Discussion on Motor Vibration by Rongcheng Electric Machinery Factory
The Shandong motor manufacturer encountered a problem where there were no abnormalities during the type test of a motor. However, after disassembling and reassembling the motor, serious shaking problems occurred. After re adjusting the assembly, the problem was resolved. Following this question, let's explore the vibration issue of the motor.
During the use and testing of the motor, it is inevitable that there will be similar abnormal situations, some of which are even severe enough to cause shaking and even the whole machine to bounce. There are many reasons that can cause motor vibration, often accompanied by noise. Therefore, when it comes to motor vibration issues, noise is inevitably associated. Today, Ms Based on practical cases, analyze the mechanism of motor vibration and noise generation, exchange and share experiences and related knowledge.
The vibration noise of electric motors can be classified into three categories based on their causes: electromagnetic, mechanical, and comprehensive. The characterization of electromagnetic reasons is that as soon as there is a power outage, the fault disappears immediately; Mechanical reasons are closely related to the rotation speed of the motor. As long as the motor is in a rotating state, there will be more or less problems. Generally, the higher the speed, the more serious the problem. Some may experience resonance and whistling at a certain speed; The most common comprehensive reason is the coexistence of electromagnetic force and mechanical polarization force, sometimes resulting in a superposition effect.
● Power supply system issues. There are two common situations: the motor power supply has a three-phase voltage imbalance problem, which leads to a significant imbalance in the three-phase current of the motor, accompanied by varying degrees of vibration; Another situation is phase loss, where the motor vibrates at 50Hz frequency and emits a low and strange sound, causing it to smoke and burn out in a very short period of time.
● Stator malfunction issue. This problem is mainly manifested as mechanical issues such as stator core ovality, eccentricity, and loose laminations. The most direct manifestation of this type of problem during motor operation is low-frequency electromagnetic sound or obvious beat frequency sound. For the problem of loose laminations, sometimes the problem can be improved by re coating, but in most cases, the effect is not significant.
● Rotor malfunction issue. Uneven air gap: Mechanical factors such as ovality, eccentricity, and looseness of the rotor iron core, among which ovality and eccentricity mostly occur in large-sized rotors. On the one hand, this is due to the rotor's self weight and eccentricity during the rotor turning process; Another aspect is that the center hole of the shaft is damaged or the tip of the equipment is worn, resulting in the rotor being out of center with the shaft after turning.
Electrical defects include open welding between rotor cage bars and end rings, broken rotor cage bars, incorrect winding, poor contact of electric brushes, etc. In any of the above situations, vibration noise is caused by unbalanced electromagnetic force excitation.
The magnetic center of the fixed rotor is not aligned
The motor itself has defects. Factors such as rotor imbalance, shaft deflection deformation, deformation or unevenness of the collector ring of the wound rotor motor, uneven air gap between the stator and rotor (which can lead to chamber sweeping in severe cases; some motors may exhibit low-frequency electromagnetic sound under no-load conditions, resulting in chamber sweeping after being loaded), bearing failure, etc.
Poor foundation installation, insufficient strength of structural components, resonance, loose anchor screws, damaged motors and fans, etc.
● Connection issues with the device. Coupling damage, poor coupling connection, inaccurate centering of the coupling, mechanical imbalance of the load, system resonance, etc.
Motor vibration is often caused by uneven air gap, leading to unilateral magnetic pulling force, which in turn exacerbates the uneven air gap. This electromechanical hybrid effect manifests as motor vibration.
The axial movement of the motor is caused by the electromagnetic tension due to the gravity or installation level of the rotor itself, as well as the incorrect magnetic center, resulting in axial movement of the motor and increased vibration. In severe cases, the shaft of the bearing motor may wear the bearing root, causing a rapid increase in the temperature of the bearing.
