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Hongbo Qiu,Yuedong Guo,Wenfei Yu,Bingxia Tang,Cunxiang Yang 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.3
With the development of electric electron technology and controlling technology, controller for driving permanent magnet synchronous motors is used widely. The using of a controller can expand the motor speed range and improve motor runtime performances. However, the output current of a controller contains lots of time harmonics that will have bad infl uences on motor torque and losses. In order to analyze the infl uences of the time harmonics on the motor performances, diff erent time harmonic currents were injected into the motor armature. Taking a 750 W, 250 r/min permanent magnet synchronous motor with hybrid magnet poles (HPPMSM) as an example, the 2-D fi nite model was established. On this basis, the torque ripple and eddy current losses of permanent magnets with diff erent time harmonics were obtained. The infl uences of time harmonics on motor torque ripple and eddy current losses were determined, and the impacting mechanism was revealed. The analyses may be helpful for the optimal design of HPPMSM.
Yongjun Tan,Xuedan Luo,Mingfu Mao,Dehua Shu,Wenfei Shan,Guizhi Li,Dongcai Guo 한국물리학회 2018 Current Applied Physics Vol.18 No.11
In the present study, the SrMoO4:Eu3+ phosphors has been synthesized through hydro-thermal co-precipitation method, and single factor and orthogonal experiment method was adopted to find optimal synthesis condition. It is interesting to note that hydro-thermal temperature is a prominent effect on the luminescent intensity of SrMoO4:Eu3+ red phosphor, followed by co-precipitation temperature, calcining time, and the doping amount of Eu3+. The optimal synthesis conditions were obtained: hydro-thermal temperature is 145 °C, co-precipitation temperature is 35 °C, the calcining time is 2.5 h, and the doping amount of activator Eu3+ is 25%. Subsequently, the crystalline particle size, phase composition and morphology of the synthesized phosphors were evaluated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results show that these phosphors possess a scheelite-type tetragonal structure, and the particle size is about 0.2 μm. Spectroscopic investigations of the synthesized phosphors are carried out with the help of photo-luminescence excitation and emission analysis. The studies reveal that SrMoO4: Eu3+ phosphor efficiently convert radiation of 394 nm–592 and 616 nm for red light, and the luminescence intensity of SrMoO4:Eu3+ phosphors is improved. SrMoO4:Eu3+ phosphors may be a potential application for enhancing the efficiency of white LEDs.