1、Construction and Application of D.C. Machines 直流电机的结构与应用A D.C. Machines is made up of two basic components:一个直流电机是由两个基本元素组成：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 pole (compoles)
2、and winding; end shield with ball or sliding bearing; brushes and brush holders; the terminal box.定子是电机固定的部分。它由以下基础组成；在结构中有一个磁轭；励磁磁极和绕组；换向极和绕组；有滑动轴承的端罩；电刷和电刷固定器；出线盒。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
3、 slots into which the armature winding is fitted. A commutator, and often a fan, are also located on the machine shaft.转子是电机旋转的部分。它构成了一个中心，这个中心是安放在设备轴上并且已经平均地隔开，把电枢绕组放入槽中。还有一个换向器和一个风扇组成，被放在设备的轴上。The frame is fixed to the floor by means of a bedplate and bolts. On low-power machine the frame and yoke
4、 are one and the same components, through which the magnetic flux produced by the excitation poles closes. The frame and the yoke are built of cast iron or cast steel or sometimes from welded steel plates. 它用螺栓和底座固定在地板上。低压电机的磁轭和本身的结构是一体的，穿过励磁磁极闭合而产生的磁通量。它的结构和磁轭是用生铁和铸钢制造成的，有时候也用焊接的钢板。In low-power and
5、 controlled rectifier-supplied machine the yoke is built up of (0.51mm) laminated iron sheets. The yoke is usually mounted inside a non-ferromagnetic frame(usually made of alumininum alloys, to keep down the weight). To either side of the frame there are bolted two end shields, which contain the bal
6、l or sliding bearing. 在低压和可控补偿整流器电机中，磁轭是由 0.51 毫米的薄铁板制成的。磁轭经常被安放在一个非铁磁性的结构内（通常是由铝合金制成，为了缩减重量） 。在内部有两个端盖并且都包含球体和滑动轴承。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 t
7、he excitation current. 励磁磁极由用 0.51mm 的铁片通过用螺栓钉牢互相支撑。磁极被放入结构内的依靠螺栓固定。它们支撑绕组，让它运送励磁流动。On the rotor side, at the end of the pole core is the so-called pole-shoe which is meant to facilitate a given distribution of the magnetic flux through the air gap. The winding is placed inside an insulated frame mo
8、unted on the core, and secured by the pole-shoe. 在电枢上，磁极铁心的末端是极靴，它通过气隙有助于磁通量的分布。绕组被放置在一个绝缘结构内的中心处，被极靴保护。The excitation winding are made of insulated round or rectangular conductors, and are connected either in series or in parallel. The windings are linked in such a way that the magnetic flux of one
9、 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) .励磁绕组是由绝热的圆形物或矩形的导体制成，并且和另一个连续或平行的相连接。绕组是以一个磁极的磁通量穿过气隙，然后被指引由极靴向电枢（北极） ，下一个磁极的磁通量由电枢到极靴（南极） 。The commutating pole
10、s, 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. 换向极的磁极就像主磁极，它组成了一个中心，末端在极靴中并且一个绕组绕在中心周
11、围。它们被放在两个主磁极中间的对称轴，拴在磁轭上。换向极的磁极是由生铁或铸铁制成。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. 换向极的绕组是由周围绝缘的或垂直的导线制成。它们相互平行或首尾连接，带动设备的主电流。The rotor core is built of 0
12、.5-1mm silicon-alloy sheets. The sheets are insulated from one another by a thin film of varnish or by an oxide coating, both some 0.03-0.05mm thick. The purpose is to ensure a reduction of the eddy currents which arise in the core when it rotates inside the magnetic field. These currents cause ener
13、gy losses which turn into heat. In solid cores, these losses could become very high, reducing machine efficiency and producing intense heating.转子的中心是由 0.51 毫米硅合金薄板制成。薄板是通过清漆薄膜或氧化物涂层和其他物质绝缘。绝缘物质厚度为 0.030.05 毫米。目的是当它在磁场中旋转时涡流升高时，减少涡流。它变得很热将导致能量损失。在实心物的中心，它损失得很高，减少电机的效率和产生剧烈的热量。The rotor core consists
14、of a few packets of metal sheet. Redial or axial cooling ducts (8-10mm inside) are inserted between the packets to give better cooling. Pressure is exerted to both sides of the core by pressing devices foxed on to the shaft. The length of the rotor usually exceeds that of the poles by 2-5mm on eithe
15、r 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.转子的中心包含了一些金属薄片。轴向的冷却管（810 毫米）被嵌在金属薄片中给它更好的冷却。压力施加在中心的两端。转子的长度超过磁极 25 毫米，作用是减少磁力渗透性
16、导致的轴向位移。转子的外围提供了槽放入电枢绕组。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.每个转子绕
17、组包含了一个线圈直接绕在转子槽中依靠特殊设计机械或成行的线圈。绕组是绝缘的，依靠木制的或绝缘物质制成的槽楔保护它。The winding overcharge are bent over and tied to one another with steel wire in order to resist the deformation which could be caused by the centrifugal force.绕组过载是其弯曲，用钢丝相互连接为了抵抗由地心引力产生的变形。The coil-junctions of the rotor winding are connected
18、 to thecommutator mounted on the armature shaft. Thecommutator is cylinder made of small copper segments insulated from one another, and also from the clamping elements by a layer of mica. The ends of the rotor coil are soldered to each segment.转子绕组的线圈交叉点连接到放在电枢轴的换向器上。换向器是圆柱体含有少量的铜。换向片是绝缘的。转子线圈被焊接在换
19、向片上。On low-power machines, the commutator segments form a single unit, insulated from one another by means of a synthetic resin such as bakelite.低压电机的换向器片被分割成一个独立的单元，依靠合成树脂互相绝缘，例如人造树脂。To link the armature winding to the fixed machine terminals, a set of carbon brushes slide on the commutator surface
20、 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. 为了连接电枢绕组固定接线端，一组电刷在换向器的表面上依靠支架滑动。电刷通过弹簧给予不变的压力连接换向片。卡钉安放在端盖上并且支撑碳刷支架。The brushes are connected electricallywith
21、 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.奇数的炭刷连接到电机的一个接线端上，偶数的炭刷连接到另一个接线端上。炭刷围绕换向器的外围等
22、距隔开，有多少排炭刷就有等量的励磁磁极Application of DC MotorsWith the advent of controlled rectifiers of various kinds，the importance of D C generators has subsided somewhat since it is cheaper to convert to DCwith a transformer and rectifier rather than with an ACmotor and DCgeneratorThe rectifier performance is inf
23、erior in terms of power factor，simplicity of control，regenerative and reversing ability and harmonic generation，but score on cost，in most cases，space ，noise and maintainance；the latter considerations weighing more heavily in a modem age DC generators will continue to be made for their virtues but wi
24、ll lose certain traditional fields of applicationThey are invaluable for use as dynamometers coupled mechanically to engines and motors of various kinds to control and measure the outputBy mounting the stator in bearings SO that the torque reaction can be exerted against a spring balance，the torque
25、output can be read off directlyGenerators are also useful for imparting special characteristics to a load in a simple manner，egautomatic current limitation for DCwelding generators utilizing series windings and exaggerating armature reaction demagnetizing effects随着各种类型的可控型整流器的发展，由于用变压器和整流器组将电能转换成直流电
26、比用交流电动机一直流发电机组更为便宜，因此直流电动机的重要性已逐步减弱。整流器的性能在功率因数、控制的简单性、再生和回馈能力及谐波的产生方面都较差，但它在价格、占地面积、噪声和维护等方面却占优势；而在当今时代对于后者的考虑占有更大比重。直流发电机凭着它的优点会继续存在，但它必定会失去某些传统的应用领域。直流发电机与各种发动机和电动机机械连接在一起用作测功计，用于控制及测量输出是极为有用的。将定子装配于轴承上，则力矩反应可施加在弹簧秤上，输出力矩便可直接读出来。直流发电机也可用于以一种简单的方式将某些特性传递给负载，例如，利用串励绕组并扩大电枢反应的去磁作用，直流电焊发电机可实现自动限流。As
27、far as motors are concerned，there are continual attempts to obtain infinitely variable speed motors which Can be directly connected to the ACmains and thus dispense with the intermediate ACDC -conversion apparatusA recent development involves the substitution of controlled rectifiers for the commuta
28、torSince the commutator and brushes act to direct the coil currents in a particular sense when the coil is related to a particular position in the field systems，this function can be performed by an external reversing circuit actuated by shaftposition sensing devicesTappings from the armature winding
29、，which could not be on the stator，are brought out to this circuitSome Success has been achieved with these various methods but there are always disadvantages and it seems likely that the demand for DC motors will continue for many years to comeShunt , compound and separatelyexcited motors are used f
30、or the drives which have to operate over a wide range of constant speeds and in automatic control systemsSeries motors are used when heavy starting torques and overloads are characteristic automatically limits and power demand and gives a high torque per ampere on overload. 就电动机而言，人们一直在努力寻求可直接接在交流电网
31、上，且中间无需交直流转换装置的无级调速电动机。目前已发展到用可控型整流器代替换向器。由于当线圈处于磁场中某一特定位置时，换向器和电刷以一种特定的方式导通电流，因此这种作用可以由一种由转轴位置传感器控制的外部逆变电路来完成，将不能位于定子上的电枢绕组的电流引到该电路。采用这种方法已取得了一些成功，但仍然存在一些不足之处，因此对直流电动机的需求很可能还要继续许多年。并励、复励和他励电动机用在宽恒速范围运行的驱动装置和自动控制系统中，而串励电动机用于起动转矩大、过载时能自动限制速度，以及功率增大时单位安培的转矩也增大的场合。Summarizing then，the DCmotor can be us
32、ed for practically any application though it has lower limit on maximum power and maximum speed than the synchronous and induction motors总而言之，直流电机实际上几乎可用于任何场合，尽管它与同步电机和感应电机相比，最大功率和最大转矩受到更大的限制。Discussion of DCmachine applications involves recapitulation of the highlights of the machines performance f
33、eaturestogether with economic and technical evaluation of the machines position with respect to competing energy-conversion devicesFor DCmachines in general，the outstanding advantage lies in their flexibility and versatilityThe principal disadvantage is likely to be the initial investment concernedY
34、et the advantages of D C motors are such that they retain a strong competitive position for industrial applications直流电机应用的讨论涉及电机的主要运行特性，以及电机相对于与其竞争的电能转换装置的经济技术指标的优劣。一般说来，直流电机的显著优点在于灵活性和多功能，其主要缺点可能是就其初投资大而言的。但是，直流电机的优点还是使得其在工业应用中保持着强劲的竞争优势。DC generators are the obvious answer to the problem of conver
35、ting mechanical energy into electric energy in DC formWhen the consumer of electric energy is geographically removed from the site of energy conversion by any appreciable distance，however，the advantages of ACgeneration voltage transformation，and transmission are such that energy conversion and trans
36、mission in ACform are almost always adopted，ACto D C transformation at or near the consumer【2】 When largepower rectification from A Cto constant-voltage DCform is involved，the electronic methods usually offer determining economic advantagesThe principal applications of DC generators，therefore，are to
37、 cases where the primary energy conversion occurs very near the point of consumption and cases where the ability to control output voltage in a prescribed manner is necessary，although solid-state controlled rectification using silicon controlled rectifiers(SCRs)and Triacs is finding widespread appli
38、cation【3】 直流发电机显然是解决将机械能转换成直流形式的电能问题的一种方式。然而，只要当用户离电站有一段距离，用交流发电机发电，经变压器变压而输电这种方式便具有其优势，以至于几乎总是采用交流发电和输电的方式，只是到了用户处或其附近，才将交流转换成直流。对于交一直流变换，作为交一直流电动机一发电机组一部分的直流发电机，必须与半导体整流器系统竞争。当涉及从交流至恒压直流的大功率整流时，电子方法通常提供了决定性的经济上的优势。因此，直流发电机常应用在一次能量转换位于用户附近的场合，以及尽管可控硅整流和三端双向可控硅整流开关元件正在开辟广泛的运用市场，但仍必须具备用前述方式控制输出电压的能力的
39、场合。Among DC generators themselves，separately excited and cumulatively compounded self-excited machines are the most commonSeparately excited generators have the advantage of permitting a wide range of output voltages，whereas self-excited machines may produce unstable voltage in the lower ranges，wher
40、e the field-resistance line becomes essentially tangent to the magnetization curveCumulatively compounded generators may produce a substantially flat voltage characteristic or one which rises with load，whereas shunt or separately excited generators(assuming no series field in the latter，which，of Cou
41、rse，is not at all a practical restriction)produce a drooping voltage characteristic unless external regulating means are addedSo far as the control potentialities of DCgenerators are concernedthe controltype generators represent the results of a fuller exploration of the inherent possibilities在直流发电机
42、中，他励发电机和积复励自励发电机是最为常用的。他励发电机具有输出电压范围宽的优点，而自励发电机却可能在较小的范围内产生不稳定的电压，此时磁场电阻线基本上是磁化曲线的切线。积复励发电机可产生一种基本上是水平的电压特性或随负载增大而上翘的特性。而并励或他励发电机(假设后者无串励磁场，当然仅仅是假设，但并不是说实际当中就一定没有) 如果不外加调节方法，就会产生下垂的电压特性。就直流发电机在控制方面的潜在能力而言，电机放大机和模拟机呈现出一种潜在丰富的开发可能性。Among DC motors，the outstanding characteristics of each type are as fo
43、llows . The motor operates with a decidedly drooping sped as load is added，the no-load speed usually being prohibitively high；the torque is proportional to almost the square of the current at low saturations and to some power between 1 and 2 as saturation increasesThe shunt motor at constant field c
44、urrent operates at a slightly drooping but almost constant speed as load is added，the torque being almost proportional to armature current；equally important，however，is the fact that its speed can be controlled over wide ranges by shunt-field control , armature-voltage control , or a combination of b
45、othDepending on the relative strengths of shunt and series field，the cumulatively compounded motor is intermediate between the other two and may be given essentially the advantages of one or the other在直流电动机中，各种类型电动机的显著特性如下所述：随着负载的增大，串励电动机以一种期望的下降的转速运行，空载转速通常高得超出限制；在低饱和状态下转矩近似与电流的平方成正比，而随着饱和程度不断增加，转矩
46、与电流的 12 次方成正比例。在恒定的励磁电流下，随着负载增大，并励电动机的转速略微下降但还算几乎不变，转矩近似与电枢电流成正比；然而同样重要的是，并励电动机可通过调节并励磁场、调节电枢电压或两者结合而在很大范围内调节转速。积复励电动机特性处于两者之间，而究竟以何方优点为主，则取决于是并励磁场强，还是串励磁场强。By virtue of its ability to handle heavy torque overloads while cushioning the associated power overload with a speed drop，and by virtue of its
47、 ability to withstand severe starting duties，the series motor is best adapted to hoist，crane，and traction-type loadsIts ability is almost unrivaled in this respectSpeed changes are usually achieved by armature-resistance controlIn some instances，the wound-rotor induction motor with rotor-resistance
48、control competes with the series motor，but the principal argument concerns the availability and economics of a DCpower supply rather than inherent motor characteristics由于串励电动机能随转速下降避免相应的功率过载，因而能承受大转矩过载。由于它还能担负起繁重的起动任务，串励电动机最适用于起重机吊车和牵引类负载，它在这方面的能力无与伦比，它通常通过调节电枢电阻来调速。在某些场合中，通过转子电阻调速的绕线转子感应电动机可与串励电动机竞
49、争，但二者谁优谁劣，基本的争议集中在直流电源供电的效率和经济性方面，而并非电动机内在特性。Compound motors with a heavy series field have performance features approaching those of series motors except that the shunt field limits the no-load speed to safe values；the general remarks for series motors therefore applyCompound motors with lighter series windings not infrequently find competition from squirrel-cage induction motors with highresistance rotorssocalled highslip motorsBoth motors provide a definitely drooping
