Search

Bearingless flywheel battery has many advantages, such as high specific power, high specific energy, high current receiving capacity (recharge and regenerative braking), long service life, fast charge and discharge, and it is considered to be the most competitive auxiliary batteries for electric vehicle. However, there are some problems in bearingless flywheel motors and some magnetic bearings in bearingless flywheel battery systems, such as low integration, large energy loss and low reliability. Aiming at above problems, an axially suspended hybrid magnetic bearing with asymmetric excitation and unloading which consists a lower stator, a upper stator with permanent magnet ring and a rotor is proposed in this paper. First of all, the mechanical structure of the axially suspended hybrid magnetic bearing with asymmetric excitation and unloading is introduced, and the different operating mechanisms under the conditions of unloading, demagnetization, down disturbance and upward disturbance are discussed. The design criteria is set according to the operating mechanisms under different working conditions. According to the design criteria and the working curve of rare earth permanent magnet materials, the numerical model of unloading force and the axial compensation under demagnetization/maximum eccentricity are deduced. Then, the structural parameters of upper stator and permanent magnet are designed, and the windings of the upper stator and lower stator are calculated considering the constraint conditions of demagnetization and eccentricity. Based on this, three-dimensional finite element model is established. Simulation results show that the flux density is about 0.605 T between upper stator and air gap under unloading mode which verifies the validity of the design method for permanent magnet and upper stator parameters. The suspension force of finite analysis is about 100 N and the relative error with theoretical suspension force value (104 N) is 4%. When working under the demagnetization mode, the flux density is about 0.53 T between upper stator and air gap which approximately equals to the theoretical value(0.54 T). The suspension force of finite analysis is about 78 N and the relative error with the theoretical suspension force value(81N) is 3.7%. When the maximum downward eccentricity is 0.2 mm, the flux density is 0.515 T which approximately equals to the 0.5 T of theoretical value, the suspension force of finite analysis is about 65 N and the relative error with the theoretical suspension force value(69 N) is 5.8%. When the maximum upward eccentricity is 0.2 mm, the flux density is 0.65 T and the suspension force of finite analysis is about 110 N. Finally, in order to further verify the correctness of theoretical analysis, a prototype is manufactured according to the design results. The results of prototype test show that the maximum error between theoretical calculation value and measured value of unloading force is about 4%, and the average error is 2%, the rotor radial displacement is about 25 μm when the axial load is 80 N, the rotor radial displacement is about 35 μm when the axial load is 120 N. The results indicate the proposed magnetic bearing has a good unloading and suspension performance of the magnetic bearing, which provides a new idea and method for the design of high integration, low loss and high reliability flywheel battery system. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)