Motor shafts---housings---loop currents in the base shaft currents.
Causes of shaft currents:
(1) magnetic field is asymmetric;
(2) supply current harmonics;
(3) bad manufacturing, installation, and as a result air gap eccentricity is not uniform;
(4) removable stator gap between two semicircular;
(5) number of stator core chip fan-folded unsuitable.
The motor bearings or ball on the surface erosion-shaped drive micro-porous, deterioration of the bearing performance of friction loss and heat increases, resulting in
(1) Elimination of fluctuating magnetic flux and power supply harmonics (such as retrofitting output side AC reactor in inverter);
(2) motor design, bearing housings and the base insulation, rolling bearing outer ring and end cap insulator.