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Default Motor: Is it possible? Is it likely?

Some time back I was given a 230V 5HP DeWalt radial arm saw. I took it for
possible salvage. I already have a fair Delta 230V RAS. I didn't really
"know" what I wanted to do with it at the time. This is no light weight or
middle weight saw like we are used to associating with DeWalt. This thing
is a beast. It took four of us to pick it up and move it, and none of us
were weaklings.

I'd been playing with ideas for various metal cutting saws. One idea was an
overhead tracked circular saw. The idea is simply to be able to cut down
larger stock than I can manage on my band saw. Preferably a little closer
to final dimensions than I feel safe attempting with my little cheap band
saw. Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a saw for
the purpose... I do this as much for the experience and education as for
any financial gain. In my searching I found that atleast one company
already makes a RAS for metal cutting. SO!!!!!!! The premise is already
proven.

I took a look at the DeWalt because the guy who gave it to me said it was
"converted" to run on single phase. When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a VFD to
get the surface speed down in the range for steel cutting, and replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes done
to run a 3 phase motor on single phase at a reduced capacity. The thing is
the motor is labeled as single phase. Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind inside
the connection box. I decided to look things over, and there are five wires
coming out of the motor case. 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor. The
other two come out in a different spot each one shows continuity to one of
the three wires that come out together. Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such? Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a bench
and hook up the three wires that come out together to see what happens, but
I don't. Worst that would happen is I'd trip a breaker or maybe cook the
motor. The motor was free so either way I'd not be out much. All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises. I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw. Making one of my motors fit up would be quite a fabrication
chore.








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Default Motor: Is it possible? Is it likely?

On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw. I took it for
possible salvage. I already have a fair Delta 230V RAS. I didn't really
"know" what I wanted to do with it at the time. This is no light weight or
middle weight saw like we are used to associating with DeWalt. This thing
is a beast. It took four of us to pick it up and move it, and none of us
were weaklings.

I'd been playing with ideas for various metal cutting saws. One idea was an
overhead tracked circular saw. The idea is simply to be able to cut down
larger stock than I can manage on my band saw. Preferably a little closer
to final dimensions than I feel safe attempting with my little cheap band
saw. Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a saw for
the purpose... I do this as much for the experience and education as for
any financial gain. In my searching I found that atleast one company
already makes a RAS for metal cutting. SO!!!!!!! The premise is already
proven.

I took a look at the DeWalt because the guy who gave it to me said it was
"converted" to run on single phase. When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a VFD to
get the surface speed down in the range for steel cutting, and replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes done
to run a 3 phase motor on single phase at a reduced capacity. The thing is
the motor is labeled as single phase. Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind inside
the connection box. I decided to look things over, and there are five wires
coming out of the motor case. 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor. The
other two come out in a different spot each one shows continuity to one of
the three wires that come out together. Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such? Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a bench
and hook up the three wires that come out together to see what happens, but
I don't. Worst that would happen is I'd trip a breaker or maybe cook the
motor. The motor was free so either way I'd not be out much. All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises. I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw. Making one of my motors fit up would be quite a fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric
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Default Motor: Is it possible? Is it likely?

On 11/26/2017 5:54 PM, wrote:
On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw. I took it for
possible salvage. I already have a fair Delta 230V RAS. I didn't really
"know" what I wanted to do with it at the time. This is no light weight or
middle weight saw like we are used to associating with DeWalt. This thing
is a beast. It took four of us to pick it up and move it, and none of us
were weaklings.

I'd been playing with ideas for various metal cutting saws. One idea was an
overhead tracked circular saw. The idea is simply to be able to cut down
larger stock than I can manage on my band saw. Preferably a little closer
to final dimensions than I feel safe attempting with my little cheap band
saw. Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a saw for
the purpose... I do this as much for the experience and education as for
any financial gain. In my searching I found that atleast one company
already makes a RAS for metal cutting. SO!!!!!!! The premise is already
proven.

I took a look at the DeWalt because the guy who gave it to me said it was
"converted" to run on single phase. When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a VFD to
get the surface speed down in the range for steel cutting, and replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes done
to run a 3 phase motor on single phase at a reduced capacity. The thing is
the motor is labeled as single phase. Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind inside
the connection box. I decided to look things over, and there are five wires
coming out of the motor case. 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor. The
other two come out in a different spot each one shows continuity to one of
the three wires that come out together. Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such? Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a bench
and hook up the three wires that come out together to see what happens, but
I don't. Worst that would happen is I'd trip a breaker or maybe cook the
motor. The motor was free so either way I'd not be out much. All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises. I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw. Making one of my motors fit up would be quite a fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric


Bob,
My first thought would be that the motor was converted by a motor shop
and as such they would have properly put a name plate on it to give
it correct specification.

As for testing and not knowing the original voltage I would first
consider trying to read the ohms of each windings and compare to
an existing 3 phase motor.

The other choice for this free motor would be take to a local
motor shop (if it exist) and get them to convert it back.

Good luck and have fun with your new (among many) adventures.

Les

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Default Motor: Is it possible? Is it likely?

On 11/26/2017 5:18 PM, ABLE1 wrote:
On 11/26/2017 5:54 PM, wrote:
On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw.Â* I took
it for
possible salvage.Â* I already have a fair Delta 230V RAS.Â* I didn't
really
"know" what I wanted to do with it at the time.Â* This is no light
weight or
middle weight saw like we are used to associating with DeWalt.Â* This
thing
is a beast.Â* It took four of us to pick it up and move it, and none
of us
were weaklings.

I'd been playing with ideas for various metal cutting saws.Â* One idea
was an
overhead tracked circular saw.Â* The idea is simply to be able to cut
down
larger stock than I can manage on my band saw.Â* Preferably a little
closer
to final dimensions than I feel safe attempting with my little cheap
band
saw.Â* Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a
saw for
the purpose...Â* I do this as much for the experience and education as
for
any financial gain.Â* In my searching I found that atleast one company
already makes a RAS for metal cutting.Â* SO!!!!!!!Â* The premise is
already
proven.

I took a look at the DeWalt because the guy who gave it to me said it
was
"converted" to run on single phase.Â* When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a
VFD to
get the surface speed down in the range for steel cutting, and
replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes
done
to run a 3 phase motor on single phase at a reduced capacity.Â* The
thing is
the motor is labeled as single phase.Â* Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind
inside
the connection box.Â* I decided to look things over, and there are
five wires
coming out of the motor case.Â* 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor.Â* The
other two come out in a different spot each one shows continuity to
one of
the three wires that come out together.Â* Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such?Â* Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a
bench
and hook up the three wires that come out together to see what
happens, but
I don't.Â* Worst that would happen is I'd trip a breaker or maybe cook
the
motor.Â* The motor was free so either way I'd not be out much.Â* All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises.
I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw.Â* Making one of my motors fit up would be quite a
fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric


Bob,
My first thought would be that the motor was converted by a motor shop
and as such they would have properly put a name plate on it to give
it correct specification.

As for testing and not knowing the original voltage I would first
consider trying to read the ohms of each windings and compare to
an existing 3 phase motor.

The other choice for this free motor would be take to a local
motor shop (if it exist) and get them to convert it back.

Good luck and have fun with your new (among many) adventures.

Les


Thanks Les. I had not considered that the motor shop at DeWalt might
have done that. It just threw me that it looks like a 3 phase motor,
but was labeled single phase. I may just see if I can find a place to
strap the motor down and see if she will rope start.


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Default Motor: Is it possible? Is it likely?

On Wed, 29 Nov 2017 14:28:03 -0700, Bob La Londe
wrote:

On 11/26/2017 5:18 PM, ABLE1 wrote:
On 11/26/2017 5:54 PM, wrote:
On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw.* I took
it for
possible salvage.* I already have a fair Delta 230V RAS.* I didn't
really
"know" what I wanted to do with it at the time.* This is no light
weight or
middle weight saw like we are used to associating with DeWalt.* This
thing
is a beast.* It took four of us to pick it up and move it, and none
of us
were weaklings.

I'd been playing with ideas for various metal cutting saws.* One idea
was an
overhead tracked circular saw.* The idea is simply to be able to cut
down
larger stock than I can manage on my band saw.* Preferably a little
closer
to final dimensions than I feel safe attempting with my little cheap
band
saw.* Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a
saw for
the purpose...* I do this as much for the experience and education as
for
any financial gain.* In my searching I found that atleast one company
already makes a RAS for metal cutting.* SO!!!!!!!* The premise is
already
proven.

I took a look at the DeWalt because the guy who gave it to me said it
was
"converted" to run on single phase.* When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a
VFD to
get the surface speed down in the range for steel cutting, and
replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes
done
to run a 3 phase motor on single phase at a reduced capacity.* The
thing is
the motor is labeled as single phase.* Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind
inside
the connection box.* I decided to look things over, and there are
five wires
coming out of the motor case.* 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor.* The
other two come out in a different spot each one shows continuity to
one of
the three wires that come out together.* Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such?* Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a
bench
and hook up the three wires that come out together to see what
happens, but
I don't.* Worst that would happen is I'd trip a breaker or maybe cook
the
motor.* The motor was free so either way I'd not be out much.* All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises.
I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw.* Making one of my motors fit up would be quite a
fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric


Bob,
My first thought would be that the motor was converted by a motor shop
and as such they would have properly put a name plate on it to give
it correct specification.

As for testing and not knowing the original voltage I would first
consider trying to read the ohms of each windings and compare to
an existing 3 phase motor.

The other choice for this free motor would be take to a local
motor shop (if it exist) and get them to convert it back.

Good luck and have fun with your new (among many) adventures.

Les


Thanks Les. I had not considered that the motor shop at DeWalt might
have done that. It just threw me that it looks like a 3 phase motor,
but was labeled single phase. I may just see if I can find a place to
strap the motor down and see if she will rope start.


If it has a capacitor..it IS single phase.


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Default Motor: Is it possible? Is it likely?

On 11/29/2017 3:04 PM, Gunner Asch wrote:
On Wed, 29 Nov 2017 14:28:03 -0700, Bob La Londe
wrote:

On 11/26/2017 5:18 PM, ABLE1 wrote:
On 11/26/2017 5:54 PM, wrote:
On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw.Â* I took
it for
possible salvage.Â* I already have a fair Delta 230V RAS.Â* I didn't
really
"know" what I wanted to do with it at the time.Â* This is no light
weight or
middle weight saw like we are used to associating with DeWalt.Â* This
thing
is a beast.Â* It took four of us to pick it up and move it, and none
of us
were weaklings.

I'd been playing with ideas for various metal cutting saws.Â* One idea
was an
overhead tracked circular saw.Â* The idea is simply to be able to cut
down
larger stock than I can manage on my band saw.Â* Preferably a little
closer
to final dimensions than I feel safe attempting with my little cheap
band
saw.Â* Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a
saw for
the purpose...Â* I do this as much for the experience and education as
for
any financial gain.Â* In my searching I found that atleast one company
already makes a RAS for metal cutting.Â* SO!!!!!!!Â* The premise is
already
proven.

I took a look at the DeWalt because the guy who gave it to me said it
was
"converted" to run on single phase.Â* When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a
VFD to
get the surface speed down in the range for steel cutting, and
replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes
done
to run a 3 phase motor on single phase at a reduced capacity.Â* The
thing is
the motor is labeled as single phase.Â* Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind
inside
the connection box.Â* I decided to look things over, and there are
five wires
coming out of the motor case.Â* 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor.Â* The
other two come out in a different spot each one shows continuity to
one of
the three wires that come out together.Â* Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such?Â* Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a
bench
and hook up the three wires that come out together to see what
happens, but
I don't.Â* Worst that would happen is I'd trip a breaker or maybe cook
the
motor.Â* The motor was free so either way I'd not be out much.Â* All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises.
I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw.Â* Making one of my motors fit up would be quite a
fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric


Bob,
My first thought would be that the motor was converted by a motor shop
and as such they would have properly put a name plate on it to give
it correct specification.

As for testing and not knowing the original voltage I would first
consider trying to read the ohms of each windings and compare to
an existing 3 phase motor.

The other choice for this free motor would be take to a local
motor shop (if it exist) and get them to convert it back.

Good luck and have fun with your new (among many) adventures.

Les


Thanks Les. I had not considered that the motor shop at DeWalt might
have done that. It just threw me that it looks like a 3 phase motor,
but was labeled single phase. I may just see if I can find a place to
strap the motor down and see if she will rope start.


If it has a capacitor..it IS single phase.


Not necessarily. It is quite possible to run a three phase motor off
single phase... by using a capacitor. The fact that when it was given
to me I was told it had been converted to single phase from 3 phase and
that it has totally the wrong number of wires for single phase or single
phase cap start sort of throws a monkey wrench in the works too.






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Default Motor: Is it possible? Is it likely?

On Wed, 29 Nov 2017 15:10:23 -0700, Bob La Londe
wrote:

On 11/29/2017 3:04 PM, Gunner Asch wrote:
On Wed, 29 Nov 2017 14:28:03 -0700, Bob La Londe
wrote:

On 11/26/2017 5:18 PM, ABLE1 wrote:
On 11/26/2017 5:54 PM, wrote:
On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw.* I took
it for
possible salvage.* I already have a fair Delta 230V RAS.* I didn't
really
"know" what I wanted to do with it at the time.* This is no light
weight or
middle weight saw like we are used to associating with DeWalt.* This
thing
is a beast.* It took four of us to pick it up and move it, and none
of us
were weaklings.

I'd been playing with ideas for various metal cutting saws.* One idea
was an
overhead tracked circular saw.* The idea is simply to be able to cut
down
larger stock than I can manage on my band saw.* Preferably a little
closer
to final dimensions than I feel safe attempting with my little cheap
band
saw.* Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a
saw for
the purpose...* I do this as much for the experience and education as
for
any financial gain.* In my searching I found that atleast one company
already makes a RAS for metal cutting.* SO!!!!!!!* The premise is
already
proven.

I took a look at the DeWalt because the guy who gave it to me said it
was
"converted" to run on single phase.* When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a
VFD to
get the surface speed down in the range for steel cutting, and
replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes
done
to run a 3 phase motor on single phase at a reduced capacity.* The
thing is
the motor is labeled as single phase.* Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind
inside
the connection box.* I decided to look things over, and there are
five wires
coming out of the motor case.* 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor.* The
other two come out in a different spot each one shows continuity to
one of
the three wires that come out together.* Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such?* Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a
bench
and hook up the three wires that come out together to see what
happens, but
I don't.* Worst that would happen is I'd trip a breaker or maybe cook
the
motor.* The motor was free so either way I'd not be out much.* All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises.
I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw.* Making one of my motors fit up would be quite a
fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric


Bob,
My first thought would be that the motor was converted by a motor shop
and as such they would have properly put a name plate on it to give
it correct specification.

As for testing and not knowing the original voltage I would first
consider trying to read the ohms of each windings and compare to
an existing 3 phase motor.

The other choice for this free motor would be take to a local
motor shop (if it exist) and get them to convert it back.

Good luck and have fun with your new (among many) adventures.

Les


Thanks Les. I had not considered that the motor shop at DeWalt might
have done that. It just threw me that it looks like a 3 phase motor,
but was labeled single phase. I may just see if I can find a place to
strap the motor down and see if she will rope start.


If it has a capacitor..it IS single phase.


Not necessarily. It is quite possible to run a three phase motor off
single phase... by using a capacitor. The fact that when it was given
to me I was told it had been converted to single phase from 3 phase and
that it has totally the wrong number of wires for single phase or single
phase cap start sort of throws a monkey wrench in the works too.





You're absolutely correct Bob, a three phase motor can be started and
run with a capacitor. Single phase motors with a cap are actually two
phase motors and the cap is used for phase shifting. You knew this
already I'm sure but others may not. In fact, I can't think of any
single phase motor that isn't actually a two phase motor. Typically
the second shifted phase is disconnected once the motor comes up to
about 85% oiperating speed but not always.
Eric
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On Sun, 26 Nov 2017 15:09:18 -0700
"Bob La Londe" wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw. I took it for
possible salvage. I already have a fair Delta 230V RAS. I didn't really
"know" what I wanted to do with it at the time. This is no light weight or
middle weight saw like we are used to associating with DeWalt. This thing
is a beast. It took four of us to pick it up and move it, and none of us
were weaklings.

major snip

Try this old forum listing:

http://www.practicalmachinist.com/vb...tactor-265980/

That sure sounds like your saw or very similar...

--
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Grand Rapids MI/Zone 5b
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On 2017-11-30, wrote:

[ ... ]

You're absolutely correct Bob, a three phase motor can be started and
run with a capacitor. Single phase motors with a cap are actually two
phase motors and the cap is used for phase shifting. You knew this
already I'm sure but others may not.


In fact, I can't think of any
single phase motor that isn't actually a two phase motor. Typically
the second shifted phase is disconnected once the motor comes up to
about 85% oiperating speed but not always.
Eric


Is disconnected once it reaches the threshold speed, unless it
is a "run" cap (oil filled AC cap) instead of a starting cap (Non-Polar
electrolytic, and not capable of surviving very long with AC) Also, the
run cap is typically lower in capacity than the starting cap.

Also ... "universal" motors (AC/DC motors, with commutators and
brushes) are single phase only, but *induction* motors (AC only) are
typically either three-phase or two-phase used as cap start or cap run.

Also, there are "Hysteresis Synchronous" motors (also AC only)
with permanent magnet rotors which are run cap equipped and two phase
unless wound as three phase. They are normally used only when totally
stable motor speed is needed -- no slip like in induction motors. These
were commonly used for capstan motors in high quality tape recorders and
turntables where audio pitch shifts with speed.

An induction motor normally experiences slip, and a 2-pole one
on 60 Hz will run at about 3500 RPM or so, depending on load, while a
H-S will run at a fixed 3600 RPM.

And -- what makes an induction motor what is is is that the
rotor has a number of poles which are each surrounded by a cast metal to
make a shorted turn. Often, all of the parts between the poles are
joined to two rings of the same metal at the ends. When there is an AC
field, it inductively couples to the poles and creates a current in the
loops which makes temporary magnetic fields on the rotor poles, which
are dragged towards the stator poles. These fields decay and new ones
form on adjacent poles so the rotor "slips" behind the rotating fields
in the motor stator.

Enjoy,
DoN.

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I would not call a cap start motor a two phase at all.

I would call it a dual winding single phase. The starter winding -
large diameter short winding with a cap - dumps the AC power through
the winding as XL is canceled by XC for the tech guys.

The run winding is used once up to speed and an internal switch throws
at speed - switching run in and start out.

When the power company runs low voltage - starter winding is used
longer, meaning more power used and then the run is enabled.

Two phase is 2 of 3 phase in a Delta wiring of a 3 phase motor.
It is called an "Inverted V" or lost leg.

This is a basis of very high rel 3 phase. Input and output are 3 phase.
If a phase is lost on the input the output has 3 phase at 66% power IIRC.

One could in theory loose two one inside and outside. Dropping more,
but still running just fine. Hospitals and Police/Mil run these like
this in case of attack.

Martin

On 11/30/2017 10:49 AM, wrote:
On Wed, 29 Nov 2017 15:10:23 -0700, Bob La Londe
wrote:

On 11/29/2017 3:04 PM, Gunner Asch wrote:
On Wed, 29 Nov 2017 14:28:03 -0700, Bob La Londe
wrote:

On 11/26/2017 5:18 PM, ABLE1 wrote:
On 11/26/2017 5:54 PM,
wrote:
On Sun, 26 Nov 2017 15:09:18 -0700, "Bob La Londe"
wrote:

Some time back I was given a 230V 5HP DeWalt radial arm saw.Â* I took
it for
possible salvage.Â* I already have a fair Delta 230V RAS.Â* I didn't
really
"know" what I wanted to do with it at the time.Â* This is no light
weight or
middle weight saw like we are used to associating with DeWalt.Â* This
thing
is a beast.Â* It took four of us to pick it up and move it, and none
of us
were weaklings.

I'd been playing with ideas for various metal cutting saws.Â* One idea
was an
overhead tracked circular saw.Â* The idea is simply to be able to cut
down
larger stock than I can manage on my band saw.Â* Preferably a little
closer
to final dimensions than I feel safe attempting with my little cheap
band
saw.Â* Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a
saw for
the purpose...Â* I do this as much for the experience and education as
for
any financial gain.Â* In my searching I found that atleast one company
already makes a RAS for metal cutting.Â* SO!!!!!!!Â* The premise is
already
proven.

I took a look at the DeWalt because the guy who gave it to me said it
was
"converted" to run on single phase.Â* When the idea to use it for steel
cutting came to me I figured I'd convert it back to 3 phase and use a
VFD to
get the surface speed down in the range for steel cutting, and
replace the
wood table with a metal table.

My thought was maybe they had used a CAP on one phase as is sometimes
done
to run a 3 phase motor on single phase at a reduced capacity.Â* The
thing is
the motor is labeled as single phase.Â* Now there is a big ass cap on the
side of the motor and there is a starter relay mechanism of some kind
inside
the connection box.Â* I decided to look things over, and there are
five wires
coming out of the motor case.Â* 3 wires come out in one spot and show
continuity in pairs like you would expect from a three phase motor.Â* The
other two come out in a different spot each one shows continuity to
one of
the three wires that come out together.Â* Like you might expect for a cap
connection to the floating leg.

Is it possible it was a 3 phase motor that was configured with a CAP and
starter to run as single phase, and relabeled as such?Â* Is it likely?

Now if I had regular 3 phase power I'd probably strap the motor to a
bench
and hook up the three wires that come out together to see what
happens, but
I don't.Â* Worst that would happen is I'd trip a breaker or maybe cook
the
motor.Â* The motor was free so either way I'd not be out much.Â* All my 3
phase equipment runs on VFDs, and we know VFDs don't like surprises.
I do
not want to blow one up to find out.

I actually do have a couple spare 3 phase motors on the shelf, (smaller
ones) but the case for the one on the saw is already setup to bolt right
onto the saw.Â* Making one of my motors fit up would be quite a
fabrication
chore.







One way to test would be to connect two of those three windings to
single phase power through a momentary switch. Then wrap a rope around
the motor shaft and pull it to spin the motor up. as soon as the rope
comes off the shaft hit the switch. If the motor continues to spin up
and then runs with some vibration then it is probably a three phase
motor. I have spun up three phase motors this way to get them running
on single phase power. You need to get the shaft spinning at a pretty
good clip but it does work.
Eric


Bob,
My first thought would be that the motor was converted by a motor shop
and as such they would have properly put a name plate on it to give
it correct specification.

As for testing and not knowing the original voltage I would first
consider trying to read the ohms of each windings and compare to
an existing 3 phase motor.

The other choice for this free motor would be take to a local
motor shop (if it exist) and get them to convert it back.

Good luck and have fun with your new (among many) adventures.

Les


Thanks Les. I had not considered that the motor shop at DeWalt might
have done that. It just threw me that it looks like a 3 phase motor,
but was labeled single phase. I may just see if I can find a place to
strap the motor down and see if she will rope start.


If it has a capacitor..it IS single phase.


Not necessarily. It is quite possible to run a three phase motor off
single phase... by using a capacitor. The fact that when it was given
to me I was told it had been converted to single phase from 3 phase and
that it has totally the wrong number of wires for single phase or single
phase cap start sort of throws a monkey wrench in the works too.





You're absolutely correct Bob, a three phase motor can be started and
run with a capacitor. Single phase motors with a cap are actually two
phase motors and the cap is used for phase shifting. You knew this
already I'm sure but others may not. In fact, I can't think of any
single phase motor that isn't actually a two phase motor. Typically
the second shifted phase is disconnected once the motor comes up to
about 85% oiperating speed but not always.
Eric



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On 2017-12-03, Martin Eastburn wrote:
I would not call a cap start motor a two phase at all.


Call it a "temporary two phase", as that is present only as the
motor is starting, and is generated by the start cap.

I would call it a dual winding single phase. The starter winding -
large diameter short winding with a cap - dumps the AC power through
the winding as XL is canceled by XC for the tech guys.


Yes, two windings, but one gets standard phase, and the other
gets shifted phase, by the XL and XC causing a shift. This provides a
second magnetic field at an angle to start the motor spinning. You
*can* start the single phase motor with just one widing, if you have a
way to spin it just before you switch on power -- such as a rope wound
on the shaft.

The run winding is used once up to speed and an internal switch throws
at speed - switching run in and start out.


Not quite. The inertial (also internal) switch switches the
start winding out, but the run winding is connected full time -- as long
as there is power to the motor.

Look at the inertial switch when you have a motor open. It
only has the contacts to open the start winding -- not any more contacts
to close the run winding.

Or -- just apply an ohmmeter to the motor from outside (and with
AC power disconnected, too, to keep from frying the ohmmeter). It will
draw current and show a fairly low resistance. If the run winding were
open, you would only see a swing of the needle (if a meter) or a short
display of low resistance moving slowly to infinite resistance, as the
start cap charges. (Well ... some leakage in the cap, so you won't
really get all the way to infinite, as a perfect capacitor would.)

If you apply power *only* to the start winding, you still lack
the shifted phase relative to the run winding, so the motor still won't
start, without something external to spin it up. But, because it is
sitting there drawing lots of current, it *will* blow up the start cap
in short order. :-)

When the power company runs low voltage - starter winding is used
longer, meaning more power used and then the run is enabled.


And then the start winding is switched out, leaving just the run
winding which was already enabled.

Now -- I grant that this is not a precise phase relationship
between the two windings -- dependent on the value of the cap and the
inductance of the winding -- as well as the frequency of the AC applied
to it.

Two phase is 2 of 3 phase in a Delta wiring of a 3 phase motor.
It is called an "Inverted V" or lost leg.


This is when the phases are 120 degrees apart. There are also
two phase power lines (uncommon these days) which have a 90 degree phase
relationship -- and a tricky transformer circuit can convert between
true two phase and true three phase -- either direction. I forget the
full name of it, but 'T' is part of the name.

This is a basis of very high rel 3 phase. Input and output are 3 phase.
If a phase is lost on the input the output has 3 phase at 66% power IIRC.

One could in theory loose two one inside and outside. Dropping more,
but still running just fine. Hospitals and Police/Mil run these like
this in case of attack.


Understood -- but this is still talking about phases shifted 120
degrees relative to each other. So you could call them "partial three
phase". The two phase for motor starting is different, with 90 degrees
being ideal, but usually not hit precisely.

Enjoy,
DoN.

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You can get this on a common / ground lead and a power lead that
is hooked to the internal switch. The switch is in the start winding
at dead stop. Once turning fast, the switch flips and the run winding
is powered and the start is turned off. It is a Single Pole, double
throw switch that is controlled my speed.

Having a phase shifted internal winding gives you on a scope a waveform
and the non-shifted is only the power line. The run doesn't get anything.

The funny motor you are talking about is a milk station that has

A neutral/GND and two Legs of xxx volts that are really 2 legs of 3
phase.

I have 2 phase on my property. Two Highlines and I could have 3 phase
if I wanted with three transformers. I created my own from Single phase.

Martin

On 12/3/2017 10:41 PM, DoN. Nichols wrote:
On 2017-12-03, Martin Eastburn wrote:
I would not call a cap start motor a two phase at all.


Call it a "temporary two phase", as that is present only as the
motor is starting, and is generated by the start cap.

I would call it a dual winding single phase. The starter winding -
large diameter short winding with a cap - dumps the AC power through
the winding as XL is canceled by XC for the tech guys.


Yes, two windings, but one gets standard phase, and the other
gets shifted phase, by the XL and XC causing a shift. This provides a
second magnetic field at an angle to start the motor spinning. You
*can* start the single phase motor with just one widing, if you have a
way to spin it just before you switch on power -- such as a rope wound
on the shaft.

The run winding is used once up to speed and an internal switch throws
at speed - switching run in and start out.


Not quite. The inertial (also internal) switch switches the
start winding out, but the run winding is connected full time -- as long
as there is power to the motor.

Look at the inertial switch when you have a motor open. It
only has the contacts to open the start winding -- not any more contacts
to close the run winding.

Or -- just apply an ohmmeter to the motor from outside (and with
AC power disconnected, too, to keep from frying the ohmmeter). It will
draw current and show a fairly low resistance. If the run winding were
open, you would only see a swing of the needle (if a meter) or a short
display of low resistance moving slowly to infinite resistance, as the
start cap charges. (Well ... some leakage in the cap, so you won't
really get all the way to infinite, as a perfect capacitor would.)

If you apply power *only* to the start winding, you still lack
the shifted phase relative to the run winding, so the motor still won't
start, without something external to spin it up. But, because it is
sitting there drawing lots of current, it *will* blow up the start cap
in short order. :-)

When the power company runs low voltage - starter winding is used
longer, meaning more power used and then the run is enabled.


And then the start winding is switched out, leaving just the run
winding which was already enabled.

Now -- I grant that this is not a precise phase relationship
between the two windings -- dependent on the value of the cap and the
inductance of the winding -- as well as the frequency of the AC applied
to it.

Two phase is 2 of 3 phase in a Delta wiring of a 3 phase motor.
It is called an "Inverted V" or lost leg.


This is when the phases are 120 degrees apart. There are also
two phase power lines (uncommon these days) which have a 90 degree phase
relationship -- and a tricky transformer circuit can convert between
true two phase and true three phase -- either direction. I forget the
full name of it, but 'T' is part of the name.

This is a basis of very high rel 3 phase. Input and output are 3 phase.
If a phase is lost on the input the output has 3 phase at 66% power IIRC.

One could in theory loose two one inside and outside. Dropping more,
but still running just fine. Hospitals and Police/Mil run these like
this in case of attack.


Understood -- but this is still talking about phases shifted 120
degrees relative to each other. So you could call them "partial three
phase". The two phase for motor starting is different, with 90 degrees
being ideal, but usually not hit precisely.

Enjoy,
DoN.

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"DoN. Nichols" wrote in message
...
....You
*can* start the single phase motor with just one widing, if you have
a
way to spin it just before you switch on power -- such as a rope
wound
on the shaft.
.....

Enjoy,
DoN.


My father's bench grinder had such a motor, probably assembled by my
somewhat more technically savvy uncle from a bad appliance motor. To
use it I had to plug it in and quickly yank on the vee belt, being
careful to let go before my hand reached the front pulley. Once I
wasn't quick enough but the belt was so loose I didn't get hurt.
-jsw


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On 2017-12-04, Martin Eastburn wrote:
You can get this on a common / ground lead and a power lead that
is hooked to the internal switch. The switch is in the start winding
at dead stop. Once turning fast, the switch flips and the run winding
is powered and the start is turned off. It is a Single Pole, double
throw switch that is controlled my speed.


Not any which I have seen when I opened them up. They are
single pole single throw NC (Normally closed), and in series with the
start winding and the start cap.

For a two-voltage motor (120/240VAC), when wired for 120 VAC,
there are two run windings connected in parallel, and the start winding
cap and centrifugal switch are connected from line to neutral.

When wired for 240 VAC, the two run windings are in series,
making the junction point a tap on an autotransformer which gives a
voltage which is 120 VAC different from each end. The switch, cap and
start winding are connected between the center tap formed by the two run
windings and one end. Actually, to reverse the motor (only at start
time), you can select whether the other end of the start winding is
connected to one or the other of the 240 VAC line inputs. (I say "only
at start time", because the relative phase of the run and start windings
only determines the direction it is spun until the centrifugal switch
opens. Afterwards, you can switch quickly between the two positions and
the motor will keep spinning in the same direction. (You can also
switch ends on the start winding, leaving it connected to the same end,
but that requires a bit more complex a switching setup -- especially if
you are using a normal drum switch and want the entirity of the motor to
be disconnected from power in the "stop" position.

Having a phase shifted internal winding gives you on a scope a waveform
and the non-shifted is only the power line. The run doesn't get anything.


The run gets the normal phase from the power line, from 120 VAC
or 240 VAC single phase. The cap and start winding between them
generate a temporary phase in the start winding which differs from that
in the run winding, and which gives the angular field to start the motor
spinning.

The funny motor you are talking about is a milk station that has

A neutral/GND and two Legs of xxx volts that are really 2 legs of 3
phase.


A "milk station"? IIRC, the funny motor which I remember
writing about is the Hysteresis Synchronous motor, with a permanent
magnet rotor and speed locked to the power line frequency. Nothign to
do with milk that I know.

Looking below, I see that I must have written that about the
Hysteresis Synchronous motors in some other article, perhaps in a
different newsgroup or mailing list.

I have 2 phase on my property. Two Highlines and I could have 3 phase
if I wanted with three transformers. I created my own from Single phase.


Two highs and a neutral (if the two highs are fed from two
phases of a three phase power line), yes. If you are calling the two
lines of a 240 VAC power with neutral center tap, you can call those
only either "in phase" or "180 degrees out of phase", depending on how
you look at it, but you cannot generate three phase from that. You need
a 120 degree phase difference to allow this to work.

Of course, you can approximate three phase with a three phase
motor wired to 240 VAC, with a run capacitor shifting the phase to the
third winding. What the actual phase angle is will depend in part on
the value of the capacitor, and the inductance of the motor winding.
This is a rotary converter, and it can be self starting if the
run capacitance is connected only to one of the other windings, not
equally to both.

Or, you can have a separate start capacitor which is
automatically switched by the current in the main two windings.

Or -- you can start it with a pull rope just before switching on
the power. Some people on this newsgroup do this. A bit of a problem
if you walk out of the shop with a machine running, the power drops, and
then returns while you were away. The rotary motor sits there not
starting and getting quite hot.

Martin

On 12/3/2017 10:41 PM, DoN. Nichols wrote:
On 2017-12-03, Martin Eastburn wrote:
I would not call a cap start motor a two phase at all.


Call it a "temporary two phase", as that is present only as the
motor is starting, and is generated by the start cap.

I would call it a dual winding single phase. The starter winding -
large diameter short winding with a cap - dumps the AC power through
the winding as XL is canceled by XC for the tech guys.


Yes, two windings, but one gets standard phase, and the other
gets shifted phase, by the XL and XC causing a shift. This provides a
second magnetic field at an angle to start the motor spinning. You
*can* start the single phase motor with just one widing, if you have a
way to spin it just before you switch on power -- such as a rope wound
on the shaft.

The run winding is used once up to speed and an internal switch throws
at speed - switching run in and start out.


Not quite. The inertial (also internal) switch switches the
start winding out, but the run winding is connected full time -- as long
as there is power to the motor.

Look at the inertial switch when you have a motor open. It
only has the contacts to open the start winding -- not any more contacts
to close the run winding.

Or -- just apply an ohmmeter to the motor from outside (and with
AC power disconnected, too, to keep from frying the ohmmeter). It will
draw current and show a fairly low resistance. If the run winding were
open, you would only see a swing of the needle (if a meter) or a short
display of low resistance moving slowly to infinite resistance, as the
start cap charges. (Well ... some leakage in the cap, so you won't
really get all the way to infinite, as a perfect capacitor would.)

If you apply power *only* to the start winding, you still lack
the shifted phase relative to the run winding, so the motor still won't
start, without something external to spin it up. But, because it is
sitting there drawing lots of current, it *will* blow up the start cap
in short order. :-)

When the power company runs low voltage - starter winding is used
longer, meaning more power used and then the run is enabled.


And then the start winding is switched out, leaving just the run
winding which was already enabled.

Now -- I grant that this is not a precise phase relationship
between the two windings -- dependent on the value of the cap and the
inductance of the winding -- as well as the frequency of the AC applied
to it.

Two phase is 2 of 3 phase in a Delta wiring of a 3 phase motor.
It is called an "Inverted V" or lost leg.


This is when the phases are 120 degrees apart. There are also
two phase power lines (uncommon these days) which have a 90 degree phase
relationship -- and a tricky transformer circuit can convert between
true two phase and true three phase -- either direction. I forget the
full name of it, but 'T' is part of the name.

This is a basis of very high rel 3 phase. Input and output are 3 phase.
If a phase is lost on the input the output has 3 phase at 66% power IIRC.

One could in theory loose two one inside and outside. Dropping more,
but still running just fine. Hospitals and Police/Mil run these like
this in case of attack.


Understood -- but this is still talking about phases shifted 120
degrees relative to each other. So you could call them "partial three
phase". The two phase for motor starting is different, with 90 degrees
being ideal, but usually not hit precisely.

Enjoy,
DoN.



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On Sunday, November 26, 2017 at 5:09:23 PM UTC-5, Bob La Londe wrote:
Some time back I was given a 230V 5HP DeWalt radial arm saw. I took it for
possible salvage. I already have a fair Delta 230V RAS. I didn't really
"know" what I wanted to do with it at the time. This is no light weight or
middle weight saw like we are used to associating with DeWalt. This thing
is a beast. It took four of us to pick it up and move it, and none of us
were weaklings.

I'd been playing with ideas for various metal cutting saws. One idea was an
overhead tracked circular saw. The idea is simply to be able to cut down
larger stock than I can manage on my band saw. Preferably a little closer
to final dimensions than I feel safe attempting with my little cheap band
saw. Then I thought I already had a saw that might just do the job.

Now before the wealthy amongst you tell me to just go out and buy a saw for
the purpose... I do this as much for the experience and education as for
any financial gain. In my searching I found that atleast one company
already makes a RAS for metal cutting. SO!!!!!!! The premise is already
proven.

I took a look at the DeWalt because the guy who gave it to me said it was
"converted" to run on single phase.


If your near there, you could always go to a DeWalt factory site to ask and make sure. Here's one at: 7957 Central Ave; Capitol Heights, Maryland 20743 - (301) 333-0863


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A medium saw mill was sitting 20 yards from this chair. The 3 phase
runs down both sides of the highway. I am a tap, two high line fuses
and 2000 feet of poles. (After a hurricane, it was four 100' boom
trucks to fix my power lines. They shortened it by 200' but it is real
2 phase. This is in the country, the 2.5 miles away micro-plex town is
moving in on my acreage.

I used to teach the stuff. And know what I have.
Martin

On 12/4/2017 10:53 PM, DoN. Nichols wrote:
On 2017-12-04, Martin Eastburn wrote:
You can get this on a common / ground lead and a power lead that
is hooked to the internal switch. The switch is in the start winding
at dead stop. Once turning fast, the switch flips and the run winding
is powered and the start is turned off. It is a Single Pole, double
throw switch that is controlled my speed.


Not any which I have seen when I opened them up. They are
single pole single throw NC (Normally closed), and in series with the
start winding and the start cap.

For a two-voltage motor (120/240VAC), when wired for 120 VAC,
there are two run windings connected in parallel, and the start winding
cap and centrifugal switch are connected from line to neutral.

When wired for 240 VAC, the two run windings are in series,
making the junction point a tap on an autotransformer which gives a
voltage which is 120 VAC different from each end. The switch, cap and
start winding are connected between the center tap formed by the two run
windings and one end. Actually, to reverse the motor (only at start
time), you can select whether the other end of the start winding is
connected to one or the other of the 240 VAC line inputs. (I say "only
at start time", because the relative phase of the run and start windings
only determines the direction it is spun until the centrifugal switch
opens. Afterwards, you can switch quickly between the two positions and
the motor will keep spinning in the same direction. (You can also
switch ends on the start winding, leaving it connected to the same end,
but that requires a bit more complex a switching setup -- especially if
you are using a normal drum switch and want the entirity of the motor to
be disconnected from power in the "stop" position.

Having a phase shifted internal winding gives you on a scope a waveform
and the non-shifted is only the power line. The run doesn't get anything.


The run gets the normal phase from the power line, from 120 VAC
or 240 VAC single phase. The cap and start winding between them
generate a temporary phase in the start winding which differs from that
in the run winding, and which gives the angular field to start the motor
spinning.

The funny motor you are talking about is a milk station that has

A neutral/GND and two Legs of xxx volts that are really 2 legs of 3
phase.


A "milk station"? IIRC, the funny motor which I remember
writing about is the Hysteresis Synchronous motor, with a permanent
magnet rotor and speed locked to the power line frequency. Nothign to
do with milk that I know.

Looking below, I see that I must have written that about the
Hysteresis Synchronous motors in some other article, perhaps in a
different newsgroup or mailing list.

I have 2 phase on my property. Two Highlines and I could have 3 phase
if I wanted with three transformers. I created my own from Single phase.


Two highs and a neutral (if the two highs are fed from two
phases of a three phase power line), yes. If you are calling the two
lines of a 240 VAC power with neutral center tap, you can call those
only either "in phase" or "180 degrees out of phase", depending on how
you look at it, but you cannot generate three phase from that. You need
a 120 degree phase difference to allow this to work.

Of course, you can approximate three phase with a three phase
motor wired to 240 VAC, with a run capacitor shifting the phase to the
third winding. What the actual phase angle is will depend in part on
the value of the capacitor, and the inductance of the motor winding.
This is a rotary converter, and it can be self starting if the
run capacitance is connected only to one of the other windings, not
equally to both.

Or, you can have a separate start capacitor which is
automatically switched by the current in the main two windings.

Or -- you can start it with a pull rope just before switching on
the power. Some people on this newsgroup do this. A bit of a problem
if you walk out of the shop with a machine running, the power drops, and
then returns while you were away. The rotary motor sits there not
starting and getting quite hot.

Martin

On 12/3/2017 10:41 PM, DoN. Nichols wrote:
On 2017-12-03, Martin Eastburn wrote:
I would not call a cap start motor a two phase at all.

Call it a "temporary two phase", as that is present only as the
motor is starting, and is generated by the start cap.

I would call it a dual winding single phase. The starter winding -
large diameter short winding with a cap - dumps the AC power through
the winding as XL is canceled by XC for the tech guys.

Yes, two windings, but one gets standard phase, and the other
gets shifted phase, by the XL and XC causing a shift. This provides a
second magnetic field at an angle to start the motor spinning. You
*can* start the single phase motor with just one widing, if you have a
way to spin it just before you switch on power -- such as a rope wound
on the shaft.

The run winding is used once up to speed and an internal switch throws
at speed - switching run in and start out.

Not quite. The inertial (also internal) switch switches the
start winding out, but the run winding is connected full time -- as long
as there is power to the motor.

Look at the inertial switch when you have a motor open. It
only has the contacts to open the start winding -- not any more contacts
to close the run winding.

Or -- just apply an ohmmeter to the motor from outside (and with
AC power disconnected, too, to keep from frying the ohmmeter). It will
draw current and show a fairly low resistance. If the run winding were
open, you would only see a swing of the needle (if a meter) or a short
display of low resistance moving slowly to infinite resistance, as the
start cap charges. (Well ... some leakage in the cap, so you won't
really get all the way to infinite, as a perfect capacitor would.)

If you apply power *only* to the start winding, you still lack
the shifted phase relative to the run winding, so the motor still won't
start, without something external to spin it up. But, because it is
sitting there drawing lots of current, it *will* blow up the start cap
in short order. :-)

When the power company runs low voltage - starter winding is used
longer, meaning more power used and then the run is enabled.

And then the start winding is switched out, leaving just the run
winding which was already enabled.

Now -- I grant that this is not a precise phase relationship
between the two windings -- dependent on the value of the cap and the
inductance of the winding -- as well as the frequency of the AC applied
to it.

Two phase is 2 of 3 phase in a Delta wiring of a 3 phase motor.
It is called an "Inverted V" or lost leg.

This is when the phases are 120 degrees apart. There are also
two phase power lines (uncommon these days) which have a 90 degree phase
relationship -- and a tricky transformer circuit can convert between
true two phase and true three phase -- either direction. I forget the
full name of it, but 'T' is part of the name.

This is a basis of very high rel 3 phase. Input and output are 3 phase.
If a phase is lost on the input the output has 3 phase at 66% power IIRC.

One could in theory loose two one inside and outside. Dropping more,
but still running just fine. Hospitals and Police/Mil run these like
this in case of attack.

Understood -- but this is still talking about phases shifted 120
degrees relative to each other. So you could call them "partial three
phase". The two phase for motor starting is different, with 90 degrees
being ideal, but usually not hit precisely.

Enjoy,
DoN.



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Default Motor: Is it possible? Is it likely?

"Martin Eastburn" wrote in message
...
A medium saw mill was sitting 20 yards from this chair. The 3 phase
runs down both sides of the highway. I am a tap, two high line
fuses
and 2000 feet of poles. (After a hurricane, it was four 100' boom
trucks to fix my power lines. They shortened it by 200' but it is
real
2 phase. This is in the country, the 2.5 miles away micro-plex town
is
moving in on my acreage.

I used to teach the stuff. And know what I have.
Martin


So you have 208V between phases?


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