Balancing of rotor suspended on magnetic bearings

[Vrijemenova]

Hi,

Do you have any idea how to perform balancing of the rotor which is not suspended on conventional bearings, but on active magnetic bearngs (rotor is levitating in electromagnetic field).

Is it possible to perform balancing with the clasical weights (as in the case of conventional bearings), or some control algorithms have to be implemented. Would it be a good idea to perform clasical balancing while the rotor is on the retainer bearings (while there is no control) and afterwards apply control algorithms to levitate the rotor?

Thanks a lot.

 

[PetroSynergy]

This is a tricky question, I have never seen it done, but theoretically I assume that it could be. However, any dissimilar material will affect the e-mag field. You need to make sure the weights are made of the identical material used on the rotor. And the weights need to be flush, if not it will also affect the fields. Think of a gaussian sphere.

William Hammett
Synergetic Engineering Consultants

 

[turb1]

What kind of machine is it?

In some AMB turbo-machinery, low speed balancing of the rotor is common just as you would for a oil bearing machine.

 

[MikeHalloran]

If they're active bearings, their control system >should be able< to tell you exactly how much weight is required in exactly which planes in order to effect better mechanical balance. Whether it will tell you is a different issue.



Mike Halloran
Pembroke Pines, FL, USA

 

[Vrijemenova]

I am working on simple experimental test rig which has to be balanced (rotor with a disk suspended on two active magnetic bearings).

If the low speed balancing is performed, the PID gains sholud be tuned first or the rotor should be on retainer bearings (not levitating)? What can be expected to happen after such balancing if, afterwards, the rotor passes the first critical speed? Will it be stable?

 

[ornerynorsk]

It must be assumed that the machinery is going to be rotating at a very high RPM, such as in a gas centrifuge ??? Some investigation into that balancing procedure might reveal the various aspects that need to be considered.

 

[turb1]

The AMB machinery that I am familiar with is all subcritical. Even in this type of machinery, the amplifiers can saturate trying to damp high order (4th, 5th, 6th) modes.

It seems like a supercritical rotor would be fairly difficult for AMB's to deal with.