ween the coil and the core and the spacers at the winding ends, wearing down the insulation surface, but also cause frictional vibration between the conductor and insulation, and between conductor turns and strands, leading to problems such as loosening of winding turns and strands, short circuits, and wire breaks. Simultaneously, additional losses occur at short-circuit points, causing a sharp increase in local winding temperature, a decrease in insulation strength, and insulation breakdown faults. Therefore, electromagnetic vibration is the primary cause of coil insulation damage.The composition of components such as insulation materials, laminated iron cores, and coil wires used in electric motors makes their structural rigidity and the conditions for thermal expansion and contraction during operation quite complex, which is one of the causes of motor vibration. Imbalance in the motor rotor, electromagnetic forces within the motor, torsional impacts experienced by the motor when driving a load, and impacts from the power grid can all lead to motor vibration.
Motor vibration can cause significant damage. For example, it can cause the motor rotor to bend or break; it can loosen the motor rotor magnetic poles, resulting in rubbing and stator rubbing between the stator and rotor; it can accelerate the wear of motor bearings to a certain extent, greatly shortening the normal life of the bearings; it can cause the ends of the motor windings to loosen, resulting in mutual friction between the end windings, reducing insulation resistance, shortening insulation life, and in severe cases, causing insulation breakdown.
The main components affecting motor vibration include the stator core, stator windings, motor frame, rotor, and bearings. Stator core vibration is primarily caused by electromagnetic forces, producing elliptical, triangular, and quadrilateral vibration modes. When an alternating magnetic field passes through the laminated stator core, axial vibration occurs. If the core is not properly compressed, it will vibrate violently, potentially causing tooth breakage. To prevent this type of vibration, stator cores are generally clamped using pressure plates and screws; however, care should be taken to prevent damage caused by excessive local pressure on the core.
During motor operation, the stator windings are frequently affected by the forces of current and leakage flux within the windings, rotor magnetic pull, and the forces of thermal expansion and contraction of the windings, causing system frequency or harmonic vibrations in the windings. In motor design, the slot and top vibrations of the stator windings caused by electromagnetic forces deserve particular consideration. To prevent these two types of vibrations, slot bar fastening structures and axial rigid supports at the ends are often employed.
The vibration of the machine base originates from the electromagnetic vibration of the stator core, transmitted through the connection between the core and the base, causing harmonic vibration of the base, which increases with the increase of single-unit capacity. Another factor contributing to the base vibration is the excitation force of the rotor vibration. To reduce the base vibration, an elastic structure is adopted for the connection between the core and the base to reduce the impact of core vibration on the base and foundation; alternatively, the natural frequency of the base can be controlled to avoid the harmonic vibration frequency of the core and the vibration frequency .
Rotor mass imbalance is the main cause of mechanical vibration. Rotor mass imbalance can be classified as static imbalance, dynamic imbalance, or a combination of both. In order to minimize the impact of mass imbalance, rigorous dynamic and static balancing tests should be conducted during rotor manufacturing.
Torsional vibration of the rotor system caused by transient changes in external torque can lead to cumulative fatigue failure, shortening rotor life and causing serious motor accidents. Solving this problem requires accurate calculation of the natural torsional vibration frequency of the shaft system, ensuring that the rotor design avoids its operating frequency and its harmonics.
The type of bearing used in an electric motor varies depending on its power rating. Rolling bearings are commonly used in small and medium-sized motors, while sliding bearings are more common in large motors. These different bearing types lead to different causes of vibration.
Post time: Jun-17-2026