《电气专业英语.doc》由会员分享，可在线阅读，更多相关《电气专业英语.doc（9页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、【精品文档】如有侵权，请联系网站删除，仅供学习与交流电气专业英语.精品文档. 存档资料 成绩： 课 程 设 计 报 告 书所属课程名称 分 院 专 业 班 级 学 生 姓 名 学 号 指 导 教 师 2013 年 11 月 10 日Electrical Specialized English电气专业英语摘 要：变压器是指一种静止的电磁机械（即没有可以活动的部件）。变压器经常用于改变既定电气系统中的电压和电流大小，建立电绝缘、阻抗匹配，也用于测量仪表的领域。电源变压器和输电变压器在电力系统中是广泛使用的，目的是用最经济核算的发电机电压来发电，用最经济核算的电压来输送和分配电力，以及以最经济核算、
2、适合、安全的电压来用电。关键词：1 变压器简介；2变压器构造3；变压器用途中图分类号： 文献标识码：ATransformer变压器1.1 Introduction1.1简介引言内容。引言作为论文的开场白，In general, a transformer is a static electromagnetic machine (i.e., it has no moving parts). Transformers are commonly used for changing the voltage and current levels in a given electrical system,
3、 establishing electrical isolation, impedance matching, and measuring instruments. Power and distribution transformers are used extensively in electrical power systems to generate the electrical power at the most economical generator voltage level; to transmit and distribute electrical power at the
4、most economical voltage level; and to utilize power at the most economical, suitable, and safe voltage level.通常，变压器是指一种静止的电磁机械（即没有可以活动的部件）。变压器经常用于改变既定电气系统中的电压和电流大小，建立电绝缘、阻抗匹配，也用于测量仪表的领域。电源变压器和输电变压器在电力系统中是广泛使用的，目的是用最经济核算的发电机电压来发电，用最经济核算的电压来输送和分配电力，以及以最经济核算、适合、安全的电压来用电。Isolating transformers are used
5、to electrically isolate electrically isolate electric circuits from each other or to block DC signals while maintaining AC continuity between the circuits, and to eliminate electromagnetic noise in many types of circuits. Transformers are widely used in communication systems that vary in frequency f
6、rom audio to radio to video levels. They perform various tasks, such as impedance matching for improved power transfer, and are used as input transformers, output transformers, and insulation apparatus between electric circuits, and interstage transformers. Transformers are used in the whole frequen
7、cy spectrum in electrical circuits, from near DC to hundreds of megahertz, including both continuous sinusoidal and phase waveforms. For example, they can be found in use at power line frequencies (between 60Hz and 400Hz), audio frequencies (20Hz to 20000Hz), ultrasonic frequencies (20000Hz to 10000
8、0Hz), and radio frequencies (over 300kHz). 隔离变压器是用来将电路隔开或在保持交流电畅通时阻断电路间的直流电，以及消除多种电路中的电磁噪声。变压器广泛使用于声频无线电视频相互之间频率变化较大通信系统中。它们可以应用于很多场合，比如用于改良的电力输送的阻抗匹配，用作输入变压器、输出变压器、级间变压器，以及电路间的绝缘装置。变压器用于电路中所有的频谱，不论是从直流电还是到几百兆赫，包括正弦波形和相位波形。例如，变压器可以用于60Hz到400Hz之间的电力线频率，20Hz到20000Hz之间的音频，20000Hz到100000Hz之间的超声频率，以及300k
9、Hz以上的无线电频率。Transformers are also used in measuring instruments. Instrument transformers are used to measure high voltages and large currents with standard small-range voltmeters (120V), ammeters (5A), and wattmeters, and to transform voltages and currents to activate relays for control and protectio
10、n. Voltage transformers (VTs) (also known as PTs, i.e., potential transformers) are single-phase transformers that are used to step down the voltage to be measured to a safe value. Current transformers (CTs) are used to step down currents to measurable levels. The secondaries of both voltage and cur
11、rent transformers are normally grounded.变压器也用于测量仪表的领域。仪表变压器可以用来测量高压以及用小量程的电压表（120V）测量大规模电流、电流表（5A）、功率表，以及出于控制和保护角度用于改变电压和电流以此来激活继电器。电压互感器（VTs）（也称作PTs，即测量用变压器）是单相变压器，用来将电压降低到安全值。电流变压器（CTS）是用来将电压降低到能够测量的范围内。电压互感器和电流变压器的二次绕组通常都是接地的。A transformer consists of a primary winding and a secondary winding lin
12、ked by a mutual magnetic field. Transformers may have an air core, an iron core, or a variable core, depending upon their operating frequency and application. Transformers are also quite different in size and shape depending on the application. In power system applications, the single-or three-phase
13、 transformers with ratings up to 500kVA are defined as distribution transformers, whereas those transformers with ratings over 500 kVA at voltage levels of 69kV and above, are defined as power transformers.变压器是由一个一次绕组和一个二次绕组构成的，且两个绕组被一个相互的磁场连接起来。变压器内部有空气磁芯、铁芯、或其他材质的芯，这是由其工作频率和应用领域决定的。变压器有多种大小规格，这是由其
14、应用领域决定的。在电力系统领域，电流不超过500kVA单相或三相变压器都可以定义为输电变压器，同时电流超过500kVA且电压不低于69kV的变压器都可以定义为电源变压器。A transformer is basically made up of two or more windings coupled by a mutual magnetic field. Ferromagnetic cores are employed to develop tight magnetic coupling and high flux densities. When such a coupling exists
15、, the transformer is called an iron-core transformer. Most distribution and power transformers are immersed in a tank of oil for better insulation and cooling purposes. The leads of the windings are brought to the outside of the tank through insulating bushings which are attached to the tank. Such t
16、ransformers are used in high-power applications. When there is no ferromagnetic material but only air present, such a transformer is called an air-core transformer. These transformers have poor magnetic coupling and are usually used in lower-power applications such as in electronic circuits. In this
17、 unit the focus is set exclusively on iron-core transformers.变压器大体来说是由两个或更多由相互磁场连接起来的绕组构成的。用铁磁芯来构建磁力耦合器和高漏磁通量密度。当这样的耦合存在时，该变压器就被称为铁芯变压器。大多配电变压器和电源变压器都被置于油槽中来达到更好的绝缘和冷却效果。绕组的引线放置在紧贴油槽的绝缘套管中并分布在油槽的外侧。这样的变压器通常用于使用大功率设备的领域。如果里面是空气磁芯而不是铁磁芯，这种变压器就被称作空冷式变压器。这些变压器的磁力耦合器性能较差，通常使用于使用小功率设备的领域，如电子回路。这个单元中重点是铁芯变
18、压器。1.2 Construction of Transformer1.2变压器的构造The magnetic cores of transformers used in power systems are built either in core form or shell form, either case, the magnetic cores are made up of stacks of laminations cut from silicon-steel. Silicon-steel sheets usually contain about 3 percent silicon a
19、nd 97 percent steel. The silicon content decreases the magnetizinglosses, especially those due to hysteresis. The laminations are coated with a non-conducting and insulating varnish on one side. Such a laminated core substantially reduces the core loss due to eddy currents. Most laminated materials
20、are cold rolled and often specially annealed to orient the grain or iron crystals. This causes a very high permeability and low hysteresis to flux in the direction of rolling. Thus, in turn, it requires a lower exciting current. The laminations for the core-type transformer, shown in Fig., may be ma
21、de up of L-shape, or U-and I shaped laminations. The core for the shell-type transformer, shown in Fig, is usually made up of E-and I-shaped laminations. To minimize the use of copper and decrease copper loss, the magnetic cores of large transformers are built in stepped cores, as shown in Fig。 在电力系
22、统中用到的变压器的磁芯通常是内铁式或壳式的，不论那种情况，磁芯都是由硅钢切片层堆叠而成的。硅钢片通常是3%的硅和97%的钢。硅可以降低磁化损失，尤其是由磁滞引起的磁化损失。硅钢层片的一面涂有绝缘漆。这样的叠片铁芯可以很大程度上减少涡电流引起的磁芯损耗。大多数层压材料是冷轧的，并经过特殊退火以确定晶粒或铁原子晶体的方向。这会在滚轧方向产生很高的导磁系数和较少的磁滞。这样，反过来就需要低一些的励磁电流。是由L形、U形状、或I形的层片构成的。壳式变压器的磁芯）所示，通常由E形和I形的层片构成。为了节约铜材料和减少铜损，大型变压器的磁芯都是阶梯式的。shows a core-form construc
23、tion that has the total number of primary winding turns located on one leg of the core and the total number of secondary winding turns placed on the other leg. This design causes large leakage flux and therefore results in a smaller mutual flux for a given primary voltage. To keep the leakage flux w
24、ithin a few percent of the mutual flux, each winding may be divided into two coils; the two half coils are then mounted on two sides of the rectangle. A large reduction in leakage flux can be obtained by further subdividing and sandwiching the primary and secondary turns, however, at considerable co
25、st. Leakage flux can be greatly decreased by using the shell-form construction shown in Fig However, the steel-to-copper weight ratio is greater in the shell-form transformer. It is more efficient but more costly in material. The coils employed in shell-form transformers are usually of a “pancake” f
26、orm unlike the cylindrical forms used in the core-form transformer, where the coils are placed one on top of the other and the low-voltage winding is placed closer to the core with the high-voltage winding on top. This design simplifies the problem of insulating the high-voltage winding from the cor
27、e and reduces the leakage flux considerably.展示了铁芯式变压器磁芯的构造，该变压器磁芯的一个边上是完整的一次绕组匝圈，另一个边上是完整的二次绕组匝圈。这样的设计会造成大的漏磁通量，因此会给一次电压造成较小的互感磁通。为了将漏磁通量控制在互感磁通量较小的比例内，每一个绕组可以被分成两个线圈；这两个线圈被安装在矩形的两个边上。可以通过进一步细分和增多一次绕组和二次绕组的线圈使其靠近让漏磁通量的大幅度降低，然而这样的经济成本比较高。漏磁通量也可以通过使用壳式构造来减少。但是在壳式变压器中，钢铜重量比要相对大些。这样效率很高，但是比较耗材料。壳式变压器中的线
28、圈通常是“饼状”的，不是铁芯式变压器线圈圆柱体的形状。在铁芯式变压器中，线圈是一圈一圈摞着缠绕上去的。这样的设计就简化了高压绕组和磁芯之间的绝缘问题，也大大减少了漏磁通量。1.3 The Ideal Transformer1.3理想变压器Consider a transformer with two windings, a primary winding of N1 turns and a secondary winding of N2 turns, as shown in Fig. The core is made up of a ferromagnetic material. Assume
29、 that the transformer is an ideal transformer with the following properties:设想一个由两个绕组的变压器，一次绕组由N1匝，二次绕组有N2匝。变压器的磁芯是由铁磁材料构成。假设一个理想的变压器具备以下性质： The winding resistances are negligible. 绕组电阻可以忽略不计。 All magnetic flux is confined to the ferromagnetic core and links both windings, i.e., leakage fluxes so no
30、t exist. 所有的漏磁通量都受到铁磁芯的限制并且连结起两个绕组，即漏磁通量不存在。 The core losses are negligible. 磁芯损耗可以忽略不计。 The permeability of the core material is almost infinite so that negligible net magnetic motive force (mmf) is required to establish the flux in the core. In other words, the excitation current required to estab
31、lish flux in the core is negligible. 磁芯材料的导磁系数几乎可以无限扩大，因此用很微小的净磁动势就可以在磁芯中建立通量。也就是说，需要在磁芯中建立通量的励磁电流是很微小的。 The magnetic core material does not saturate. 磁芯的材料不会饱和。If the primary winding is connected to an energy source with a timevarying voltage u1, a time-varying flux and a flux linkage 1of winding N
32、1 is established in the core. If u1 varies with time, then i1, and1will vary with time, and an electromotive force (emf) e2will be induced in winding N1. Therefore,如果将一次绕组和时变电压是u1的电源连接在一起，设变压器磁芯中时变通量为，绕组N1的磁链为1，和1就会随着时间变化，电动势e2就会在绕组N1中生成。因此，u1=e1=d1/dt=N1*d/dt Because there is no leakage flux, the f
33、lux must link all N2turns of the secondary winding. Since the resistance of the secondary winding is assumed to be zero in an ideal transformer, it induces a voltage e2which is the same as the terminal voltage u2. Thus,因为没有漏磁通量，通量必须连接二次绕组N2中所有的匝圈。因为理想的变压器中二次绕组的电阻已假定为0，就会生成电压e2，该电压和终端电压u2相同。所以，u2=e2=
34、d2/dt=N2*d/dt (1)From Eq. (1) and Eq. (2),根据方程（1）和方程（2），u1/u2=e1/e2=N1/N2= (3)which many also be written in terms of root mean square (rms) values as这也可以写成均方根值的形式，如下U1/U2=E1/E2=N1/N2= (4)where is known as the turns ratio. Note that the potential ratio is equal to the turns ratio. (Here, lowercase le
35、tters are used for instantaneous values and uppercase letters are used for rms values.) From Eq. (4),其中就是匝比。要注意到电位比和匝比是等值的。（这里瞬时值用小写字母，均方根值用大写字母。）从方程（4）可以得到，U1=N1U1/N2=U2 (5)Assume that a load (energy sink) with an impedance Zl is connected at the terminals of the secondary winding, as shown in Fig.
36、 Therefore, a load current (i.e., secondary current) will flow in the secondary winding. Since the core of an ideal transformer is infinitely permeable, the net mmf will always be zero. Thus,假设一个负载（能阱）的阻抗是Zl，该负载和二次绕组的终端连接。因此，负载电流（即二次电流）将流经二次绕组。因为理想状态下的变压器磁芯有无限的导磁能力，净磁动势始终是0。所以，N1i1-N2i2=R=0 (6)where
37、 R is the reluctance of the magnetic core. Since the reluctance of a magnetic core of a well-designed modern transformer is very small (almost zero) before the core is saturated, then该式中，R是磁芯的磁阻。因为优良的现代变压器的磁芯的磁阻在磁芯饱和前通常都很低（几乎为零）。接下来N1i1-N2i2=0 (7)or或N1i1=N2i2 (8)That is, the primary and secondary mm
38、fs are equal and opposite in direction. From Eq. (7.8)也就是说，一次和二次电动势是等值的，并且在方向上相反。根据方程（8）i1/i2=N2/N1=1/ (9)which may be written in terms of rms values as（方程（8）也可以写成均方根值的形式，如下）i1/i2=N2/N1=1/ (10)Hence, the currents in the windings are inversely proportional to the turns of the windings. From Eq. (10),
39、所以，绕组中的电流和绕组的匝数是成反比的。根据方程（10），得到，I1=N2I2/N1=I2/ (11)From Eq. (3) and Eq. (9),根据方程（3）和方程（9），得到，u1i1=u2i2(12)or in terms of rms values或根据均方根值，得到U1I1=(N1U2/N2)(N2I2/N1)=U2I2 (13)That is, in an ideal transformer, the input power is equal to the output power. In other words, the value of the apparent pow
40、er remains the same. This is the power invariance principle which means that the volt-amperes are conserved. Furthermore, the complex power supplied to the primary is equal to the complex power delivered by the secondary to the load. Thus,就是说，一个理想状态下的变压器，输入功率和输出功率相同。换句话说，视在功率值始终保持不变。这就是功率不变性原理，该原理意味
41、着伏安是守恒的。此外，供给一次绕组的复功率和供给二次绕组的复功率是等值的。因此，U1I1*=U2I2*(14)In the event that the primary and secondary turns are equal, these transformers are usually known as the isolating transformers, as previously stated. In power systems, if the number of turns of the secondary winding is greater than the number o
42、f turns of the primary winding, the transformer is known as a step-up transformer. On the other hand, if the number of turns of the primary winding is greater than that of the secondary winding, the transformer is known as a step-down transformer.如上文所述，一次绕组和二次绕组的匝数相等的变压器被称为隔离变压器。在电力系统中，二次绕组的匝数比一次绕组的
43、匝数多的变压器被称为升压变压器。同时，一次绕组的匝数比二次绕组的匝数多的变压器被称为降压变压器。 参考文献:论文集中的析出文献1 1 Frischknecht, R. et al.: koinventare fr Energiesysteme Grundlagen fr denkologischen Vergleich von Energiesystemen und den Einbezug vonEnergiesystemen in kobilanzen fr die Schweiz. 3rd Edition. ETHZ/PSI, Zrich,1996.2 Dones, R. Gantner
44、, U., Hirschberg S., Doka G., Knoepfel I.: EnvironmentalInventories for Future Electricity Supply Systems for Switzerland. PSI ReportNo. 96-07, Wrenlingen and Villigen, February 1996.3 Andreani-Aksoyoglu, S., Keller, J.: Short-term Impacts of Air Pollutants in Switzerland: Model Evaluations and Prel
45、iminary Scenario Calculations for Selected Swiss Energy Systems. In Brebbia C.A., Ratto C.F., and Power H. (Eds.), Air Pollution VI, Computational Mechanics Publications (1998) 799-808.4 Institut fr Energiewirtschaft und Rationalle Energieanwendung: EcoSense 2.0 Users Manual. Stuttgart University, 1
46、997.5 Hirschberg, S., Spiekerman, G., Dones, R.: Severe Accidents in the Energy Sector. PSI Report No. 98-16, Wrenlingen and Villigen, November 1998.6 Kypreos, S.: Assessment of CO2 Reduction Policies for Switzerland, in Knowledge Infrastructures and Decision Support Systems for Integrated Modelling
47、 in Energy Management and Policies. Int. Journal of Global Energy Issues, 12 Nos.1-6 (1999) 7 Hirschberg, S., Jakob, M.: Cost Structure of the Swiss Electricity Generation under Consideration of External Costs. SAEE Seminar “Strompreise zwischen Markt und Kosten: Fhrt der freie Strommarkt zum Kostenwarheit?” Bern, 11 June 1999.8 Dones, R., Hirschberg, S., Vamanu, D.: Decision Support Tool for Sensitivity Mapping of Electricity Supply Systems Choices for Switzerland: Specification of the Concept and Software for the Interactive “EnergyGame