基于磁热耦合法的电机模型参数计算

基于有限元法与集总热网络法建立电机温升模型,仿真计算电机瞬态温升。针对电机温升模型参数繁多且计算复杂的问题,从损耗分布和热量传递的角度,系统研究了电机的电磁参数和热参数。根据电机的结构参数建立物理模型,通过电磁仿真结合解析计算修正漏感参数,计算配置端部及外壳换热系数,等效处理定转子气隙对流系数,采用磁热耦合法计算温升。通过试验与仿真对比电机主要部位温升,验证了电机参数计算的准确性。     

基于等效热网络法的永磁同步电机温升计算

永磁同步电机体积小,功率密度高,导致它的单位热损耗大,由此引起的温升不可忽视。因此,本文采用等效热网络方法对永磁同步电机进行温升计算,首先建立了永磁同步电机的热网络模型,然后对模型中的各个节点的热阻,和部分节点的损耗进行计算和分析,最后对热网络图中的各个节点建立热平衡方程,求解方程组,得出各部分的稳态温升并通过实验进行了验证。     

混合磁悬浮系统电磁装置的温度计算与降温处理

电磁装置的发热问题是影响磁悬浮系统工作稳定的重要因素之一,本文首先分析了装置的发热机理,采用ANSYS软件建立电磁装置的三维有限元模型,并将装置中动铁芯随大轴旋转时与空气产生的风摩擦损耗包含在模型中.通过瞬态仿真分析,计算出电磁装置的温度分布及温度随时间的变化趋势,由计算结果发现电磁装置长期运行后其内部温度较高,超出了系统内部正常工作的温升允许范围.继而提出冷却方案,即采用冷却管进行散热,并初步设计冷却管的安装位置、形状、参数等.最后进行仿真计算,结果表明其冷却效果非常明显,符合温升允许要求.热分析中计及了热参数随温升的变化.     

电机热路参数影响的计算

一、前言电机温升计算最常用的方法是等值热路法。我们想象电机是由各个损耗源与热阻相互联接所组成。在稳定的情况下,电机的各种热损耗最后传给冷却介质流和温度已知的外部空间。热路的性质取决于它的各个参数:热阻、损耗和冷却介质及环境温度的数值。这些数值可从已知的结构尺寸和数据来计算,其有限的准确性,依赖于对电机发热现象的正确认识和计算基础的可靠。这些冷却参数的不准确性和损耗计算的误差,影响电机温升计算的结果。     

动态电磁感应加热方式初探-电机与电器温升反问题的研究

在概述了传统的电热方式与特点的基础上,从电机与电器温升反问题的角度出发,提出了利用电磁理论和旋转电机中损耗的概念,将输入的电能或其它能量完全充分地转换为热能,即将"损耗"转化为有效热能的动态电磁感应加热方法.使用该方法可以设计制作电磁致热器.该电磁致热器可以由电动机、水轮机和风机等原动机拖动,构成环保型动态电磁感应加热装置.     

磁悬浮承重装置中发热与温升分析计算

准确的热分析是磁悬浮系统电磁装置优化设计、防止过热的前提。提出了基于等效热路模型的电磁装置发热及温升计算方法,并与基于"场"的仿真分析结果进行比较,验证其正确性。首先,利用ANSYS软件建立电磁装置的瞬态温度场模型,并将装置中动铁心随大轴旋转时与空气产生的风摩擦损耗包含在模型中,通过仿真分析,得到电磁装置温度分布;然后,通过对散热路径的分析建立了电磁装置的等效热路模型,从"路"的角度计算出本电磁装置各位置的温升;最后,将基于"路"的计算结果与基于"场"的仿真结果进行了比较分析,各部分温升误差均在允许范围内,验证了等效热路模型计算电磁装置发热及温升方法的准确性和可行性。在基于"场"和"路"的两种分析中,均考虑了电阻率随温升的变化,散热分析中均计及了导热系数和对流散热系数随温度的变化。     

IGBT热模型的硬件在环实时仿真方法研究

在现有电压源型三相桥式逆变器的理想硬件在环(HIL)实时仿真模型的基础上,建立了IGBT损耗及温升的HIL实时仿真模型。模型是在基于FPGA的HIL平台上搭建。采用数据手册结合线性插值的方法建立了IGBT损耗模型。采用等效热网络电路方法,建立了IGBT温升模型。同时也可根据散热器结构参数计算热阻,增强了模型的适用性。为了扩展模型的实用性,采用Lab VIEW进行了上位机通信设计,实现了模型参数实时输入功能,以及模型数据实时采集并传输到上位机界面显示功能。最后将MATLAB仿真模型与HIL实时仿真模型进行对比,以验证模型的数据精度,并与实物测试进行对比,以验证模型的可靠性。     

旋转电磁致热器热功率与结构参数关系的研究

为了分析新型电磁加热装置—旋转电磁致热器的设计方法,对致热器的热功率进行了研究。首先分析了致热器的热功率分布规律,提出定子热功率透入深度的概念作为致热器设计的准则,给出了透入深度随转速变化的规律,分析了透入深度在致热器设计中的作用。以此为依据,为提高致热器的热功率密度,比较了闭口槽、半开口槽和开口槽三种不同定子结构的致热器在不同转速下的热功率密度。分析了开槽结构的致热器槽深和槽宽变化对热功率密度的影响,最后对开口槽和闭口槽样机的热功率进行了测试。实验结果表明了分析的正确性。     

基于等效热网络法的轴向磁通永磁电机热分析

为避免在轴向磁通永磁电机的初始设计及优化设计中,使用有限元或有限体积等三维方法计算电机温升时耗费大量建模及计算时间,本文建立了双定子单转子轴向磁通永磁电机的等效热网络模型,分析了模型的各等效热阻,建立各节点热平衡方程组并求解。通过样机温升试验,验证了本文提出的轴向磁通永磁电机等效热网络模型的正确性。最后,利用热网络模型计算分析了不同水速和装备间隙对电机温升影响,为同类电机的设计和温升计算提供了参考依据。     

起重机用永磁电机等效热阻法瞬态温度场计算

对起重机用细长型外转子永磁同步电机瞬态温度场计算分析,由于细长型特殊结构,铜损耗约占总损耗的90%;同时定子绕组处于电机中心,散热能力差,温升计算成为永磁电机设计的关键环节。以采用S3工作制40%通电持续率对起重机用永磁电机进行温升考核,建立了起重机用永磁电机的瞬态等效热网络模型。重点分析了影响瞬态热网络准确计算温升的影响因素,提出了铜损耗热源时变加载方式。基于ANSYS有限元仿真和样机温升试验对比分析,验证了所建立的起重机用永磁电机瞬态等效热网络模型的正确性。     

基于Maxwell的电动汽车轮毂电机电磁损耗特性分析

电动汽车轮毂电机经常要在复杂的运行工况和恶劣环境下运行,导致轮毂电机电流和内部电磁损耗不断发生变化,对电机温升分析和可靠运行产生严重影响。以1台4 kW轮毂电机为例,利用Maxwell电磁有限元分析软件,建立轮毂电机的电磁有限元模型并对电磁场进行计算。通过选取加速和过载中常见的8种工况进行计算,分析了轮毂电机各部件的电磁损耗分布状态和数值变化规律。由分析结果可知,定子铁耗随转速的上升而增加,随过载倍数增加的变化不大;转子产生的铁心损耗可以忽略不计;永磁体涡流损耗同时随着加速和过载的增加而增加,但加速工况产生的影响更强;绕组铜耗主要受过载倍数变化的影响,占总损耗的比重最大,是主要热源。研究结果为轮毂电机温度场的分析和冷却结构的设计提供重要的参考依据。     

电磁感应高温空气加热特性试验研究

将电磁感应加热技术应用到空气加热领域,研制新型高温空气加热装置。在电磁感应磁场中依靠加热装置内部感应加热件所产生的感应热对空气进行加热。在高温空气加热试验装置上,进行加热功率、空气流量、加热件初始温度对空气加热特性的影响规律的试验研究。结果表明：电磁感应高温空气加热装置能够快速方便地产生高温空气,空气终温可达900℃以上;通过改变电源功率或进入加热装置的空气流量,可以产生不同终温的高温空气。     

Electric drive based on double-inverter-fed induction machine with minimization of power losses

An electric drive based on a double-inverter-fed induction machine is presented. The control system of the electric drive minimizes the electromagnetic losses both at constant flux linkage in the gap and during its regulation at the optimal level. The considered variant of control permits one to significantly increase the acceptable electromagnetic torque during two-region rate regulation and to improve the energy characteristics.     

Energy-saving speed control of frequency-controlled induction motors on starting and decelerating

Energy-saving speed control of frequency-controlled induction motors over a broad power range has been developed. Such control minimizes the primary electromagnetic energy losses on starting and decelerating.     

瞬变负荷对电力设备能耗的影响及消除

由于我国经济的高速发展，电力短缺问题变得异常突出。据统计2003-2004年数省份出现了拉闸限电现象，缺电严重时上海的南京路也曾出现路灯和霓虹灯被迫关闭情况。为缓解电力供需矛盾，国家在加快电源建设的同时，还采取种种措施和手段提高终端用户电能使用效率。电网中瞬变功率对电磁设备的能耗有较大影响，通过分析电网中瞬变功率产生原因及对电能消耗的影响，然后采取有效措施，减少电网中瞬变功率导致的电能损失。     

Adaptation of a traction DC power system for high-speed traffic

Ways to develop and improve traction power-supply systems and adapt them for high-speed highways are considered. One way to improve a traction power-supply system and make it more efficient is to increase the nominal voltage in the dc traction network up to 24 kV. This allows one to increase the throughput and carrying capacities of railways, increase the distance between substations, reduce the cross section of traction-network wires, and significantly reduce power losses in power-supply facilities. All this, alongside the absence of unbalanced supply voltage and inductive losses, as well as a significantly lower electromagnetic action on the infrastructure under dc conditions, results in a greater efficiency than in the case of any alternating- current traction power systems of alternating current. A mathematical model of dynamic electromagnetic processes in electrical circuits with semiconductor converters is fleshed out. Analysis and synthesis of electromagnetic processes and the main characteristics of multipulse converters, as well as a comprehensive technical and economic comparison, shows that 24-pulse rectifying circuits with a serial connection of threephase bridge are most efficient for these systems. These rectifiers provide an improvement in the quality of electrical energy not only for the primary power-supply system, but also for the traction network. They allow one to use simpler and more economical active-passive smoothing filters that provide the electromagnetic compatibility (EMC) of a new traction dc power system with the communication and railway automation facilities. In addition, the use of 24-pulse rectifiers can allow one to significantly reduce the consumption of reactive energy, reduce power losses in a traction network, and increase the efficiency of traction substations.     

Comparative evaluations of the energy properties of an asynchronous electric drive in transient processes

This article shows the possibility of more effective control of an asynchronous motor with a squirrel- cage rotor than in the formation of an electromagnetic torque under flux linkage stabilization. A comparative analysis of energy properties of asynchronous machine operation under different kinds of control in similar conditions was performed. One means of control provides the premagnetization of the motor and creates electromagnetic torque upon stabilization of the rotor flux linkage in the first control zone, ensuring a transition into the second zone. In another means of control, in accordance with the developed method of sequential synthesis, premagnetization of the motor is not carried out, and at a low rotor rotational speed creates the electromagnetic torque with a minimum of total loss. When the speed increases, the electromagnetic torque is created under the stabilization of efficiency owing to reducing the reactive power in the function of the rotor-rotation speed. With a further increase in speed, the control is fulfilled with a minimum of reactive power, regardless of the motor load. The energy properties of the motor operation were compared depending on the load and rotation speed under the different means of control. The change in the energy properties of electric-drive operation when generating a motor angular velocity up to double the rate under conditions of limitation of voltage of the power-supply source was considered.     

一种永磁自锁型电磁气门驱动装置

在传统双弹簧、双电磁铁电磁气门驱动机构的基础上,提出了一种新型电磁驱动装置,它在气门开启或关闭保持阶段由永磁体产生的电磁力实现自锁功能而线圈不必通电;解锁后,它又是一台能够四象限工作的圆筒式永磁直流直线电动机,为动子运动时提供轴向电磁力,补充由摩擦等带来的动能损失,使得气门顺利落座。对该装置建立了动态有限元分析模型,分别讨论了弹簧、静铁心、永磁体等对电磁气门驱动装置的影响,对装置进行了优化设计。对该电磁驱动装置的空载反电动势、线圈电感、电磁力等重要参数进行了深入分析和计算,得到了有益的结论。     

A novel approach for determining temperature in an appliancewithout using a sensor

An electronic control design is described which approximates the temperature of a heating element without measuring it. Because no sensor or closed-loop electronics are utilized, and because the control uses the same circuits and ROM of an existing electronic control system, the incremental cost is zero. The control system monitors the power setting selected by the user and then utilizes an electronic counter (called the heater energy counter), which is incremented or decremented at a rate that is approximately proportional to the rate of increase or decrease of temperature of the heating element for that power setting. By knowing the user setting and counting zero crossover points, the raw power into the heating unit is determined, and by empirically determining the thermal losses for different power levels, the effective energy in the heating unit is determined     

Experimental study to reduce the distribution-transformers stray losses using electromagnetic shields

This paper examines the effects of using aluminum electromagnetic shields in a distribution transformer. The goal of placing electromagnetic shields in the distribution transformer tank walls is to reduce the stray losses. A 500 kVA shell-type transformer is used. The overall results presented in this research work indicate that stray losses can be considerably reduced when electromagnetic shielding is applied to the transformer tank. In the experiment, the walls of the steel tank of the transformer were lined with aluminum foil. A section of this paper is devoted to the characterization of stray losses against the transformer rating (kVA) and the stray losses over load losses against the transformer rating (kVA). The experimental data presented in this work, will be helpful for a practicing engineer in the transformer industry.