| The energy consumption of motor-driven fans or pumps loads accounts for more than one-third of industrial production.The speed or flow is adjusted by the magnetic coupler,the power of the motor will change with the load speed in cubic times,so the energy saving is significant.Although the magnetic coupler has the advantages of soft start,overload protection and reliable operation,its eddy current loss will cause the problem of temperature rise or even demagnetization of the permanent magnet.This problem can be solved by adding air-cooled device,but it leads to structure of the magnetic coupler complexed and accompanying wind resistance loss.In order to solve the above problems,a magnetic coupler structure of "external squirrel cage rotor + Halbach array" is proposed,which is based on the excellent unilateral magnetic concentrating characteristics of the permanent magnet Halbach array and the low loss of the squirrel cage structure,that is,the Long Air Gap External-cage Rotor Magnetic Coupler(LAEMC),in order to use the heat insulation effect of the long air gap to block the conduction of heat from the conductor rotor to the permanent magnet rotor;since the length of the air gap of LAEMC is 10 mm,which is more than 3 times longer than the length of the air gap of the traditional cylindrical magnetic coupler,so it can effectively block the heat transfering to the permanent magnet rotor,and it can meet the working temperature requirements of the permanent magnet without installing any air-cooled device on the conductor rotor.In this paper,the operation mechanism of LAEMC is analyzed,and the LAEMC air-gap magnetic field model and electromagnetic torque model are established based on the equivalent magnetic circuit method,and the influencing factors of electromagnetic torque and the mechanism of speed regulation are analyzed.The intrinsic demagnetization curve and thermal stability of permanent magnet materials were analyzed,and allowable temperature ranges were determined for subsequent temperature field analysis.The structural parameters of the LAEMC that meet the design requirements are given,the mechanical characteristic curves and characteristic points are analyzed,and the influence of each main structural parameters on the electromagnetic torque of LAEMC is analyzed.To enhance LAEMC electromagnetic torque,BBD response surface method is used to obtain the fitting equation of the electromagnetic torque and the main influencing parameters.In this way,the maximum electromagnetic torque value under the constraint condition is obtained,which is only 0.3% different from the finite element simulation,the good accuracy of optimization results obtained by the BBD response surface method is proved.The influence of the main structural parameters on its electromagnetic torque is analyzed through the LAEMC three-dimensional response surface,and the optimized LAEMC peak torque and starting torque are obtained,which are 19.8% and 28.8% higher than those before optimization.The speed regulation performance and operating efficiency of LAEMC under different load conditions are analyzed,the eddy loss ratio is introduced,from which the operating efficiency of LAEMC under different load characteristics is analyzed.The comparison shows that LAEMC is most suitable for centrifugal load regulation.The speed regulation range is0～100% and the operating efficiency is the highest among three different load characteristics.The LAEMC temperature field was analyzed,and the LAEMC temperature cloud diagram and the temperature values of the main components were obtained,and the influence characteristics of different air gap length on the LAEMC temperature field were studied.Among them,the temperature of the permanent magnet with g=10mm is 57℃,which is far lower than its allowable operating temperature,which proves that under the condition of medium and low power,long air gap structure can replace the traditional air-cooled devices. |
