| CNC turntable is a crucial component of CNC machine tools,and its performance determines the processing performance of CNC machine tools.With the continuous progress of direct drive technology,direct drive CNC turntables driven by permanent magnet synchronous motors are increasingly used in the field of CNC machine tools,making significant progress in the dynamic stiffness,response speed,processing efficiency,and accuracy of CNC machine tools.In this topic,the main task is to design a direct-drive permanent magnet synchronous motor(DD-PMSM)that meets the requirements of a vertical direct-drive rotary table of a numerical control machine tool.The electromagnetic performance,temperature,and vibration noise characteristics of the direct-drive permanent magnet synchronous motor need to meet the design requirements.In this paper,after designing the motor,the cogging torque is optimized,and the temperature and vibration noise characteristics of the motor are studied based on multi physical field coupling.According to the target performance parameters of the direct drive permanent magnet synchronous motor,the key parameters of the direct drive permanent magnet synchronous motor(stator size,pole slot fit,stator slot type,winding form,permanent magnet size,etc.)are analyzed and calculated,and the preliminary scheme of the motor is determined.The electromagnetic analysis model of the motor is established using the finite element simulation software Ansys Maxwell,and the magnetic field,back electromotive force,radial air gap magnetic density,load current The electromagnetic characteristics such as cogging torque were analyzed,and the cogging torque,a unique attribute of permanent magnet motors,was analyzed and optimized for suppression.By changing the pole arc coefficient and the stator slot width,the no-load cogging torque was reduced by 14.4% and 13.7%,respectively.Analyze the temperature characteristics of motor materials,solve the motor losses at different operating temperatures,and obtain the relationship between losses and temperature.From the loss results,it can be seen that the traditional coupling calculation model for unidirectional magnetothermal coupling temperature field simulation cannot feedback the temperature calculation results back to the electromagnetic field to update the material properties of the motor,resulting in inaccurate loss calculation,which directly affects the accuracy of temperature rise calculation for the motor.Therefore,a feedback link is added to simulate the bidirectional magnetothermal coupling temperature field of the motor,obtaining a steady-state temperature of 75.4 ℃ under rated load.Two experimental methods,temperature sensor and infrared thermometer,are used to measure the temperature of the motor under rated load.The error between the experimental and simulation results is small,verifying the reliability of the bidirectional magnetothermal coupling temperature field simulation.The temperature of the motor under rated load will not cause demagnetization of permanent magnet materials,The temperature performance of the motor is good.The main source of vibration and noise in permanent magnet motors is radial electromagnetic force.The spatial order and frequency spectrum characteristics of electromagnetic force at the air gap are analyzed.The harmonic order and frequency points with higher amplitude of electromagnetic force in the motor are analyzed using analytical methods and finite element methods.Both analysis methods show that the amplitude of electromagnetic force waves is higher when the order is multiple of the motor pole number and the frequency is even multiple of the fundamental frequency.Establish a model of the stator core and the entire motor for modal analysis,and obtain that the low order modal natural frequencies of the stator and the entire motor are not close to the frequency points with larger radial electromagnetic forces,verifying that the motor will not resonate.The electromagnetic force calculated from the electromagnetic field is coupled to the structural field through harmonic response analysis.The vibration displacement and directional velocity of the stator and casing of the motor are calculated using harmonic response analysis.The solution results are coupled to the harmonic sound field.A disk sound field model is established to calculate the motor noise and compare it with the noise limit values in the national standard documents to verify that the motor noise meets the requirements. |
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