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.

RWL

It is definitly possible since I do the same thing, with 10 and 7.5 HP
idlers. Been doing this for perhaps 4 years by now. Gives you numerous
advantages.

i

On 2008-10-06, GeoLane at PTD dot NET GeoLane wrote:
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.

RWL


--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
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On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

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.

RWL

You can, and they need not be mechanically connected.

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

On 2008-10-06, DrollTroll wrote:

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 will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

i

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.


--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

I will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

I also have a dual motor unit. 10 and 15 in my case. I'll just emphasize
that you need to delay the starting of motor 2 by several seconds. Spreads
start load.

Karl

On 2008-10-06, Karl Townsend wrote:
I will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

I also have a dual motor unit. 10 and 15 in my case. I'll just emphasize
that you need to delay the starting of motor 2 by several seconds. Spreads
start load.


That's what I do also. I have a starting switch and a button. I flip
the switch, which starts the first motor. At this point there is no
power on the output of phase converter, and the first motor is noisy,
because it is unbalanced electrically.

When I hear that it started, I push a button. That closes the
contactor that starts the second motor, and also connects balancing
caps for the other leg, and enables output.

At that point the RPC is running and producing balaned 3 phase power,
and quiet.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

"Ignoramus14503" wrote in message
...
On 2008-10-06, Karl Townsend wrote:
I will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

I also have a dual motor unit. 10 and 15 in my case. I'll just emphasize
that you need to delay the starting of motor 2 by several seconds.
Spreads
start load.


That's what I do also. I have a starting switch and a button. I flip
the switch, which starts the first motor. At this point there is no
power on the output of phase converter, and the first motor is noisy,
because it is unbalanced electrically.

When I hear that it started, I push a button. That closes the
contactor that starts the second motor, and also connects balancing
caps for the other leg, and enables output.

At that point the RPC is running and producing balanced 3 phase power,
and quiet.

I have a phase convertor that runs my downdraft grinding table. The Phase
convertor is a 7.5hp the table is 3hp. On occasion I shut the phase
convertor off without shutting the table off. I also once in a while, start
the phase convertor with the switch on the grinding table on. Does this
practice hurt anything?
Steve

On 2008-10-06, Up North wrote:

"Ignoramus14503" wrote in message
...
On 2008-10-06, Karl Townsend wrote:
I will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

I also have a dual motor unit. 10 and 15 in my case. I'll just emphasize
that you need to delay the starting of motor 2 by several seconds.
Spreads
start load.


That's what I do also. I have a starting switch and a button. I flip
the switch, which starts the first motor. At this point there is no
power on the output of phase converter, and the first motor is noisy,
because it is unbalanced electrically.

When I hear that it started, I push a button. That closes the
contactor that starts the second motor, and also connects balancing
caps for the other leg, and enables output.

At that point the RPC is running and producing balanced 3 phase power,
and quiet.

I have a phase convertor that runs my downdraft grinding table. The Phase
convertor is a 7.5hp the table is 3hp. On occasion I shut the phase
convertor off without shutting the table off. I also once in a while, start
the phase convertor with the switch on the grinding table on. Does this
practice hurt anything?

Could hurt the person who is changing the saw blade at the moment.

Otherwise, if that stuff starts quickly, I do not think so.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

"Ignoramus14503" wrote in message
...
On 2008-10-06, Up North wrote:

"Ignoramus14503" wrote in message
...
On 2008-10-06, Karl Townsend wrote:
I will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

I also have a dual motor unit. 10 and 15 in my case. I'll just
emphasize
that you need to delay the starting of motor 2 by several seconds.
Spreads
start load.


That's what I do also. I have a starting switch and a button. I flip
the switch, which starts the first motor. At this point there is no
power on the output of phase converter, and the first motor is noisy,
because it is unbalanced electrically.

When I hear that it started, I push a button. That closes the
contactor that starts the second motor, and also connects balancing
caps for the other leg, and enables output.

At that point the RPC is running and producing balanced 3 phase power,
and quiet.

I have a phase convertor that runs my downdraft grinding table. The Phase
convertor is a 7.5hp the table is 3hp. On occasion I shut the phase
convertor off without shutting the table off. I also once in a while,
start
the phase convertor with the switch on the grinding table on. Does this
practice hurt anything?

Could hurt the person who is changing the saw blade at the moment.

Otherwise, if that stuff starts quickly, I do not think so.

I can't tell a difference in startup time either way. There are no exposed
moving parts. Basically a vacuum cleaner inside a table with grates on top.
Here is a link to a newer model.
http://www.airflowsystems.com/products/specs/?n=dt-3000
Mine uses five large air filters similar to a truck air filter to clean the
air before exhausting it back into the shop. Sure beats having dust all over
the shop and in the winter there is no need to exhaust all the warm air
outside.
Steve

On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

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.

Others have given you good advice on rotary phase converters, but I'll
give you my take. Having run Bridgeports on rotary converters, static
converters and VFDs, a rotary would be my last choice. A VFD is much
more convenient, even with a 2J variable speed head, and a static
converter is more than adequate. RCM dogma says that you can't plug
reverse a BP with a static converter, but I did it for many years, as
does a friend of mine with 3 mills in a commercial shop.

--
Ned Simmons

On 2008-10-06, Ned Simmons wrote:
On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

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.

Others have given you good advice on rotary phase converters, but I'll
give you my take. Having run Bridgeports on rotary converters, static
converters and VFDs, a rotary would be my last choice. A VFD is much
more convenient, even with a 2J variable speed head, and a static
converter is more than adequate. RCM dogma says that you can't plug
reverse a BP with a static converter, but I did it for many years, as
does a friend of mine with 3 mills in a commercial shop.


Of everything, VFDs are the best option for a Bridgeport. Despite
having a phase converter, I run mine on a VFD and could not be any
happier.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

"Ned Simmons" wrote in message
...
On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

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.

Others have given you good advice on rotary phase converters, but I'll
give you my take. Having run Bridgeports on rotary converters, static
converters and VFDs, a rotary would be my last choice. A VFD is much
more convenient, even with a 2J variable speed head, and a static
converter is more than adequate. RCM dogma says that you can't plug
reverse a BP with a static converter, but I did it for many years, as
does a friend of mine with 3 mills in a commercial shop.

What is "plug reverse"?

The reversing issue on a static converter:

On static conversion, the motor can be reversed via the BP switch, as long
as the leads being interchanged are L1 and L2 -- or so I think. AND, of
course, the starting caps placed between L1-L3 or L2-L3.

The problem with static converters is that they seem to strain the motor
after startup, unless they are switched out, and balanced run capacitors are
switched in.

But if this is done, then I agree, static conversion, at least for one
motor, may be preferable -- altho, you will have to de-rate that motor.

Another 3 ph motor elsewhere on the grid would help "re-rate" the motor, but
then you have the curious scenario where the statically converted motor is
acting like an rpc!

So I would say that if you only have one motor, and you don't mind de-rating
it, static conversion would be preferable to an rpc.

But otherwise (1 motor, no de-rating), an rpc would proly make more sense.
I'm thinking of statically converting a compressor motor.

AND, interestingly enough, I have a residential central air unit that I just
discovered has a 3-ph compressor with... you guessed it.... static
conversion!!

Which is possibly why the compressor is so goddamm noisy, cuz of the
inherently imbalanced start capacitors, that are never switched out, of
course. Will be a chore to wire this up properly....

I've had two VFD's for some time, but haven't hooked them up yet -- thinking
of making a kalamazoo 9x13 hydraulic the first guinea pig -- but then I
could only put the blade motor on the VFD.

I'm still in rpc-mode.
VFDs, tho, are theoretically Da Bomb.
--
DT



--
Ned Simmons

"Up North" wrote in message
...

"Ignoramus14503" wrote in message
...
On 2008-10-06, Karl Townsend wrote:
I will list them, and I know that you mentioned quite a few.

1. Being able to use what you have
2. Lower startup current
3. Ability to add extra capacitors at the same time as switching in
the other motor, for perfectly balanced third phase

My phase converter is one of relatively few homemade things that I am
actually very happy with and that does not give me any trouble.

I also have a dual motor unit. 10 and 15 in my case. I'll just emphasize
that you need to delay the starting of motor 2 by several seconds.
Spreads
start load.


That's what I do also. I have a starting switch and a button. I flip
the switch, which starts the first motor. At this point there is no
power on the output of phase converter, and the first motor is noisy,
because it is unbalanced electrically.

When I hear that it started, I push a button. That closes the
contactor that starts the second motor, and also connects balancing
caps for the other leg, and enables output.

At that point the RPC is running and producing balanced 3 phase power,
and quiet.

I have a phase convertor that runs my downdraft grinding table. The Phase
convertor is a 7.5hp the table is 3hp. On occasion I shut the phase
convertor off without shutting the table off. I also once in a while,
start the phase convertor with the switch on the grinding table on. Does
this practice hurt anything?

Well, it does "violate" motor recommendations, but if the larger motor is
not started under load, it doesn't seem to hurt much. Small motors can
start larger ones, and I do it myself.

It just goes to show that 3-ph motors form a kind of 3-ph grid, and once one
is started, any other 3-ph motor can be started. Which is quite apropos of
the OP, ito of ganging motors.
--
DT




Steve

On Mon, 6 Oct 2008 11:28:41 -0400, "DrollTroll"
wrote:


"Ned Simmons" wrote in message
.. .
On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

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.

Others have given you good advice on rotary phase converters, but I'll
give you my take. Having run Bridgeports on rotary converters, static
converters and VFDs, a rotary would be my last choice. A VFD is much
more convenient, even with a 2J variable speed head, and a static
converter is more than adequate. RCM dogma says that you can't plug
reverse a BP with a static converter, but I did it for many years, as
does a friend of mine with 3 mills in a commercial shop.

What is "plug reverse"?

Plugging is reversing or decelerating the motor by rapidly switching
two motor leads. E.g., reversing a Bridgeport by switching directly
from forward to reverse without pausing at off.


The reversing issue on a static converter:

On static conversion, the motor can be reversed via the BP switch, as long
as the leads being interchanged are L1 and L2 -- or so I think. AND, of
course, the starting caps placed between L1-L3 or L2-L3.

It's been quite a while since I've had a BP connected to a static
converter, but that sounds right.


The problem with static converters is that they seem to strain the motor
after startup, unless they are switched out, and balanced run capacitors are
switched in.

But if this is done, then I agree, static conversion, at least for one
motor, may be preferable -- altho, you will have to de-rate that motor.

I'm not aware of any undue strain on the motor without run caps, as
long as, as you say, you don't push the motor too hard. And if you're
driving a Bridgeport's motor to capacity, the machine is probably
dancing across the floor.

--
Ned Simmons

"Ned Simmons" wrote in message
...
On Mon, 6 Oct 2008 11:28:41 -0400, "DrollTroll"
wrote:


"Ned Simmons" wrote in message
. ..
On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

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.

Others have given you good advice on rotary phase converters, but I'll
give you my take. Having run Bridgeports on rotary converters, static
converters and VFDs, a rotary would be my last choice. A VFD is much
more convenient, even with a 2J variable speed head, and a static
converter is more than adequate. RCM dogma says that you can't plug
reverse a BP with a static converter, but I did it for many years, as
does a friend of mine with 3 mills in a commercial shop.

What is "plug reverse"?

Plugging is reversing or decelerating the motor by rapidly switching
two motor leads. E.g., reversing a Bridgeport by switching directly
from forward to reverse without pausing at off.


The reversing issue on a static converter:

On static conversion, the motor can be reversed via the BP switch, as long
as the leads being interchanged are L1 and L2 -- or so I think. AND, of
course, the starting caps placed between L1-L3 or L2-L3.

It's been quite a while since I've had a BP connected to a static
converter, but that sounds right.


The problem with static converters is that they seem to strain the motor
after startup, unless they are switched out, and balanced run capacitors
are
switched in.

But if this is done, then I agree, static conversion, at least for one
motor, may be preferable -- altho, you will have to de-rate that motor.

I'm not aware of any undue strain on the motor without run caps, as
long as, as you say, you don't push the motor too hard. And if you're
driving a Bridgeport's motor to capacity, the machine is probably
dancing across the floor.

I can "tune" an rpc almost by ear -- the combination of caps across the
various legs that results in the quietest motor operation corresponds with
the most uniform voltage across all three legs!!

I assume this noise is some kind of electromechanical imbalance in the
motor -- in the stator winding(s), the rotor, etc.

Needless to say, stock commercial rpc's with those big-assed start caps that
are never switched out make a helluva racket, AND yield a 270 V third leg.

--
DT




--
Ned Simmons