Three factors of motor vibration

31/08/2019

During the use and test of the motor, it is inevitable that there will be similar abnormal conditions, and some even become so jittery that the whole machine "jumps". There are many reasons for the vibration of the motor, and it is often accompanied by noise. Therefore, when it comes to motor vibration, the noise will be associated. Today Ms. Participate in the actual case, analyze the mechanism of motor vibration and noise generation, exchange, share experience and related knowledge.

Motor vibration noise can be basically classified into three categories according to electromagnetic, mechanical and comprehensive causes. The characterization of the electromagnetic cause is that as soon as the power is turned off, the fault disappears immediately; the mechanical cause is closely related to the rotational speed of the motor, as long as the problem of the rotating state is more or less present, the higher the speed, the more severe, the individual will occur at a certain speed. Resonance and howling phenomenon; the most common cause is the simultaneous existence of electromagnetic force and mechanical polarization, sometimes with superposition effect.

Electromagnetic cause

● Power supply system problems. There are two common situations: there is a three-phase voltage imbalance problem in the motor power supply, resulting in a significant imbalance of the three-phase current of the motor, accompanied by different degrees of vibration; the other case is phase loss, vibrating at 50 Hz power frequency. And a low and weird sound, the motor will burn out in a very short time.

● Stator failure problem. The problem is mainly caused by mechanical problems such as ellipse, eccentricity, and looseness of the lamination of the stator core. The most direct performance of this type of problem is the low frequency electromagnetic sound or the obvious beat frequency sound when the motor is running. The problem can be improved by dip-coating again, but in most cases the effect is not obvious.

● Rotor failure problem. Uneven air gap: mechanical factors such as ellipse, eccentricity and looseness of the rotor core. Most of the ellipse and eccentricity appear in large-size rotors. On the one hand, the rotor is self-important, and the rotor is eccentric during turning; the other is the shaft. The center hole is damaged or the tip of the device is worn, causing the rotor to be distracted from the shaft after turning. Electrical defects include open welding of the rotor cage and the end ring, breakage of the rotor cage, faulty winding, poor brush contact, etc. In either case, the vibration noise is excited by the unbalanced electromagnetic force.

● The center of the stator and rotor is not aligned.

Mechanical cause

● The motor itself is defective. The rotor is unbalanced, the deflection of the rotating shaft is deformed, the winding ring of the wound rotor motor is deformed or uneven, and the air gap of the fixed rotor is uneven. (In severe cases, the broom is caused; some of the motors are characterized by low-frequency electromagnetic sound, which occurs after loading. Broom), bearing failure and other factors.

● Poor foundation installation, insufficient structural strength, resonance, loose foot screws, motor fan damage, etc.

● Problems with the connection to the device. The coupling is damaged, the coupling is poorly connected, the coupling is not centered, the load is mechanically unbalanced, and the system is resonant.


Comprehensive reason

● Motor vibration is often caused by uneven air gap, causing single-sided magnetic pulling force, and single-sided electromagnetic pulling force makes air gap unevenness more serious. This electromechanical mixing action is represented by motor vibration.

● The axial movement of the motor is caused by the gravity of the rotor itself or the installation level and the magnetic center is not correct. The electromagnetic tension caused by the motor causes the motor to move in the axial direction, causing the motor vibration to increase. For the bearing motor, the shaft grinding occurs in serious cases. Increase the temperature of the bearing shells quickly.