powerful MIGs etc. I have seen a MIG that gets 350A from 240 volt, but
it was a new model, brand new with a VERy "new" price!

You have to understand that most of the designs you
see are highly optimized. Using an oversized idler
motor that is started with a pony motor means you
don't need any power factor correction, no balancing,
and no starting circuitry.


************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

In article ,
Old Nick wrote:
On 25 Aug 2004 13:18:31 -0700, jim rozen
vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

I did some reading. I remember now what my reservation was. While you
can throw plenty into the RPC, they are not good at allowing the
driven motor to produce full power.

This is a problem with a "static" phase converter, but for a
reasonably sized rotary converter -- especially one which has been
tuned and balanced by tweaking capacitance on the windings -- you should
be able to get full power out of the driven motor.

I am wondering what happens to
welders etc. Welding is one area where I see real bargains for very
powerful MIGs etc. I have seen a MIG that gets 350A from 240 volt, but
it was a new model, brand new with a VERy "new" price!

No experience with this, but I can't see any serious reason to
expect problems running it from a RPC. Here, I am not sure what will
happen from a VFD -- given that you have a switching regulator
synthesizing the output of the VFD, and possibly another one converting
the input to the welder into DC, so they might interfere with each
other. (I would also expect similar problems running a typical computer
from a VFD, too.)

But welders (and computers) don't need the variable frequency,
so I see little reason for using a VFD for this.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 26 Aug 2004 00:17:46 -0400, (DoN. Nichols)
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

I am probably thinking of the fact that the rotary part of the
converter needs a driver that is at least 1.5 times the power of the
driven gear, because of the trouble with the fact that it running as
if started by a static...on two legs only.

This is a problem with a "static" phase converter, but for a
reasonably sized rotary converter -- especially one which has been
tuned and balanced by tweaking capacitance on the windings -- you should
be able to get full power out of the driven motor.

************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

In article , Old Nick says...

I did some reading. I remember now what my reservation was. While you
can throw plenty into the RPC, they are not good at allowing the
driven motor to produce full power.

This is news to me. Where did you read that? For a reasonably
sized rotary converter (at least 50% larger than the driven
motor) you can develop full hp on the driven motor.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On 26 Aug 2004 09:22:39 -0700, jim rozen
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

In article , Old Nick says...

I did some reading. I remember now what my reservation was. While you
can throw plenty into the RPC, they are not good at allowing the
driven motor to produce full power.

This is news to me. Where did you read that? For a reasonably
sized rotary converter (at least 50% larger than the driven
motor) you can develop full hp on the driven motor.



D'OH. Now I have to find it again! G

I do take your and Don's point that the big muvva idea and some tuning
sound OK. It would appear that I was getting muxed ip with the static
converter.

http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

"The static converter is basically only a start circuit that once the
motor starts, disengages and lets the motor run on single phase power.
The disadvantage of this method is that the motor winding currents
will be very unbalanced and the motor will not be able to run above
about two-thirds its rated horsepower. The rotary converter provides
current in all 3 phases and although not perfect, will allow a motor
to provide all or nearly all its rated horsepower. If the motor has a
service factor of 1.15 to 1.25 then you should be able to use full
rated horsepower. The service factor can be found on the motor
nameplate and is usually abbreviated S.F. "

http://www.deselectric.com/
"Either a static converter or rotary phase converter can make it
possible to run a three phase motor on single phase power. The Static
Phase Converter does not actually generate three phase but only starts
an electric motor and then allows the motor to operate on only two of
the three windings in the motor. This being the case, the motor
then is running at 2/3 of its rated Hp.

A Rotary Phase Converter does provide full rated three phase power to
operate equipment without this loss of Hp. Rotary Converters are
always the best way to go, if you size them correctly for the
application."

Apart from that, I can remember discussions here about it.


************************************************** ***
I have decided that I should not be offended by
anybody's behaviour but my own......the theory's
good, anyway.

On 25 Aug 2004 13:18:31 -0700, jim rozen
wrote:


You have to understand that most of the designs you
see are highly optimized. Using an oversized idler
motor that is started with a pony motor means you
don't need any power factor correction, no balancing,
and no starting circuitry.

It gets built for free, runs forever, and never
has to be thought about. Example is the patented
"jim's stone age converter" seen he

http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg

Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting
to be turned into a RPC. Pony motors Ive got by the score.

Gunner, who was given a Hardinge DV-59 today. Disassembled but
complete....sigh

Anyone need any Federal air gauges? Got about a dozen of them G

Schaublin Lever action tailstock with built in collet holder in the
nose of the ram?

Scored today.... VBG)


"In my humble opinion, the petty carping levied against Bush by
the Democrats proves again, it is better to have your eye plucked
out by an eagle than to be nibbled to death by ducks." - Norman
Liebmann

In article ,
Gunner wrote:
On 25 Aug 2004 13:18:31 -0700, jim rozen
wrote:


You have to understand that most of the designs you
see are highly optimized. Using an oversized idler
motor that is started with a pony motor means you
don't need any power factor correction, no balancing,
and no starting circuitry.

It gets built for free, runs forever, and never
has to be thought about. Example is the patented
"jim's stone age converter" seen he

http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg

Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting
to be turned into a RPC. Pony motors Ive got by the score.

*What* wiring diagram? Switch power to two windings of the
idler motor, and to the single-phase pony motor to spin it up, then
switch off the pony after it has thrown its belt. (Based on what I
remember of Jim's setup.) Wire the three windings of the idler to the
three inputs of the target tool.

You just need a larger idler than with a well tuned one, and
since you are not tuning for the power factor, you may blow circuit
breakers more often than you would like, depending on the size of the
idler motor.

You also might have problems running electronics from the
generated power if it is across the wild (generated) leg. If you can be
sure that all electronics are connected to the primary two input lines
from the power company, you should be fine.

Note, also, that this has *no* safety circuit to disconnect the
idler when the power fails, so when it comes back on, the motor will sit
there humming until it burns up, or trips the breaker. So *always* turn
it off when you walk away.

If *I* were going for a rotary, I would want the safety circuits,
self starting, and properly tuned to reduce the reactive current drawn
from the wall.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article , DoN. Nichols says...

Note, also, that this has *no* safety circuit to disconnect the
idler when the power fails, so when it comes back on, the motor will sit
there humming until it burns up, or trips the breaker. So *always* turn
it off when you walk away.

Well nobody would be dumb enough to leave the darn thing on all
night.

Ahem.

Trouble is, this converter is really really quiet. I simply
cannot hear it running inside the little root celler it sits
in. The rubber stoppers do a great job of vibration isolation,
and I think it's a pretty high quality motor to start with.

I've got it powered off of a 15 amp breaker, through number
12 wire. The fuses in the knife switch are 10 amp, so it's on
a pretty short leash. I've had momentary lapses of grey matter
on occasion and threw the knife switch *before* spinning the
idler up - and the result is that it grunts for about a second
before one of the fuses pops.

Still a drop-out contactor is now on my list-O-stuff to do.

Until then I'll just be sure to turn the damn thing off before
leaving the shop, religiously. Maybe a note on the cellar door,
or a big red light in parallel with the drive.

Ahem.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On 26 Aug 2004 00:26:56 -0400, (DoN. Nichols) wrote:
In article ,
Gunner wrote:
Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting
to be turned into a RPC. Pony motors Ive got by the score.

*What* wiring diagram? Switch power to two windings of the
idler motor, and to the single-phase pony motor to spin it up, then
switch off the pony after it has thrown its belt. (Based on what I
remember of Jim's setup.) Wire the three windings of the idler to the
three inputs of the target tool.

Bad plan. Spin it up, *then* throw power to the rotary. With your
wiring scheme, you'd face a starting surge of well over 800 amps.
By spinning it up to nameplate RPM first, there will be no monster
starting surge when you throw power to the rotary.

Throwing belts isn't a very good idea either. Just kill power to the
pony once the rotary is started. It'll just freewheel then, with only
a small amount of extra windage drag over the windage of the
big rotary itself.

This is how I have my 20 HP rotary set up. The biggest single
load motor it ever sees is the 7.5 HP motor in my lathe, which
gives it plenty of headroom since it is capable of driving a 13.3
HP motor (20/1.5).

Ideal 100% efficiency current draw with that load should be 23.28
amps. Real world, it runs off a 30A motor rated breaker with no
nuisance trips. Of course I did tune it, and use power factor
correction caps. Without them, it'd need a much larger breaker.

At first, I had it wired your way, and it blew a 50A breaker every
time I tried to start it up. Based on my research, I now know it
would have blown the 200A main breaker if I'd wired it straight
to the main. Uncontrolled starting surge on a 20 HP motor is
*fierce*. By spinning it up with the pony first, I've eliminated that
huge starting surge.

Gary

Hey Gunner,

I was going to use a 20HP motor too. I kicked it into gear with a
pony motor, and it was drawing 80 plus amps. I've settled for a
7-1/2HP, which is still drawing 20 or so.

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXXXXXXX
On Thu, 26 Aug 2004 03:52:18 GMT, Gunner
wrote:

On 25 Aug 2004 13:18:31 -0700, jim rozen
wrote:


You have to understand that most of the designs you
see are highly optimized. Using an oversized idler
motor that is started with a pony motor means you
don't need any power factor correction, no balancing,
and no starting circuitry.

It gets built for free, runs forever, and never
has to be thought about. Example is the patented
"jim's stone age converter" seen he

http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg

Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting
to be turned into a RPC. Pony motors Ive got by the score.

Gunner, who was given a Hardinge DV-59 today. Disassembled but
complete....sigh

Anyone need any Federal air gauges? Got about a dozen of them G

Schaublin Lever action tailstock with built in collet holder in the
nose of the ram?

Scored today.... VBG)


"In my humble opinion, the petty carping levied against Bush by
the Democrats proves again, it is better to have your eye plucked
out by an eagle than to be nibbled to death by ducks." - Norman
Liebmann