VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of the
motor?

Approximately of course. Mileage will vary I am sure.

Bob La Londe wrote:

VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of
the motor?

Approximately of course. Mileage will vary I am sure.
Depends a bit on the motor and more on the VFD. Flux vector VFDs
(more expensive) can run down to zero RPM at full torque, if the motor
has adequate forced cooling. For general purpose motors and VFDs,
you can usually go to 50% RPM (watch out for motor overheating)
up to 200% rated RPM. You get constant torque below rated speed,
and constant HP above.

Jon

On Mon, 19 Dec 2011 12:35:44 -0700, "Bob La Londe"
wrote:

VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of the
motor?

Approximately of course. Mileage will vary I am sure.

I get good results from 6Hz to 90Hz on my mill (3HP) and small lathe
(1 HP). They're both running open loop. so there's a significant drop
in torque at the very low end, but those speeds are still useful in
many cases, e.g., spot, drill, and power tap without changing belt
speeds. I've never had a problem with overheating, but I'll typically
switch to a lower belt or gear ratio rather than running at low motor
RPM for long periods of time.

I'm getting ready to install a VFD on my big (10HP) lathe, and will
probably implement a similar speed range, but expect the low Hz range
will be most useful for gear changes and jogging.

A sensorless flux vector drive will improve low end torque somewhat. A
closed loop (encoder feedback) vector drive can produce close to full
torque down to zero speed.

If you have the option of changing belts or gears when you really need
lots of torque at low spindle speeds, an open loop drive is probably
all you need.

--
Ned Simmons

Ned Simmons fired this volley in
:

If you have the option of changing belts or gears when you really need
lots of torque at low spindle speeds, an open loop drive is probably
all you need.

And forced-air cooling isn't all that big a task to build, for almost any
ventilated motor (might be hard on a TENV! G)

LLoyd

On Mon, 19 Dec 2011 12:35:44 -0700, "Bob La Londe"
wrote:

VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of the
motor?

Approximately of course. Mileage will vary I am sure.

From about 8% to 200% of original rated speed range.

Simply because the bearings in the motor may not take higher
speeds..this for a 1750 RPM motor

A 3600 RPM motor shouldnt be run any faster than about 150% of rated
speed..for the bearings and the armature (might shatter)

Gunner







One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Mon, 19 Dec 2011 15:47:54 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Ned Simmons fired this volley in
:

If you have the option of changing belts or gears when you really need
lots of torque at low spindle speeds, an open loop drive is probably
all you need.

And forced-air cooling isn't all that big a task to build, for almost any
ventilated motor (might be hard on a TENV! G)

LLoyd


Well, yeah... You can put a fan blowing over the motor case, but
unless you've got the inside fan stirring the air and eliminating hot
spots it's still going to release the Magic Smoke.

Works much better to externally ventilate an open motor.

-- Bruce --

On Mon, 19 Dec 2011 18:50:42 -0800, Gunner Asch
wrote:

On Mon, 19 Dec 2011 12:35:44 -0700, "Bob La Londe"
wrote:

VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of the
motor?

Approximately of course. Mileage will vary I am sure.

From about 8% to 200% of original rated speed range.

Simply because the bearings in the motor may not take higher
speeds..this for a 1750 RPM motor

A 3600 RPM motor shouldnt be run any faster than about 150% of rated
speed..for the bearings and the armature (might shatter)

If all else fails, Read The Friendly Manual for the motor.

The ones that are rated for "Inverter Duty" (a VFD) will have all that
info listed in the catalog and on the cut sheets.

-- Bruce --

Gunner Asch wrote:

From about 8% to 200% of original rated speed range.

Simply because the bearings in the motor may not take higher
speeds..this for a 1750 RPM motor

A 3600 RPM motor shouldnt be run any faster than about 150% of rated
speed..for the bearings and the armature (might shatter)

I did a speed trial on a 3 phase motor. Documented in an RCM thread:
http://tinyurl.com/6wv35tu

I ran a 1775 rpm motor to 10,700 rpm (360 Hz) without consequence.
Which was disappointing, as I had my camera on it and expected something
dramatic. :-(

Single-sample trial, your mileage may vary, etc, etc.

Bob

On Tue, 20 Dec 2011 09:49:46 -0500, Bob Engelhardt
wrote:

Gunner Asch wrote:

From about 8% to 200% of original rated speed range.

Simply because the bearings in the motor may not take higher
speeds..this for a 1750 RPM motor

A 3600 RPM motor shouldnt be run any faster than about 150% of rated
speed..for the bearings and the armature (might shatter)

I did a speed trial on a 3 phase motor. Documented in an RCM thread:
http://tinyurl.com/6wv35tu

I ran a 1775 rpm motor to 10,700 rpm (360 Hz) without consequence.
Which was disappointing, as I had my camera on it and expected something
dramatic. :-(

Single-sample trial, your mileage may vary, etc, etc.

Bob

What kind? How many horsepower? Very interesting! Details!!!!

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

Gunner Asch wrote:
Bob Engelhardt wrote:
I did a speed trial on a 3 phase motor. Documented in an RCM thread:
http://tinyurl.com/6wv35tu
....

What kind? How many horsepower? Very interesting! Details!!!!

The tinyurl link is to the Google Groups archive of the thread. My
posts 1, 36, 46, 53, & 57 have more detail than I could remember. The
pictures & video are gone, though.

Bob

Bob Engelhardt wrote:
... The pictures & video are gone, though.

No, wait ... they're there. Bob

On Tue, 20 Dec 2011 00:20:30 -0800, "Bruce L. Bergman (munged human
readable)" wrote:

On Mon, 19 Dec 2011 18:50:42 -0800, Gunner Asch
wrote:

On Mon, 19 Dec 2011 12:35:44 -0700, "Bob La Londe"
wrote:

VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of the
motor?

Approximately of course. Mileage will vary I am sure.

From about 8% to 200% of original rated speed range.

Simply because the bearings in the motor may not take higher
speeds..this for a 1750 RPM motor

A 3600 RPM motor shouldnt be run any faster than about 150% of rated
speed..for the bearings and the armature (might shatter)

If all else fails, Read The Friendly Manual for the motor.

The ones that are rated for "Inverter Duty" (a VFD) will have all that
info listed in the catalog and on the cut sheets.

-- Bruce --

True indeed. But few Hardinges (for example) were made or intended for
use with inverters so such info can be very very hard to find. And
until the last decade or less..inverter duty motors were exceptionally
rare.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Tue, 20 Dec 2011 12:49:09 -0500, Bob Engelhardt
wrote:

Gunner Asch wrote:
Bob Engelhardt wrote:
I did a speed trial on a 3 phase motor. Documented in an RCM thread:
http://tinyurl.com/6wv35tu
...

What kind? How many horsepower? Very interesting! Details!!!!

The tinyurl link is to the Google Groups archive of the thread. My
posts 1, 36, 46, 53, & 57 have more detail than I could remember. The
pictures & video are gone, though.

Bob

I browsed through them..but didnt see the HP rating in my admittedly
quick trip.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

"Gunner Asch" wrote in message
...
On Tue, 20 Dec 2011 00:20:30 -0800, "Bruce L. Bergman (munged human
readable)" wrote:

On Mon, 19 Dec 2011 18:50:42 -0800, Gunner Asch
wrote:

On Mon, 19 Dec 2011 12:35:44 -0700, "Bob La Londe"
wrote:

VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase
motor
off of a VFD what is your speed range relative to the original speed of
the
motor?

Approximately of course. Mileage will vary I am sure.

From about 8% to 200% of original rated speed range.

Simply because the bearings in the motor may not take higher
speeds..this for a 1750 RPM motor

A 3600 RPM motor shouldnt be run any faster than about 150% of rated
speed..for the bearings and the armature (might shatter)

If all else fails, Read The Friendly Manual for the motor.

The ones that are rated for "Inverter Duty" (a VFD) will have all that
info listed in the catalog and on the cut sheets.

-- Bruce --

True indeed. But few Hardinges (for example) were made or intended for
use with inverters so such info can be very very hard to find.


And
until the last decade or less..inverter duty motors were exceptionally
rare.


And from what I have been able to find a quite a bit more expensive.

Bob La Londe wrote:
VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of
the motor?

Approximately of course. Mileage will vary I am sure.

I'm running VFD's on my mill, metal lathe and
drill press. They all have general-purpose,
non VFD motors on them. I set the upper
frequency to 90hz on all the drives and have
no problems at all.

I've run them very slow and not had any over
heating problems. Despite the nay-sayers,
I don't think there is a big overheating
problem at low speeds as the drive will
lower the operating voltage as it lowers
the frequency.

"Jim Stewart" wrote in message
...
Bob La Londe wrote:
VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of
the motor?

Approximately of course. Mileage will vary I am sure.

I'm running VFD's on my mill, metal lathe and
drill press. They all have general-purpose,
non VFD motors on them. I set the upper
frequency to 90hz on all the drives and have
no problems at all.

I've run them very slow and not had any over
heating problems. Despite the nay-sayers,
I don't think there is a big overheating
problem at low speeds as the drive will
lower the operating voltage as it lowers
the frequency.

Thanks. I've been playing the range and trying to do my homework on this
one. I have a small to mid size lathe I want to convert to CNC. A software
controlled spindle (VFD) with RPM feedback is the way I want to go. I
considered putting a servo on the spindle, but I am not going to be doing
much threading, and I highly doubt I'll do any precision threading. H3 V
groove at best. Its got a cap start 110V 3/4 HP motor on it now that grunts
a bit to get started. (before I got it all re-lubed I sometimes had to give
it a push. I was thinking a 3/4 or 1 HP 3 phase motor might be just the
ticket for this application. Find a nice middle of the road pulley speed
and leave it there. Then adjust everything else with the VFD and voltage
input control.

I browsed through them..but didnt see the HP rating in my admittedly
quick trip.

Gunner
Just one more data point, I have 100s of hours running a 7.5 horse at
4500 (1750 motor) on my CHNC.

Karl

There's another issue. A VFD delivers square waves to the motor.
Those sharp edged waves are hard on the motor insulation; an
"inverter-rated" motor has an extra margin in the insulation.

With ordinary ones, you want to add a "load reactor" between
the VFD & motor. It's a filter that will round off those square
waves a bit.

--
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 Tue, 20 Dec 2011 12:33:03 -0700, "Bob La Londe"
wrote:


The ones that are rated for "Inverter Duty" (a VFD) will have all that
info listed in the catalog and on the cut sheets.

-- Bruce --

True indeed. But few Hardinges (for example) were made or intended for
use with inverters so such info can be very very hard to find.


And
until the last decade or less..inverter duty motors were exceptionally
rare.


And from what I have been able to find a quite a bit more expensive.




Well...I just quoted a guy on a GE motor for his Hardinge HC
Chucker...new from Hardinge...$3804.27

I think he is going to go with a VFD....G

Gunner


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Tue, 20 Dec 2011 15:11:47 -0800, Jim Stewart
wrote:

Bob La Londe wrote:
VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of
the motor?

Approximately of course. Mileage will vary I am sure.

I'm running VFD's on my mill, metal lathe and
drill press. They all have general-purpose,
non VFD motors on them. I set the upper
frequency to 90hz on all the drives and have
no problems at all.

I've run them very slow and not had any over
heating problems. Despite the nay-sayers,
I don't think there is a big overheating
problem at low speeds as the drive will
lower the operating voltage as it lowers
the frequency.

The OmniTurn CNC lathes I sell and service are good down to about 60 rpm
but need to have a muffin fan installed on the motor shroud to keep it
cool if run for hours.

Wegg 5hp inverter motors.


Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Tue, 20 Dec 2011 16:36:44 -0700, "Bob La Londe"
wrote:

"Jim Stewart" wrote in message
...
Bob La Londe wrote:
VFDs & 3 Phase Motors

All-righty then. This may sound stupid, but when you run a 3 phase motor
off of a VFD what is your speed range relative to the original speed of
the motor?

Approximately of course. Mileage will vary I am sure.

I'm running VFD's on my mill, metal lathe and
drill press. They all have general-purpose,
non VFD motors on them. I set the upper
frequency to 90hz on all the drives and have
no problems at all.

I've run them very slow and not had any over
heating problems. Despite the nay-sayers,
I don't think there is a big overheating
problem at low speeds as the drive will
lower the operating voltage as it lowers
the frequency.

Thanks. I've been playing the range and trying to do my homework on this
one. I have a small to mid size lathe I want to convert to CNC. A software
controlled spindle (VFD) with RPM feedback is the way I want to go. I
considered putting a servo on the spindle, but I am not going to be doing
much threading, and I highly doubt I'll do any precision threading. H3 V
groove at best. Its got a cap start 110V 3/4 HP motor on it now that grunts
a bit to get started. (before I got it all re-lubed I sometimes had to give
it a push. I was thinking a 3/4 or 1 HP 3 phase motor might be just the
ticket for this application. Find a nice middle of the road pulley speed
and leave it there. Then adjust everything else with the VFD and voltage
input control.


I like Marathon, used a lot of them at work. I put a 1 hp. on my
Hardinge TM mill. It's inverter rated, TENV, so fan cooling doesn't
exist. It was about $230 new five years ago, no idea what they're
running now.

Pete Keillor