永磁无刷单相电机场路耦合有限元仿真与实验研究

针对永磁无刷单相电机在异步起动时必须借助起动副绕组而需进行电容切换,导致电机结构复杂和可靠性降低的问题,首先从电机的电磁设计入手,提出了一种电机磁路不对称、具有自起动能力的永磁无刷单相电机结构,然后采用V/f控制的变频控制方法,实现了电机带额定负载的平滑自起动和稳定运行。并利用Maxwell软件建立了电机的场路耦合有限元仿真模型,对电机及其控制系统进行了仿真分析。最后利用样机及其控制器的实验平台对样机系统的各种运行状态进行了实验测试,并将实验结果与有限元仿真结果进行了对比分析,两者达到了很好的一致性。研究结果表明,气隙不对称永磁无刷单相电机系统具有自起动迅速、运动平稳、效率较高的特性,在空调等家用电器领域具有很好的应用前景。

基于有限元仿真的模态宽频时效技术的应用研究

通过有限元法的仿真分析,预测构件或毛坯中残余应力的分布情况,确定需要均化残余应力的具体部位,就可以根据工件的材料与几何形状确定所需的振动模态。结合北京翔博科技有限责任公司自有的模态宽频时效设备对机械加工件进行有针对性(定位残余应力)的时效处理,可以达到降低和均化残余应力的目的,从而获得兼顾尺寸稳定性与低残余应力幅值的长寿命结构件。

±800kV直流高速开关断口外绝缘特性仿真研究

直流高速开关(high speed switch,HSS)作为多端柔性直流输电系统的关键设备,其可靠性具有重要意义,而断口外绝缘特性是影响HSS安全稳定运行的重要因素。文中采用有限元法针对HSS实际运行工况进行建模仿真,根据断口内绝缘及外绝缘的电场分布获得最恶劣的运行工况,研究该运行工况下HSS断口外绝缘在淋雨与污秽等环境下的电场分布特性,分析有限空间内断口加长提高外绝缘性能的可靠性。研究结果表明:实际运行过程中,HSS一侧隔离开关拒动、一侧通过阀侧接地为最恶劣的运行工况,在该运行工况下,淋雨环境中断口伞裙电场分布均匀,但电场强度整体增加,污秽条件下外绝缘电场分布与干燥条件下相似,但在高压端电场畸变程度显著增加;随着断口长度、外绝缘爬电距离增加,外绝缘电场模值整体下降,断口长度的改变对隔离开关外绝缘性能影响较小。以上研究对HSS断口外绝缘优化设计具有一定参考意义。

基于电场仿真的淋雨状态下大直径复合支柱绝缘子伞裙参数优化

伞裙结构是影响复合支柱绝缘子雨闪电压的重要因素之一,通过伞裙结构优化可以改善绝缘子雨闪特性。为此用正交试验方法选取伞裙参数,利用有限元软件ANSYS对复合支柱绝缘子建模仿真,研究淋雨状态下伞间距、大伞伸出、大小伞伸出差对一大一小伞型绝缘子电场分布的影响,提出伞裙沿面电场、空气间隙电场作为绝缘子伞裙优化判据。结果表明:大伞伸出对沿面场强影响最大,伞间距次之,伞伸出差最小;伞间距对空气间隙场强影响最大,大伞伸出次之,伞伸出差最小。通过与试验研究对比发现以空气间隙电场为判据较为准确,为绝缘子伞裙优化试验选取合适的伞裙参数试品提供参考。

考虑死区时间的直线感应电机参数静止自整定方法

针对直线感应电机初级和次级漏感不相等的特点,对直线感应电机静止状态下的参数辨识方法进行研究.首先,分别针对死区时间为0、1、2、3和4μs的情况进行场路联合有限元法仿真.利用PWM逆变器依次向直线感应电机中通入单相直流电压、单相交流高频电压和单相交流低频电压来获得等效电路中的各个参数.然后,将不同死区时间下的辨识结果与实际值进行比较,并进行误差对比,讨论不同的死区时间对辨识精度的影响.最后,分别分析死区效应对初级电阻及漏感、互感、次级电阻及漏感的辨识结果产生的影响.结果表明:在考虑到直线感应电机的初、次级漏感不相等的情况下提出的基于PWM逆变器的静止状态下参数辨识方法,辨识结果比较精确,验证了方法的正确性,死区效应的存在对直线电机各个参数的辨识结果均产生影响.

隔雨伞对淋雨状态下复合支柱绝缘子电场的影响

支柱绝缘子在实际运行的降雨天气下发生闪络是影响电网安全运行的重要因素。对在运行的绝缘子加装隔雨伞是最有效的提高抗雨闪能力的措施。为探究隔雨伞参数的选择方法,文中用有限元法对加装隔雨伞的一大一小伞型复合支柱绝缘子进行建模,研究隔雨伞数量和隔雨伞伸出对一大一小伞型复合支柱绝缘子电场分布的影响,提出沿面平均场强以及空气间隙场强作为2个隔雨伞参数的选择判据。结果表明:安装隔雨伞会使得隔雨伞周围大伞与小伞之间空气间隙场强变大,其自身场强相比没有加装隔雨伞时也会增大。将仿真结果进行对比后,根据场强大小关系推荐选用以空气间隙场强为判据进行参数选择,对隔雨伞的安装以及防雨闪措施有一定的指导意义。

Multi-field dynamic modeling and numerical simulation of aluminum alloy resistance spot welding

In order to explore the influence of welding parameters and to investigate the Al alloy (AA) nugget formation process, a comprehensive model involving electrical-thermal-mechanical and metallurgical analysis was established to numerically display the resistance spot welding (RSW) process within multiple fields and understand the AA-RSW physics. A multi-disciplinary finite element method (FEM) framework and a empirical sub-model were built to analyze the affecting factors on weld nugget and the underlying nature of welding physics with dynamic simulation procedure. Specifically, a counter-intuitive phenomenon of the resistance time-variation caused by the transient inverse virtual variation (TIVV) effect was highlighted and analyzed on the basis of welding current and temperature distribution simulation. The empirical model describing the TIVV phenomenon was used for modifying the dynamic resistance simulation during the AA spot welding process. The numerical and experimental results show that the proposed multi-field FEM model agrees with the measured AA welding feature, and the modified dynamic resistance model captures the physics of nugget growth and the electrical-thermal behavior under varying welding current and fluctuating heat input.

Finite Element Simulation of the Vibratory Characteristics for Quartz Tuning Fork Gyroscope

The micro quartz crystal tuning fork gyroscope is a new type of vibratory gyroscope. The gyroscope should be analyzed and simulated early in the design stage in order to offer reliable basis for design and to shorten the period of development. Thus the vibratory characteristics of the gyroscope is simulated with the finite element method of coupled field. The optimum exciting frequency and the factors which influence the gyroscope sensitivity are determined. The method for adjusting the frequency deviation between driving and detecting modes is also proposed.

Finite Element Analysis of the Dynamic Behaviour of Transmission Line Conductors Using MATLAB

The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature such as wind loading. This imposes a periodic force on the conductors which is highly undesirable. It is therefore important for engineers to account for the possible effect of the wind loading when designing the power line. Investigations have shown that modeling the exact dynamic behaviour of a conductor is very difficult. Based on this fact, getting the exact analytical solution to conductor vibration is difficult, which is almost impossible, hence the numerical approximation becomes an option. This paper presents the developed finite element method used to analyse the dynamic behaviour of transmission line conductors. The developed FEM （finite element method） is implemented on MATLAB. The numerical analysis using MATLAB that is presented in this paper is used to simulate the response of the conductor when subjected to external loading in the time domain. The simulation is used to analyse the transverse vibration of the conductor. The formulation of the stiffness matrix and load vector is done and the results obtained are used to evaluate the conductor＇s internal energy dissipation. This finite element solution is compared with the results documented in literature. This numerical simulation is also used to investigate the effects of varying the axial tension on energy dissipation within the strands. Hence, this evolved in physically appropriate energy characterization process that can be used to evaluate the conductor self-damping with respect to line contact.

Structure reliability analysis based on supercavity vehicle steady motion

Taking the steady motion status as a starting point,according to the modeling of actual state of theoretical analysis,a predigested model of supercavity vehicle was established,and relationship expressions of these angles were obtained when the movement of supercavity vehicle was stable.A theoretical analysis on the stability of underwater high-speed movement in the movement simulation program was conducted and the simulation results were given.Then the force status of the supercavity vehicle was elicited from the results.The finite element analysis was carried out based on the stability at all angles obtained from simulation results.Taking a pilot model as example,the Monte Carlo method was adopting to analyze the reliability with the given state of force and displacement.The result indicates that this method is feasible.

Simulation study on ultrasonic tomography for grouted reinforced concrete by finite element

A finite element reconstruction algorithm for ultrasound tomography based on the Helmholtz equation in frequency domain is presented to monitor the grouting defects in reinforced concrete structures.In this algorithm,a hybrid regularizations-based iterative Newton method is implemented to provide stable inverse solutions.Furthermore,a dual mesh scheme and an adjoint method are adopted to reduce the computation cost and improve the efficiency of reconstruction.Simultaneous reconstruction of both acoustic velocity and attenuation coefficient for a reinforced concrete model is achieved with multiple frequency data.The algorithm is evaluated with numerical simulation under various practical scenarios including varied transmission/receiving modes,different noise levels,different source/detector numbers,and different contrast levels between the heterogeneity and background region.Results obtained suggest that the algorithm is insensitive to noise,and the reconstructions are quantitatively accurate in terms of the location,size and acoustic properties of the target over a range of contrast levels.

Distributed parametric modeling and simulation of light polarization states using magneto-optical sensing based on the Faraday effect

To solve the problems encountered in practical processes of magneto-optical sensing, the infinitesimal distributed-parameter model and finite-element accumulation of different dielectric properties of micromaterials were used to describe the evolution of light polarization states, instead of the previously commonly used method of lumped-parameter simulation, thus essentially explaining the mechanism of sensing, magneto-optical effects, and related factors, and achieving multiphysics coupling using the COMSOL finite-element analysis method. Considering the cases of the Faraday effect without and with line birefringence, the magneto-optical effect and output characteristics of an infinitesimal magneto-optical sensor were simulated and studied. The results verified the effectiveness of the infinitesimal sensor model. Because the magnetic field, stress, and temperature changes alter the dielectric properties of magneto-optical materials, the finite-element accumulation method lays a good foundation for research on theoretical analysis and performance of magneto-optical sensors affected by factors such as the magnetic field, temperature, and stress.

System-level simulation of microbolometer and read-out integrated circuit

A method for system-level simulation between microbolometer designing and Read-Out Integrated Circuit(ROIC) was studied. Three-dimensional(3D) structure modeling of the microbolometer was built. Thermal capacity, thermal conductivity and resistance of the model were obtained from thermoelectric coupling Finite Element Method(FEM) based on the model. An electrical equipment circuit of microbolometer which contains these three parameters was established. By using Verilog-AMS language, the electrical equipment circuit was described as a reduced-order macro-model. Then, the reduced-order macromodel was compiled in cadence to form IP unit of microbolometer, which could be used and identified in cadence. Systemlevel simulation between microbolometer and ROIC was accomplished. Key performances of the device, including input and output characteristics, were obtained in simulation and verified by experimental results.