直流电动机能耗制动设计【自动化毕业论文开题报告外文翻译说明书】.zip
收藏
资源目录
压缩包内文档预览：(预览前15页/共34页)
编号：22399567
类型：共享资源
大小：2.75MB
格式：ZIP
上传时间：2019-10-16
上传人：小***
认证信息
个人认证
林**（实名认证）
福建
IP属地：福建
50
积分
- 关 键 词：
-
自动化毕业论文开题报告外文翻译说明书
电动机能耗制动
- 资源描述：
-
直流电动机能耗制动设计【自动化毕业论文开题报告外文翻译说明书】.zip,自动化毕业论文开题报告外文翻译说明书,电动机能耗制动
- 内容简介：
-
毕 业 设 计（论 文）任 务 书1本毕业设计（论文）课题应达到的目的： 通过毕业设计，使学生受到自动化工程师所必备的综合训练，在不同程度上提高各种设计及应用能力，具体包括以下几方面： 1. 调查研究、中外文献检索与阅读的能力。 2. 综合运用专业理论、知识分析解决实际问题的能力。 3. 定性与定量相结合的独立研究与论证的能力。 4. 设计方案的制定、仪器设备的选用、安装、调试及实验数据的测试、采集与分析处理的能力。 5. 设计、计算与绘图的能力，包括使用计算机的能力。 6. 逻辑思维与形象思维相结合的文字及口头表达的能力。 7. 撰写设计说明书或论文的能力。 2本毕业设计（论文）课题任务的内容和要求（包括原始数据、技术要求、工作要求等）： 1.本次毕业设计的对象是他励直流电机能耗制动，设计出能耗制动电路，并确定参数，采用Matlab中的Simulink软件对整个能耗制动系统进行仿真研究。 2按时完成开题报告书。 3按时完成毕业设计外文参考资料。 4能够圆满完成指导老师布置的课题任务，设计方案合理，能够体现一定的创新性。 5按时参加答辩，在答辩前各项规定的资料要齐全。 毕 业 设 计（论 文）任 务 书3对本毕业设计（论文）课题成果的要求包括图表、实物等硬件要求： 1.按期完成一篇符合金陵科技学院论文规范的毕业设计说明书（毕业论文），能详细说明设计步骤和思路； 2.能有结构完整，合理可靠的技术方案； 3.能有相应的电气部分硬件电路设计说明； 4.有相应的图纸和技术参数说明。 5.有相应的软件程序流程图，并给出调试成功后的结论。 4主要参考文献： 1. 清华大学，唐介主编：电机与拖动 (第二版) M.高等教育出版社.2007年 2. 电子工业大学. 陈勇，陈亚爱主编.电机与拖动基础M.电子工业出版社.2007年 3. 清华大学，彭红才主编电机原理与拖动(第二版) M.机械工业出版社.2006年 4. 人民邮电大学，梁南丁，滕颖辉主编.电机与拖动M.北京大学出版社.2008年 5周青苗永磁同步电动机直接转矩控制理论分析J西北工业大学学报,2000,18(2)：273-276 6李方圃变频器的起动制动方式J自动化博览20085：4347 7杨明秦，齐国政变频器的制动应用分析J机床电器2007(3)：5658 8王树变频调速系统设计与应用北京：机械工业出版社,2005 9李晓明电气制动的研究J山西电力200110(5)78,12 10张选正变频器的电器制动J电气时代20043：112114 11赵永成，宋立群，张国力变频调速系统中能耗制动电路的设计与实现J江苏电器2007(1)：28-30 12徐国忠，诸静变频器供电的异步电动机制动过程分析及控制J浙江人学学报，2000(2)：222-226 13黄立培电动机控制D北京：清华大学出版社，20039 14李忠文，安生辉实用电机控制电路M北京：化学工业出版社,2003 15明立娟直流电机控制系统D电子科技大学硕士论文2008,11 16袁任光实用电动机控制电路150例M北京：机械工业出版社,2007 毕 业 设 计（论 文）任 务 书5本毕业设计（论文）课题工作进度计划：2015.11.2-2015.11.5在毕业设计管理系统里选题 2015.11.6-2015.11.10在毕业设计管理系统里选题 2015.11.11-2015.12.11指导教师下发任务书，收集相关资料 2015.12.14-2016.1.6提交开题报告、外文参考资料及译文、论文大纲 2016.1.7-2016.4.13进行毕业设计（论文），填写学生中期检查表，提交论文草稿等 2016.4.14-2016.5.8按照要求按时完成论文或设计说明书等材料,提交论文定稿 2016.5.9-2016.5.13评阅教师评阅学生毕业设计；学生查看毕业设计答辩安排 2016.5.14.-2016.5.15参加毕业设计答辩 所在专业审查意见：通过负责人： 2015 年 12 月21 日 毕 业 设 计（论文） 开 题 报 告 1结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写不少于1000字左右的文献综述： （1）课题内容简介直流电动机的制动方式有多种：能耗制动、反接制动和回馈制动。在此我选择的研究方向是能耗制动。直流电动机开始制动后，电动机的转速从稳态转速到零或反向一个转速值（下放重物的情况）的过程称为制动过程。对于电动机来讲，我们有时候希望它能迅速制动，停止下来，如在精密仪器的制动过程中，液晶显示屏幕的切割等等，但有的时候我们却希望电机能够慢慢地停下来，利用惯性来工作。于是，直流电动机能耗制动又分为迅速停机和下放重物两种方式。首先，本设计先介绍了直流电动机的结构组成和工作原理。其次，是制动的详细过程，包括迅速停机和下放重物，迅速停机和下放重物又同时用机械特性和状态分析两种角度进行描述和分析。使用Matlab 仿真环境 Simulink 中的电力系统工具箱，可以简便快捷地对电动机的运行状态进行仿真，通过改变各种电气参数，得到不同的仿真结果，对比仿真结果可以确定电动机的最佳运行状态，避免了在实际电路上的反复调试，节省了大量的人力物力 ，提高了工作效率。（2）发展历史常用的控制直流电动机有以下几种:第一，最初的直流调速系统是采用恒定的直流电压向直流电动机电枢供电，通过改变电枢回路中的电阻来实现调速。这种方法简单易行设备制造方便，价格低廉。但缺点是效率低、机械特性软、不能在较宽范围内平滑调速，所以目前极少采用。第二，三十年代末，出现了发电机-电动机(也称为旋转变流组)，配合采用磁放大器、电机扩大机、闸流管等控制器件，可获得优良的调速性能，如有较宽的调速范围(十比一至数十比一)、较小的转速变化率和调速平滑等，特别是当电动机减速时，可以通过发电机非常容易地将电动机轴上的飞轮惯量反馈给电网，这样，一方面可得到平滑的制动特性，另一方面又可减少能量的损耗，提高效率。但发电机、电动机调速系统的主要缺点是需要增加两台与调速电动机相当的旋转电机和一些辅助励磁设备，因而体积大，维修困难等。第三，自出现汞弧变流器后，利用汞弧变流器代替上述发电机、电动机系统，使调速性能指标又进一步提高。特别是它的系统快速响应性是发电机、电动机系统不能比拟的。但是汞弧变流器仍存在一些缺点:维修还是不太方便，特别是水银蒸汽对维护人员会造成一定的危害等。第四，1957年世界上出现了第一只晶闸管，与其它变流元件相比，晶闸管具有许多独特的优越性，因而晶闸管直流调速系统立即显示出强大的生命力。由于它具有体积小、响应快、工作可靠、寿命长、维修简便等一系列优点，采用晶闸管供电，不仅使直流调速系统经济指标上和可靠性有所提高，而且在技术性能上也显示出很大的优越性。随着计算机，微电子技术的发展以及新型电力电子功率器件的不断涌现，电动机的控制策略也发生了深刻的变化。电动机控制技术的发展得力于微电子技术，电力电子技术，传感器技术，永磁材料技术，微机应用技术的最新发展成就。（3）目前现状数字直流调速装置，从技术上，它能成功地做到从给定信号、调节器参数设定、直到触发脉冲的数字化，使用通用硬件平台附加软件程序控制一定范围功率和电流大小的直流电机，同一台控制器甚至可以仅通过参数设定和使用不同的软件版本对不同类型的被控对象进行控制，强大的通讯功能使它易和PLC等各种器件通讯组成整个工业控制过程系统，而且具有操作简便、抗干扰能力强等特点，尤其是方便灵活的调试方法、完善的保护功能、长期工作的高可靠性和整个控制器体积小型化，弥补了模拟直流调速控制系统的保护功能不完善、调试不方便、体积大等不足之处，且数字控制系统表现出另外一些优点，如查找故障迅速、调速精度高、维护简单，使其具备了广一阔的应用前景。我国从20世纪60年代初试制成功第一只硅晶闸管以来，晶闸管直流调速系统也得到迅速的发展和广泛的应用。目前，晶闸管供电的直流调速系统在我国国民经济各部门得到广泛的应用。我国关于数字直流调速系统的研究主要有:综合性最优控制，补偿PID控制，PID算法优化，也有的只应用模糊控制技术。随着新型电力半导体器件的发展，IGBT(绝缘栅双极型晶体管)具有开关速度快、驱动简单和可以自关断等优点，克服了晶闸管的主要缺点。因此我国直流电机调速也正向着脉宽调制（pulse width modulation,简称PWM）方向发展。参考文献1唐介.电机与拖动M.清华大学:高等教育出版社.20072陈勇，陈亚爱.电机与拖动基础M.电子工业大学:电子工业出版社.20073彭红才.电机原理与拖动M.清华大学:机械工业出版社.20064梁南丁，滕颖辉.电机与拖动M.人民邮电大学:北京大学出版社.20085王晓明.电动机的单片机控制M.北京：北京航空航天大学出版社.2002.056邓建国.直流电动机电气制动过程的仿真研究J.中国知网.2003.037付惠琪.一种电容放电式能耗制动J.设备管理与维修.2007(08)8陈超山，杨达飞.一种简单实用的新型能耗制动电路J.机床电器.2007(04)9周安山.一种简便经济实用的能耗制动J.电动技术杂志.2002(02)10黄健，黄永春，盖同祥.直流电动机采用能耗制动网络后的特性分析J.延边大学学报（自然科学版）.1999(04)11焦悦，商亚丹，董波，等.能耗制动中制动电阻的分析计算J.重型机械.2013(02)12刘伟，王兆强，孙群力.浅议电机的制动方法及应用J.周口师范学院学报.2009(05)13余瑜，刘开培.基于电阻能耗制动和双频制动的新型电机制动方法的研究J.电力电子.2008(04)14杨斌文，陶增杰，许俊.一种经济实用的能耗制动电路J.电气时代.2006(11)15杨勇.直流他励电动机的制动方法分析J.山东工业技术.2014(23)毕 业 设 计（论文） 开 题 报 告 2本课题要研究或解决的问题和拟采用的研究手段（途径）： 1、本课题要解决的的问题直流的电动机是将输入的直流电能转变为机械能的电气设备，即有直流电能机械能。在直流电动机中，为了产生不变的电磁转矩，尽量减小气隙，以达到最强的磁场与最高的效率，就要利用磁场的作用，由通电导体形成绕组，由转子铁心和定子磁极形成磁场，通过换向器使转子的磁极的极性始终保持和定子的极性相反，形成旋转的力矩，从而外部电路中的直流电流通过换向转变成电机内部的交流电流，将电能转化为机械能。（1）能耗制动过程即迅速停机是如何实现的，以及迅速停机的机械特性是怎样的。（2）能耗制动运行即下放重物的过程是怎样的，以及迅速停机的机械特性是什么。（3）直流电动机的仿真是使用什么软件，及如何进行仿真。2、拟采用的研究途径（1）制动之前，转速n不为零，甚至相对较大，电动机平稳的运行。此时直流电动机的反电动势(E=Ce*n)存在甚至在某些场合很大，由于电枢电阻Ra较小，Ia=（U-E）Ra。当我们开始制动瞬间，电动机系统因为惯性继续旋转，n的方向不变，由于磁场方向不变，故E的方向也不变。由于电源被瞬间切除，此时相对于之前正常运转状态，电流方向Ia改变，而磁场方向不变，使得T反向成为制动转矩。此时电动的转速就迅速下降至零（在T和TL的共同作用下）。当n=0时，E=0;Ia=0;制动转矩和负载转矩都消失，电动机自动停机。（2） 如果电动机位能性很转矩负载。制动前，系统工作在机械特性1与负载特性3的交点a上，电动机以一定的速度提升重物。在需要稳定下放重物时，速度不会突变，则由a点移动b点，此时电动机处于能耗制动状态，此时由b点移动到O点，这个过程与能耗制动的迅速停机过程情况一样。但此时电动机不会停止不动而是，在负载转矩的作用下，电动机反转，即反向启动，工作点开始在第四象限继续下移，此时n反向，Ia又回到正向，那么T依旧提供向上拉力，TL不变，则当下降速度越来越大，E（正向）也越来越大（E=Ce*n），Ia也越来越大，T也越来越大（T=CT*Ia），最终在c点处达到平衡。这是能耗制动下放重物的过程。能耗制动运行与能耗制动过程相比，由于n反向，引起E反向，使得Ia与最初的上升时方向相同，T也同样。下图是能耗制动过程中，n0，T0;在能耗制动运行时，n0的情况。（3）使用传统手段进行电路设计时，一般都是依据电路图，焊接成实际电路，再进行调试，费时耗力。而现在可以利用 Matlab 的电力系统工具箱对机电系统进行仿真，检验设计的系统是否满足实际需求，节省设计时间。电力系统是电路、机电设备(如电动机，发电机)的组合体，因此这种系统经常是非线性的，对这种系统进行分析的唯一办法是进行仿真。电力系统工具箱提供了这样一个现代化的设计分析工具，允许快速方便地建立仿真模型，仿真使用Matlab 中的simulink 环境，允许通过拖放的方式建立模型，不仅可以快速建立电路结构，而且可以分析内部机械 及控制部件之间的相互影响，反复调整参数使整个系统工作在最佳状态。毕 业 设 计（论文） 开 题 报 告 指导教师意见：1对“文献综述”的评语：赵明明同学针对直流电动机能耗制动设计进行研究，该生查阅文献资料能力较强，能较为全面收集关于直流电动机能耗制动设计的资料。对毕业论文的各个环节非常重视，开题报告格式符合学校的有关毕业生论文的写作要求，报告说明充分，思路清晰。 2对本课题的深度、广度及工作量的意见和对设计（论文）结果的预测：论文题目选择合理，符合本专业要求，和专业学习相符，有研究价值，工作量适中。预计该论文应该能够达到预期水平。 3.是否同意开题： 同意 不同意 指导教师： 2016 年 03 月 30 日所在专业审查意见：同意 负责人： 2016 年 03 月 30 日 Introduction to D.C. MachinesD.C. machines are characterized by their versatility. By means of various combinations of shunt-, series-, and separately excited field windings they can be designed to display a wide variety of volt-ampere or speed-torque characteristics for both dynamic and steady state operation. Because of the ease with which they can be controlled, systems of D.C. machines are often used in applications requiring a wide range of motor speeds or precise control of motor output.The essential features of a D.C. machine are shown schematically. The stator has salient poles and is excited by one or more field coils. The air-gap flux distribution created by the field winding is symmetrical about the centerline of the field poles. This is called the field axis or direct axis.As we know, the A.C. voltage generated in each rotating armature coil is converted to D.C. in the external armature terminals by means of a rotating commutator and stationary brushes to which the armature leads are connected. The commutator-brush combination forms a mechanical rectifier, resulting in a D.C. armature voltage as well as an armature m.m.f. Wave then is 90 electrical degrees from the axis of the field poles, i.e. in the quadrature axis. In the schematic representation the brushes are shown in quadrature axis because this is the position of the coils to which they are connected. The armature m.m.f. Wave then is along the brush axis as shown. (The geometrical position of the brushes in an actual machine is approximately 90 electrical degrees from their position in the schematic diagram because of the shape of the end connections to the commutator.)The magnetic torque and the speed voltage appearing at the brushes are independent of the spatial waveform of the flux distribution; for convenience we shall continue to assume a sinusoidal flux-density wave in the air gap. The torque can then be found from the magnetic field viewpoint.The torque can be expressed in terms of the interaction of the direct-axis air-gap flux per pole and space-fundamental component of the armature m.m.f.wave. With the brushes in the quadrature axis the angle between these fields is 90 electrical degrees, and its sine equals unity. For a pole machine （1-1）In which the minus sign gas been dropped because the positive direction of the torque can be determined from physical reasoning. The space fundamental of the sawtooth armature m.m.f.wave is times its peak. Substitution in above equation then gives （1-2）Where, =current in external armature circuit; =total number of conductors in armature winding; =number of parallel paths through winding.And （1-3）is a constant fixed by the design of the winding.The rectified voltage generated in the armature has already been discussed before for an elementary single-coil armature. The effect of distributing the winding in several slots is shown in figure. In which each of the rectified sine wave is the voltage generated in one of the coils, commutation taking place at the moment when the coil sides are in the neutral zone. The generated voltage as observed from the brushes and is the sum of the rectified voltages of all the coils in series between brushes and is shown by the rippling line labeled in figure. With a dozen or so commutator segments per pole, the ripple becomes very small and the average generated voltage observed from the brushes equals the sum of the average values of the rectified coil voltages. The rectified voltage between brushes, Known also as the speed voltage, is （1-4）where is the design constant. The rectified voltage of a distributed winding has the same average value as that of a concentrated coil. The difference is that the ripple is greatly reduced.From the above equations, with all variable expressed in SI units, （1-5）This equation simply says that the instantaneous power associated with the speed voltage equals the instantaneous mechanical power with the magnetic torque. The direction of power flow being determined by whether the machine is acting as a motor or generator. The direct-axis air-gap flux is produced by the combined m.m.f. of the field windings. The flux-m.m.f. Characteristic being the magnetization curve for the particular iron geometry of the machine. In the magnetization curve, it is assumed that the armature m.m.f. Wave is perpendicular to the field axis. It will be necessary to reexamine this assumption later in this chapter, where the effects of saturation are investigated more thoroughly. Because the armature e.m.f. is proportional to flux times speed, it is usually more convenient to express the magnetization curve in terms of the armature e.m.f. at a constant speed . The voltage for a given flux at any other speed is proportional to the speed, i.e. （1-6）There is the magnetization curve with only one field winding excited. This curve can easily be obtained by test methods, no knowledge of any design details being required.Over a fairly wide range of excitation the reluctance of the iron is negligible compared with that of the air gap. In this region the flux is linearly proportional to the total m.m.f. of the field windings, the constant of proportionality being the direct-axis air-gap permeance.The outstanding advantages of D.C. machines arise from the wide variety of operating characteristics that can be obtained by selection of the method of excitation of the field windings. The field windings may be separately excited from an external D.C. source, or they may be self-excited; i.e. the machine may supply its own excitation. The method of excitation profoundly influences not only the steady-state characteristics, but also the dynamic behavior of the machine in control systems. The connection diagram of a separately excited generator is given. The required field current is a very small fraction of the rated armature current. A small amount of power in the field circuit may control a relatively large amount of power in the armature circuit; i.e. the generator is a power amplifier. Separately excited generators are often used in feedback control systems when control of the armature voltage over a wide range is required. The field windings of self-excited generators may be supplied in three different ways. The field may be connected in series with the armature, resulting in a series generator. The field may be connected in shunt with the armature, resulting in a shunt generator, or the field may be in two sections, one of which is connected in series and the other in shunt with the armature, resulting in a compound generator. With self-excited generators residual magnetism must be present in the machine iron to get the self-excitation process started.In the typical steady-state volt-ampere characteristics, constant-speed prime movers being assumed. The relation between the steady state generated e.m.f. and the terminal voltage is （1-7）where is the armature current output and is the armature circuit resistance. In a generator, is larger than and the electromagnetic torque is a counter torque opposing rotation.The terminal voltage of a separately excited generator decreases slightly with increase in the load current, principally because of the voltage drop in the armature resistance. The field current of a series generator is the same as the load current, so that the air-gap flux and hence the voltage vary widely with load. As a consequence, series generators are normally connected so that the m.m.f. of the series winding aids that of the shunt winding. The advantage is that through the action of the series winding the flux per pole can increase with load, resulting in a voltage output that is nearly usually contains many turns of relatively small wire. The series winding, wound on the outside, consists of a few turns of comparatively heavy conductor because it must carry the full armature current of the machine. The voltage of both shunt and compound generators can be controlled over reasonable limits by means of rheostats in the shunt field.Any of the methods of excitation used for generators can also be used for motors. In the typical steady-state speed-torque characteristics, it is assumed that motor terminals are supplied from a constant-voltage source. In a motor the relation between the e.m.f. generated in the armature and terminal voltage is （1-8）where is now the armature current input. The generated e.m.f. is now smaller than the terminal voltage , the armature current is in the opposite direction to that in a generator, and the electron magnetic torque is in the direction to sustain rotation of the armature.In shunt and separately excited motors the field flux is nearly constant. Consequently increased torque must be accompanied by a very nearly proportional increase in armature current and hence by a small decrease in counter e.m.f. to allow this increased current through the small armature resistance. Since counter e.m.f. is determined by flux and speed, the speed must drop slightly. Like the squirrel-cage induction motor, the shunt motor is substantially a constant-speed motor having about 5% drop in speed from no load to full load. Starting torque and maximum torque are limited by the armature current that can be commutated successfully.An outstanding advantage of the shunt motor is case of speed control. With a rheostat in the shunt-field circuit, the field current and flux per pole can be varied at will, and variation of flux causes the inverse variation of speed to maintain counter e.m.f. approximately equal to the impressed terminal voltage. A maximum speed range of about 4 or 5 to I can be obtained by this method. The limitation again being commutating conditions. By variation of the impressed armature voltage, very speed ranges can be obtained.In the series motor, increase in load is accompanied by increase in the armature current and m.m.f. and the stator field flux (provided the iron is not completely saturated). Because flux increase with load, speed must drop in order to maintain the balance between impressed voltage and counter e.m.f. Moreover, the increased in armature current caused by increased torque is varying-speed motor with a markedly drooping speed-load characteristic. For applications requiring heavy torque overloads, this characteristic is particularly advantageous because the corresponding power overloads are held to more reasonable values by the associated speed drops. Very favorable starting characteristics also result from the increase flux with increased armature current.In the compound motor the series field may be connected either cumulatively, so that its m.m.f. adds to that of the shunt field, or differentially, so that it opposes. The differential connection is very rarely used. A cumulatively compounded motor has speed-load characteristic intermediate between those of a shunt and a series motor, the drop of speed with load depending on the relative number of ampere-turns in the shunt and series fields. It does not have disadvantage of very high light-load speed associated with a series motor, but it retains to a considerable degree the advantages of series excitation.The application advantages of D.C. machines lie in the variety of performance characteristics offered by the possibilities of shunt, series and compound excitation. Some of these characteristics have been touched upon briefly in this article. Still greater possibilities exist if additional sets of brushes are added so that other voltages can be obtained from the commutator. Thus the versatility of D.C. machine system and their adaptability to control, both manual and automatic, are their outstanding features.A D.C machines is made up of two basic components:The stator which is the stationary part of the machine. It consists of the following elements: a yoke inside a frame; excitation poles and winding; commutating poles (composes) and winding; end shield with ball or sliding bearings; brushes and brush holders; the terminal box.The rotor which is the moving part of the machine. It is made up of a core mounted on the machine shaft. This core has uniformly spaced slots into which the armature winding is fitted. A commutator, and often a fan, is also located on the machine shaft.The frame is fixed to the floor by means of a bedplate and bolts. On low power machines the frame and yoke are one and the same components, through which the magnetic flux produced by the excitation poles closes. The frame and yoke are built of cast iron or cast steel or sometimes from welded steel plates.In low-power and controlled rectifier-supplied machines the yoke is built up of thin (0.51mm) laminated iron sheets. The yoke is usually mounted inside a non-ferromagnetic frame (usually made of aluminum alloys, to keep down the weight). To either side of the frame there are bolted two end shields, which contain the ball or sliding bearings.The (main)excitation poles are built from 0.51mm iron sheets held together by riveted bolts. The poles are fixed into the frame by means of bolts. They support the windings carrying the excitation current.On the rotor side, at the end of the pole core is the so-called pole-shoe that is meant to facilitate a given distribution of the magnetic flux through the air gap. The winding is placed inside an insulated frame mounted on the core, and secured by the pole-shoe.The excitation windings are made of insulated round or rectangular conductors, and are connected either in series or in parallel. The windings are liked in such a way that the magnetic flux of one pole crossing the air gap is directed from the pole-shoe towards the armature (North Pole), which the flux of the next pole is directed from the armature to the pole-shoe (South Pole).The commutating poles, like the main poles, consist of a core ending in the pole-shoe and a winding wound round the core. They are located on the symmetry (neutral) axis between two main poles, and bolted on the yoke. Commutating poles are built either of cast-iron or iron sheets.The windings of the commutating poles are also made from insulated round or rectangular conductors. They are connected either in series or in parallel and carry the machines main current.The rotor core is built of 0.51mm silicon-alloy sheets. The sheets are insulated from one another by a thin film of varnish or by an oxide coating. Both some 0.030.05mm thick. The purpose is to ensure a reduction of the eddy currents that arise in the core when it rotates inside the magnetic field. These currents cause energy losses that turn into heat. In solid cores, these losses could become very high, reducing machine efficiency and producing intense heating.The rotor core consists of a few packets of metal sheet. Redial or axial cooling ducts (810mm inside) are inserted between the packets to give better cooling. Pressure is exerted to both side of the core by pressing devices foxed on to the shaft. The length of the rotor usually exceeds that of the poles by 25mm on either sidethe effect being to minimize the variations in magnetic permeability caused by axial armature displacement. The periphery of the rotor is provided with teeth and slots into which the armature winding is inserted.The rotor winding consists either of coils wound directly in the rotor slots by means of specially designed machines or coils already formed. The winding is carefully insulated, and it secured within the slots by means of wedges made of wood or other insulating material.The winding overcharge are bent over and tied to one another with steel wire in order to resist the deformation that could be caused by the centrifugal force.The coil-junctions of the rotor winding are connected to the commutator mounted on the armature shaft. The commutator is cylinder made of small copper. Segments insulated from one another, and also from the clamping elements by a layer of minacity. The ends of the rotor coil are soldered to each segment.On low-power machines, the commutator segments form a single unit, insulated from one another by means of a synthetic resin such as Bakelite.To link the armature winding to fixed machine terminals, a set of carbon brushes slide on the commutator surface by means of brush holders. The brushes contact the commutator segments with a constant pressure ensured by a spring and lever. Clamps mounted on the end shields support the brush holders.The brushes are connected electricallywith the odd-numbered brushes connected to one terminal of the machine and the even-numbered brushes to the other. The brushes are equally spaced round the periphery of the commutatorthe number of rows of brushes being equal to the number of excitation poles.直流电机的介绍直流电机的特点是他们的多功用性。依靠不同的并励、串励和他励励磁绕组的组合，他们可以被设计为动态的和静态的运转方式从而呈现出宽广范围变化的伏安、特性或速度转矩特性。因为它简单的可操纵性，直流系统经常被用于需要大范围发动机转速或精确控制发动机的输出量的场合。直流电机的总貌如图所示。定子上有凸极，而且由一个或几个励磁线圈励磁。气隙磁通量以磁极中心线为轴线对称分布。这条轴线叫做磁场轴线或直轴。我们都知道，在每个旋转电枢线圈中产生的交流电压，经由一与电枢联接的旋转的换向器和静止的电刷，在电枢线圈出线端转换成直流电压。换向器电刷组合构成了一个机械整流器，它形成了一个直流电枢电压和一个被固定在空间中的电枢磁势波形。电刷的位置应使换向线圈也处于磁极中性区，即两磁极之间。这样，电枢磁势波的轴线与磁极轴线相差90度,也就是在交轴上。在示意图中，电刷位于交轴上，因为这是线圈和电刷相连的位置。这样，电枢磁势波的轴线也是沿着电刷轴线的（在实际电机中，电刷的几何位置大约偏移图例中所示位置90度，这是因为元件的末端形状构成图示结果与换向器相连。）。电刷上的电磁转矩和旋转电势与磁通分布的空间波形无关；为了方便我们可以假设在气隙中有一个正弦的磁通密度波形。转矩可以从磁场的观点分析得到。转矩可以用每个磁极的直轴气隙磁通和电枢磁势波的空间基波分量相互作用的结果来表示。在交轴上的电刷和这个磁场的夹角为90度，其正弦值等于1，对于一台极电机 （1-1）式中带负号被去掉因为转矩的正方向可以由物理的推论测定出来。锯齿电枢磁势波的空间基波是它最大值的。代替上面的等式可以给出： （1-2）其中：=电枢外部点路中的电流； =电枢绕组中总导体数； =通过绕组的并联支路数；及 （1-3）其为一个由绕组设计而确定的常数。简单的单个线圈的电枢中的整流电压前在面已被讨论过。将绕组分散在几个槽中的效果可用图形表示，在图示中每一个整流的正弦波是在线圈中产生的电压,换向线圈边处于磁中性区。从电刷观察到的电压是电刷间所有串联线圈中整流电压的总和，在图中标以的文波表示。每个磁极用12个或更多换向片,可以使波动变得很小。从电刷中观测到平均产生的电压等于整流线圈电压的平均值的总和。电刷之间整流电压，即旋转电势为 （1-4）为常数。分布绕组的整流电压与集中绕组有相同的平均值，不同的是波动大大减低了。在上面的等式中，所有的变量都是标准国际单位制。 （1-5）这个等式清楚地说明，与旋转电势相关的瞬间功率等于与磁场转矩有关的瞬时机械功率，能量的流向是由设备的确定，是发动机还是发电机。直轴气隙磁量由励磁绕组的合成磁势产生，其磁通磁势曲线就是电机的具体铁磁材料的几何尺寸决定的磁化曲线。在磁化曲线中, 假设电枢磁势波的轴线与磁场轴垂直，因此假定电枢磁势对直轴磁通不产生作用。在本文的后面有必要重新检验这一假设，饱和效应会深入研究。因为电枢电势是与磁通、时间、速度成比例，所以通常用恒定转速下的电枢电势来表示磁化曲线更为方便。任意转速电压时，任一给定磁通下的电压与转速成正比，也就是说 （1-6）图中磁化曲线只有一个励磁绕组励磁的，这种曲线可以通过测试的方法轻松获得，不需要任何设计步骤的知识。大范围励磁下的铁磁阻与空气气隙相比可以忽略不计，在这种情况下磁通与励磁绕组的总磁势成线性比例关系，比例常数就是直轴的气隙导磁性。直流电机的显著优势源自于通过选择励磁绕组的励磁方式而获得不同的运转方式。励磁绕组可以从外部直流电源以他励的方式励磁，也可以以自励的方式励磁。换句话，直流电机可以提供自身励磁。励磁方式不仅极大地影响它的静态特性，而且极大地影响在控制系统中电机的动态性能。他励发电机的联接图解已经给出的。所需的励磁电流只是电枢电流中的一小部分。在励磁电路中少量的功率可以控制相对一大部分电枢电路的功率。换句话说，发电机是一个功率放大器，当需要在大范围控制电枢电压时，他励发电机通常在反馈控制系统中使用。自励
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号