| With the improvement of the requirements for environmental protection and energy saving in the warehousing and logistics industry,the electric forklift has become the mainstream with its advantages of high efficiency and low noise instead of internal combustion forklift.The vibration and noise level of the motor are an important factor to determine whether the noise of the electric forklift truck is qualified,and the quiet motor is very necessary.Double skewed rotor induction motor has the advantages,such as low acoustic noise and vibration.And it also has not the defects which axial endplay problems and synchronous additional torque often occur in conventional skew rotor induction motors.In this paper,in view of the topological structure of the double skewed slot rotor,the noise reduction effect of the double skewed slot rotor in eccentricity is further analyzed.On this basis,the influence of the different inclined slot topology on the vibration and noise of the motor is explored,and the main work is as follows:1.Based on the basic theory of electromagnetic field,the expression of the mean radial electromagnetic force of the motor with single skewed slot rotor and double skewed slot rotor is derived,and the order and frequency of electromagnetic force wave under different working conditions are analyzed.It is found that the radial force wave produced by the interaction between the harmonic magnetic field and the fundamental magnetic field of the rotor is reduced to nearly zero by the double skewed slot rotor.The weakening degree of the radial force waves produced by the interaction of the harmonic magnetic field with the stator fundamental wave magnetic field is the same as that of the single skewed slot rotor2.The complex air gap magnetic conductivity model was established by the analytical method,which considered the rotor slotting,the double skewed slot and the different types of eccentricity.The expression of the complex air gap magnetic field in the eccentricity of the double skewed slot rotor is further obtained.According to Maxwell's law,the frequency and order of various electromagnetic waves in the air gap are further obtained with the expression of the air gap magnetic field.The theoretical analysis shows that the structure of the double skewed slot rotor also has the weakening effect on the additional force waves caused by the eccentricity.The electromagnetic wave of 50%static eccentricity and 50%dynamic eccentricity is calculated with the multi-layer model of double inclined slot,and the correctness of the theoretical analysis is verified.3.The two skewed slots rotors with different structures and four skewed slots rotors with different structures are analyzed.It is found that different skewed slot rotor structures have different effects on the vibration and noise of the motor.The skewed slot rotor structure with the middle ring structure and different segments of the rotor are separated from each other has better noise reduction effect.In general,the more the number of oblique slots,the better the noise reduction effect.The method of multi physical field coupling simulation is used to analyze the vibration and noise of different motor with different skewed slots,and the analysis results are verified. |
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