Browsing by Author "Hao, He"

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    Development of a magnetic-geared permanent-magnet brushless motor
    (IEEE, 2009-09-22T00:00:00Z) Wang, L. L.; Shen, Jian-Xin; Luk, Patrick Chi-Kwong; Fei, Wei-Zhong; Wang, Can-Fei; Hao, He
    High-torque and low-speed electrical drives are often employed for applications where mechanical gearing cannot be accommodated. On the other hand, permanent-magnet (PM) gear has drawn significant attention from both academies and industries due to the conspicuous merits, such as reduced acoustic noise, maintenance free, improved reliability, precise peak torque transmission capability, and inherent overload protection. In this paper, a magnetic-geared PM brushless motor is presented. It is a novel low-speed and high-torque motor which merges the advantages of conventional PM brushless motor and PM gear. Its topology and operation principle are introduced. Some techniques are employed to optimize and improve the motor performance, while the validity of the proposed techniques is verified with finite-element analysis. Moreover, an alternative operation condition, which can further reduce the motor speed and increase its output torque, is proposed and analyzed.
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    Sensorless high-speed BLDC machine using hardware-RFO
    (2011-12-31T00:00:00Z) Shen, Jian-Xin; Hao, He; Jin, Meng-Jia; Fei, Wei-Zhong
    High-speed permanent magnet (PM) brushless dc (BLDC) motor often needs a continuous rotor position signal for dynamic phase-advancing control, whist such kind of position signal cannot be directly obtained from the conventional Hall effect sensors or via the traditional back-EMF-based sensorless control strategy. Furthermore, during high-speed operation, the inverter free-wheeling diodes may conduct for more than 30 elec-deg, obscuring the back-EMF zero- crossings. Hence, the traditional back-EMF-based sensorless control strategy becomes unworkable. To overcome these problems, a new sensorless control method is proposed in this paper. It uses full hardware to observe the flux vector which is excited by rotor magnets. Thus, it can provide the rotor position which is the same as the phase angle of the observed flux vector. The proposed sensorless control method is validated with a 2Kw, 85000rpm PM BLDC motor system.