I don't have the three phase power turned on, the tenant doesn't need
it. I could use all the three-phase machine tools a few hours a month
but it's just not worth the bill and deposit for power. I do have a VFD
that's good for three hp. Rather than hook up the VFD to each tool as I
need it, could I hook up all the building up to the output of the VFD
and just use one tool at a time? The lathe is 5hp but if I use it for
light work, will it be OK?

"Tom Gardner" wrote in message
...
I don't have the three phase power turned on, the tenant doesn't need it.
I could use all the three-phase machine tools a few hours a month but it's
just not worth the bill and deposit for power. I do have a VFD that's good
for three hp. Rather than hook up the VFD to each tool as I need it, could
I hook up all the building up to the output of the VFD and just use one
tool at a time? The lathe is 5hp but if I use it for light work, will it
be OK?

Because of the mass of the chuck and spindle the starting current of the
lathe could very well be too much for the VFD. ( likely? ) Polyspede makes
bigger single to 3 rated VFDs.

Not sure what you mean hook up all the building.

I've only read a few VFD manuals, but I seem to recall most said that the
motor should be within a certain distance of the VFD. How about a cart
option?

On 10/26/2015 10:40 PM, Bob La Londe wrote:
"Tom Gardner" wrote in message
...
I don't have the three phase power turned on, the tenant doesn't need it.
I could use all the three-phase machine tools a few hours a month but it's
just not worth the bill and deposit for power. I do have a VFD that's good
for three hp. Rather than hook up the VFD to each tool as I need it, could
I hook up all the building up to the output of the VFD and just use one
tool at a time? The lathe is 5hp but if I use it for light work, will it
be OK?

Because of the mass of the chuck and spindle the starting current of the
lathe could very well be too much for the VFD. ( likely? ) Polyspede makes
bigger single to 3 rated VFDs.

Not sure what you mean hook up all the building.

I've only read a few VFD manuals, but I seem to recall most said that the
motor should be within a certain distance of the VFD. How about a cart
option?






The cart was the original idea and probably the best option.

On 10/26/2015 09:40 PM, Bob La Londe wrote:
"Tom Gardner" wrote in message
...
I don't have the three phase power turned on, the tenant doesn't need it.
I could use all the three-phase machine tools a few hours a month but it's
just not worth the bill and deposit for power. I do have a VFD that's good
for three hp. Rather than hook up the VFD to each tool as I need it, could
I hook up all the building up to the output of the VFD and just use one
tool at a time? The lathe is 5hp but if I use it for light work, will it
be OK?

Because of the mass of the chuck and spindle the starting current of the
lathe could very well be too much for the VFD. ( likely? ) Polyspede makes
bigger single to 3 rated VFDs.

Not sure what you mean hook up all the building.

I've only read a few VFD manuals, but I seem to recall most said that the
motor should be within a certain distance of the VFD. How about a cart
option?

They also typically warn against putting any sort of switching between
the VFD and the motor.

--
Bob Nichols AT comcast.net I am "RNichols42"

On 2015-10-27, Tom Gardner wrote:
I don't have the three phase power turned on, the tenant doesn't need
it. I could use all the three-phase machine tools a few hours a month
but it's just not worth the bill and deposit for power. I do have a VFD
that's good for three hp. Rather than hook up the VFD to each tool as I
need it, could I hook up all the building up to the output of the VFD
and just use one tool at a time? The lathe is 5hp but if I use it for
light work, will it be OK?

It is generally bad news to have switches between the VFD and
the motor (as would normally be the case with the setup you are
proposing). The switching can produce HV sparks which can zap the
output transistors.

Now -- if you replaced each switch on the machines with a remote
FWD/OFF/REV switch, and added a rotary switch *at* the VFD to change
which tool is fed, you could probably do it with no problems. (Make
sure that the output is off before switching the VFD to the next
machine).

Now -- if you have an extremely over-rated VFD, you can probably
get away with switching between the VFD and the motor. I did with a 1
HP motor on a Nichols horizontal mill, and a 7-1/2 HP VFD. Once that
VFD got cooked by the heat from a fire in the shop, and I had to move to
a smaller one, I set it up so the machine's switch commanded the VFD for
FORWARD/STOP/REV, and added a pot for setting the speed, so I don't need
to switch belts as often.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) 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 ---

No, it sill not work as it the controls ill be inoperative if powered
from a VFD. You need a phase converter, which is very easy to make or
buy.

i

On 2015-10-27, Tom Gardner wrote:
I don't have the three phase power turned on, the tenant doesn't need
it. I could use all the three-phase machine tools a few hours a month
but it's just not worth the bill and deposit for power. I do have a VFD
that's good for three hp. Rather than hook up the VFD to each tool as I
need it, could I hook up all the building up to the output of the VFD
and just use one tool at a time? The lathe is 5hp but if I use it for
light work, will it be OK?

On Tue, 27 Oct 2015 18:31:05 -0500, Robert Nichols
wrote:

On 10/26/2015 09:40 PM, Bob La Londe wrote:
"Tom Gardner" wrote in message
...
I don't have the three phase power turned on, the tenant doesn't need it.
I could use all the three-phase machine tools a few hours a month but it's
just not worth the bill and deposit for power. I do have a VFD that's good
for three hp. Rather than hook up the VFD to each tool as I need it, could
I hook up all the building up to the output of the VFD and just use one
tool at a time? The lathe is 5hp but if I use it for light work, will it
be OK?

Because of the mass of the chuck and spindle the starting current of the
lathe could very well be too much for the VFD. ( likely? ) Polyspede makes
bigger single to 3 rated VFDs.

Not sure what you mean hook up all the building.

I've only read a few VFD manuals, but I seem to recall most said that the
motor should be within a certain distance of the VFD. How about a cart
option?

They also typically warn against putting any sort of switching between
the VFD and the motor.

Absolutely true. Ive had customers call asking me to come replace new
VFDs that they blew up by putting a switch between the VFD output and
the motor.

ALWAYS let the VFD do the work..never switch between it and the motor
Ever.

Gunner

Gunner Asch fired this volley in
:

ALWAYS let the VFD do the work..never switch between it and the motor
Ever.


Ayup! I can do a "slam reverse" with mine (using the VFD's input
signals), and have never had a problem, but I've seen guys blow up even
bigger ones on smaller motors by switching the outputs, instead of using
the functions almost all VFDs offer natively.

FWIW, doing a slam reverse with a VFD isn't quite as 'instant' as with a
switch on a 3-phase line, but still pretty quick.

Lloyd

On Wed, 28 Oct 2015 16:19:29 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Gunner Asch fired this volley in
:

ALWAYS let the VFD do the work..never switch between it and the motor
Ever.


Ayup! I can do a "slam reverse" with mine (using the VFD's input
signals), and have never had a problem, but I've seen guys blow up even
bigger ones on smaller motors by switching the outputs, instead of using
the functions almost all VFDs offer natively.

FWIW, doing a slam reverse with a VFD isn't quite as 'instant' as with a
switch on a 3-phase line, but still pretty quick.

Depends on the mass and what you have the drive programmed to do. I
regularly spin a Wegg 5hp motor, and 25lb spindle in .5 seconds or
less...as does every OmniTurn cnc lathe. Same with retrofits on
Hardinge HCs, AHCs, DV59s and so forth. Can I do the same with a
Smith Lyman 42" lathe? nope. The chuck alone is 500 lbs...

Lloyd

Gunner Asch fired this volley in
:

Depends on the mass and what you have the drive programmed to do.

Of COURSE it does, but you avoided addressing my statement in order to
make your own rules, Gunner!

A VFD (unless VASTLY oversized) won't slam-reverse a motor at ANY setting
that won't blow it up as fast as a reversing switch on essentially
unlimited-current 3-phase house power!

I _wholly_ approve of using VFDs, and they perform just fine (including
with [about] 0.5 second reverses on my 14" Chicom lathe). But it's silly
to say they'll perform like a 'zero-impedance' power line! (quoted,
because nothing's _really_ zero impedance/resistance/fusing/whatever)

Lloyd

On Wed, 28 Oct 2015 17:27:05 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Gunner Asch fired this volley in
:

Depends on the mass and what you have the drive programmed to do.

Of COURSE it does, but you avoided addressing my statement in order to
make your own rules, Gunner!

A VFD (unless VASTLY oversized) won't slam-reverse a motor at ANY setting
that won't blow it up as fast as a reversing switch on essentially
unlimited-current 3-phase house power!

I _wholly_ approve of using VFDs, and they perform just fine (including
with [about] 0.5 second reverses on my 14" Chicom lathe). But it's silly
to say they'll perform like a 'zero-impedance' power line! (quoted,
because nothing's _really_ zero impedance/resistance/fusing/whatever)

Lloyd

Slam reversing even Omniturns takes a finite amount of time (as an
example)..simply due to overcoming the mass/inertia. Yes..Ive built a
number of them without VFDs and regularly use Hardinge machines that
come without VFDs..and they reverse in close to .5 seconds when run at
max rpms. They too have inertia problems, spinning down the vari-drive
gear/belts, pulleys etc etc. Everything has mass..and sometimes that
mass can slow down a slam reverse significantly. The slower the
better.

Chuckle..remember..I repair machinery for a living..having done this
for almost 20 yrs. But yes..you are correct..slam reversing CAN be
quicker than use of a VFD in some applications. Indeed it can!

Milling machines with direct drive applications can do that..milling
machines with gear heads/belt driven heads..not so much.
And of course we all know that the bigger the VFD the better. The DC
buss helps handle the loads better. Which is why one does not power a
3hp motor with a 3hp vfd..one always goes up one or more hp when
picking a vfd.... when there is a need for high speed reverse.


Gunner

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
Gunner Asch fired this volley in
:

Depends on the mass and what you have the drive programmed to do.

Of COURSE it does, but you avoided addressing my statement in order
to
make your own rules, Gunner!

A VFD (unless VASTLY oversized) won't slam-reverse a motor at ANY
setting
that won't blow it up as fast as a reversing switch on essentially
unlimited-current 3-phase house power!

I _wholly_ approve of using VFDs, and they perform just fine
(including
with [about] 0.5 second reverses on my 14" Chicom lathe). But it's
silly
to say they'll perform like a 'zero-impedance' power line! (quoted,
because nothing's _really_ zero
impedance/resistance/fusing/whatever)

Lloyd

Some practical numbers:
http://www.cooperindustries.com/cont...ing_Rating.pdf

On Wed, 28 Oct 2015 15:15:41 -0700, Gunner Asch
wrote:

On Wed, 28 Oct 2015 16:19:29 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Gunner Asch fired this volley in
m:

ALWAYS let the VFD do the work..never switch between it and the motor
Ever.


Ayup! I can do a "slam reverse" with mine (using the VFD's input
signals), and have never had a problem, but I've seen guys blow up even
bigger ones on smaller motors by switching the outputs, instead of using
the functions almost all VFDs offer natively.

FWIW, doing a slam reverse with a VFD isn't quite as 'instant' as with a
switch on a 3-phase line, but still pretty quick.

Depends on the mass and what you have the drive programmed to do. I
regularly spin a Wegg 5hp motor, and 25lb spindle in .5 seconds or
less...as does every OmniTurn cnc lathe. Same with retrofits on
Hardinge HCs, AHCs, DV59s and so forth. Can I do the same with a
Smith Lyman 42" lathe? nope. The chuck alone is 500 lbs...

Don't they just throw juice to windings in both directions at once,
essentially freezing up the motor magnetically? That's a little safer
and easier on the hardware than what SawStop does, huh? vbg

-
To change one's self is sufficient. It's the idiots who want
to change the world who are causing all the trouble.
--Anonymous

Larry Jaques fired this volley in
:

Don't they just throw juice to windings in both directions at once,
essentially freezing up the motor magnetically?

Since a switched 'slam reverse' is just reversing the relationship of two
of the phases, that's exactly what they do on most VFDs, with the
exception that some can also impose some DC, or connect-in some braking
resistors to make the slowdown quicker; and all of them worth a penny
limit the current to what is safe for the VFD.

A simple DPDT switch on a line-fed setup can't do either of those things,
and it works fine, too (if the breaker doesn't pop). All it does is swap
two legs on the motor, and you have to deal with the other issues.

Lloyd

On Thu, 29 Oct 2015 19:59:17 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Larry Jaques fired this volley in
:

Don't they just throw juice to windings in both directions at once,
essentially freezing up the motor magnetically?

Since a switched 'slam reverse' is just reversing the relationship of two
of the phases, that's exactly what they do on most VFDs, with the
exception that some can also impose some DC, or connect-in some braking
resistors to make the slowdown quicker; and all of them worth a penny
limit the current to what is safe for the VFD.

A simple DPDT switch on a line-fed setup can't do either of those things,
and it works fine, too (if the breaker doesn't pop). All it does is swap
two legs on the motor, and you have to deal with the other issues.

I know you were saying "slam reverse", but I read that as a judicious
application of power by the crafty and knowledgeable VFD to stop the
spindle, taking into account all the above. Toggles don't do that,
let alone "right", but I've seen it done on other machinery over the
years in long-past garages.

-
To change one's self is sufficient. It's the idiots who want
to change the world who are causing all the trouble.
--Anonymous

On 10/29/2015 8:40 PM, Larry Jaques wrote:

Don't they just throw juice to windings in both directions at once,
essentially freezing up the motor magnetically? That's a little safer
and easier on the hardware than what SawStop does, huh? vbg

-
To change one's self is sufficient. It's the idiots who want
to change the world who are causing all the trouble.
--Anonymous


On a bunch of my 3-phase machines, I used what is called a plugging
switch that was controlled with a V-belt coming off a main shaft to stop
the motor.

On Fri, 30 Oct 2015 15:51:13 -0400, Tom Gardner
wrote:

On 10/29/2015 8:40 PM, Larry Jaques wrote:

Don't they just throw juice to windings in both directions at once,
essentially freezing up the motor magnetically? That's a little safer
and easier on the hardware than what SawStop does, huh? vbg

-
To change one's self is sufficient. It's the idiots who want
to change the world who are causing all the trouble.
--Anonymous


On a bunch of my 3-phase machines, I used what is called a plugging
switch that was controlled with a V-belt coming off a main shaft to stop
the motor.

Huh? How does a switch (electrical) controlled by a belt (mechanical)
stop a motor (electrical)? Ya lost me there, Tawmmy me boy. Are you
running a steam engine and mainshaft in yer shoppe?

Zis you? http://tinyurl.com/o2lctvz

--
Sound character provides the power with which a person may ride
the emergencies of life instead of being overwhelmed by them.
Failure is... the highway to success.
--Og Mandino

On 10/30/2015 8:40 PM, Larry Jaques wrote:

On a bunch of my 3-phase machines, I used what is called a plugging
switch that was controlled with a V-belt coming off a main shaft to stop
the motor.

Huh? How does a switch (electrical) controlled by a belt (mechanical)
stop a motor (electrical)? Ya lost me there, Tawmmy me boy. Are you
running a steam engine and mainshaft in yer shoppe?

Zis you? http://tinyurl.com/o2lctvz



There are still overhead shafts throughout the building and were used up
until the '50s. The shaft was run by a 1-cylinder natural gas engine.
All the babbited bearings are smooth as silk,

A Plugging switch stops a motor quickly. A speed switch with normally
open contacts is used in conjunction with a contactor or starter wired
to reverse the field windings of a squirrel cage motor. In plugging
applications, the device, when properly adjusted to given conditions,
will provide the control circuit logic to apply reverse energy to the
motor to reach zero speed. The motor, electrical power distribution, and
machine must be designed to handle sudden stopping.

On 2015-10-31, Tom Gardner wrote:
On 10/30/2015 8:40 PM, Larry Jaques wrote:

On a bunch of my 3-phase machines, I used what is called a plugging
switch that was controlled with a V-belt coming off a main shaft to stop
the motor.

Huh? How does a switch (electrical) controlled by a belt (mechanical)
stop a motor (electrical)? Ya lost me there, Tawmmy me boy. Are you
running a steam engine and mainshaft in yer shoppe?

Zis you? http://tinyurl.com/o2lctvz



There are still overhead shafts throughout the building and were used up
until the '50s. The shaft was run by a 1-cylinder natural gas engine.
All the babbited bearings are smooth as silk,

A Plugging switch stops a motor quickly. A speed switch with normally
open contacts is used in conjunction with a contactor or starter wired
to reverse the field windings of a squirrel cage motor. In plugging
applications, the device, when properly adjusted to given conditions,
will provide the control circuit logic to apply reverse energy to the
motor to reach zero speed. The motor, electrical power distribution, and
machine must be designed to handle sudden stopping.



Very interesting, I learned something new today, thanks a lot.

http://www.electrotechnik.net/2011/0...in-motors.html

On Sat, 31 Oct 2015 08:25:53 -0400, Tom Gardner
wrote:

On 10/30/2015 8:40 PM, Larry Jaques wrote:

On a bunch of my 3-phase machines, I used what is called a plugging
switch that was controlled with a V-belt coming off a main shaft to stop
the motor.

Huh? How does a switch (electrical) controlled by a belt (mechanical)
stop a motor (electrical)? Ya lost me there, Tawmmy me boy. Are you
running a steam engine and mainshaft in yer shoppe?

Zis you? http://tinyurl.com/o2lctvz



There are still overhead shafts throughout the building and were used up
until the '50s. The shaft was run by a 1-cylinder natural gas engine.
All the babbited bearings are smooth as silk,

Yeah, they're cool old tech. The only one I've seen in action was
powered by a steam engine (Vista museum) 30' away and it ran the power
hammer. I'd love to see one where I didn't have to listen to the
engine and hammer. OSHA doesn't like them much, though, wot?


A Plugging switch stops a motor quickly. A speed switch with normally
open contacts is used in conjunction with a contactor or starter wired
to reverse the field windings of a squirrel cage motor. In plugging
applications, the device, when properly adjusted to given conditions,
will provide the control circuit logic to apply reverse energy to the
motor to reach zero speed. The motor, electrical power distribution, and
machine must be designed to handle sudden stopping.

OK, I get all that, but how does it relate to the v-belted mainshaft?

--
Sound character provides the power with which a person may ride
the emergencies of life instead of being overwhelmed by them.
Failure is... the highway to success.
--Og Mandino

On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

On 2015-10-31, Tom Gardner wrote:
On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

How often do they reverse and how long do the motors last?

On 10/31/2015 1:51 PM, Ignoramus8568 wrote:
On 2015-10-31, Tom Gardner wrote:
On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.i
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

How often do they reverse and how long do the motors last?


The cycle is typically 30 to 40 seconds and pluggs for Less than a
second and I can't remember ever replacing a motor. The motors are
typically 3/4hp and could probably replaced with a 1/4hp. Excessive
plugging like when the machine is being repaired or tested and the motor
gets rather warm.

I just started installing VFD's on machines and would have put one on
every machine just for the speed control and ramp-up.

Now, I'll be using s VFD just for power conversion. I should build a
rotary, I'll see if there are some good motors laying around.

On 2015-10-31, Tom Gardner wrote:
f On 10/31/2015 1:51 PM, Ignoramus8568 wrote:
On 2015-10-31, Tom Gardner wrote:
On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.i
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

How often do they reverse and how long do the motors last?


The cycle is typically 30 to 40 seconds and pluggs for Less than a
second and I can't remember ever replacing a motor. The motors are
typically 3/4hp and could probably replaced with a 1/4hp. Excessive
plugging like when the machine is being repaired or tested and the motor
gets rather warm.

I just started installing VFD's on machines and would have put one on
every machine just for the speed control and ramp-up.

Now, I'll be using s VFD just for power conversion. I should build a
rotary, I'll see if there are some good motors laying around.

Used Motors are very cheap nowadays, you can get a scrap motor and
change out the bearings. It will give it 50 more years to go.

i

On Sat, 31 Oct 2015 10:48:33 -0400, Tom Gardner
wrote:

On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

Well why didn't you _say_ it was a mechanical logic switch? whap

--
Sound character provides the power with which a person may ride
the emergencies of life instead of being overwhelmed by them.
Failure is... the highway to success.
--Og Mandino

On Sat, 31 Oct 2015 12:51:45 -0500, Ignoramus8568
wrote:

On 2015-10-31, Tom Gardner wrote:
On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

How often do they reverse and how long do the motors last?

I think the vote goes to VFDs with braking resistors if you have to do
many quick stops. The article on pluggers noted that they heat up
quickly if you do much repetition.

--
Sound character provides the power with which a person may ride
the emergencies of life instead of being overwhelmed by them.
Failure is... the highway to success.
--Og Mandino

On Sat, 31 Oct 2015 20:12:59 -0700, Larry Jaques
wrote:

On Sat, 31 Oct 2015 12:51:45 -0500, Ignoramus8568
wrote:

On 2015-10-31, Tom Gardner wrote:
On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

How often do they reverse and how long do the motors last?

I think the vote goes to VFDs with braking resistors if you have to do
many quick stops. The article on pluggers noted that they heat up
quickly if you do much repetition.
Depending on the motor plugging may be OK. For example, my Bridgeport
mill motor has "Tropical Insulation" according to the nameplate. So I
guess that means it can tolerate heat better. There have been many
days over the years where I plug reversed the motor all day power
tapping holes and the motor never ran too hot. I have owned this mill
since 1981. If a motor can be kept cool enough then plugging will be
fine. Just adding a fan might be good enough and loads cheaper than a
VFD with a resistor bank. The switch on my mill is still the original
with the original contacts. It has been used to plug the motor
thousands of times.
Eric

On Sat, 31 Oct 2015 18:21:37 -0500, Ignoramus8568
wrote:

On 2015-10-31, Tom Gardner wrote:
f On 10/31/2015 1:51 PM, Ignoramus8568 wrote:
On 2015-10-31, Tom Gardner wrote:
On 10/31/2015 10:07 AM, Larry Jaques wrote:

OK, I get all that, but how does it relate to the v-belted mainshaft?

--

The v-belt tells the switch if the machine is going forward, revrse or
stopped. In a brush machine (like a BIG sewing machine) when it reaches
the "end of the brush" switch or the operator hits the "STOP" switch,
the plugging switch switches two legs of the 3-phase power to the motor
for as long as the shaft is moving and electrically brakes the motor.i
When the shaft stops turning, the contacts open and the motor/machine
can start again in forward.

Old tech but it works just fine.

How often do they reverse and how long do the motors last?


The cycle is typically 30 to 40 seconds and pluggs for Less than a
second and I can't remember ever replacing a motor. The motors are
typically 3/4hp and could probably replaced with a 1/4hp. Excessive
plugging like when the machine is being repaired or tested and the motor
gets rather warm.

I just started installing VFD's on machines and would have put one on
every machine just for the speed control and ramp-up.

Now, I'll be using s VFD just for power conversion. I should build a
rotary, I'll see if there are some good motors laying around.

Used Motors are very cheap nowadays, you can get a scrap motor and
change out the bearings. It will give it 50 more years to go.

i

Absolutely true.

Scrap steel is about $25 a ton at the moment here in California, scrap
copper is about a buck. Used motors are cheap as hell.