Design And Analysis Of Single-Winding Bearingless Switched Reluctance Machine For Flywheel Batteries

With the development of new energy,energy storage technology has become a hot topic.Among numerous energy storage technologies,flywheel batteries are highly valued at home and abroad for their advantages of high power,high efficiency,long life,high energy density,and clean and pollution-free.As the core component of the flywheel battery,the machine plays an important role in energy storage and power generation.In recent years,the new single-winding bearingless switched reluctance machine(SWBSRM)has become the first choice for flywheel batteries due to their simple structure,stable operation,and simple control.The external rotor topology adopted in SWBSRM can directly connect the rotor with the flywheel.Accordingly,the structure of the flywheel system is more compact,and the flywheel system can be driven with a smaller axial length,and the transmission efficiency is higher.Therefore,this paper proposes an external rotor SWBSRM for the flywheel battery.It has been designed according to design specifications and its mathematical model has been derived.In addition,the harsh environment of the flywheel system has the higher requirements on the performance of the machine.We not only need to ensure that the electromagnetic performances of the machine reach the design standards,but also its temperature and vibration must meet the design criteria of the flywheel system as well.Hence,it is necessary to investigate and analyze the temperature and vibration of the proposed external rotor SWBSRM individually.This paper takes the 12/8-pole external rotor SWBSRM as the research object.Based on the establishment of precise mathematic model,the paper investigates the design and optimization of machine,analysis of loss,temperature,vibration and noise.The main tasks are shown as follows:(1)By using the virtual displacement method,the mathematic model of 12/8-pole external rotor SWBSRM considering the influence of the radial displacement of the rotor and neglecting the magnetic saturation is derived in detail and verified by finite element method.(2)Based on the parameter design of the switched reluctance machine,the parameter design equation of the external rotor SWBSRM is derived,and the external rotor SWBSRM for flywheel batteries is designed.In order to improve the levitation force,the finite element method,the extreme learning machine and particle swarm optimization are used to optimize the parameters.The prototype is processed and manufactured according to the optimal parameters.(3)Three kinds of analytical methods of the iron loss are introduced in detail,and their advantages and disadvantages are discussed respectively.Finally,an analytical method suitable for the external rotor SWBSRM is selected for analytical calculation.And the analytical results are verified by finite element method.In addition,the heat sources such as copper loss,mechanical loss,and stray loss of the external rotor SWBSRM have also been analyzed to make the thermal analysis of the prototype.Finally,based on the calculated values of loss,the temperature of the prototype is analyzed by using Motor-CAD software.The results show that the temperature distribution of each part of the external rotor SWBSRM meets the design requirements of the flywheel system.(4)Based on the analysis of the main sources of the external rotor SWBSRM noise,the electromagnetic noise is taken as the research object.The analytical method and the finite element method are applied to calculate the natural frequency of the rotor,respectively,and the comparison shows that both two results are within the error range.Finally,LMS Virtual.Lab software is applied to simulate the vibration cloud and noise cloud of the external rotor SWBSRM.The results show that the maximum vibration acceleration and sound pressure level of the external rotor SWBSRM meet the design requirements of the flywheel battery system.