Design and analysis of mechanical flux‑weakening device of axial flux permanent magnet machines

Shaopeng Wang,Jiawei Lu,Bin Li,Chengcheng Liu,Youhua Wang,Gang Lei,Youguang Guo,Jianguo Zhu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.4

Due to the low inductance of an axial flux permanent magnet machine (AFPMM), the constant power speed regulation range is small. A new mechanical flux-weakening method for single-rotor single-stator AFPMMs is proposed in this paper. By installing a mechanical flux-weakening device on one side of the stator and rotating it certain angle, the speed regulation of the flux-weakening can be realized. The device is simple in structure, easy to operate, and can be operated in the process of machine operation. The validity of the device is verified by applying it to a machine. Finite-element software is used to calculate and analyze the performances of two machines with the device.

Effect of 3C-SiC Intermediate Layer in GaN-Based Light Emitting Diodes Grown on Si(111) Substrate

Youhua Zhu,Meiyu Wang,Yi Li,Shuxin Tan,Honghai Deng,Xinglong Guo,Haihong Yin,Takashi Egawa 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.2

GaN-based light emitting diodes (LEDs) have been grown by metalorganicchemical vapor deposition on Si(111) substrate with and without3C-SiC intermediate layer (IL). Structural property has been characterizedby means of atomic force microscope, X-ray diffraction, andtransmission electron microscope measurements. It has been revealedthat a significant improvement in crystalline quality of GaN and superlatticeepitaxial layers can be achieved by using 3C-SiC as IL. Regardingof electrical and optical characteristics, it is clearly observed that theLEDs with its IL have a smaller leakage current and higher light outputpower comparing with the LEDs without IL. The better performance ofLEDs using 3C-SiC IL can be contributed to both of the improvementsin epitaxial layers quality and light extraction efficiency. As aconsequence, in terms of optical property, a double enhancement of thelight output power and external quantum efficiency has been realized.

Power Quality Optimal Control of Railway Static Power Conditioners Based on Electric Railway Power Supply Systems

Youhua Jiang,Wenji Wang,Xiangwei Jiang,Le Zhao,Yilong Cao 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

Aiming at the negative sequence and harmonic problems in the operation of railway static power conditioners, an optimization compensation strategy for negative sequence and harmonics is studied in this paper. First, the hybrid RPC topology and compensation principle are analyzed to obtain different compensation zone states and current capacities. Second, in order to optimize the RPC capacity configuration, the minimum RPC compensation capacity is calculated according to constraint conditions, and the optimal compensation coefficient and compensation angle are obtained. In addition, the voltage unbalance EU and power factor requirements are satisfied. A PSO (Particle Swarm Optimization) algorithm is used to calculate the three indexes for minimum compensating energy. The proposed method can precisely calculate the optimal compensation capacity in real time. Finally, MATLAB simulations and an experimental platform verify the effectiveness and economics of the proposed algorithm.

Study on the lubrication state and pitting damage of spur gear using a 3D mixed EHL model with fractal surface roughness

Youhua Li,Lubing Shi,Zhongming Liu,Xiaopeng Wang,Xuetao Qiao,Zhihong Zhang,Shidang Yan 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

For high-speed, heavy-load gear units, the meshing tooth surfaces are generally under the mixed lubrication state, which is crucial for gear pitting or micro pitting damage. To clarify the effects of lubrication state on tooth pitting damage, carrying out both numerical and experimental studies on the contact severity of gears under different lubrication states is necessary. In this paper, a 3D line-contact elasto hydrodynamic lubrication model considering fractal surface roughness was developed and used to investigate the lubrication characteristics of involute gears. Both the distributions of pressure and film thickness fluctuated under the rolling contact of rough surfaces. The fluctuations became more substantial with the increase of load and roughness. Furthermore, from the calculated film thickness ratio λ, the contact of gear tooth surfaces with a fractal roughness of Ra = 0.8 μm was always under full lubrication state (λ > 1). When the roughness was increased to Ra = 3.2 μm, the contact was first transmitted into the mixed lubrication state (0.2 < λ < 1) under the load of 1000 N*m and finally deteriorated to boundary lubrication state (λ < 0.2) under the load of 2000 N*m. The boundary lubrication state that occurred under the contact of highly rough surfaces could induce the formation of gear pitting damage. The contact fatigue test showed the gear tooth surface roughness increased from 0.7 μm to around 2.7 μm after 8 million running cycles and then suffered pitting failure after another 2 million cycles, which was consistent with the simulation analysis prediction.

Power Quality Optimal Control of Railway Static Power Conditioners Based on Electric Railway Power Supply Systems

Jiang, Youhua,Wang, Wenji,Jiang, Xiangwei,Zhao, Le,Cao, Yilong The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

Aiming at the negative sequence and harmonic problems in the operation of railway static power conditioners, an optimization compensation strategy for negative sequence and harmonics is studied in this paper. First, the hybrid RPC topology and compensation principle are analyzed to obtain different compensation zone states and current capacities. Second, in order to optimize the RPC capacity configuration, the minimum RPC compensation capacity is calculated according to constraint conditions, and the optimal compensation coefficient and compensation angle are obtained. In addition, the voltage unbalance ${\varepsilon}_U$ and power factor requirements are satisfied. A PSO (Particle Swarm Optimization) algorithm is used to calculate the three indexes for minimum compensating energy. The proposed method can precisely calculate the optimal compensation capacity in real time. Finally, MATLAB simulations and an experimental platform verify the effectiveness and economics of the proposed algorithm.

A Novel Algorithm for Improving the SINR of D2D Communication in the Cellular Network

Cheng Huan,Youhua Fu,Jin Wang 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.6

In this paper, we investigate the interference scenario where multiple Device-to-Device (D2D) pairs reuse the spectrum resources allocated to one cellular user, and propose a novel algorithm for improving the signal-to-interference-plus-noise ratio (SINR) of D2D communication. We call this D2D SINR improvement algorithm as DSIA, and design it from the perspective of precoding and decoding. With the DSIA, each D2D pair involved in the network can obtain the corresponding precoding and decoding vectors which make the SINR of its receiver being maximized. In order to clearly describe the design procedure of the proposed algorithm, we first formulate an optimization problem with multiple variables to maximize the SINR of each D2D receiver, then simplify the objective function through mathematical derivation and seek out the relationship between the optimized variables which can transform the optimization problem to one of solving nonlinear equations, and finally propose the DSIA to work out the nonlinear equations. Numerical results show that the DSIA will enable D2D to achieve significant performance gains in terms of SINR and bit-error rate (BER) compared with the traditional spectrum orthogonal scheme.

ω-MODULES OVER COMMUTATIVE RINGS

Yin, Huayu,Wang, Fanggui,Zhu, Xiaosheng,Chen, Youhua Korean Mathematical Society 2011 대한수학회지 Vol.48 No.1

Let R be a commutative ring and let M be a GV -torsionfree R-module. Then M is said to be a $\omega$-module if $Ext_R^1$(R/J, M) = 0 for any J $\in$ GV (R), and the w-envelope of M is defined by $M_{\omega}$ = {x $\in$ E(M) | Jx $\subseteq$ M for some J $\in$ GV (R)}. In this paper, $\omega$-modules over commutative rings are considered, and the theory of $\omega$-operations is developed for arbitrary commutative rings. As applications, we give some characterizations of $\omega$-Noetherian rings and Krull rings.

ω-MODULES OVER COMMUTATIVE RINGS

Huayu Yin,Fanggui Wang,Xiaosheng Zhu,Youhua Chen 대한수학회 2011 대한수학회지 Vol.48 No.1

Let R be a commutative ring and let M be a GV -torsionfree R-module. Then M is said to be a w-module if Ext<수식> for any J ∈ GV (R), and the ω-envelope of M is defined by Mω = {x ∈E(M)ㅣJx ⊆ M for some J ∈ GV (R)}. In this paper, ω-modules over commutative rings are considered, and the theory of ω-operations is de-veloped for arbitrary commutative rings. As applications, we give some characterizations of ω-Noetherian rings and Krull rings.

Multiphysical Design and Optimization of High-Speed Permanent Magnet Synchronous Motor with Sinusoidal Segmented Permanent Magnet Structure

Liu Chengcheng,Zhang Hongming,Wang Shaoheng,Wang Youhua,Lei Gang,Zhu Jianguo 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3

High speed permanent magnet synchronous motor (HSPMSM) is an important driving motor for electric vehicles. Compared with the electric motor operated under normal speed, it is critical to reduce the torque ripple, vibration, and noise of the HSPMSM. Furthermore, The air-gap fux density total harmonic distortion and electromotive force total harmonic distortion determine by torque performance and vibration noise. This article uses analytical methods to analyze the infuence of permanent magnet sinusoidal segmentation (PMS) on the electromagnetic performance of surface-mounted HSPMSM. The fnite element method is used to calculate the infuence of diferent permanent magnet segmentation numbers, diferent adjacent permanent magnet decreasing thickness, and diferent center PM width on the electromagnetic performance of permanent magnet sinusoidal segmented surface-mounted high-speed permanent magnet synchronous motor (M2). Comparing the efectiveness of PMS in surface-mounted HSPMSM and interior HSPMSM. Furthermore, the rotor dynamics analysis and vibration noise analysis on M2 are performed, and the infuence of PMS on the stress and vibration noise of both motors’ rotors is summarized. This article proposes a parameter preprocessing grouping multiphysical multi-objective high-dimensional multilevel optimization method. Taking M2 as an example, a global optimization design was carried out for the high-dimensional structural parameters brought by PMS, which improved the electromagnetic performance of M2 and reduced the vibration noise and rotor stress.

Analysis and Design Optimization of Axial–Radial Flux Hybrid Excitation Permanent Magnet Eddy Current Coupling

Zhang Hongming,Liu Chengcheng,Zhang Shiwei,Wang Youhua,Lei Gang,Zhu Jianguo 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.6

This paper proposes an axial–radial flux hybrid excitation permanent magnet eddy current coupling (HE-PMEC), where the ferrite magnet is employed for producing the radial flux and the DC excitation current is adopted for producing the axial flux. Moreover, a shielding layer is developed to regulate the radial magnetic field. Its magnetic field distribution, electromagnetic performance, and temperature distribution are calculated based on the 3D finite element method (FEM). By adjusting the applied DC excitation current density and the insertion depth of the shielding layer, the variable current starting process, the variable current braking process, and the speed regulation characteristic of the proposed HE-PMEC are obtained. It can be seen that the starting process, braking process, and speed regulation ability of the HE-PMEC have been enhanced greatly. Furthermore, the copper ring shape of the HE-PMEC is optimized by using the proposed improved multilevel optimization method. It can be seen that the performance of the HE-PMEC can be improved by using the new optimized copper ring shape. Lastly, compared with the conventional PMECs, the proposed HE-PMEC has shown its superior electromagnetic performance.