The harm of axial force of three-phase asynchronous motor

Update:15 Jul 2021

When a three-phase asynchronous motor is running, when the stator winding is connected to the power supply, a rotating magnetic field will be generated. Therefore, for a three-phase asynchronous motor, a current is felt in the rotor due to electromagnetism; the rotor of the motor is magnetized and rotates due to electromagnetic attraction. The rotation of the three-phase asynchronous motor has slipped.

In this way, the three-phase asynchronous motor will inevitably appear to be remote due to the non-coincidence of the machine center line and the electromagnetic center line in actual operation, that is, the error of the installation of the motor and the coupling of the coupling, and the generated force is the axial force of the motor.

Why does axial force occur during motor operation?

1. The axial force generated by the airflow of the cooling atmosphere when the motor rotor fan is running at no load.

2. Sometimes, due to factors such as the machining and manufacturing process of the motor manufacturer and the assembly error of the motor, the stator and rotor cause the center line of the machine and the electromagnetic center line of the motor to move away and generate axial force.

3. In the design of the motor manufacturer, in order to eliminate the influence of the harmonics of the teeth, the stator and the rotor may be made into a skewed slot layout. Therefore, when the load is running, the electromagnetic force forces the rotor to move away from one end and generate axial force.

The electromagnetic center line of the motor is the reference line for the connection between the shaft of the motor and the coupling of the driven machinery and equipment. However, since the design and manufacture of the motor does not have an electromagnetic center line symbol, the calibration size of the installation drawing provided by the accompanying document when the motor is installed and the coupling is based on the designed machine center.

In this way, the motor in actual operation will inevitably present the axial force due to the misalignment of the machine center line and the electromagnetic center line, that is, the error of the installation of the motor and the coupling of the coupling. The remote direction of the axial force is the axial force of pushing or pulling for the driven machinery and equipment, which causes damage to the motor and the bearings of the driven machinery and equipment or the whole machine.

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