If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

On Wed, 06 Jan 2010 14:15:20 -0600, Ignoramus5111
wrote:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

There's no loss in power above 60Hz with a volts/Hz VFD set up
normally. Below 60Hz power is proportional to RPM, above 60Hz power is
constant. In other words, torque is constant below 60Hz, HP is
constant above.

--
Ned Simmons

On 2010-01-06, Ned Simmons wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, Ignoramus5111
wrote:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

There's no loss in power above 60Hz with a volts/Hz VFD set up
normally. Below 60Hz power is proportional to RPM, above 60Hz power is
constant. In other words, torque is constant below 60Hz, HP is
constant above.


I thought that there was some loss of power at higher than 60 Hz, but
I am very glad to hear otherwise.

i

"Ignoramus5111" wrote in message
...
On 2010-01-06, Ned Simmons wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, Ignoramus5111
wrote:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

There's no loss in power above 60Hz with a volts/Hz VFD set up
normally. Below 60Hz power is proportional to RPM, above 60Hz power is
constant. In other words, torque is constant below 60Hz, HP is
constant above.


I thought that there was some loss of power at higher than 60 Hz, but
I am very glad to hear otherwise.

i

It might be wise to contact the motor manufacture and verify that the motor
design is capable of operating above the rpm name plate rating. You dont
want a
catastrophic failure of the rotor.

Best Regards
Tom.

On Wed, 06 Jan 2010 14:15:20 -0600, the infamous Ignoramus5111
scrawled the following:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

Holy ****, Ig. Got flak jackets and armored viewing ports?

P.S: You're trolling, aren't you? Shameful.

--
We rightly care about the environment. But our neurotic obsession
with carbon betrays an inability to distinguish between pollution
and the stuff of life itself. --Bret Stephens, WSJ 1/5/10

On Jan 6, 5:46*pm, Ned Simmons wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, Ignoramus5111

wrote:
If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

There's no loss in power above 60Hz with a volts/Hz VFD set up
normally. Below 60Hz power is proportional to RPM, above 60Hz power is
constant. In other words, torque is constant below 60Hz, HP is
constant above.

--
Ned Simmons

The motor may run hotter at higher frequencies due to more eddy
current heating in the iron.

On 2010-01-07, Larry Jaques novalidaddress@di wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, the infamous Ignoramus5111
scrawled the following:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

Holy ****, Ig. Got flak jackets and armored viewing ports?

P.S: You're trolling, aren't you? Shameful.


Do you think that a 1800 RPM motor would self destruct at 3600 RPM?

i

On Wed, 06 Jan 2010 21:32:47 -0600, Ignoramus5111
wrote:

On 2010-01-07, Larry Jaques novalidaddress@di wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, the infamous Ignoramus5111
scrawled the following:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

Holy ****, Ig. Got flak jackets and armored viewing ports?

P.S: You're trolling, aren't you? Shameful.


Do you think that a 1800 RPM motor would self destruct at 3600 RPM?

i

Probably not, but I'd hate to find out the hard way. Most inverter
duty motors have a max rpm listed on the nameplate, which I like to
see to know the safe range. I've used plenty with max rpm about 4300.
No way I'd run 120 Hz on a 3600 rpm motor, though. You might look on
line at the motor manufacturer's web site for max speed data.

Also, consider that since the horsepower stays constant above 60 Hz,
the torque is dropping proportionally to the speed increase.

I was told of the aftermath of a sudden stoppage on a slow speed 2300
V. 100 hp. pump motor in a plant I worked in. Part of the plant lore.
Apparently something really big dropped into the impeller. This was
on a production scale caustic evaporator circulation pump. The motor
(3' in diameter IIRC) tore off its foundation and wrapped the pump
shaft into a corkscrew as it rolled across the ground floor of the
plant, coming to rest outside in a ditch. Since it would have dumped
the whole evaporator of hot caustic, glad I wasn't around to see it.
Throwing the armature windings would cause a similar sudden stoppage.

Pete Keillor

Pete Keillor

On Wed, 06 Jan 2010 21:32:47 -0600, Ignoramus5111
wrote:

On 2010-01-07, Larry Jaques novalidaddress@di wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, the infamous Ignoramus5111
scrawled the following:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

Holy ****, Ig. Got flak jackets and armored viewing ports?

P.S: You're trolling, aren't you? Shameful.


Do you think that a 1800 RPM motor would self destruct at 3600 RPM?

i

A failure is possible both mechanically and electrically - Inverter
Duty motors have to handle much higher voltage spikes coming from the
inverter than they would ever see from mains power, and you can easily
flashover and short or ground the windings on an old motor. Or to put
it in simpler terms, the Magic Smoke escapes.

This is why you do not run a very expensive or irreplaceable old
motor on a VFD. Stuff like the purpose built motors that are a part
of the machine casting (old Bridgeport vertical mills, some Shapers,
etc.) that will cost you a bloody fortune to tear the motor out and
get it rebuilt, and FWIH many of the old ones are not inverter rated.

You use the VFD on inverter duty rated motors, or on something that
uses a cheap and easily replaced motor like 1 HP 56-C mount. You can
get a new motor for pennies that are inverter rated if that old one
goes kablooey.

I know it goes against the r.c.m credo, but Real Men do in fact read
the (friendly) manual first. At least a quick once-over.

-- Bruce --

On 2010-01-07, Bruce L Bergman wrote:
On Wed, 06 Jan 2010 21:32:47 -0600, Ignoramus5111
wrote:
Holy ****, Ig. Got flak jackets and armored viewing ports?
P.S: You're trolling, aren't you? Shameful.
Do you think that a 1800 RPM motor would self destruct at 3600 RPM?

A failure is possible both mechanically and electrically - Inverter
Duty motors have to handle much higher voltage spikes coming from the
inverter than they would ever see from mains power, and you can easily
flashover and short or ground the windings on an old motor. Or to put
it in simpler terms, the Magic Smoke escapes.

Bruce, windings were not really what my question was about. (though I
read your post with great interest).

I was interested in whether a motor can run at higher frequency
without self destructing.

I looked at Baldor.com website (since they have a very easy to access
catalog).

I selected 3 phase, 230/460, 3 HP, inverter duty motors.

I checked out some of them

Motor RPM Max RPM
IDWNM3611T 1750 6000
IDCSWDM3611T 1760 6000
IDXM7142T 1750 2700
IDXM7542T 1750 2700
IDM3661T 1760 6000
several more 1750 6000

I also called a US Motors distributor in my area (the motor in
question is a US motors motor).

He said that a 1750 RPM motor is safe to overspeed to 2750 RPM.

i

On Wed, 06 Jan 2010 21:32:47 -0600, the infamous Ignoramus5111
scrawled the following:

On 2010-01-07, Larry Jaques novalidaddress@di wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, the infamous Ignoramus5111
scrawled the following:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

Holy ****, Ig. Got flak jackets and armored viewing ports?

P.S: You're trolling, aren't you? Shameful.


Do you think that a 1800 RPM motor would self destruct at 3600 RPM?

No, I mentioned flak jackets for no reason. heh heh heh

--
We rightly care about the environment. But our neurotic obsession
with carbon betrays an inability to distinguish between pollution
and the stuff of life itself. --Bret Stephens, WSJ 1/5/10

On Thu, 07 Jan 2010 10:04:48 -0600, Ignoramus30285
wrote:

I also called a US Motors distributor in my area (the motor in
question is a US motors motor).

He said that a 1750 RPM motor is safe to overspeed to 2750 RPM.

And last I checked, 3600 is more than 2750. You might be able to
get a few percent over, but anything past 3000 is a crap-shoot.

They usually set those limits because the test motor started to come
apart at 3600 but held long-term at 2750, and they left a cushion in
the max speed ratings.

-- Bruce --

On Jan 8, 3:30*am, Bruce L. Bergman
wrote:
On Thu, 07 Jan 2010 10:04:48 -0600, Ignoramus30285

wrote:
I also called a US Motors distributor in my area (the motor in
question is a US motors motor).

He said that a 1750 RPM motor is safe to overspeed to 2750 RPM.

* And last I checked, 3600 is more than 2750. *You might be able to
get a few percent over, but anything past 3000 is a crap-shoot.

* They usually set those limits because the test motor started to come
apart at 3600 but held long-term at 2750, and they left a cushion in
the max speed ratings.

-- Bruce --

All small ac motors can be operated safely at 3600. Many can are
wound on the same frame for either 2 or 4 pole windings. A one HP
56C motor has no physical changes, other than the windings, at either
speed.

Bruce L. Bergman wrote:
....
They usually set those limits because the test motor started to come
apart at 3600 but held long-term at 2750, and they left a cushion in
the max speed ratings.

I doubt it. 3600 rpm motors are usually max'ed at 5400 & it's unlikely
that 1750 motors are much differently constructed. I don't think that
I'd run a 1750 at 5400, but I would & do run 1750 at 3600 (on DP with VFD).

Bob

On Sat, 09 Jan 2010 10:59:21 -0500, Bob Engelhardt
wrote:

Bruce L. Bergman wrote:
...
They usually set those limits because the test motor started to come
apart at 3600 but held long-term at 2750, and they left a cushion in
the max speed ratings.

I doubt it. 3600 rpm motors are usually max'ed at 5400 & it's unlikely
that 1750 motors are much differently constructed. I don't think that
I'd run a 1750 at 5400, but I would & do run 1750 at 3600 (on DP with VFD).


I agree, Bob. The construction of a squirrel cage rotor lends itself
to high speed operation. If you look into high RPM motors most of them
are 2-pole induction motors running on high frequency supplies. It's
much easier to keep the rotor bars in place in an induction motor than
the brittle magnets in a DC or brushless motor. Even small brushless
motors top out around 7000 RPM, while 20KRPM induction motors are not
difficult to source.

This is not to say that a vanilla 1800 RPM motor is safe at 400Hz, but
I wouldn't worry about the rotor coming unglued at 3600 RPM.

--
Ned Simmons