common problem
1. Why does the motor generate shaft current?
The shaft of the motor---bearing---the current in the base circuit is called the shaft current.
Reasons for shaft current generation:
(1) Asymmetry of the magnetic field;
(2) There are harmonics in the supply current;
(3) The manufacturing and installation are not good, and the air gap is not uniform due to the eccentricity of the rotor;
(4) There is a gap between the two semicircles of the detachable stator core;
(5) The number of tiles having the stator cores stacked in a fan shape is not properly selected.
harm:
The surface of the motor bearing or the ball is eroded, and the shaped micro-holes are formed, which deteriorates the running performance of the bearing, increases the friction loss and heat, and ultimately causes
The bearing burned.
prevention:
(1) Eliminate the pulsating magnetic flux and power supply harmonics (such as adding an AC reactor on the output side of the inverter);
(2) When designing the motor, the bearing housing and the base of the sliding bearing are insulated, and the outer ring and the end cover of the rolling bearing are insulated.
