Suppressing of humping bead using an external magnetic field in high-speed gas metal arc welding

During high-speed gas metal arc welding （GMAW）, the backward flowing molten jet with high momentum in the weld pool is considered to be responsible for the occurrence of humping bead. To suppress humping bead, an electromagnetic device is developed and coupled with the welding system. By adjusting the conditions of external magnetic field, forward electromagnetic force is obtained to reduce the momentum of the backward flow of molten metal in weld pool. Consequently, the humping bead can be suppressed by adjusting the external magnetic field. Bead-on-plate welding experiment was conducted on mild steel plates, and the influence of magnetic flux density on the arc deflection angle and weld bead quality is investigated. It is found that external magnetic field can remarkably adjust the momentum of backward flow jet and significantly improve the quality of weld bead.

Optimization Design of High-speed Interior Permanent Magnet Motor with High Torque Performance Based on Multiple Surrogate Models

In order to obtain better torque performance of high-speed interior permanent magnet motor(HSIPMM) and solve the problem that electromagnetic optimization design is seriously limited by its mechanical strength, a complete optimization design method is proposed in this paper. The object of optimization design is a 15 kW、20000 r/min HSIPMM whose permanent magnets in rotor is segmented. Eight structural dimensions are selected as its optimization variables. After design of experiment(DOE), multiple surrogate models are fitted, a set of surrogate models with minimum error is selected by using error evaluation indexes to optimize, the NSGA-II algorithm is used to get the optimal solution. The optimal solution is verified by load test on a 15 kW, 20000 r/min HSIPMM prototype. This paper can be used as a reference for the optimization design of HSIPMM.

High-Speed Permanent Magnet Electrical Machines - Applications, Key Issues and Challenges

In this paper,application examples of high-speed electrical machines are presented,and the machine structures are categorized.Key issues of design and control for the high-speed permanent magnet machines are reviewed,including bearings selection,rotor dynamics analysis and design,rotor stress analysis and protection,thermal analysis and design,electromagnetic losses analysis and reduction,sensorless control strategies,as well as comparison and selection of sine-wave and square-wave drive modes.Some challenges are also discussed,so that future studies could be focused.

Calculation for Stator Loss of High-Speed Permanent Magnet Synchronous Machine in Torque-speed Envelope and Restraint Approach for Circulating Current in Windings

Iron loss and copper loss are the significant parts of electrical loss of machines,which are the major parts particularly under high frequency condition.High-speed permanent magnet synchronous machines(HS-PMSM)have the benefits of high power density,high efficiency and wide speed range.Which causes the calculation for iron loss and copper loss in whole operating range complex.By analyzing the components and influencing factors of iron loss and copper loss in stator,we have deduced the calculation formula of iron loss and copper loss in whole operating range based on the analytical solution and finite element approach(EFA)solution.According to the calculation solution,taking the influence of operating temperature on the iron loss and copper loss into account,we propose a temperature correction factor and establish the calculation method for the iron loss and copper loss with temperature influences.Finally,by the conductor transposition,we restrain the circulating current under high-frequency operating condition.

Analysis of Temperature Rise in High-Speed Permanent Magnet Synchronous Traction Motors by Coupling the Equivalent Thermal Circuit Method and Computational Fluid Dynamics

To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.

UNBALANCE RESPONSE AND TOUCH-RUBBING THRESHOLD SPEED OF ROTOR SUBJECTED TO NONLINEAR MAGNETIC FORCES

Because of the effect of unbalance excitation and nonlinear magnetic force, the large vibration of the rotor supported by active magnetic bearing（AMB） will go beyond the radial gap of the bearing, even causing mechanical touch-rubbing when the system works at an operational speed closer to the critical speed. In order to investigate this problem, the linear model and nonlinear model of the single mass symmetric rigid rotor system supported by AMB are established respectively and the corresponding transfer functions of close-loop system are given. To pass through the numerical calculation by using MATLAB/Simulink, the effect of both the unbalance response and threshold speed of touch-rubbing of the system subjected to nonlinear magnetic forces and nonlinear output current of power amplifier are studied. Furthermore, threshold speed of touch-rubbing of the rotor-bearing system is defined and the results of numerical simulation are presented. Finally, based on above studies, two methods of increasing the touch-rubbing threshold speed are discussed.

Development of new electromagnetic suspension-based high-speed Maglev vehicles in China:Historical and recent progress in the field of dynamical simulation

High-speed Maglev is a cutting-edge technology brought back into the focus of research by plans of the Chinese government for the development of a new 600 km/h Maglev train.A Chinese‐German cooperation with industrial and academic partners has been established to pursue this ambitious goal and bring together experts from multiple disciplines.This contribution presents the joint work and achievements of CRRC Qingdao Sifang,thyssenkrupp Transrapid,CDFEB,and the ITM of the University of Stuttgart,regarding research and development in the field of high‐speed Maglev systems.Furthermore,an overview is given of the historical development of the Transrapid in Germany,the associated development of dynamical simulation models,and recent developments regarding high-speed Maglev trains in China.

铜金属网格技术在电子纸书写应用上的探索

为了进一步发挥电子纸优势,提升其原笔迹书写功能,介绍手写交互和笔写交互技术,通过对ITO工艺与铜金属网格(Cu Metal Mesh)工艺进行比较,并对手写触控磁容一体的铜金属网格进行技术分析,阐述了磁容一体手写触控技术原理,通过与目前主流书写技术进行比较,得出磁容一体手写触控技术的优势。证明了采用最先进的铜金属网格磁容一体技术,可以大幅降低电子纸手写触控应用成本并带来更好的人机交互体验,对电子纸应用普及和推广起到积极作用。

Influence of longitudinal magnetic field on metal transfer in MIG arc welding

Metal transfer is an important phenomenon in metal inert gas （MIG） arc welding with longitudinal alternating magnetic field. It is of great significance to observe the metal transfer modes under different excitatory currents and frequencies. However, it is very difficult to view the metal transfer process directly during welding, due to the strong interference from the arc light. To obtain the relationship between the metal transfer modes and the different magnetic fields, a high-speed video camera was used to acquire the images of globules. Different metal transfer modes under the conditions of different magnetic fields and welding parameters were studied. The experiment shows clear images of droplet transfer as well as influence of longitudinal magnetic field on both metal transfer and globule shape.

Numerical analysis of external magnetic field for mitigating backward flow momentum in weld pool

The external magnetic field is applied to mitigating backward flow jet of molten metal in weld pool so that humping bead may be suppressed during high speed gas metal arc welding（GMAW）. Therefore, the external magnetic field distribution in workpiece is critical to understand the interaction mechanisms of the external magnetic field with molten metal flow. In this study, the steady state external magnetic field induced by excitation device is numerically analyzed by using the the finite element software ANSYS and the three dimensional static magnetic scalar method. The distribution of external transverse magnetic field By in workpiece and arc area is calculated, and the influence of excitation current and air-gap distance on the distribution of transverse magnetic field By has been discussed. The magnetic field distribution in workpiece is measured by using a Tesla-Meter and compared with the simulated result. It is found that both are in good agreement.

The Influence of Longitudinal Magnetic Field on the CO_2 Arc Shape

The COarc welding was carried out under a longitudinal magnetic field,and the arc shape has been studied by using a high-speed camera.From the camera images,we know that under the action of the longitudinal magnetic field,the upper end of the arc will constrict and the lower end of the arc will expand.It would become a bell-type shape and rotate at a highspeed in the optimum range of magnetic field parameters.The arc shape was simulated using a mathematical model,which was established based on experiment data and theoretical knowledge,and mechanism analysis has been carried out regarding the effect of longitudinal magnetic field on COwelding arcs.

A sensorless efficiency test system for a high-speed permanent magnet synchronous motor

We present a sensorless efficiency test system with energy recovery for a high-speed permanent magnet synchronous motor(PMSM). In the system, two identical high-speed PMSMs are used as the motor under test(MUT)and the load machine(LM),respectively.A new sensorless vector control(VC) method based on a hypothetical reference frame is presented to control both the MUT and the LM.Also,a regenerating unit is used to implement energy circulation to save energy.Experiments were carried out on a prototype, with a digital controller based on the TMS320 F28335, to verify the adequacy of the sensorless VC method.As a result,the efficiency test system achieves the load test at the speed of 21000 r/min without any reduction equipment. During the test, the energy regenerated by the LM could be fed back to the MUT by the regenerating unit, and 81.31% electrical power was saved.In addition, with the proposed sensorless VC method,both the MUT and the LM can work at i_d = 0 without a position sensor.

Development progress of China's 600 km/h high-speed magnetic levitation train

1outline Launched in 2016 with a focus on the key technologies relatedtohigh-speed magnetic levitation,China's 600 km/h high-speed maglev train project has provided a number of engineering breakthroughs.Focusing on the development process of China's high-speed maglev system,this paper provides a description ofits development history,the innovations achieved,and the capabilities formed throughout the project.The paper commences by introducing the performance and technical innovation of thehigh-speedmaglevsystem interms of aerodynamic design,system dynamics,system energy consumption,vibration and noise reduction,and electromagnetic compatibility,among others.

Multiphysics Design of a High-Speed Permanent Magnet Machine for a Micro Gas Turbine Application

This paper presents a detailed and comprehensive multiphysics design process of an 80 kW, 60 000 r/min high-speed permanent magnet machine (HSPMM) for a micro gas turbine application. First, the preliminary design of the HSPMM is carried out according to the mechanical and electromagnetic theory. Afterwards, the influence of carbon fiber sleeve (CFS) thickness, rotor diameter and core length on rotor stress and rotor dynamics is carefully analyzed to obtain the optimal range of rotor diameter and core length. On this basis, the electromagnetic and power loss characteristics are analyzed in detail to obtain the final design scheme. Fluid-solid coupling model is used to calculate the temperature field of the HSPMM to verify the rationality of the scheme. The rotor thermal stress analysis considering the multi-layer and multi-angle winding of CFS is carried out to obtain the rotor models suitable for prototype and mass production, respectively. Finally, the prototypes are manufactured and tested to verify the reliability of the multiphysics design process.

Experimental Study on Characteristics Variation of Permanent Magnets for High-speed Machine Applications

High-speed permanent magnet(PM)electric machines are widely used.However,their extreme operating conditions,e.g.,high temperature and high mechanical stress,lead to variations of the PM characteristics and affect the machine performance.In the present study,an experimental device is designed to test the PM characteristics by simulating the stress and temperature conditions of high-speed machines.The experimental results indicate that the PM remanence not only varies at high temperatures,which is well known,but also changes under high mechanical stress.It is shown that the PM remanence increases with the mechanical stress but decreases with the temperature rise.Accordingly,a new demagnetization-curve model of the magnets under multiple stresses is refined to better express the PM characteristics.The performance of a high-speed PM machine is then analyzed as an example to indicate the necessity of the model refinement.The effects of the temperature and mechanical stress on the conductivity of the PMs are also examined.The experimental results indicate that the conductivity of the PM increases with the temperature and pressure.

基于触摸屏的夹具磁性开关信号故障诊断方法

焊夹具是一种对白车身进行定位和固定的工装,主要由气缸、气管、阀岛、磁性开关、操作按钮盒等构成,在出现电气信号故障后因磁性开关数量多难以快速定位,导致维修处理时间长。基于这一问题,文章通过对夹具的控制方式和触摸屏的应用技术进行分析,设计一种能够将夹具磁性开关信号状态快速反映到人机界面(HMI)上的诊断方法,并在HMI上建立三维视图和状态图形,以此来快速诊断夹具的磁性开关信号故障,减少设备的停机时间,为生产效率提供必要的保障。

圆柱电磁齿轮传动机理与轮齿结构的研究

基于电磁场原理,研究了圆柱电磁齿轮的结构和传动机理,以及主要结构参数的确定方法。对轮齿的结构形状进行了探讨,并利用ANSYS有限元分析软件对几种不同形状的轮齿进行仿真分析,提出了合理的轮齿结构。

无接触传动技术

基于对无接触传动的传动机理和技术特点的研究和分析,给出了该种传动与传统传动方式相比所具有独特优点:无磨损、低噪音、不需润滑介质、传动效率高、无污染。介绍了影响该传动方式的动力传动的主要因素:磁对的磁场强度、磁感的有效面积、磁对之间的间距。通过对制造工艺、结构特点的分析,展望了无接触传动的应用前景。

基于多CPU控制的3.3kV组合磁力控制站通讯系统的研究

本文分析了3.3kV组合磁力控制站中各CPU之间以及CPU与智能显示屏之间通讯的重要性,介绍了通讯原理,设计了单片机与PLC、PLC与PLC、PLC与触摸屏之间通讯的总体方案,并给出了软、硬件实现方法,提出了通过单片机与PLC实时通讯来协调控制电力负荷的新方法。试验结果表明:通讯系统方案可行,数据传输实时性好、准确度高。

SLon磁选机自动控制系统的设计与实现

为了使SLon磁选机具有更优异的选矿性能,设计了一种先进的磁选机自动控制系统。采用西门子公司的S7-200 PLC+TP170B触摸屏的控制结构,对主要控制参数———励磁电流采用PID控制算法,实现对磁选机系统的最优控制。该控制系统已经投入使用,运行结果表明,使SLon磁选机的整机性能得到了进一步的提高。