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

[williamoh]

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?

 

[whitehendrix]

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

 

[Skogsgurra]

No. Not even remotely the same thing.

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

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[cswilson]

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

 

[Skogsgurra]

"You're a big help"

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

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ozmosis]

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.

 

[whitehendrix]

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.

 

[cswilson]

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

 

[Skogsgurra]

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

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...