Why Does Generator Set Generate Shaft Current

When the cause of shaft current generated by 1000kw generator set is attributed to electromagnetic effects, it causes serious damage to 1000kw generator set with a longer operating cycle. The main manifestation is that the shaft current generates electric spark discharge in the radial bearings, thrust bearings, floating ring seals, couplings, and transmission gears of the generator set, damaging the metal surface and damaging the oil film. If not discovered for a long time, it will cause serious damage to the mechanical components of the generator set. Why does the generator set generate shaft current?

The reasons are as follows:

In the case of 1000kw generator set with an electric motor rotor, the main reason is the asymmetric effect of the magnetic field line distribution and the magnetization effect of the shaft, which generates shaft current. The asymmetric distribution of the magnetic field line is usually caused by the asymmetric gap of the laminated layer.

Another is the phenomenon that shaft current is generated due to the application of external potential. The reason is that the rotating magnetic field of mobile generator sets cuts the conductor or the rotor is unbalanced, resulting in the magnetization of the shaft. Friction, welding, collision and eddy current devices may cause the equipment to be magnetic and establish a magnetic field.

When the rotating magnetic field cuts the conductor, a certain potential will be induced in these parts. When the potential rises enough to break through the oil film, a current circuit will be formed. This current circuit may pass through the entire rotor, or it may only form local short-circuit currents in the bearings or floating ring seals, which in turn generate new magnetic fields to magnetize the rotor shaft or other parts. Therefore, this type of magneto electric conversion creates a strong magnetic field and high current in the generator set. The voltage that causes the generator set to generate shaft current is above 20V, and the voltage that causes damage is between 30-100V. Therefore, ensuring the normal operation of the generator set can effectively limit the voltage of the generator set. Once the voltage is below 1V, shaft current will definitely not be generated.