CAPACITANCE CALCULUS OF A BEARING
CAPACITANCE CALCULUS OF A BEARING
(OP)
I would like to calculate theoretically the capacitance of a bearing with metallic rings and ceramic spheres (see http:/ /www.aliba ba.com/cat alog/10516 334/Cerami c_Bearing_ Balls.html).
The expression for a cylindrical capacitor is: (2*pi*eps0*l)/(lnb/a).
However, when adding some spherical balls inside the cylinder, how should I proceed?
Thank u,
logic
The expression for a cylindrical capacitor is: (2*pi*eps0*l)/(lnb/a).
However, when adding some spherical balls inside the cylinder, how should I proceed?
Thank u,
logic





RE: CAPACITANCE CALCULUS OF A BEARING
You should also look at the IEEE paper by Chen, Lipo, Fitzgerald "Modeling of bearing currents in PWM inverter drives" and also the classic papers by Erdman, Kerkman, Schlegel and Skibinski published by Allen-Bradley/Rockwell Automation.
I have never seen any calculation of ceramic (hybrid) ball bearing capacitance. I do not think that the ceramic balls contribute very much to the capacitance. Relative epsilon of the ceramic is usually in the 3 - 8 range and the Hertzian contact area is very small. The error in the capacitance calculation that you get from assuming a cylindrical capacitor is probably larger than ball contribution.
And, in the over-all picture, capacitance between rotor and stator is dominating over bearing capacitance.
Google can probably find something for you. I will have a look, too.
Gunnar Englund
www.gke.org
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