ADD:No.789,liming South Road,RongCheng City,Shandong Province,China.
Noise suppression of high voltage motor
Measures are taken to reduce the sound of the motor when it runs. In theory, there should be no sound in the operation of the motor, so any sound produced in the motor can be attributed to the noise of the motor. These noises include electromagnetic noise, mechanical noise and aerodynamic noise.
The electromagnetic noise is mainly caused by the periodic radial electromagnetic force in the motor or the unbalanced magnetic pulling force, which causes the magnetostrictive and vibration of the core. Electromagnetic noise is also related to the vibration characteristics of the stator and rotor (such as natural frequency, damping, mechanical impedance and acoustic characteristics, etc.). For example, when the excitation force and the natural frequency resonate, even if the electromagnetic force is very small, great noise can be produced. The suppression of electromagnetic noise can be carried out in many ways. For asynchronous motor, the proper number of fixed and rotor slots must be selected first. Generally speaking, the number of rotor grooves is quite different from the number of stator slots. When the so-called far groove fits, the electromagnetic noise is small (there are a few exceptions, such as 24 slot of stator and 22 slot of rotor). For the slotted motor, the inclined slot can make the radial force generate the phase shift along the axis of the motor, so the axial mean radial force is reduced and the noise is reduced. If the double inclined slot structure is used, the noise reduction effect is better. The structure of double inclined slot is to divide the rotor into two segments along the axis. The twisting direction of each slot is opposite. There is also a middle ring between the two sections. In order to reduce the harmonics of magnetic flux potential, double short moment windings can be used. And avoid the use of fractional slot winding. Sinusoidal winding should be used in single phase motor. In order to reduce the cogging of electromagnetic noise caused by the use of magnetic slot wedge or narrowing of the stator and rotor slot width until the use of closed slot. The three-phase motor should maintain the symmetry of the voltage as far as possible, and the single-phase motor should run in a circular magnetic field. In addition, the manufacturing process of motor, should reduce the stator inner circle and the outer circle of the rotor and ensure the ellipticity of stator and rotor concentric, so that uniform air gap. Reducing the air gap flux density and using a larger air gap can reduce the noise. In order to avoid the inherent frequency resonance of the electromagnetic force and the shell, the appropriate elastic structure can be used.
Mechanical noise is mainly caused by the rotor and bearing. The bearing is the connecting member of the rotor and stator of the motor. It bears the excitation of various forces in the motor and transfers the excitation force, thus producing vibration and noise. Mechanical noise can also be produced by the brush of the motor and the friction of the slip ring or commutator.
For motor with higher speed or longer rotor, balance correction is required. This motor bearing should be used in low noise bearing special motor, in the operation of the motor, the inner and outer rings of bearings should not be harmful but also to prevent the sliding bearing and shaft or bearing end cover and bearing chamber is too tight, too small to avoid the radial clearance of the bearing and bearing inner ring deformation. The machining accuracy and surface finish of the bearing and end cover bearing rooms of the rotor shaft are high. In order to prevent the rotor from moving in the axial direction, a wave spring should be used to apply the axial prestress to the outer ring of the bearing. The bearings must be carefully cleaned before they are assembled. It is suitable to use the hot sleeve or the inner ring to load the bearing on the shaft and select the suitable grease. Sliding bearings should be used for low noise motor.
The gap between the brush and the brush handle should be properly designed and the commutator or slip ring has a smooth surface and the correct geometric size, etc.
Aerodynamic noise consists of a fan, rotating rotor and airflow noise formed by the flow of air along the wind path. The main measure to reduce the aerodynamic noise is to control the air volume. The air volume is minimized in the range of ensuring that the temperature of the motor does not exceed the limit of license. The improvement of the structure of the fan and the rational design of the wind system can reduce the aerodynamic noise. The stator and rotor radial ventilation Road Alignment, the possible, at this time should be to stagger each other.