| Compared with conventional permanent magnet machines(PM machines),high-speed permanent magnet machines(HSPM machines)have smaller volume,higher efficiency and higher power density.With the development of materials,processing technic and control technology,the maximum limitation speed of electrical machines is becoming much higher than before.Meanwhile,HSPM machines have been more widely used in numerous domains recently.The design of HSPM machines are difficult due to the coupling of electromagnetic,mechanical and thermal.Now,the design method of HSPM machines is immature,and there are still many key technologies to be solved.Aiming at the HSPM machines used in fans,the design flow is proposed and the key technologies are summarized at first in this paper.What's more,the optimal electromagnetic design is highlighted.A special method for winding connection is proposed to solve the winding design problems in HSPM machines.And the rotor eddy-current losses are also deeply analyzed.Firstly,when choosing the stator and rotor structure of HSPM machines,electrical machines with different pole number and slot number are compared.And the winding design problems are also illuminated.Therefore,a special method of winding connection is proposed to solve winding design problems by increasing the choice of parallel branch number.And the viability of this method is verified by FEM analysis.Secondly,the influence of stator slot opening,pole arc and relative permeability of magnetic wedge to the electromagnetic performance are analyzed in optimal electromagnetic design of HSPM machines.Meanwhile,the radial magnetization and parallel magnetization are also compared.Thus the final optimum electromagnetic scheme is decided.At the end,when studying the rotor eddy-current losses,segmentations in circumference direction and axial direction of magnet and segmentations in axial direction of sleeve are used to reduce the rotor eddy-current losses.The influence of segmentations number to reduction of rotor eddy-current losses is also analyzed.Moreover,the influence of sleeve conductivity to rotor eddy-current losses is highlighted.According to the conclusion,composite sleeve is recommended.Meanwhile,the influence of harmonic currents in inverters to the rotor eddy-current losses is studied to simulate the actual situations better.Based on the electromagnetic design method above,after finishing mechanical and thermal verification,a HSPM machine with 200kW@40000rpm has been designed.The prototype and test platform have been built at present.After accomplishing the assembling work of prototype and bearing,the prototype test will be done soon. |
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