I have a milling machine that's starting to show its age. It has a 5 Hp,
208V, 3 Ph spindle motor that's currently on a full voltage Fwd/Rev starter.
Motor really slams when turned on and has damaged the variable speed sheaves
and keyways.

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be the
best choice.

Does anybody have a favorite unit to recommend?
Ones I've seen so far have a SCR in series with two of the three legs and
control starting voltage and ramp-up time. If you keep them powered, they
can also control ramp-down time. A contactor bypasses the reduced voltage
system after the ramp time. All fine and well but only some of the vendors
seem to rate # of starts per hour. I would assume that this is due to heat
generation when the SCRs are carrying the load and the need to dissipate it.

Thanks in advance for any answers
Oppie

On Mar 3, 9:36*am, "Oppie" wrote:

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be the
best choice.

Oppie


You might ask if there is anyone that has had problems using a vfd on
an old motor. I know it is possible to have a problem, but I have not
had a problem. However I have not used that many VFD's with old
motors. So I would ask others with more experience.

Dan

On Mar 3, 8:36*am, "Oppie" wrote:
I have a milling machine that's starting to show its age. It has a 5 Hp,
208V, 3 Ph spindle motor that's currently on a full voltage Fwd/Rev starter.
Motor really slams when turned on and has damaged the variable speed sheaves
and keyways.

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be the
best choice.

Does anybody have a favorite unit to recommend?
Ones I've seen so far have a SCR in series with two of the three legs and
control starting voltage and ramp-up time. If you keep them powered, they
can also control ramp-down time. *A contactor bypasses the reduced voltage
system after the ramp time. All fine and well but only some of the vendors
seem to rate # of starts per hour. *I would assume that this is due to heat
generation when the SCRs are carrying the load and the need to dissipate it.

Thanks in advance for any answers
Oppie

I have two mills that I've installed VFDs on. The WELLS INDEX 645,
has a 3HP C-Face motor not inverter duty ~1968. I've used this now
for 11 years without problems. Hitachi SJ300. Also a Rockford
horizontal mill, that someone a long time ago put a overhead
conversion to drive the flat belt of this antique beast. This has a
5HP motor from some time in the 50s, this has a TECO 7200 drive. Also
put a 10HP drive on a 7.5 HP lathe motor (not inverter duty). But I
generally never push the HP envelope while machining, as I dry cut, so
slow feed and SFPM on the mills, and ceramic tooling light feeds on
the lathes. I've installed 3ph motors on my 1976 Jet 12x24 lathe,
drill press and vertical bandsaw, but these were 1HP motor with drive
kits from dealerselectric.com and were the older TECO FM100 that would
not run the motors smoothly down below 20-30Hz (the motors were
inverter duty). I recommend the sensorless vector drives, as I've had
very good luck with controlled low RPM operation.
All my wiring is short, all 240VAC single phase in. So as of yet I
have not punched through any insulation of the motors and caused
arching.
Someone here will probably beat me up over this.
ignator

On Mar 3, 4:04*pm, ignator wrote:
On Mar 3, 8:36*am, "Oppie" wrote:









I have a milling machine that's starting to show its age. It has a 5 Hp,
208V, 3 Ph spindle motor that's currently on a full voltage Fwd/Rev starter.
Motor really slams when turned on and has damaged the variable speed sheaves
and keyways.

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be the
best choice.

Does anybody have a favorite unit to recommend?
Ones I've seen so far have a SCR in series with two of the three legs and
control starting voltage and ramp-up time. If you keep them powered, they
can also control ramp-down time. *A contactor bypasses the reduced voltage
system after the ramp time. All fine and well but only some of the vendors
seem to rate # of starts per hour. *I would assume that this is due to heat
generation when the SCRs are carrying the load and the need to dissipate it.

Thanks in advance for any answers
Oppie

I have two mills that I've installed VFDs on. *The WELLS INDEX 645,
has a 3HP C-Face motor not inverter duty ~1968. *I've used this now
for 11 years without problems. *Hitachi SJ300. * Also a Rockford
horizontal mill, that someone a long time ago put a overhead
conversion to drive the flat belt of this antique beast. *This has a
5HP motor from some time in the 50s, this has a TECO 7200 drive. *Also
put a 10HP drive on a 7.5 HP lathe motor (not inverter duty). But I
generally never push the HP envelope while machining, as I dry cut, so
slow feed and SFPM on the mills, and ceramic tooling light feeds on
the lathes. *I've installed 3ph motors on my 1976 Jet 12x24 lathe,
drill press and vertical bandsaw, but these were 1HP motor with drive
kits from dealerselectric.com and were the older TECO FM100 that would
not run the motors smoothly down below 20-30Hz (the motors were
inverter duty). *I recommend the sensorless vector drives, as I've had
very good luck with controlled low RPM operation.
All my wiring is short, all 240VAC single phase in. *So as of yet I
have not punched through any insulation of the motors and caused
arching.
Someone here will probably beat me up over this.
ignator

Found this link
http://www1.eere.energy.gov/manufact...ployment/pdfs/
motor_tip_sheet14.pdf
This references standing waves with long cables. Maybe that's why
I've been lucky. I'm just using standard SO cord to connect the mains
to the VFD and VFD to the motor.
ignator

"ignator" wrote in message
...
On Mar 3, 4:04 pm, ignator wrote:
I have two mills that I've installed VFDs on. The WELLS INDEX 645,
has a 3HP C-Face motor not inverter duty ~1968. I've used this now
for 11 years without problems. Hitachi SJ300. Also a Rockford
horizontal mill, that someone a long time ago put a overhead
conversion to drive the flat belt of this antique beast. This has a
5HP motor from some time in the 50s, this has a TECO 7200 drive. Also
put a 10HP drive on a 7.5 HP lathe motor (not inverter duty). But I
generally never push the HP envelope while machining, as I dry cut, so
slow feed and SFPM on the mills, and ceramic tooling light feeds on
the lathes. I've installed 3ph motors on my 1976 Jet 12x24 lathe,
drill press and vertical bandsaw, but these were 1HP motor with drive
kits from dealerselectric.com and were the older TECO FM100 that would
not run the motors smoothly down below 20-30Hz (the motors were
inverter duty). I recommend the sensorless vector drives, as I've had
very good luck with controlled low RPM operation.
All my wiring is short, all 240VAC single phase in. So as of yet I
have not punched through any insulation of the motors and caused
arching.
Someone here will probably beat me up over this.
ignator

Found this link
http://www1.eere.energy.gov/manufact...ployment/pdfs/
motor_tip_sheet14.pdf
This references standing waves with long cables. Maybe that's why
I've been lucky. I'm just using standard SO cord to connect the mains
to the VFD and VFD to the motor.
ignator


Informative, Thank you!

I had read in the past that putting a "non-inverter" qualified motor on a
VFD caused the motor to overheat (due to iron hysteresis and eddy current
losses) from the high frequency harmonics and bearings to fail from
circulating currents that caused current flow through the bearings. The
exception was if a "line reactor" (basically a 3 ph inductor) was added
between the VFD and motor to smooth out the high frequency content of the
drive waveform. You seem to have disproved this though. VFD technology is
rapidly changing and hard to keep up with.

I had originally posted this inquiry to news:sci.electronics.design under
thread "Soft starter or VFD" and added a bunch of links for soft starters I
had found.

Cheers - Oppie

"Oppie" wrote:

"ignator" wrote in message
...

Someone here will probably beat me up over this.
ignator

Found this link
http://www1.eere.energy.gov/manufact...ployment/pdfs/
motor_tip_sheet14.pdf
This references standing waves with long cables. Maybe that's why
I've been lucky. I'm just using standard SO cord to connect the mains
to the VFD and VFD to the motor.
ignator


Informative, Thank you!

I had read in the past that putting a "non-inverter" qualified motor on a
VFD caused the motor to overheat (due to iron hysteresis and eddy current
losses) from the high frequency harmonics
really only an issue if you are trying to squeeze every little bit of
power out of the motor. AS I understand them,
"inverter duty " motors largely have better insulation.

and bearings to fail from
circulating currents that caused current flow through the bearings.
This can happen to motors run from any source, but is worse in motors
run from a vfd, but not really a big deal IMO, unless again, you are
running the motor to the ragged edge.
The
exception was if a "line reactor" (basically a 3 ph inductor) was added
between the VFD and motor to smooth out the high frequency content of the
drive waveform.
That is not really why they are there.
The motor itself acts as sufficient inductance to smooth out the
current. It is the voltage that is a problem that the line reactors
(which are just 3 inductors) are meant to solve.

The sharp rise time of the voltage wave forms are more stressful to
the insulation. The frequency is also an issue (switching frequency
that is) because with LONG cable lengths you can reach a point where
the Cable capacitance, and the system inductance resonate, causing
MUCH worse voltage stress at the motor. Unless you are putting the
motor 100s of feet away from the VFD, I wouldn't worry. It is an
issue for something like a down hole pump.
You seem to have disproved this though. VFD technology is
rapidly changing and hard to keep up with.

He doesn't really disprove it, just shows how much of a non issue it
really is for his sort of usage.

If he wants to run his motors at max power or 24/7 then the issue
could be more critical.

Simple basic motors, in basic applications are run from VFDs all the
time in the real world, without a problem.

I had originally posted this inquiry to news:sci.electronics.design under
thread "Soft starter or VFD" and added a bunch of links for soft starters I
had found.

Cheers - Oppie
As A PS, Soft starters are not intended to be SOFT for the Load, but
instead are SOFT (ish) for the power system that feeds them. They may
not do a whole lot for your issue.
jk

The two basic cautions for VFD use are that the output of VFDs consists of a
fast risetime voltage waves, similar in appearance to squarewaves (as
opposed to the gradual rise/fall of sinewaves normally applied to a motor
without a VFD).

Ideally, a VFD should be used with motors rated for "inverter duty" which
means they have a higher voltage rated insulation.. but many dual-voltage
motors operate without problems when the output of the VFD is set to the
lower dual-voltage spec (at 240V rather than the 480V rating), and the
motor's power leads are arranged/wired for the lower voltage, of course.

The second issue is heat related, not so much because the output of VFDs
cause more internal motor heat, but instead, less cooling efficiency of
motors running at reduced speeds.. since most heavy duty induction motors
utilize a cooling fan (even totally enclosed cases), and when the fan spins
slower at reduced motor RPMs, the fans move less air.
Many HSMs install a separate, constant speed fan or small blower to maintain
adequate airflow over the motor at all times.

Soft-start doesn't necessarily imply that the mortor starts softly, the term
used for increasing the duration of time for the motor to reach it's full
operating speed is a feature of many VFDs, and is typically a programmable
preference for the speed "Ramp Up" or increase of time during starting.

As JK commented, the actual "soft start" feature is intended to put a
minimal strain on the machine's supply voltage, such as in installations
where the high inrush startup currents of a large HP motor would cause
problems with other equipment connected to the same supply (lights dimming
excessively, unecessary/frequent circuit breaker trips/interruptions etc).

I don't have much experience with VFDs, but this is the first time I've
heard of a recommended limited number of starts-per-hour for 3-phase motors
with VFDs.

Please let us know what solution you find which best fits your application.

--
WB
..........


"Oppie" wrote in message
...
I have a milling machine that's starting to show its age. It has a 5 Hp,
208V, 3 Ph spindle motor that's currently on a full voltage Fwd/Rev
starter.
Motor really slams when turned on and has damaged the variable speed
sheaves
and keyways.

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be
the
best choice.

Does anybody have a favorite unit to recommend?
Ones I've seen so far have a SCR in series with two of the three legs and
control starting voltage and ramp-up time. If you keep them powered, they
can also control ramp-down time. A contactor bypasses the reduced voltage
system after the ramp time. All fine and well but only some of the vendors
seem to rate # of starts per hour. I would assume that this is due to
heat
generation when the SCRs are carrying the load and the need to dissipate
it.

Thanks in advance for any answers
Oppie

"Oppie" writes:

I have a milling machine that's starting to show its age. It
has a 5 Hp, 208V, 3 Ph spindle motor that's currently on a full
voltage Fwd/Rev starter. Motor really slams when turned on and
has damaged the variable speed sheaves and keyways.

Was thinking of adding a soft start system in series with the
original starter. Considered a VFD but have heard that using
one with a motor not designed for such makes problems. Even
adding a line reactor to remove harmonic content may be
required.

Given a VFD gives you lots of pluses, you may reevaluate this.
They are inexpensive. You'll get soft-start, variable speed,
and protection, all in one package.


Yes, you want a load reactor. BFD, it's off the shelf. You can
skip it, but especially on older motors, that's carrying a KICK
ME sign. Here is why....

The PoCo gives you nice smooth sine waves, gently undulating
up and down. {It says so right here in their ad...}. The VFD
gives you square waves.

Now a clever guy name Fourier proved that you can mathematically
create a waveform from a series of sinewaves....but for square
waves, some of those are HIGH voltage sine waves.

What this means is: square waves have a HV component that is
hard on motor insulation. A load reactor smoothes them down, and
gives you less-square, more sine-ish, waveforms; and thus is less
stressful on the motor insulation.

On Mar 4, 1:55*pm, David Lesher wrote:


Now a clever guy name Fourier proved that you can mathematically
create a waveform from a series of sinewaves....but for square
waves, some of those are HIGH voltage sine waves.


The harmonics are of lesser amplitude than the fundamental frequency.

http://mathworld.wolfram.com/Fourier...quareWave.html

Dan

"Gunner Asch" wrote in message
...
On Sat, 3 Mar 2012 09:36:30 -0500, "Oppie" wrote:

If you are seeing/hearing "motor slamming" where you didnt before..it
means you have rotational wear in your drive/gear train. Even with a
VFD..that wear will grow worse until its repaired. It will just grow
slower.


Yep, I already refurbished the motor shaft and bushings on the vari-drive
sheaves. That's now in good shape but wanted to minimize future wear due to
high starting torques.

This is a 230/460V motor that is currently wired for 230V (Delta). The 460V
connection would be a Wye iirc. How are VFDs typically wired to the motor?
Is it a three wire or six wire connection? This is all new to me.

On 2012-03-05, Oppie wrote:
"Gunner Asch" wrote in message
...
On Sat, 3 Mar 2012 09:36:30 -0500, "Oppie" wrote:

If you are seeing/hearing "motor slamming" where you didnt before..it
means you have rotational wear in your drive/gear train. Even with a
VFD..that wear will grow worse until its repaired. It will just grow
slower.


Yep, I already refurbished the motor shaft and bushings on the vari-drive
sheaves. That's now in good shape but wanted to minimize future wear due to
high starting torques.

Makes sense.

This is a 230/460V motor that is currently wired for 230V (Delta). The 460V
connection would be a Wye iirc. How are VFDs typically wired to the motor?
Is it a three wire or six wire connection? This is all new to me.

What I'm describing is for the USA for Bridgeport sizes machine
tools. Things are done differently in Europe.

I've never seen a VFD use six wires to the motor. And the VFD
does not care whether the motor is Delta or Wye -- as long as the
voltage is right.

For the 230/460 (or 240/480) motors, it is not a change between
Wye and Delta. That gives a voltage change which is not a factor of
two.

Instead, the motor typically has nine wires brought out, as
follows (use a fixed-pitch font to view the ASCII graphics to avoid
distortion):

First Winding Second Winding

+---WWWWWWWWWWWWW---(A) (D)---WWWWWWWWWWWWW---(G)
|
+---WWWWWWWWWWWWW---(B) (E)---WWWWWWWWWWWWW---(H)
|
+---WWWWWWWWWWWWW---(C) (F)---WWWWWWWWWWWWW---(I)

I've used letters instead of numbers, because the motors use numbers,
and I don't want to risk getting the location of the numbers wrong. You
can get the correct wiring information from the data plate on the motor.

Note that the left-hand end of all three of the "first winding"
group are tied together inside the motor housing where you can't access
them, and are not given a letter (or number) designation. You might
call it all 'Z' if you have to call it something. :-)

Now -- for the high voltage (460V in your listing) they are
wires as follows:


First Winding Second Winding

+---WWWWWWWWWWWWW---(A)+-------+(D)---WWWWWWWWWWWWW---(G)+--(L1)
|
+---WWWWWWWWWWWWW---(B)+-------+(E)---WWWWWWWWWWWWW---(H)+--(L2)
|
+---WWWWWWWWWWWWW---(C)+-------+(F)---WWWWWWWWWWWWW---(I)+--(L3)

The A-D and similar pairs are wired together and insulated in
the connection box. Only the G, H, and I ones are brought out to the
power line connections (through a switch, of course, if not from a VFD).

Now -- for the lower voltage, it is done differently.


First Winding Second Winding

+---WWWWWWWWWWWWW---(A)+-------------------------------------+----(L1)
| |
| +--+(D)---WWWWWWWWWWWWW---(G)+---+
| |
+---WWWWWWWWWWWWW---(B)+-------------------------------------+----(L2)
| | | |
| +--+(E)---WWWWWWWWWWWWW---(H)+---+
| |
+---WWWWWWWWWWWWW---(C)+-------------------------------------+----(L3)
| | |
+--+(F)---WWWWWWWWWWWWW---(I)+---+

Note that the D-E-F wires are connected together and insulated in the
wiring box. (I can't easily draw them jumping over the horizontal wires
without taking up even more space, so I'm mentioning it here to be
clear. Everywhere there is a '+' is a connection

And -- of course -- to make the motor run in reverse, you
exchange any two of the three L# wires. (Or, push the reverse button on
the VFD or the remote control wired to it.

Good Luck,
DoN.

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

On 2012-03-04, Wild_Bill wrote:
The two basic cautions for VFD use are that the output of VFDs consists of a
fast risetime voltage waves, similar in appearance to squarewaves (as
opposed to the gradual rise/fall of sinewaves normally applied to a motor
without a VFD).

With a bit of a complication. Those square waves repeat quite a
few times per cycle, starting out on for a small percentage of the time
and off for the rest, then a bit more on and less off until it reaches
the time when you should have the peak voltage of the sine wave, at
which point is is on the full time before it starts decreasing again.
This is to approximate the shape of the sine wave, and is more gentle to
the motor than a square wave of the full width of the half cycle would
be. This is called PWM (Pulse Width Modulation).

I've already spent too much time with ASCII graphics elsewhere
in this thread, and I won't bother doing it again here. :-)

Enjoy,
DoN.

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

On Mar 4, 8:45*pm, "Oppie" wrote:
"Gunner Asch" wrote in message

...

On Sat, 3 Mar 2012 09:36:30 -0500, "Oppie" wrote:

If you are seeing/hearing "motor slamming" where you didnt before..it
means you have rotational wear in your drive/gear train. *Even with a
VFD..that wear will grow worse until its repaired. It will just grow
slower.

Yep, I already refurbished the motor shaft and bushings on the vari-drive
sheaves. That's now in good shape but wanted to minimize future wear due to
high starting torques.

This is a 230/460V motor that is currently wired for 230V (Delta). The 460V
connection would be a Wye iirc. How are VFDs typically wired to the motor?
Is it a three wire or six wire connection? This is all new to me.

Before you buy the VFD download the user manual. You'll find lots of
installation info. It's amazing how they have a general set of
discrete I/O that is programmable in it's usage. Look at the remote
start-stop programming. They generally support the 3 wire start stop
push button interface. But there are many others, and you may find
you have the switches in your "parts box". Also the remote
potentiometer has several options in some VFDs. Look at the
recommended ohms for this.
The VFD does provide a ground terminal, that you want to ensure is
connected to the motor and your mains earth connection.
Also I would recommend not attaching the VFD to the mill so the
vibration is not coupled to the electronics in the VFD. As you have a
variable speed belt drive, you probably won't make used of the VFD
programmable digital read out to have it display spindle RPM. But all
of the various ones I've used can have it display output current or
voltage. Also some VFDs have "autotune" where you disconnect the
load, and push it's panel buttons to have it acquire the motor's
electrical parameters. But this is not a required feature, as you can
key in most of the known parameters like HP. As you have 3phase
input, you don't need to oversize the VFD like you would if using
single phase input (generally this is an issue when using 1ph input
for motors larger then 3HP). Again the user manual will tell all.
There are some VFDs that sense 3PH input loss, and shut down. But of
the 5 brands I've used, none of them required this.
ignator

Thank you all for the replies and recommendations.
I agree that a VFC will give the best control. Granted that their prices
have come down lately but they are still much more than the simple soft
starter. Bottom line is that the economy sucks and we're on an austerity
budget. Now I have to try to justify the additional cost to management.
Oppie

This thread looped about so much so wasn't sure the best place to reply.

" writes:


Now a clever guy name Fourier proved that you can mathematically
create a waveform from a series of sinewaves....but for square
waves, some of those are HIGH voltage sine waves.


The harmonics are of lesser amplitude than the fundamental frequency.

http://mathworld.wolfram.com/Fourier...quareWave.html

That's not my memory, but it's been 25 years since I did that
homework, so I could easily be wrong.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Mar 7, 1:54*am, David Lesher wrote:

The harmonics are of lesser amplitude than the fundamental frequency.
http://mathworld.wolfram.com/Fourier...quareWave.html

That's not my memory, but it's been 25 years since I did that
homework, so I could easily be wrong.


Take a look at the url. It shows that a square wave is composed of
the fundamental and the odd harmonics. The amplitude of each harmonic
is 1/n where n is the harmonic number. That is the 3rd harmonic is
1/3 of the fundamental, the 5th harmonic is 1/5 of the fundamental,
ect.

Dan

By its very nature a vfd can be configured to "soft start" as one of many
selectable parameters. Most old motors weren't designed for vid operation
but many of them are ok so long as their insulation has not become too
degraded over time.

Bob Swinney

wrote in message
...

On Mar 3, 9:36 am, "Oppie" wrote:

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be
the
best choice.

Oppie


You might ask if there is anyone that has had problems using a vfd on
an old motor. I know it is possible to have a problem, but I have not
had a problem. However I have not used that many VFD's with old
motors. So I would ask others with more experience.

Dan

Howdy, Bob.. haven't seen you around for a couple of blue moons.

--
WB
..........


wrote in message
...
By its very nature a vfd can be configured to "soft start" as one of many
selectable parameters. Most old motors weren't designed for vid operation
but many of them are ok so long as their insulation has not become too
degraded over time.

Bob Swinney

wrote in message
...

On Mar 3, 9:36 am, "Oppie" wrote:

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be
the
best choice.

Oppie


You might ask if there is anyone that has had problems using a vfd on
an old motor. I know it is possible to have a problem, but I have not
had a problem. However I have not used that many VFD's with old
motors. So I would ask others with more experience.

Dan

In article ,
wrote:

By its very nature a vfd can be configured to "soft start" as one of many
selectable parameters. Most old motors weren't designed for vid operation
but many of them are ok so long as their insulation has not become too
degraded over time.

Bob Swinney

wrote in message
...

On Mar 3, 9:36 am, "Oppie" wrote:

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be
the
best choice.

Oppie


You might ask if there is anyone that has had problems using a vfd on
an old motor. I know it is possible to have a problem, but I have not
had a problem. However I have not used that many VFD's with old
motors. So I would ask others with more experience.

I think what saves us using old motors on VFDs is that most HSMs use 220
volt single phase feeds, and the motors were built for dual-voltage,
typically 220/440, and so have stout insulation.


Joe Gwinn