Research On Direct-drive Permanent Magnet Motor Of High Temperature Chemical Mixer

Chemical mixers are widely used in the industrial field.At present,most low-speed chemical mixers use asynchronous motors combined with reducers.This structure exists frequent maintenance,complex structure,low work efficiency and other problems,and the reducer of vertical structure mixer is easy to leak oil and pollute the material,the use of direct drive permanent magnet motor to provide power for the mixer can effectively solve the above problems.At the same time,there are many cases of stirring high-temperature materials in the chemical field,and the impact on various parts of the motor cannot be ignored.Under the above background,it is of great significance to develop such low-speed high-temperature chemical mixers.This paper takes the original chemical mixer motor parameters of an enterprise as the design index to design the direct drive permanent magnet motor.First of all,from the perspective of electromagnetic design,the use of fractional-slot concentrated winding can reduce the length of the winding end to improve efficiency and reduce copper consumption.Considering that the motor should have low vibration and electromagnetic noise,the radial force waves of different numbers of slots per pole and phase are analyzed,and the performance of 20-pole,24-slot and 30-pole,36-slot motors is further compared to determine the appropriate pole-slot fit;The relationship between the thickness of the permanent magnet and the air gap magnetic density and the effect of different thicknesses of the permanent magnet on the actual installation of the permanent magnet are analyzed;The size of the thermal load directly affects the temperature rise of the motor,so the selection of the thermal load is analyzed.Secondly,due to the long cantilever of the chemical mixer and the close distance between the stirring paddle and the inner wall of the cylinder,the output torque should be stable during operation.Therefore,this paper optimizes the cogging torque.According to the cogging torque analytical model,the relationship between the uneven air gap,the slot width and the pole-slot fit and the cogging torque is respectively studied,and the influence of the uneven air gap on the cogging torque under the optimal slot width is analyzed.Aiming at the phenomenon of viscosity change of material during stirring,the influence of load change on tooth magnetic density,torque,loss and efficiency is analyzed.A prototype was made in the factory and experimental tests were carried out,and the results showed that the motor can operate reliably.Finally,the chemical mixer will directly transfer heat to the inside of the motor when mixing high-temperature materials,so the temperature field needs to be analyzed.Based on the basic theory of fluid mechanics and heat transfer,this paper has pioneered the calculation of the heat transfer coefficient of the motor casing and the shaft ventilation channel and the temperature when the external temperature is introduced into the motor shaft end face.The Ansys software was used to simulate and compare the temperature distribution of each component with and without external temperature introduced into the motor shaft,and the influence of the external temperature and relevant parameters of the rotating shaft on the main components of the motor is analyzed,the relationship between different heat load values and motor temperature and material usage is compared and analyzed.Aiming at the problem of the introduction of external temperature into the motor,the effects of water-cooled structure and heat-insulated shaft structure on the suppression of external temperature introduction were analyzed,and the effects of the two structures on the axial temperature of the shaft were compared.The proposed design ideas and schemes provide a reference for the heat load design and external high temperature suppression of high temperature chemical mixers.