advantages and disadvantages of permanent magnet synchronous motors are favored by consumers for their elegant appearance, light weight and resistance to wear and rust. Noise isa common problem in the motor world. advantages and disadvantages of permanent magnet synchronous motor are no exception.

Generation and control of electromagnetic noise

Electromagnetic noise is a kind of low-frequency noise generated by the vibration of the stator, rotor and the entire motor structure caused by the pulsation of the magnetic field in the air gap of the motor. From the perspective of magnetic field influence, electromagnetic noise is mainly caused by the asymmetry of magnetic field force waves and magnetic flux distribution.

In the stator and rotor windings, there exist fundamental magnetic potentials and various harmonic magnetic potentials. Their interaction can generate a series of force waves. The frequency of the fundamental magnetic field is relatively low, and its influence is not significant. The noise caused by the force waves generated by the harmonic magnetic field is related to the amplitude and order of the force waves. In terms of process, select the appropriate stator and rotor slots for matching and adopt the inclined groove method to avoid generating low-order force waves.

② Eccentricity of the stator and rotor or asymmetry of the magnetic circuit will cause asymmetry in magnetic flux distribution, resulting in a phenomenon where one side is subjected to greater force and the other to less force, thereby generating electromagnetic noise. Therefore, when designing or processing, the roundness of the stator and rotor must meet the requirements, and the magnetic circuit must be symmetrical and even. The machining accuracy of the end cover of the synchronous motor and the assembly from the stator core die-casting to the frame are related to the coaxiality of the stator and rotor. The precision requirements for them are related to advantages and disadvantages of permanent magnet Youdaoplaceholder0 of permanent magnet synchronous motor is very important.

The following methods can be adopted to reduce the electromagnetic noise of the advantages and disadvantages of permanent magnet synchronous motor:

① The appropriate air-gap magnetic flux density should not be too high, but if it is too low, it will affect the utilization rate of the material. The magnetic circuits of the stator and rotor need to be symmetrical and evenly superimposed loosely.

② Select the appropriate slot fit to avoid low-order force waves. Use rotor inclined slots at an Angle of one stator slot spacing.

③ During the processing and assembly of the stator and rotor, attention should be paid to their roundness and coaxiality. It is advisable to use hot sleeves as much as possible or adopt the process of pressing the stator first and then turning the end stop mouth of the frame. The structure of the frame and the end cover being integrated can be adopted to better ensure coaxiality and reduce the eccentricity of the stator and rotor.

④ Use sinusoidal windings as much as possible to reduce harmonic attenuation and avoid frequent resonance between the stator and rotor.

2. Generation and control of mechanical noise

Friction, impact, imbalance and structural resonance in the rotating parts of the synchronous motor can generate mechanical noise. The mechanical noise of synchronous motors is relatively large, usually accounting for about 10%-15%. Mechanical noise includes shaft start-up noise, noise generated by rotor imbalance, and noise caused by assembly eccentricity, etc. The noise value generated by the shaft start noise is closely related to the dimensional accuracy, surface roughness and positional tolerance of the balls and the grooves of the inner and outer rings.

The following methods can be adopted to reduce shaft start-up noise

During assembly, a strict demagnetization and cleaning process should be carried out to remove oil stains and iron filings.

② Sealed shaft couplings should be adopted to prevent foreign objects from entering. The fit between the outer ring of the shaft coupling and the shaft coupling chamber as well as the fit between the inner ring and the shaft should not be too loose.

③ To remove the axial clearance of the rotor, appropriate pressure must be applied to the shaft, the elastic gasket for sealing should be reasonably configured, and lubricants should be added appropriately to reduce friction.

For motors with special noise requirements, it is advisable to choose low-noise shaft starters. When the load is not too large, oil-impregnated sliding shaft starters can be used. Their noise can sometimes be 10dB lower than that of rolling shaft starters of the same size. In addition, performing dynamic balancing on the commutator and the fan is also an important means to reduce mechanical noise.

3. Generation and Control of Atmospheric dynamic noise

advantages and disadvantages of permanent magnet the atmosphere dynamic noise of a synchronous motor is generated by the atmosphere flow and change caused by the rotating rotor and the cooling fan rotating along with the shaft. It increases as the speed of the fan and rotor rises. The faster it flows and the more intense the change, the louder the noise. Atmospheric dynamic noise is related to rotational speed, the shape and roughness of the fan and rotor, unbalanced substances, changes in the cross-section of the air duct due to air flow, and the shape of the air duct.

The main measures to reduce atmospheric dynamic noise are:

For motors with good heat dissipation or low temperature rise, a longer fan should be adopted to eliminate noise. When designing the external fan, no ventilation margin should be left, and axial flow fans should be preferred.

② The connection between the outer fan and the rotating shaft does not require key connection but adopts the knurled straight pattern process. The outer fan should be thick and uniform, without distortion or deformation, with even spacing and dynamic balance calibration.

③ Obstacles should be reduced in the air duct. If there is a dedicated air duct, it is advisable to use a streamlined air duct. The cross-section of the air duct should not change suddenly.

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