Why is there an air gap between the motor rotor and stator?

In order to ensure that the rotor can rotate freely in the stator cavity during the operation of the motor, an air gap must be maintained between the rotor core and the stator core. Although there is no direct electromagnetic connection between the rotor and the stator, when the stator winding is energized, there is an electromagnetic connection between the rotor and the stator, similar to the principle of a transformer, thereby realizing the energy conversion function between electrical energy and mechanical energy.

The size of the air gap has a great influence on the performance and operating reliability of the asynchronous motor.

If the air gap is too large, the magnetic resistance will increase greatly, thus increasing the excitation loss, the excitation current will also increase, the power factor of the motor will also decrease, and the performance of the motor will deteriorate. In order to reduce the excitation current and improve the power factor, the air gap should be minimized.

However, if the air gap is too small, the air gap harmonic magnetic field will increase, the motor stray loss and noise will increase, and the maximum torque and starting torque will decrease. At the same time, if the air gap is too small, the rotor and stator will easily collide during operation, causing the phenomenon of sweeping the bore, which will make it difficult to start, thereby reducing the reliability of operation and making it difficult to assemble. Generally, the air gap of small asynchronous motors is about 0.25-1.5mm, and that of medium-sized asynchronous motors is about 0.75-2mm.

The gap between the stator and the rotor of the motor is fixed during the production process of the motor, unless the gap becomes larger due to various reasons such as the rotor sweeping during use, which is generally impossible. There are many reasons for the high current of the motor. Here is a brief summary for everyone:

1: Positioning magnetic steel deviation, treatment method: re-bonding;

2: The gap between the carbon brushes is uneven. Solution: Correct the gap between the carbon brushes;

3: There is a short circuit between the positive and negative poles of the battery. Solution: eliminate the short circuit;

4: Turn-to-turn short circuit, solution: re-wire;

5: The commutator segment is short-circuited. Solution: clean and polish the commutator segment;

6: The fit between the shaft and the bearing is too tight. Solution: Grind the shaft;

7: Electric vehicle zero start, treatment method: try to avoid it while driving;

8: The load is large or the vehicle's driving resistance is large. Solution: human assistance.