Advanced Materials Research Vols. 516-517

Abstract: Electromagnetic vibration is produced by radical exciting force waves acting on iron cores of permanent magnet motors. In order to reduce radial electromagnetic force, a surface mounted permanent magnet synchronous motor was analyzed. According to the electromagnetic force wave of analytical formula in the case of no-load, the main force wave order and force wave frequency were analyzed. Properly selecting the pole arc coefficient could reduce the amplitude of electromagnetic force. By finite element analysis, the results show that reduce the sinusoidal distortion rate of the flux density, electromagnetic vibration of the motor can be reduced to some extent, but not the best choice.

Abstract: Wind power is an important source of green power. The equipment, generators, and power systems are all determining factors of equipment efficiency. High efficiency generators of medium and small size are widely used in daily life. Cogging torque is a major issue affecting generator efficiency. This paper proposes an optimized design for permanent-magnet synchronous generators using arc-shaped magnets to reduce cogging torque. The proposed approach improves performance significantly.

Abstract: Because the electric system of Tai-power is increased day by day, no matter generating set, transmission line, and transformer in substation, have especially already set up and increased aircrew's model parameter newly to use the number value that the producer offers in the part of the generating set, also there are no materials that a producer offered in the old aircrew, can only use typical value to substitute. Because the model parameter surveying value of system analysis, the accuracy of analysing the result of incomes remains to be discussed, so carry on the fixed quantity on the spot and examine the parameter of models to the systematic generating set, apply it to system analysis as the very urgent important affair. The purpose of this research is to set up the.

Abstract: Very fast transient overvoltage (VFTO) can be generated during the operation of disconnect switch (DS). Especially in ultra high voltage (UHV) gas insulated substation (GIS), VFTO is a threat to the safety of the power system equipment. It is very important to measure VFTO waveforms accurately. VFTO waveforms are comprised of high frequency voltage superimposed on the power frequency voltage in source side of DS and high frequency voltage superimposed on step-wise voltage in load side. How to trigger oscilloscope to acquire data is a big problem in measuring process. According to the features of VFTO waveforms, new triggering device consisting of a high pass filter is designed. The output of measurement sensor is used as the input of the high pass filter, and the output of the high pass filter is used to trigger oscilloscope. When the DS is not operated, there are no signals output from the high pass filter and the oscilloscope is waiting for trigger. After the operation of DS, the high frequency signals will pass the filter to trigger oscilloscope to acquire data. The device can guarantee the oscilloscope to complete a data acquisition properly.

Abstract: FPGA has the user programmable ability, like the software, it can be programmed. In this paper, we designed ultasonic detection circuit, and gives the hardware and software design. The Signal Tap II the logical analyzer show that, the system can acquisition at high speed, and can work in real-time

Abstract: This paper analysis the characteristic why Halbach array field is an one side field and give the formulation from current to drive force. Modeling dynamic and designing the control system for the control of angle movement of magnetic levitation stage. Control the movement of angle with PID controller precise. Simulation result and precision analysis indicate this magnetic levitation micromotion stage has good dynamic characteristic of angle movement controlled and it can realize microscale resolution.

Abstract: In order to solve the problem of needing to build accurate mathematical model in grounding grids fault diagnosis ,a new method for applying to the study of grounding grids fault diagnosis,which was based on BP neural network and improved by PCA theory，was introduced.The PCA(Principal component analysis)method was incorporated into the network,which not only solved the linear correlation of the input, but also simplified the network structure and reduced the parameters of neural net input. It realized optimum compression of fault sample data and enhanced classification speed and precision. The experimental results demonstrated that the method could decrease the number of the network input nerve cells effectively, and enhanced study efficiency and diagnosis accuracy. The way had very good fault distinguishing ability and vast prospect.

Abstract: It is known that human body contains rich chemical energy, part of which is converted to mechanical energy up to 200W, especially when human in walking, so human body is an ideal sustainable energy resource for portable electronic devices. The motion pattern of human movement in normal walking is studied, showing that the arm swinging, knee motion and hip motion can be approximated as sinusoidal functions with relatively large amplitude. In order to harvest such human motion, several methods are investigated, including pendulum, translational spring and torsion spring, which can also be mathematically formatted as second order differential equation with damped item. This paper also gives a typical device to harvest human motion: a novel energy harvester which directly converts human motion to electricity based on electromagnetic induction. Detail structures of the harvesting device are illustrated with mathematical analysis. Simulation studies are also made.

Abstract: Abstract. High impedance fault has always been difficult for distribution network fault identification due to its unobvious fault signature and difficult detection. This paper decomposed the transient signal in multi-scale by utilizing the good localization performance of the wavelet in both time domain and frequency domain, reconstructed the wavelet coefficients under each scale, took the wavelet reconstruction coefficient which was under the scale 3, calculated the size spectrum of each feeder line in timing floating window and identified the circuits in which the faults lined according to the value of the size spectrum. The high impedance fault simulation system was built based upon the study of the various transient signals in power systems, and the high impedance fault simulation analysis of the distribution feeder was undertaken through PSCAD simulation platform using high impedance fault model. Simulation analysis showed that the method could effectively extract the feature of high impedance fault on high impedance fault identification.

Abstract: DC Vacuum Circuit Breakers based arc control has been a major topic in the last few decades. Understanding vacuum arc (VA) gives the ability to improve vacuum circuit breakers capacity. In this paper, the interaction of a DC vacuum arc with a combined Axial-Radial magnetic field was investigated. The proposed system contains an external coil to produce axial magnetic field (AMF) across the vacuum chamber. The vacuum interrupter (VI) contacts were assumed to be untreated radial magnetic field (RMF) contacts. For this purpose, Finite Element Method (FEM) based Multiphysics simulation of the immerging magnetic field influence on the VA is presented. The simulation shown the ability of the presented system to deflect high DC vacuum arc, also reveals that the vacuum arc interruption capability increases with the rise of the axial component of the magnetic field. Simulation results shown that this method can be applied to improve the interruption capability of the VI.