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Ultra high speed inverter duty motor, about 20,000 rpm
3

Ultra high speed inverter duty motor, about 20,000 rpm

Ultra high speed inverter duty motor, about 20,000 rpm

(OP)
Hello, I am looking for a motor manufacturer who sells about a 20,000 rpm, 20HP,inverter duty motor. It can be designed but the cost is an issue.  Any clues will be appreciated.  I am also curious if I can run any inverter duty motor at 20,000 rpm once I replace the bearings and balance the rotor?



 

RE: Ultra high speed inverter duty motor, about 20,000 rpm

I've used the following for high speed operation:
http://www.perske.de/en/rahmen/frame_jammer.html?../produkte.htm~inhalte
they are specifically designed for this function having low inertia rotors, special bearings and the correct winding suitable for high frequency operation circa 200~400Hz. They also have low inertia fans to facilitate correct cooling.
Modifying a 'standard motor' by replacing bearings would be a dangerous option IMHO.

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Sounds like you are looking for a spindle motor.  High speed, 2-pole, probably water-cooled for 20HP, high precision bearings.

http://www.dynospindles.com/index.html

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Strange to come from a thread asking for a 700 HP, 100 RPM motor to one asking for a 20 HP, 20000 RPM motor.

Electrical Engineering is screwy indeed.

RE: Ultra high speed inverter duty motor, about 20,000 rpm

ozmosis

Thanks for that perske motors link. They seem to make some pretty cool stuff.

One thing though that stuck was that these high speed (6000 to 24000 rpm) motors have a poor pf (0.5 to 0.7), which goes against convnetional wisdom that pf goes down with the speed.

Any theories why ?

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Edison,

It is true that PF goes down with speed - if you obtain lower speed using more poles. But, this is about using, probably, a two-pole motor and higher frequency.

Motors running off 50 or 60 Hz are optimized in every way you can think of. That results in the PF we are used to in standard ASIMs.

High-speed motors (like spindle motors) are usually PM motors and should, therefore, be able to run at PF=1. But that is not very common, I think that a motor running at a load angle around 45 degrees has better dynamic properties than around zero degrees. Just look at the torque vs load angle. It is rather flat at 0 degrees. Load angle influences PF and PF is quite low at 45 degrees. Actually, PF is close to cos(load angle).

C S Wilson should have something to say here.  

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Ultra high speed inverter duty motor, about 20,000 rpm

edison123
I think it is possibly due to the minimal material (copper/iron) in these motors that affects the PF, but others might know more about that.
williamoh-what is your application?
 

RE: Ultra high speed inverter duty motor, about 20,000 rpm

I agree on Reuland, macmckim beat me to it. I have used them on large router spindles, excellent products.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
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RE: Ultra high speed inverter duty motor, about 20,000 rpm

Also, check out Electric Apparatus Company in Howell Michigan, USA.  I've used their motors up to 22,500rpm in test cells.

They have lots of experience with high speed bearings, special balancing, and water cooling.

RE: Ultra high speed inverter duty motor, about 20,000 rpm

2
skogs -- When you are talking about power factor/torque angle in running synchronous motors, it is important that you distinguish open-loop from closed-loop operation.

In open-loop operation, it is vital that you not get too close to a torque angle of 90 degrees (PF of 1.0) because, as you note, the torque-vs-angle curve is flat. You no longer get the automatic stabilizing negative feedback of additional load increasing the generated torque, so you can "fall off the cliff" and lose synchronization.

In closed-loop operation, you can run at a torque angle of 90 degrees, and therefore a PF of 1.0, all day long, because you use the feedback to modify the angle of the output waveforms. So if you get a momentary additional load which causes deceleration, you don't advance the angle of the waveforms as much, so you never get on the side of the torque curve where torque decreases with increasing angle. Also, your servo algorithm will increase the magnitude of the waveform in response to the error in velocity/rotor angle to try to bring things back into full synchronization. Operation at a torque angle of 90 degrees is desirable because it produces the maximum torque per unit current.

If the OP selects a PM (synchronous) motor, he should definitely use closed-loop feedback control.

Also, with regard to power factor of the motor operation: When operated through an inverter, the motor PF is quite well hidden from the line due to the DC bus in between.

Curt Wilson
Delta Tau Data Systems

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Thanks Curt, much needed!

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Ultra high speed inverter duty motor, about 20,000 rpm

could someone please explain the torque-angle you've mentioned? thats a new one to me..

 i'm assuming it deals with wave form maniplulation to gain efficiency?

 again.. guessing.. that is something i didn't learn when i secured my degree :(
 

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Yes, thanks Curt.  Nice description.

whitehendrix; Talking synchronous here only.

The torque angle referred to is the phasor, (rotating vector), between the phasor of the power system and the phasor of the rotor chasing the system.  As the angle gets greater you are loading the motor more and more. At a specific point you will get pull-out and the rotor will lose synchronizm with the system.   When you aren't crowding 90 degrees the motor is on a curve that will increase the torque and provide self regulation of the torque.  As you start to crowd 90 degrees you've gotten everything you can from the motor and the curve has no more torque to offer.  Further load increase will cause pull-out.

This works the same way with generators.  My prof always complained that as the power grid gets more and more loaded every machine on the network has this angle getting closer and closer to 90 degrees.  Any subsequent brief overload will cause a machine on the fine edge to pull-out. The machine must be instantly removed from the network or something will be destroyed.  The networks loss of this machine means all the other machines are pushed closer to their pull-outs.  If another machine pulls-out you can get a rapid cascade of all the machines on the network doing it and have it all go black.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Ultra high speed inverter duty motor, about 20,000 rpm

(OP)
Thanks very much for the valuable information!  With the key word "high frequency motors" I was able to find many manufacturers although most of them were machine spindle manufacturers for milling or grinding and CNC routers.  
I will contact them to discuss the application.

One curious question: What are the major differences in the windings between 3600 rpm AC induction motor and 24,000 rpm AC induction motor (high frequency motor)? Insulation? Method of winding?

 

RE: Ultra high speed inverter duty motor, about 20,000 rpm

If we are talking about the differences between an AC induction 2 pole machine (3600 rpm) and a synchonous high speed (high frequency) permanant magnet machine, there are many differences.  Obviously, the bearings in the higher speed motor are rated for more speed.  Also, the rotor in the synchronous motor contains permanent magnets instead of rotor bars.  You will also notice that the stator diameter is often reduced, but is longer in the high speed machine.  This limits the tangential velocity of the rotor and therefore the centrifugal forces.  The winding methods are similar and so is the insulation, however for efficiency, the high speed motors may have thinner stator laminations to reduce eddy losses in the iron.
 

------------------------------------------------------------------------
If it is broken, fix it.  If it isn't broken, I'll soon fix that.

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Keith -- A small clarification on your entry. Technically, you have the direction of causality backwards. You say, "As the angle gets greater you are loading the motor more and more." This would be better phrased, "As you load the motor more, the angle gets greater."

The torque angle is the angle between the orientation of the stator magnetic field and the rotor magnetic field. The torque generated is proportional to the sine of this angle, and so reaches a maximum at 90 degrees. (The maximum torque on a compass needle is when it is pointing east-west; there is no torque on it when it is pointing north-south.)

In the "open-loop" case, operational stability comes from the change in torque with respect to torque angle. The gain in this electromagnetic feedback loop is proportional to the slope (derivative) of the torque-angle curve. Since this is a sine curve, the derivative is a cosine curve. As you approach a 90 degree torque angle, this gain goes to zero, and as you pass it, the gain changes sign, so you go unstable.

Curt Wilson
Delta Tau Data Systems

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Just a point of clarification:  There is no need for this motor to be of synchronous design.  The company I has cited above builds induction motors to this speed and frequency and the results, at least for me, have been quite acceptable.

Unless I've missed something, the original poster hasn't mentioned anything that would require a synchronous machine.

RE: Ultra high speed inverter duty motor, about 20,000 rpm

(OP)
For furthur clarification, the motor that I am interested in is open loop asychronous induction motor, not permanent magnet motor.

Thanks everyone!

 

RE: Ultra high speed inverter duty motor, about 20,000 rpm

Mr. wilson, would i be correct in saying that torque angle is about the equivalent to slip then?
 

RE: Ultra high speed inverter duty motor, about 20,000 rpm

No. Not even remotely the same thing.

Excuse for stepping in, Curt. I am sure you agree.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Ultra high speed inverter duty motor, about 20,000 rpm

I'm not sure exactly what whitehendrix's question means. There is one sense in which the torque angle of a synchronous motor is analogous to the slip frequency of an asynchronous (induction motor).

A synchronous motor running (open-loop) at no-load conditions will have a torque angle of zero degrees. As you add load, the torque angle will increase, producing enough torque to balance the load. This works all the way up to a torque angle of 90 degrees, past which generated torque decreases.

An induction motor running (open-loop) at no-load conditions will have a slip frequency of zero Hertz. As you add load, the slip frequency will increase, producing enough torque to balance the load. This works up to the slip frequency where there is a peak in the torque curve. Beyond this, the torque falls off and you would get rapid deceleration.

It is important not to carry this analogy too far. The synchronous motor maintains speed at reasonable loads, but the induction motor slows down. The internal mechanisms that create these effects are quite different.

Curt Wilson
Delta Tau Data Systems

  

RE: Ultra high speed inverter duty motor, about 20,000 rpm

"You're a big help" smile

Torque angle is not even remotely equivalent to slip. The fact that there is a maximum torque, after which the motor stalls, does not make torque angle equal to slip. That would be about as correct as saying that when a combustion engine is overloaded, it stops. And when a mule is overloaded, it also stops. Hence psychology of an ICE and a mule is equivalent.

(Part of the "analogy contest")

 

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Ultra high speed inverter duty motor, about 20,000 rpm

My understanding is that with induction motors designed for high speed, and therefore high frequency operation; they they contain lower active material and therefore as pointed out it will impact the torque angle (due to the lower magnetic properties of the stator/rotor) and therefore the PF. Using a converter to achieve the higher frequency would, as Curt points out, not impact the PF due to the capacitive devices in the VFD. Operating from a rotary converter could impact the PF quite highly as this will not improve or maintain the PF.
I trust this is in line with thinking as I got the feeling from discussions before we were leaning more to generic points on synchronous/asynchronous motors rather than high speed motors.  

RE: Ultra high speed inverter duty motor, about 20,000 rpm

gotcha.

 that was something that was VERY lightly touched on in the classed i had, but then again, that was a few years ago and i haven't applied it too much, nor have i delved into doing my own research until just now..

it was a little tough to grasp the concept!!  being that it was alien to me..

 i apologize for being dense!!

i see now how it correllates and will probably continue to research this a little more to fill the gaps that my scholing evidently left.. :(

thank you gentlemen for your time and efforts in your explainations!!

 much appreciated.

RE: Ultra high speed inverter duty motor, about 20,000 rpm

skogs -- I did say "analogous", not "equivalent". And I actually do find the analogy useful to explain to a person who is familiar with one type of motor how the self-regulation mechanism of the other type works. Perhaps it is because I come to this from a background in feedback controls...

Curt Wilson
Delta Tau Data Systems

RE: Ultra high speed inverter duty motor, about 20,000 rpm

I understand. But I was so happy with the (very bad) ICE/Mule analogy that I simply had to post it.  

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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