It is also clear that the main role of the motor is to produce driving torque, as a power source for electrical appliances various machinery.

Today, we want to take you to understand the shaft current of the motor, so let's first understand what is the shaft current of the motor. It refers to the voltage generated between the two ends of the motor shaft between the rotating shaft the bearing seat. The main reason for the shaft voltage is caused by the imbalance of the magnetic circuit around the motor shaft. The unbalanced magnetic flux cuts the rotating shaft induces the shaft voltage at both ends of the shaft.

There are many factors that cause the unbalance of magnetic circuit, such as the rotor running different core, the stator core fan-type stamping joint asymmetry. The conditions for the formation of axial current are: one is that there is axial voltage, the other is to form a loop. In a motor with normal design operating conditions, there is only a small difference in voltage between the two ends of the shaft, due to the treatment of oil film bearing insulation, it is enough to cause harm.

The shaft current will cause the motor bearing surface ball to be eroded, the shape path point microholes will deteriorate the bearing performance, increase friction loss heat, cause the bearing to burn.

The solution of permanent magnet motor manufacturers is as follows:

1. Diversion: Install a grounded carbon brush at the extension end of the shaft to make the grounded carbon brush reliably grounded in reliable contact with the rotating shaft to ensure that the rotating shaft potential is zero potential, the electrostatic charge on the motor shaft is directed to the earth at any time to eliminate the shaft current. This measure is generally used more in generators, occasionally in large AC motors.

2, block: One of the important conditions for the formation of shaft current is to form a loop. Installing an insulating pad using an insulating bearing between the non-shaft extension seat the bearing to cut off the shaft current loop is the measure adopted by most motor suppliers.