Path Integral Approach to Faraday's Law of Induction

We derive a general form of the induced electromotive force due to a time-varying magnetic field. It is shown that the integral form of Faraday's law of induction is more conveniently written in the covering space. Thus the differential form is shown to relate the induced electric field in the nth winding number to the (n+1)th time-derivative of the magnetic field.

Mutual Inductance Calculation Between Arbitrarily Positioned Polygonal Coils

Polygonal coil systems are designed for increasing and more kinds of sensors and electromagnetic systems.This paper presents a method for calculating mutual inductance between polygonal coils including irregular polygons.Based on the Biot-Savart law,the method calculates mutual inductance by dividing a polygonal coil into finite wires,and expresses the magnetic induction intensity generated by the excitation coil as a function of the spatial position of each vertex of the coil.The calculation method of the feasible region of the objective function is updated and the calculation process is simplified,so the calculation accuracy is improved.For octagon coils arbitrarily positioned in space,the accuracy of the algorithm is verified by the simulation and experiment.

非最小相位的单电感双输出Buck-Boost变换器的复合控制方法

单电感双输出Buck-Boost (SIDO Buck-Boost)变换器在电感电流连续模式(CCM)下工作存在交叉影响以及非最小相位特性的问题.为了解决上述问题,提出基于储能函数的扩张状态观测器(ESO)的改进非奇异快速终端滑模(NFTSM)和自抗扰控制(ADRC)相结合的控制策略.设计主路控制器,对系统的传递函数进行拟合得到ADRC范式,利用该范式对主路进行解耦控制.设计支路控制器,采用改进型ESO对储能函数进行观测,并将观测值反馈补偿到非奇异快速终端滑模控制律中,达到支路解耦的效果.为了抑制滑模控制的抖振问题,对趋近律进行改进.利用Lyapunov理论证明系统稳定性.基于硬件在环(HIL)实验平台进行实验验证.结果表明,所提控制策略与PI控制策略以及基于ESO的滑模控制策略相比,在超调量和响应时间上具有较好的效果.

基于电流误差加权转速自适应律的异步电机无速度传感器设计方法

针对异步电机无速度传感器低速运行不稳定的问题,提出一种基于电流误差加权转速自适应律的异步电机无速度传感器设计方法。首先,采用小信号线性化模型分析方法说明转子磁链误差与励磁电流误差之间的关系,进而得出新的转速自适应律;然后,推导所提转速自适应律的开环传递函数,采用劳斯稳定性判据得出系统稳定运行的条件,借助MATLAB软件确定加权系数的取值;最后,将反馈矩阵引入含有改进转速自适应律的系统中,分析所提方法的极点分布规律。实验分析表明,所提方法具有较好的稳定性和优越性。

The Magnetic Longitudinal (P-) Wave’s Propagation and Energy Models Underlying the Mechanisms of Its Capacity to Absorb Free Energy

The longitudinal wave term within Faraday’s law of electromagnetic induction (Faraday’s law) underwent recovery to ensure its suitability for theoretical derivation of the equation governing longitudinal electromagnetic (LEM) waves. The revised Maxwell’s equations include the crucial parameters being the attenuation time constants of magnetic vortex potential and electric vortex potential generated by external electromagnetic field within the propagation medium. Specific expressions for them are obtained through theoretical analysis. Subsequently, a model for propagating magnetic P-wave generated by the superposition of a left-handed photo and a right-handed photon in a vacuum is formulated based on reevaluated total current law and revised Faraday’s law, covering wave equations, energy equation, as well as propagation mode involving mutual induction and conversion between scalar magnetic field and vortex electric field. Furthermore, through theoretical derivations centered around magnetic P-wave, evidence was presented regarding its ability to absorb huge free energy through the entangled interaction between zero-point vacuum energy field and the torsion field produced by the vortex electric field.

综合实验试题C:永磁铁通过金属管所产生的涡旋电流损耗功率及累计损耗测量

第9届全国大学生物理实验竞赛珠海赛区综合实验试题C为测量永磁铁通过金属管所产生的涡旋电流损耗功率及累计损耗.选手需设计并搭建光电门测量装置,测量磁铁下落速度,计算出能量损耗.本文给出了详细的试题设计和参考解答,并结合选手成绩和竞赛调研的统计结果,分析出选手的知识薄弱点和不足能力,为大学物理实验的教学与改革提供参考.

可穿戴设备高效自供电结构设计研究

基于法拉第电磁感应定律和压电效应原理,该文设计一款自供电可穿戴设备。该设备包括设备主体和安装于设备主体内的供电装置,供电装置包括组合发电模块、电路板、电池,组合发电模块包含线圈、强磁体及若干组压电陶瓷片,组合发电模块通过强磁体来回穿过线圈产生电动势和强磁体撞击压电陶瓷片产生电动势实现发电,线圈和压电陶瓷片均分别与电路板电连接,电路板、电池及设备主体依次电连接。该自供电可穿戴设备通过组合发电模块能够将动能转变为电能,不仅发电快而且穿戴便捷,重要的是,这种可穿戴设备可以通过自供电系统节约能源。

2023年高考全国甲卷物理第25题的深入分析

对2023年高考物理全国甲卷第25题进行分析,从磁场中“导轨+滑杆”模型的特点出发,给出了在高中阶段此类题型的常见解答过程,并从微积分思想的角度分析微积分在解决电磁感应问题中的应用.同时,对题目中金属棒P、Q可能的碰撞次数进行了分析,题目中“碰撞一次后”的表述是十分严谨的.

A Study on the Effective Long Type Coil Shape by Multidisciplinary Method in Induction Heating

The axis symmetric analysis method can neither handle initial curved plates nor be used in the optimization of coil shapes because an axis symmetric coil is the only shape to analyze in this method. But the method using some discrete divisions and steps, can overcome these difficulties and show more accurate, reasonable results of temperatures and deflections in flat or curved plates with initial curvature, than those in the axis symmetric analysis method. Traditionally, the coil shape in induction heating is circular shape and it needs the moving process along heating lines. To overcome these, the “long type coil” with some linear parallel coils is proposed. It does not need the moving process along heating lines and reduces the heating process time. The results of experiments are compared with those of simulation.

Noncontact Driving System Using Induction-Based Method and Integrated Piezoelectric Ultrasonic Transducers

Integrated Ultrasonic Transducers (IUTs) have been developed for high-temperature nondestructive evaluation applications. In many field, it would be helpful if a pipe covered by a protective layer of about 10 cm thickness, which is under operation at several hundred Celsius, could be inspected from above the protective layer by an IUT. As a first step toward achieving the inspection of such a pipeline, an induction-based method using coils is presented together with IUTs. This study focuses on the effects of the separation distance (liftoff) between the coils on the ultrasonic signal strength and bandwidth of the IUTs. Ultrasonic signals were generated and received by the IUTs on a steel plate with a sufficient strength for thickness measurements when the liftoff was 20 cm. It was also shown that a ferrite disc together with the coils enhanced the received signal strength even when the liftoff was over 10 cm.

Variable Speed Photovoltaic Water Pumping Using Affinity Laws

Photovoltaic (PV) power is most commonly used for water pumping applications. The DC output voltage of PV arrays is connected to a DC-DC converter using a maximum power point tracking (MPPT) controller to maximize their produced energy. Then, that converter is linked to a voltage source inverter (VSI) that converts DC power to AC power. Vector control is used to control the VSI fed three phase induction motor driving the water pump. The Affinity laws are used to change the pump characteristics by changing the pump speed, and consequently, the pump flow rate, head, and power will be varied. In this paper, the Affinity laws are adapted to achieve the pump hydraulic requirements while the power delivered to the pump motor remains unchanged by constructing new pump curves. A Matlab/Simulink model of the PV pumping system is observed over a wide range of weather and loading conditions.

磁力馈能悬架的设计与实验研究

馈能悬架在完成被动悬架相关功能的同时,可实现对振动能量的回收。本文提出了一种在保留原被动悬架弹簧与阻尼结构的基础上,融入法拉第电磁感应馈能元件的磁力馈能悬架结构,保证原有悬架的安全性,同时实现无接触、无摩擦、无需润滑的馈能功能。本文阐述了该馈能悬架的工作原理与基本结构,并对悬架结构进行优化设计。进而研制了磁力馈能悬架的原理样机及馈能实验台架,研究在变频率、变幅值的正弦激励下,悬架系统的输出电压特性。实验结果表明:馈能悬架的输出电压与正弦激励的幅值和频率呈正相关。为了验证馈能悬架的自供电性与实用性,选用传感器作为负载,在7 Hz,4 mm的正弦激励下,馈能悬架可持续输出的电压为22 V成功地为传感器供电。

电机模型中牵连运动及其动生电动势的数理表达

引入恰当的运动参考系可以简化交流电机模型推导和分析。一般地,运动参考系下空间矢量电压方程的推导分两步:(1)在“线圈固结坐标系”中运用法拉第电磁感应定律建立电压平衡式;(2)通过坐标变换的方式推导运动坐标系下的电压方程。该过程数学推导严谨,但是,对于记忆和理解运动坐标系下的电压方程的物理意义有难度。参考力学系统中“惯性参考系”的概念,根据法拉第电磁感应定律是否直接适用,引入所谓的“法拉第参考系”概念,对运动坐标系和线圈固结坐标系加以区分。对“非法拉第参考系”,借鉴“非惯性参考系”中引入“惯性力”的做法,引入附加“牵连运动电动势”,以此表征运动参考系引入的牵连运动效果。

后人口红利时代的财税法制度因应

我国逐渐步入后人口红利时代,这集中表现为两个方面:一是人口总量增速趋缓并将转为负增长,二是人口老龄化态势渐趋明显。此二者将带来财政收入增长乏力、财政支出压力激增等挑战。财税法制度要适时调整、优化自身,回应前述挑战。一方面,财税法要通过制度创新,以与经济发展相适应的方式扩张财源,其重心在于全面、准确地把握税负能力,同时在捋顺政府与市场关系的基础上,合理确定财政支出的向度和力度;另一方面,财税法不能将视野局限在财政收支层面,而须发挥诱导功能,助力后人口红利时代的经济发展和社会治理。

针对双馈风电机执行器故障的新型趋近律滑模容错控制方法

为了解决双馈风电机发电系统运行时执行器增益-偏置故障问题,提出一种新型趋近律二阶非奇异快速终端滑模容错控制方法。通过结合PID滑动面与非线性非奇异终端滑模面,以及采用新型自适应趋近律,将滑模面函数与控制增益相关联,设计二阶非奇异快速终端滑模容错控制器。利用李雅普诺夫(Lyapunov)函数来证明控制器的稳定性,仿真与试验结果表明,该控制方法与传统PID及传统滑模控制相比,削弱了抖振,响应速度提高了49.8%,减小了系统稳态误差,具有较好的容错性。

配电网电缆在线监测装置的三相取能电源设计与探讨

针对配电网三芯电缆绝缘状态在线监测设备的供能问题,对三相在线取能电流互感器(current transformer,CT)的工作原理进行研究,开发一种适用于三芯电缆在线监测设备的三相取能CT,并设计后续倍压整流电路。通过仿真和试验,对影响取能CT输出功率和电压的因素进行定性分析和探讨。结果表明,在取能CT尺寸确定的情况下,影响输出功率的主要因素是一次侧电流,影响输出电压的主要因素是二次侧绕组匝数、磁芯与缆芯垂直距离、磁芯侧面积。该取能电源的研发验证了三相在线取能的合理性与可行性。

感应电机新型自适应矢量控制极低速与零速稳定性研究

基于传统转速自适应律全阶观测器的感应电机无速度传感器矢量控制在极低速和零转速情况下不稳定的问题,该文提出新的反馈增益矩阵和新型转速自适应律的设计方法。逆变器非线性电压误差和定子电阻参数变化是造成电机极低速和零速不稳定的根本原因,其导致定子励磁电流误差增大,进而影响转子磁链误差增大,最终致使忽略磁链误差项的传统转速自适应律不再适用。因此,尽可能减小励磁电流误差和设计新型转速自适应律是确保感应电机极低速和零转速稳定的关键。通过添加数学公式上励磁电流误差项为零限制基于励磁电流误差收敛设计的反馈增益矩阵;并且推导出相比传统转速自适应律下的无近似和省略部分的新型转速自适应律,从而达到在改良后的全阶磁链观测器和新型转速自适应律下感应电机矢量控制全速度稳定的效果。通过3.7kW感应电机的dSPACE控制实验平台对该方法进行验证,该方法在额定负载条件下极低速和零转速下能稳定运行,表明该方法具有很好的稳态和动态性能。

改进扰动观测器的IM自适应滑模反步控制

针对内外部扰动问题,设计自适应滑模反步控制(ASMBC)的方法来调节异步电机速度。首先,提出了一种用自适应律改进趋近律的反步滑模控制方法,加快电机系统的动态响应速度并抑制滑模控制中的抖振现象;然后,为了消除传统扰动观测器中由于积分项累积带来的超调现象,采用饱和函数改进扰动观测器,用以估计电机内部参数的变化和外部扰动并减小超调;最后,将所设计的控制器与反步滑模控制(SMBC)等方法对比,实验结果表明该方法动态过程响应速度快、超调小,稳态过程跟踪精度高,并且具有良好的抗干扰能力。

基于新型幂次趋近律的DFIG滑模直接功率控制

针对采用PI控制时双馈风力发电系统在参数摄动情况下控制性能不佳及传统趋近律滑模控制存在抖振等问题,提出一种基于新型幂次趋近律的双馈风力发电机(Doubly-Fed Induction Generator,DFIG)滑模直接功率控制策略。首先建立DFIG的数学模型,然后针对滑模控制存在的抖振问题提出一种新型幂次趋近律,该趋近律可随着系统状态位置的变化自动调整趋近速度,使系统状态量平滑地进入滑模面,从而减小抖振。最后将此趋近律应用于DFIG滑模直接功率控制系统中。仿真结果表明提出的新型幂次趋近律滑模控制策略能够有效地降低系统抖振,增强系统鲁棒性。

GH4169合金真空感应熔炼过程中夹杂物演变规律研究

高温合金的夹杂物含量和存在形态影响合金的使用寿命及产品质量。文中系统研究了GH4169合金在真空感应熔炼过程中,O、N、Mg含量变化规律及夹杂物演变规律。结果表明,随着精炼时间的延长,GH4169合金中O含量逐渐降低,最终趋于平衡值,N含量逐渐降低;合金全熔时,夹杂物尺寸均小于1μm;精炼后,合金中氧化物含量明显减少;若在加入Al、Ti元素前未进行降温结膜操作,会加剧坩埚与熔体的反应,导致合金中Mg含量升高,夹杂物数量增多;加入Al、Ti、Mg等元素后,合金中夹杂物数量明显增加,夹杂物主要是以Mg-Ti-O为核心的Mg-Ti-Nb-O-N复合夹杂物。