Protection of rotary encoders by use of insulated ball bearings --Frequency inverters endanger bearings of electrical motors

摘要

Dissymmetries in the electromagnetic circuit as well as capacitive coupling-in of frequency invertersresult in electrical currents along the shafts of drive trains. This is mainly known at generators ofpower stations where already a small difference in the voltage may lead to damages of the bearings.This current along the shafts does not do any harm to the rotary encoder installed in the drive trainwhen insulated bearings are used in the encoder or when it is fitted with sliding contacts or insulatingcouplings.