Advances in Mechanics Engineering

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Authors: Jin Sha Yuan, Hai Kun Shang
Abstract: Partial discharge diagnosis is an important tool for detecting insulation defects in power equipments. This paper presents a pattern recognition approach based on Least Squares Support Vector Machine (LS-SVM) for Ultra High Frequency (UHF) partial discharge diagnosis of power transformer. Six different feature parameters were extracted from the data obtained from Partial Discharge (PD) on-line monitoring system. LS-SVM was used to discriminate between 4 different PD sources. Experimental results demonstrate that the proposed approach has higher recognition accuracy compared with traditional BPNN recognition method under condition of small samples, and has great potential for use of field data.
Authors: Xiao Bin Wei, Song Lu, Hua Jie Shi, She Hua Wu
Abstract: It analyzed the quantity of differ-harmonic in the output from vary pulse rectification circuit. Considering the problems of great voltage fluctuation and high harmonics content in the rectification output under the direct-supply of current source mode, put forward the method of 12-pulse rectification circuit with equilibrium rector circuit with equilibrium reactor into direct-supply of current source mode. From the simulation results it can be summarized that 12-pulse rectification circuit with equilibrium reactor can not only smooth the output but also suppressing the harmonics.
Authors: Min Sheng Yang, Si Guo Zhu
Abstract: This paper puts forward a current hysteresis control method suitable for cascaded H-bridge inverter. It has the following characteristics : The control method is similar to unipolar SPWM modulation for a single H bridge.It is simple for pulse generator and can effectively reduce the switching losses; The phase-shifted control pulse for multi H bridges of a phase with current hysteresis control can be generated which is similar to the phase shift SPWM by dynamically adjusting the width of hysteresis to keep power device switching frequency constant; It retains fast response, internal current limiting and with good stability for current hysteresis control.At last, the experimental results verify the correctness of the proposed method.
Authors: Jing Ming Zhang, Yi Yue Yuan, Hao Min Wang
Abstract: As the electricity conversion switch of electric vehicles, the inverters play an important role in vehicle’s driving and regenerative braking process. Therefore, the research in fault-tolerant control of inverters has important significance. This article applied a 5-phase fault-tolerant inverter into the electric vehicles, and researched its single-phase and double-phase fault-tolerant control. The experiment results prove that the 5-phase fault-tolerant inverter can assure the vehicles run as usual with single-phase or double-phase fault.
Authors: Jian Wei Ma, Wan Jian Yin, Jin Gang Ma, Qing Shan Ji
Abstract: The composition and function of vehicle charging system are analyzed, and basic theory of fault tree analysis method is introduced. The qualitative analysis of its reliability is carried out. Fault tree model of vehicle charging system is built, the minimum cut sets are solved and the key parts are found out. Through quantitative analysis, the occurrence probability of top event and importance of bottom event are solved, which provides theoretical basis for fault diagnoses of vehicle charging system, saves time of fault diagnoses and reduces unnecessary disassembly.
Authors: Li Jian Yang, Chun Hua Li, Song Wei Gao
Abstract: In order to improve the energy transduction efficiency of electromagnetic ultrasonic transducer (EMAT), a 2-D simulation model for the electromagnetic ultrasonic transducer is established and optimized. Aiming at the main object in EMAT optimization, the analysis of the impact that the coil and the lift-off distance of the tested pieces, incentive coil and various parameters of the permanent magnet have on the energy transduction efficiency is conducted. Ultimately, the optimum combination of the incentive coil parameters is determined.
Authors: Zi Ming Zhao, Ying Ying Yao
Abstract: Wireless energy transfer system uses separable mutual induction coil to transfer energy. According to the load characteristics of rechargeable batteries, the primary and secondary sides constitute the resonant circuit with series compensation to improve power factor and transmission capability of the system. The high frequency signal source circuit of the primary side uses frequency tracking to make the system working accurately at the resonant state. The primary side current keeps constant to make system stable. The system parameters are given optimized under the loosely coupled condition considering voltage gain, frequency bifurcation phenomena and the limit of the size of the secondary side, etc.
Authors: Ke Bin Zhu, Zai Ping Nie, Xiang Yang Sun
Abstract: Lack of efficiency in transmitting logging signals from down-hole to the top-hole server has long been one of the crucial problems for the development of LWD. This study aims to address this issue by exploring into the advanced scheme for LWD signal transmission proposed by NovatekTM. The main focus of the study is on electromagnetic coupling between two adjacent pipes. The coupler is modeled numerically by NMM efficiently according to the axial symmetry of the coupler. Through simulation and analysis which are based on the numerical model of the coupler, various parameters of the coupler are discussed, and some significant conclusions are obtained. The conclusions can guide optimization design of the coupler between the drill-pipes for signal transmission in LWD. Furthermore, the experimental results verify the good transmission performance of the coupler which is designed in this paper.
Authors: Xiu Ping Wang, Feng Ge Zhang, Xiao Ping Zhu, Guang Long Jia
Abstract: Brushless doubly fed machine (BDFM) has rapid progress in recent years, rotor modulation capability is still the role factor which limits the popularization and application. Rotor structure is designed derived from the common reluctance in this paper, finite element analysis(FEA) is used for the optimization of the rotor. By studying the optimization comparatively, design program of rotor structure can be obtained, which shows great feasibility in industrial and agricultural production.
Authors: Hong Wen He, Kai Zhao, Rui Xiong
Abstract: An unscented Kalman filter (UKF) is adopted to estimate the state of charge (SoC) of a lithium ion battery for application in hybrid electric vehicles (HEVs). Generally, the extended Kalman filter (EKF) can be selected to estimate a non-linear system state. However, it may leads to large errors since the strong non-linear and stochastic performance. In this paper, the performance of the lithium-ion battery is tested by a design of experiment, such as hysteresis, polarization, coulomb efficiency, etc. And a combined battery model is selected for SoC estimation, while the model parameter was identified by using UKF algorithm. Finally, the federal urban driving schedule (FUDS) is used to evaluate the proposed method accuracy. And the results show that the maximum SoC estimation error is less than 3%.

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