How Big Is The Shaft Current Of The Motor?

Theoretically, the shaft of the motor should not be electrified, and naturally there should be no current passing through the shaft: but for high-voltage motors, low-voltage high-power motors and frequency conversion motors, shaft current still exists, but the size of the motor shaft current is different.

During the actual test and operation of the motor, it can be found that the existing motor shaft shows the phenomenon of magnetization, that is, it can be seen that there is a certain adsorption force for the tiny iron powder. In particular, it is more harmful to the bearing system of the motor.

The necessary conditions for generating shaft current are the shaft voltage and loop. Shaft voltage, due to the motor magnetic field asymmetry and other factors, the motor shaft is magnetized, the voltage induced on the shaft, when there is a closed loop condition, that is, a large shaft current. Magnetic circuit asymmetry, capacitive coupling of motor rectification and inverter system, electrostatic induction and axial flux and remanence, etc. may lead to the generation of shaft voltage, wherein the shaft voltage caused by magnetic circuit asymmetry is present at both ends of the motor shaft AC type electromusic, for dry large motors, stator core using sector stamping plate, rotor eccentricity, magnetic permeability of sector plate is different, and cooling and clamping shaft guide groove and other motor manufacturing and operation reasons caused by asymmetry, the alternating magnetic flux of the cross-chain shaft produces potential difference at both ends of the motor shaft.

This AC shaft voltage generally does not exceed 10V, but has a large energy. If effective measures are not taken, the shaft voltage through the bearing system to form a loop will generate a large shaft current, resulting in electrical breakdown of the bearing system of the motor.

In the motor shaft current control measures, according to the motor type and application site of the different, will use the necessary circuit breaking or bypass measures, generally to the shaft voltage as the basic basis for whether to take measures, some foreign motor technical data, 350 millivolts as the shaft voltage prevention and control of the defining conditions, that is, when the shaft voltage does not reach this

This value will not have much effect on the bearing system of the motor, and exceeding this value will most likely cause serious problems in the bearing system.

Different motors, different manufacturing processes, and different quality control levels will affect the level of motor shaft voltage, and whether measures need to be taken should be determined in combination with the actual situation.