The optical isolation method of suppressing electromagnetic interference of automotive ignition system

Electromagnetic radiation, which is caused by the engine ignition system, is the most powerful electromagnetic interference (EMI) source in the vehicles, as well as the main reason of most electronic control unit (ECU) malfunction. In order to reduce interference from ignition noise on ECU, we use optical isolation technology to isolate electrical connections between the interference source and the control circuit. The formation mechanism of the ignition system EMI is analyzed. The possibility of suppressing ignition system EMI with optical isolation technology is discussed. Then, as a result we design an experimental platform of suppressing ignition system EMI. The experimental results show that the effect of suppressing ignition noise, in 20~100 MHz frequency band, is obvious after applying optical isolation circuit. It can address the issue of automotive EMC.     

Simulation of an automobile ignition system electro magnetic interference

When an ignition system operates, conducted interference caused by transient voltage of the primary circuit will impact on the accumulator and the disturbance will travel throughout the vehicle via wiring. The ignition system can disrupt the Electronic Control Unit and the normal operation of other electrical devices. Spark plug gap noise simultaneously produces very strong radiation interference in a vehicle. We analyzed the changes of the ignition coil voltage and current when an ignition switch was turned on and off. A discharged circuit model of spark plug also was set up. The electric field distribution in an automobile was calculated. For these calculations, the high voltage wire was considered to be a unipole antenna. This simulation indicates that using either damped wire or adding spark plug resistance can suppress spark noise effectively.     

An electromagnetic interference design of a high speed image acquisition system on DM642

A novel design is presented to defend against electromagnetic interference (EMI) in a high speed data acquisition system. Problems that affect signal integrity (SI) in high speed image acquisition systems, such as reflection, crosstalk and ground bounce, are deeply analyzed in a manner consistent with transmission line theory. The results can theoretically inform EMI design of important networks, including system power, ground, clocks, high speed wires and decoupling capacitors. Experiments simulating print circuit board(PCB) reflection and EMI on high speed signal wires between DM642 and SDRAM are conducted. The power and ground should be placed separately in different layers. The clock lines passing through holes should be as few as possible. The signal lines should be as close to the same length as possible. The results show that amplitude of the signal overshoot is less than 0.7 V and the EMI amplitude is within the federal communications commission(FCC) standard.     

Modeling and simulation of the conducted electromagnetic interference for permanent magnet direct current motors

A simulation model for evaluation of conducted electromagnetic interference(EMI) is developed based on analysis of the mechanism giving rise to conducted EMI. The simulation model includes high frequency effects associated with stray distributed parameter     

基于广义谐振理论的输电线路中波无源干扰谐振频率预测

现有IEEE（institute of electrical and electronics engineers）标准,目前只能明确0.5~1.7 MHz有限频段的输电线路无源干扰谐振机理。为拓展输电线路无源干扰谐振的研究频率,引入广义谐振理论,提出了一种基于电磁场能量平衡的干扰谐振频率预测构想。将大尺度空间下输电线路铁塔阵列及天线等效为广义封闭系统,从而基于复坡印廷定理,推导了电磁开放系统广义谐振因子的表达式,求解得到的广义谐振因子零值点为无源干扰谐振频点。该方法由于避开了传统将铁塔等效为半波天线的局限,因此可以实现中波频段无源干扰谐振预测。采用IEEE标准算例进行验证,结果表明：1.7 MHz频率以下,基于广义谐振理论的无源干扰谐振频率预测值和缩比模型实测值最大误差不超过±0.169 MHz。     

Novel Power Supply Method and Technology Analysis for Electrified Monorail System

The problems of industry monorail conveying system brought by tradition physical contact such as irregular contact spark, carbon laydown and unsafe, narrow the area which the material handling system can apply to in awful industry environment, e.g. forge, cleaning, lacquering. A novel monorail power supply method based on electromagnetic coupling theory is presented. Discussions are made on several problems such as frequency selection, load control, efficiency elements and harmonic effects at the same time. Moreover, solutions are brought about according to them. The monorail application of this technology provides clean, stable and safe power supply, and immunes to environment interference such as dust, water as well.     

Modeling and control of An LCL bi-directional inductive power transfer system

Since there exist high-frequency switching networks and complicated operating modes in bi-directional inductive power transfer (IPT) system, it is easy to result in high harmonics and EMI interference. An LCL filter network is introduced to effectively filter out the unwanted harmonics in track current and reduce EMI interference. Based on a mathematical model of the power transmission established by complex analysis of the AC variables, under the condition of maximum transmission efficiency, the phase angle differences between the primary input voltage and secondary output voltage U·so are ±90° and the energy is respectively transferred in forward or backward direction. Moreover, the power magnitude can be controlled by adjusting the modulus of U·pi and U·so. In addition, to keep the track current constant, different phase-shifting control strategies are designed in the primary and secondary parts. Simulation and experimental results show that these strategies can not only adjust track current to keep constant but also dynamically change the direction and magnitude of power transmission according to the working conditions and actual needs of the system load to improve the system operating efficiency.     

Identification of Minibus''s Surface Noise Source

With the study of minbus's accelerated exterior noise control,the principle of sound intensity measurement was applied,the sound intensity of a minbus's surface noise was tested,and the surface noise distribution was presented.Several identification of noise source methods including sound power,sound intensity contour map,frequency spectrum were used together for surface noise analysis and study.Engine radiation noise and exhaust noise was identified as the major noise sources.On the contrary,car body vibration noise,tyre noise,transmission agent noise,air admission noise just occupied a little proportion of surface sound radiation energy.The research provides the reliable basis to determine main projects of minibus's accelerated exterior noise control.     

Application of digital phase-locked loop and filtering technique in PWM rectifier

VHS-ADC high speed digital signal processing platform based on MATLAB and FPGA could be used to build three-phase voltage source rectifier with space voltage vector PWM(SVPWM).The initial phase of coordinate transformation from three phase static coordinate to two phase static coordinate which is called Park transformation and from two phase rotating reference frame to two phase static coordinate is uncertain. There existed noise in acquiring grid voltage and current. Digital phase-locked loop is added to follow the frequency and phase of grid voltage, FIR filter is added to process signal and reduce the interference. External voltage control loop, internal current control loop and the model of coordinate transformation are designed on the VHS-ADC platform. The small power experiment is conducted to verify the stability and feasibility of the control system. The experimental results show that the digital phase-locked loop and FIR digital filter can be applied to three-phase voltage source rectifier.     

Analysis and Countermeasures of the Power Noise During High Frequency PCB Design

The paper analyses many forms of power supply noise interference in the high frequency PCB and the relevant reasons. Combining several formulas with the relevant engineering experience, the authors bring forward a lot of related means; finally conclude the chief principle that controlling power noise should abide by.     

Relationship between Partial Discharge and Dissolved Gases Conentration in Oil

Long time partial discharge is bad for transfomers inside insulation and now partial discharge monitoring is not satisfactory because of electromagnetic interference and noise interference .This is a new way via dissolved gases concentration analysis to find partial discharge and acconding to diagnosis system to confirm partial discharge level. A basic research has been carried out to discover the correspondence relationship between partial discharge level and dissolved gases concentration,some valuable laws are gained for the first time.     

Fiber Current Sensor Based on Fabry-Perot

Fiber measurement technology has many advantages, such as no electromagnetic interference, good insulation and small volume. A kind of fiber current sensor is giver, which bases material mechanics and electromagnetic induction, and also makes a cantilever beam and F-P together for measurement. Phase demodulation way is adopted in this paper. The sensor principle and measurement principle of F-P are analyzed. This paper builds up the mathematical model of the F-P gap and gave a current measurement equation. At last some experiments are done to validate it. Advantages of this sensor are small volume, high sensitivity and comoact structure.     

Noise and Interference in Two Way CATV

The funneling effect of noise is the main difficulty in two way CATV modification works. This paper discusses the source of noise and interference, the mechanism to form noise funneling, the regularities of distribution, the characteristics of the spectrum, etc. The purpose is to find the way of reducing funnel noise. The invading noise has the greatest effect on the upstream of two way CATV system, which mainly comes from the indoor of the users. The increase of the number of cable modem will not obviously make greater funneling noise. The cable connectors are the main source of producing and invading noise in outdoor cable network, which is a threat to the safty of the whole upstream channel.     

Composite structure of sterilization and descaling system for circulating cooling water

In order to resolve the hazard of biofouling and scale in circulating cooling water system of power stations, this paper takes the lead in combining high voltage pulses and high frequency pulses for sterilization and descaling process. It analyzes both electromagnetic effects and biochemical effects on sterilizing and descaling process caused by the high voltage pulses and high frequency pulses respectively. The pulse generator is designed according to the requirements of electromagnetic parameters for effective operation. The design and improvement of process chambers are assisted by electromagnetic field simulation technology. Experimental data prove that the system can output high voltage pulse whose maximum peak value reaches 7 kV and high frequency pulse whose maximum peak value reaches 100 V the frequency ranges from 500 kHz to 2 MHz. The rate of sterilization can be as high as 91,and the rate of descaling reaches 71. This system is expected to achieve the standards of industrial water treatment through further research.     

高压交直流同塔输电线路无线电干扰与可听噪声的计算

为了寻求一种适合交直流同塔架设线路的无线电干扰与可听噪声计算方法，从理论上分析了混合线路表面场强的特点，利用线性叠加原理求出混合线路表面场强，并结合晴天和雨天对交流和直流线路电晕程度的不同影响，提出在同一种天气状况下计算交直流线路无线电干扰与可听噪声。用3种计算无线电干扰与可听噪声的方法，分晴天和雨天情况进行计算比较，结果表明3种方法中BPA修正公式计算值最大，该方法可视为目前计算交直流同塔线路无线电干扰与可听噪声的有效方法。     

Junction stiffness analysis and vibration noise prediction of wind power speed-increase gearbox

In order to study the vibration characteristics and radiation noise of wind power speed-increase gearbox, a torsional vibration model of wind power speed-increase gearbox is established based on the analysis of supporting stiffness of bearing and contact stiffness of gear pairs. By solving the vibration differential equation with the help of Matlab, the frequency and corresponding vibration mode are obtained. With taking stiffness excitation, error exaction and meshing impact exaction into account, the dynamic finite element model of speed-increase gearbox is set up, and the dynamic response simulation is carried out. Regarding vibration displacement of the nodes on gearbox surface as boundary condition, an acoustic boundary element model of speed-increase gearbox is built. The surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The results show that there is a great difference between torsion frequency and excitation frequency of wind power speed-increase gearbox, and so the resonance doesn't occur. The maximum structural noise and radiation noise mainly appear near the double octave of the gears meshing frequency of high-speed grade.     

An Experimental Investigation of the Flammability Limits of Natural Refrigerants

The most concerned issue nowadays for the refrigeration circles is to find out a certain refrigerant that could tolerate with nature, also have excellent performance and is liable to obtain as well. In the light of safety of natural refrigerants, we set up an experimental apparatus for flammability limits and analyze the experimental principle. The reasons that may influence the value of the limits are given. The experimental investigation of the flammability limits of Propane, Isobutane and Methylamine is carried out. It is shown that, if the consistency of the refrigerants in air increases approximately to the flammability limits, high-energetic ignition source is also needed to explode. However, it is necessary to take some precautions for safety.     

A floating threshold quantization algorithm to suppressmixing interferences in partial discharge

Due to the obvious difference of energy distribution frequencies from partial discharge (PD) signal and its mixing interferences (white noise and narrow brand), we uses the characteristic that node decomposition coefficients of wavelet packet transform can effectively show the energy change of signals to build up a floating threshold quantization algorithm (FTQA) varying with the noise energy of PD decomposition coefficients. It makes the node thresholds under the optimal base various with the noise strength in decomposition coefficients to self adaptively reality the choice of optimal threshold to finely partition PD decomposition coefficients. For simulated and real PD signals with mixing interferences, the conditional global threshold quantization algorithm (GTQA) and the proposed floating threshold quantization algorithm are employed to suppress the mixing interferences in PD signals and compared, and the results show that the proposed algorithm has the stronger suppression ability to mixing interference on PD signal and keeps perfect PD waveform via suppression.     

Application of Trap Filter of 50 Hz in Brainwave Data Acquisition System

It's always difficult in technology to eliminate power interference of 50 Hz in Brainwave Data Acquisition System .Though traditional ways to eliminate it can also gain some effects, they have drawbacks such as high cost and low currency at all time. The use of trap filter of 50 Hz may solve the question radically. Through the authors' repetitious experimentation, it is proved that trap filter of VCVS not only eliminate power interference of 50 Hz farthest but also have merits of simple circuit structure, convenient coupling and upper reliability. The authors offer collected brainwave in strong power interference environment. It may be seen that it is very clear and clean. Because power interference of (50 Hz) exists in almost all Data Acquisition System, this type of trap filter possesses better currency, it is expected to win extensive application in medical apparatus of measurement of other biological electricity signals and industrial observation and control system.