Re: [femm] Bearing currents and faraday cage

[hans.krieg@xxxxxxxxxxxxxxxxxxxx]

Dear Chronis

I think it is hardly possible to use FEMM in modelling this phenomenon
since the origin of it is electrical and not magnetical. Important
influence factors are the capacitances between stator windings,stator frame
and rotor body. FEMM is purely focused on the interaction between currents
and magnetic fields and not the electrical fields and voltages.

Interesting papers on the subject of bearing current due to inverter drives
can be found on the website of Allen Bradley (Rockwell Automation):

www.ab.com/drives/techpapers/ieee/ieee.html

Kind reagrds,

Hans






"Polychronis Vallianatos" <rotechen@xxxxxxxxx> on 07-12-2002 20:06:31

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cc: (bcc: Hans KRIEG/NLRID01/Transport/ALSTOM)

Subject: [femm] Bearing currents and faraday cage



Dear Dave, dear All,
there is a usual problem,in Variable Speed Drive (VSD), with fast
switching valves (eg IGBTs), the premature bearing failure, due to
Electrically induced flutting.
The common mode induced currents, break the lubricant film, discharging
the common mode voltage to the grounded end shield.
One of the remedies is the Faraday Cage, in the motor Air Gap.
this could have the form of a copper foil, or conductive paint.

How could this be modeled by FEMM ? How could FEMM take in account the
high frequencies that the phenomenon take place (or fast voltage rise
times? eg 30V / microsec)?

Has anyone done like that in FEMM, or do you propose any Paper on the
Topic?
Do anyone have any FEMM modeled Variably Frequency Driven Motor?

Thanks in Advance,

Chronis
pvallian@xxxxxxxxx
rotechen@xxxxxxxxx



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