电气专业英语课后练习翻译

PART1
U1T1、
In addition to the various power transformers, two special-purpose transformers are used with electric machinery and power systems. The first of these special transformers is a device specially designed to sample a high voltage and produce a low secondary voltage directly proportional to it. Such a transformer is a potential transformer. A power transformer also produces a secondary voltage directly proportional to that the potential transformer is designed to handle only a very small current. The second type of special transformer is a device designed to provide a secondary current much smaller than but directly proportional to its primary current. This device is called a current transformer.
除了各种电源变压器、两个专用变压器使用电动机械和电力系统。

第一个特殊变压器是一个高电压设备专门设计的样品和生产较低的二次电压成正比。

这样一个变压器电压互感器。

电力变压器也产生二次电压成正比的电压互感器的设计目的是处理只有一个很小的电流。

第二种类型的特殊变压器是一个装置,旨在提供一个次级电流小得多,但它的主要电流直接成比例。

这种装置称为电流互感器。

U1T2、
In electronic power supplies there is often a need to isolate the output from the input and reduce the weight and cost of the unit. In other applications, such as in aircraft, there is a strong incentive to minimize weight. These objectives are best achieved by using a relatively high frequency transformer. Thus, in aircraft the frequency of transformers is typically 400Hz, while in electronic power supplies the frequency of transformers may range from 5kHz to 50kHz.
在电子电源通常需要隔离的输出输入,减少单位的重量和成本。

在其他应用程序,如飞机,有强烈的动机来减少体重。

这些目标是最好通过使用一个相对高频变压器。

因此,在飞机变压器通常是400赫兹的频率,而在电子电源变压器可能范围从5 khz的频率50千赫
U2T1、In general, the outstanding advantage of DC machines lies in their flexibility and versatility. Before the widespreaded availability of AC motor drives, DC machines were essentially the only choice available for many applications requiring a high degree of control. Their principal disadvantages stem from the complexity associated complexity increase the cost over competing AC machines, it also increases the need for maintenance and reduces the potential reliability of these machines.
一般来说,直流机的突出优势在于他们的灵活性和通用性。

交流电动机驱动的广泛可用性之前,直流机基本上是唯一可用的选择对于许多应用程序要求高度的控制。

主要缺点源于复杂关联的复杂性增加了成本在竞争交流的机器,它也增加了对维护的需要,减少了潜在的这些
机器的可靠性。

U2T2、
There are three basic type of rotating machines: synchronous, induction, and DC machines. In all of them the basic principles are essentially the same. V oltages are generated by the relative motion of a magnetic field with respect to a winding, and torques are produced by the interaction of the magnetic fields of the stator and rotor windings.
有三种基本类型的旋转机器:同步,感应,直流机器。

在所有这些基本原则基本上是相同的。

电压的相对运动产生的磁场对绕组,和扭矩的交互作用是由定子和转子绕组的磁场。

U3T1、
Synchronous machines can be classified as cylindrical-rotor or salient-pole machines. The cylindrical-rotor construction is used in high-speed steam-turbine-driven generators. The armature windings consist of laminated conductors placed in the stator slots. The rotor carries the DC field winding. Most of turbine generators being built at present for 60 Hz service are 2-pole 3600 revolutions per minute machines. Because of the economies of high-speed high-temperature high-pressure steam turbines, much study and some real pioneering work have been devoted to improvements in materials and design of both generators and turbines
同步机可分为圆柱形转子或凸极机。

圆柱形转子建设用于高速steam-turbine-driven发电机。

电枢绕组由叠层导体放置在定子槽。

转子直流磁场绕组。

目前大部分涡轮发电机建60赫兹服务2-pole每分钟3600转的机器。

因为经济的高速高温高压蒸汽涡轮机,多学习和一些真正的开创性工作一直在致力于改进材料和设计的发电机和发电机
U3T2、
Rotating electric machines take many forms and are known by many names: DC, synchronous, permanent-magnet, induction, etc. Although these machines appear to be quite dissimilar and require a variety of analytical techniques, the physical principles governing their behavior are quite similar, and in fact these machines can often be explained from the same physical picture. An induction machine, in spite of many fundamental differences, works on exactly the same principle; one can identify flux distributions associated with the rotor and stator, which rotate in synchronism and which are separated by some torque-producing angular displacement.
旋转电机采取多种形式和已知许多名字:直流、同步、永磁、感应,等等。

虽然这些机器似乎是相当不同的,需要各种分析技术,管理他们的行为非常相似的物理原则,事实上这些机器通常可以解释从相同的物理图像。

感应式电机,尽管许多根本性的差异,同样的原理工作;一个可以识别通量分布与转子和定子,在同步旋转,由一些torque-producing角位移
U4T1、
The significance of VRMs in engineering applications stems from their low cost, reliability, adn controllability. Because their torque depends only on the square off applied stator currents and not on their direction, these machines can be operated from unidirectional drive systems, reducing the cost of the power electronics. However, it is only recently, with the advent of low-cost, flexible power electronic circuitry and microprocessor-based control systems, VRMs have begun to see widespread application in systems ranging from traction drives to high-torque, precision control systems for robotics applications.
VRMs在工程应用的意义源于他们的低成本、可靠性、可控性。

因为他们的转矩只取决于广场采用定子电流,而不是他们的方向,这些机器可以从单向操作驱动系统,减少电力电子的成本。

然而,直到最近,随着低成本、灵活的电力电子电路和基于微处理器控制系统,VRMs已经开始看到广泛应用系统从牵引驱动高扭矩,为机器人精度控制系统应用程序
U4T2、
The hybrid stepping motor combines characteristics of the variable-reluctance and permanent-magnet stepping motors. The hybrid stepping motor can achieve small step sizes easily and with a simple magnet structure while a purely permanent-magnet motor would require a multipole permanent magnet. In addition, the hybrid stepping motor will tend to maintain its position when the stator excitation is removed, as does the permanent-magnet design.
混合式步进电机结合可变磁阻和永磁步进电动机的特性。

混合式步进电机可以实现小步大小很容易和磁铁结构简单而纯粹的永磁电动机需要多极永磁。

此外,混合步进电机将倾向于保持其位置移除定子励磁时,永磁设计一样。

U5T1、
Relay is a key component in any power system protection scheme. It is a device that, based on information received from the power system, performs one or more switching actions. The information referred to consists of signals and currents, typically the output of instrument transformers. The relay decides to close(or open)one or more sets of normally open(or close) contacts. The switching action typically energizes the trip coil of a circuit breaker, which then opens the power circuit.
继电器是一个关键的组件在任何电力系统保护方案。

一个设备,从电力系统根据收到的信息,执行一个或多个开关动作。

指由信号和电流的信息,一般仪器的输出变压器。

继电器决定关闭(或打开)一个或多个组常开(或接近)接触。

开关行动通常激发断路器的脱扣线圈,然后打开电源电路。

U5T2、
A contactor is a large relay, usually used to switch current to an electric motor or other high-power load. Large electric motors can be protected from overcurrent damage through the use of overload heaters and over load contacts. If the series-connected heaters get too hot from excessive current, the normally-closed overload contact will open, de-energizing the contactor sending power to the motor.
接触器是一种大型继电器,通常用于切换当前电动马达或其他大功率负载。

大型电动机可以免受过载损坏通过使用超载加热器和过载联系人。

如果过度的串联暖气太热电流,将打开闭合过载来接触,接触器断开的发送功率电动机。

U6T1、
Circuit-interrupting devices in power systems are of many forms, ranging from the small key switches to the enormous circuit breakers that flow of power in high-voltage networks. Circuit breaker is a device for interrupting a circuit between separable contacts under normal or abnormal conditions. The abnormal conditions during which a circuit breaker may be asked to operate are primarily those which exist during short circuits. The circuit breaker is designed to withstand these short-duration, high-magnitude currents and to interrupt them if necessary.
断路装置在电力系统的多种形式,从巨大的小钥匙开关在高压断路器,流动的权力网络。

断路器是中断的设备电路在正常或异常条件下分离之间的联系。

异常条件中断路器操作可能会被要求主要是那些存在在短路。

断路器的设计能够承受这些短期高震级水流和必要时打断他们。

U6T2、
The main contacts of a circuit breaker are commonly made of copper, silver, or silver alloy, and are subject to diverse temperature limitations. Copper contacts are not normally fit for continuous operation; their temperature tends to rise with time. Most circuit breaker contacts are therefore made of silver alloy, which provides good conductivity and low stable temperature rise.
的主要联系人断路器通常由铜、银或银合金,受不同温度的限制。

铜接触通常不适合连续操作;他们的温度趋向于上升时间。

大多数断路器接触因此银合金做的,它提供了良好的导电性和较低的稳定的温度上升。

U7T1、
A switch can be constructed with any mechanism bringing two conductors into contact with each other in a controlled manner. This can be as simple as allowing tow copper wires to touch each other by the motion of a lever, or by directly pushing two
metal strips into contact. However, a good switch design must be rugged and reliable, and avoid presenting the operator with the possibility of electric shock. Therefore, industrial switch designs are rarely this crude.
The conductive parts in a switch used to make and break the electrical connection are called contacts. Contacts are typically made of silver or silver-cadmium alloy, whose conductive properties are not significantly compromised by surface corrosion or oxidation. Gold contacts exhibit the best corrosion resistance, but are surface corrosion or oxidation. Gold contacts exhibit the best corrosion resistance, but are limited in current-carrying capacity and may "cold weld" if brought together with high mechanical force. Whatever the choice of metal, the switch contacts are guided by a mechanism ensuring square and even contact, for maximum reliability and minimum resistance.
一个开关可以由任何机制带来了两个导体接触彼此以一种受控制的方式。

这可以简单允许两个铜导线相互接触的运动杆,或通过直接将两个金属条接触。

然而,一个好的开关设计必须坚固,可靠,并避免呈现的操作符电击的可能性。

因此,工业开关设计很少这原油。

开关的导电部分用于制造和打破的电气连接被称为联系。

联系人通常由银或银镉合金,其导电性能没有显著的表面被腐蚀或氧化。

黄金接触表现出最好的耐腐蚀性能,但表面腐蚀或氧化。

黄金接触表现出最好的耐蚀性,但在载流容量是有限的,可能“冷焊”如果与机械力高。

任何金属的选择,开关接触是由一种机制确保广场甚至接触,最大可靠性和最小阻力。

U7T2、If the parting contacts are made of low-melting-point material such as brass of copper, the arc will go out at the first current zero as the voltage is insufficient to reestablish a cathode spot after current reversal. The necessary insulation must be so positioned as to avoid charring from the heat of the arc. If charring occurs the carbon produced may serve as an electrode from which thermionic electrons may be released and so reignite the arc following current zero.
如果分开联系是由低熔点材料如铜、黄铜弧将出去第一电流零的电压不足以重建一个阴极电流换向后现货。

必要的绝缘必须定位,避免电弧的热量烧焦。

如果发生炭化生成的碳可以作为一个电极的热离子电子可能被释放,所以重燃弧后电流零。

U8T1、IN order to confirm and guarantee the reliability of electrical contacts, a lot of experience is required, especially on how to develop additional testing methods on top of the requirements given through national and international standards. It is very important that the manufacturers of devices with electrical contacts are developing such methods(temperature rise tests, short circuit tests, high voltage tests, etc.) and continuously are using them as routine tests in order to confirm the reliability of electrical contacts.
为了确认和保证电接触的可靠性,需要丰富的经验,特别是在如何开发额外的测试方法的要求通过国家和国际标准。

是非常重要的,设备的制造商与电接触正在开发这种方法(温升测试、短路测试,高压测试,等等),不断使用它们作为常规检测,以确认电接触的可靠性。

U8T2、The reliability means the ability that the product fulfills the stipulated conditions. The reliability working scope is quite large, for example: the reliability organization management, the reliability date, the reliability can give a reference to improve the circuit-breaker quality.
可靠性意味着产品满足规定条件的能力。

可靠性工作的范围是相当大的,例如:组织管理、可靠性可靠性日期,可以给一个参考改善断路器可靠性质量。

Part II u1 Text A
Electromechanical devices which employ magnetic fields often use ferromagnetic materials for guiding and concentrating these fields.Because the magnetic permeability of ferromagnetic materials can be large(up to tens of thousands times that of the surrounding space),most of the magnetic flux is confined to fairly well-defined paths determined by the geometry of the magnetic material.
机电设备,采用磁场经常使用铁磁材料进行指导和集中这些字段。

因为铁磁材料的磁导率可以大(成千上万倍,周围的空间),大多数的磁通量局限于相当明确的路径由磁性材料的几何形状决定。

Text B
Due to the hystersis effect,the relationship between B and H for a ferromagnetic material is both nonlinear and multivalued.In general,the characteristics of the material cannot be described analytically.They are commonly presented in graphical from as a set of empirically determined curves based on test samples of the material.The most common curve used to describe a magnetic material is B-H curve or hystersis loop.
由于磁滞效应,B和H之间的关系对铁磁材料的非线性和多值。

一般来说,材料的特性不能被描述分析。

它们通常在图形从一组经验确定曲线基于测试的样品材料。

最常见的曲线用于描述磁性材料磁化曲线和磁滞回路。

Unit 2
Text A
The Mesh Current Method is quite similar to the Branch Current Method in that it uses simultaneous equations,Kirchhoff`s V oltage Law,and Ohm`s Law to determine the unknown currents in a network.It differs form the Branch Current method in that it does not use Kirchhoff`s Current Law,and it is usually able to solve a circuit with less unknown variables and less simultaneous equations,which is especially nice if you`re force to solve without a calculator.
当前网格方法非常类似于分支电流方法,它使用联立方程,基尔霍夫电压定律和欧姆定律来确定网络中未知的电流。

形式分支电流方法不同,它不使用基尔霍夫电流定律,而且通常能解决电路更少的未知变量和更少的联立方程,这是特别好的如果你力量来解决没有计算器。

Text B
The strategy used in the Superposition Theorem is to eliminate all but one source of power within a network at a time,using series/parallel analysis to determine voltage drops (and/or current)within the modified network for each power source
separately.Then,once voltage drops and/or currents have been determined for each power source working separately,the values are all “superimposed”on top of each other to find the actual voltage drops/currents with all source active.
叠加定理中使用的策略是消除网络内的所有只有一个电源,使用串联/并联分析来确定电压下降(和/或电流)在修改网络分别为每个电源。

然后,一旦电压下降和/或电流已经被确定为每个单独电源工作,的值都是“叠加”的发现实际的电压/电流与所有源活性下降。

Unit 3
Text A
The finite element procedure consists of partitioning or discretizing interior domain Ωinto a number of subdomains or finite elements.The field is approximated over each element by an interpolating or shape function depending on values at discrete nodes on or in the element.To provide some degree of field continuity across element boundaries,most of the discrete nodes are defined on the element surface and shared by adjacent element.Provided that they cover the domain, the elements and shape functions may be completely arbitrary.
有限元程序由分区或离散化内部域Ω成子域或有限元素的数量。

字段由插值近似在每个元素或形状函数根据值在离散节点或元素。

提供某种程度的领域跨元素边界连续性,大多数离散节点上定义元素的表面和共享的相邻元素。

提供覆盖域,马英九的元素和形状函数。

Text B
Discrete numeral methods like finite elements or finite differences are necessarily formulated on finite spatial grids-whether actual domain being modeled is finite or infinite.This domain truncation introduces artificial boundaries that must be treated with special care in order to minimize nonphysical wave reflections.These trap energy that would otherwise be radiated and establish undesirable resonances within the grid.Note that this is true regardless of the solution scheme applied,in either the time-domain or frequency-domain.
离散的数字方法如有限元素或有限的差异必然是制定有限空间grids-whether实际域建模是有限的还是无限的。

这个领域截断引入了人工边界,必须特别小心处理,以减少非物质波反射。

这些陷阱能量,否则被辐射,建立不良网格内的共振。

注意,这是真正的不管应用解决方案,无论是在时间
Unit 4
Text A
Coupling can also occur in circuits that share common impedances.For instance,two circuits that share the conductor carrying the supply voltage and the conductor carrying the return path to ground.If one circuit creates a sudden demand in current,the other circuit`s voltage supply will drop due to the common impedance both circuits share between the supply lines and the source impedance.This coupling effect can be reduced by decreasing the supply lines and the common impedance.Coupling also can occur with radiated electric and magnetic fields which are common to all electrical circuits.Whenever current changes,electronmagnetic wares are generated.These waves can couple over to nearby conductors and interfere with other signals within the circuit.
耦合也可以发生在共享公共阻抗的电路。

例如,两个电路共享导体携带电源电压和导体携带的返回路径。

如果一个电路产生电流的突然需求,其他电路的电压供应将会下降,由于公共阻抗电路供给线之间的分享和源阻抗。

这种耦合效应可以减少减少供应线和常见的阻抗。

耦合也可能发生
Text B
The majority of modern digital integrated circuits(IC) are manufactured using complementary metal oxide semiconductor (CMOS) technology.The static power consumption of COMS devices may be lower,but with fast switching rates the CMOS device demands transient power from the supply.The dynamic power demand of a high speed clocked COMS devices may exceed an equivalent bipolar device.Therefore,decoupling capacitors must be used on these devices to reduce the transient power demand from the power supply.
大多数的现代数字集成电路(IC)制造使用互补金属氧化物半导体(CMOS)技术。

设备的静态功耗COMS可能较低,但快速交换率的互补金属氧化物半导体元件要求瞬时功率供应。

的动态电力需求高速时钟COMS设备可能超过一个等价的双极型设备。

因此,去耦电容器必须在这些设备上使用,以减少瞬态电源的电力需求。

Unit 5
Text A
Giant Magnetostrictive Material(GMM)is new functional material which has bi-directional transduction effects,it can be made into Giant Magnetostrictive Actuator (GMA) by using the direct,also can be made into sensors by using the converse pared with piezoelectric actuator,GMA owns the advantages of larger load capacity,rapider response,higher reliability and lower voltage drive,etc.It has a promising prospect in precision positioning,active noise and vibration control and fluid control (pump,value)fields.
超磁致伸缩材料(GMM)是新型功能材料具有双向传导效果,它可以制成超磁致伸缩驱动器(GMA)通过使用直接,也可以制成传感器利用相反的效果。

与压电致动器相比,该协会拥有的优势更大的负载能力,更快捷的反应,高可靠性和低电压驱动等。

它在精密定位,具有广阔的发展前景,积极的噪声和振动控制和流体控制(泵、瓦尔
Text B
Magnetostrictive (MS) linear position sensors constitute an interesting possibility as generic all-use sensors because they are by principle non-contract and absolute.These are very desirable characteristics for machine tool operation,as well as their non-optical nature which makes them resistant to typical contaminants of the machine tool environment like shavings and metalworking coolant fluid.
磁致伸缩(MS)线性位置传感器构成传感器一般都使用一个有趣的可能性,因为他们是由原则non-contract和绝对的。

机床操作,这些都是非常可取的特征以及他们为了自然使他们对机床的典型污染物环境刨花和金属加工冷却液等。

PartIII Unit1 A
So far ,all the power semiconductor devices discussed exclusively use silicon as the basic raw material ,and this will possibly continue,at least in the near future.however,new types of large band-gap materials,such as silicon carbide and semi-conducting diamond,are showing high promise for the future generation of power devices.silicon carbide is particularly more promising because its technology is more “mature”than for diamond.The material has high carrier mobility,faster minority carrier lifetime,and high electrical and thermal conductivities.These properties permit high-voltage and high-power capabilities,fast switching (i. e. ,high switching frequency),low conduction drop ,good radiation hardness ,and high junction temperature.All key devices,such as diodes,power MOSFETS,thyristors,GTO,etc,are possible with new material.
到目前为止,专门讨论的所有电力半导体器件用硅作为基本原料,而这可能会持续下去,至少在不久的将来。

然而,新类型的大带隙材料、碳化硅和半导体等钻石,显示高承诺未来一代的电力设备。

碳化硅尤为更有前途,因为其技术比钻石更“成熟”。

该材料具有高载流子迁移率,更快的少数载流子寿命,高电气和热导率。

这些属性允许高压和大功率功能,快速交换(即高开关频率),低传导,辐射硬度好,和高结温。

所有关键设备,如二极管,功率mosfet,晶体闸流管,之所以与新材料等,是有可能的。

B
Power semiconductor devices constitute the heart of modern power electronic apparatus.They are used in power electronic converters in the form of a matrix of on-off switches,and help to convert power form AC-to-AC at the same (AC controller) or different frequencies (cycloconverter).The switching mode power conversion gives high efficiency,but the disadvantage is that due to the nonlinearity of switches,harmonics are generated at both the supply and load sides.The switches are not ideal,and they have conduction and turn-on and turn-off switching losses.Converters are widely used in applications such as heating and lighting controls,AC and DC power supplies,electrochemical processes,DC and AC motor drives,active harmonic filtering,etc.Although the cost of power semiconductor devices in power electronic equipment may hardly exceed 20~30 percent , the total equipment cost and performance may be highly influenced by the characteristics of the devices.An engineer designing equipment must understand the devices and their characteristics thoroughly in order to design efficient ,reliable,and cost-effective systems with optimum performance.It is interesting to note that the modern technology evolution in power electronics has generally followed the evolution of power semiconductor devices.The advancement of microelectronics has greatly contributed to the knowledge of power device materials,fabrication ,packaging,modeling,and simulation.
功率半导体器件构成现代电力电子设备的核心。

它们用于电力电子转换器的形式的一个矩阵开关开关,同时帮助转换能量形式AC-to-AC控制器(AC)或不同频率(回旋转换器)。

开关模式电源转换效率高,但缺点是由于非线性开关、谐波产生供应和负载。

开关并不理想,他们有传导和接通和断开开关损失。

转换器广泛用于取暖和照明控制等应用,交流和直流电源、电化学过程中,直流和交流电机驱动器、有源谐波滤波等。

虽然电力半导体器件在电力电子设备
的成本可能不超过20 ~ 30%,设备总成本和性能可能会受到设备的特点。

一个工程师设计设备必须了解设备及其特点完全为了设计高效、可靠和具有成本效益的系统最优性能。

有趣的是注意到,现代电力电子技术发展已普遍遵循电力半导体器件的发展。

微电子技术的进步极大地促进了知识的力量设备材料、制造、包装、建模和仿真。

UNIT 2 A
The modern power devices include the diode,SCR,GTO,BJT,power MOSFET,IGBT,MCT and IGCT.Power semiconductor devices constitute a vast and complex subject,and the technology is going through continuous evolution.It is needless to say that a power electronics engineer responsible for designing an apparatus should be thoroughly familiar with the different devices to achieve optimum cost and the performance goals of the system.Traditionally,SCR-type devices have been very popular in power electronic systems and many applications can be found on this area .MOS-gated devices,particularly power MOS-FETs and IGBTs,have been applied extensively in recent years.
The IGCT is a recent member in the devices family with good potential,and we are yet to see its growth of applications in competition with IGBTs and GTOs.It is interesting to see that the advent of new power semiconductor devices,growth of their power ratings,and improvement of their characteristics are continually driving the power electronics and motor drives technologies forward.Suffice it to say that if the devices evolution would have stopped at the SCR level,the power electronics technology would have stalled hopelessly in the primitive stage.
现代电力设备包括二极管、可控硅,之所以是机器、电力MOSFET、IGBT,MCT和IGCT。

功率半导体器件构成一个庞大而复杂的话题,和技术正在经历不断进化。

不用说,电力电子工程师负责设计一个装置应该彻底熟悉不同的设备来实现最优成本和系统的性能目标。

传统上,SCR-type设备已经非常流行在电力电子系统和许多应用程序可以在这个地区找到。

MOS-gated设备,特别是电力MOS-FETs和igbt,近年来已被广泛应用。

IGCT是一个最近设备家族成员具有良好的潜力,我们尚未看到经济增长的应用程序的竞争对手igbt和矩形脉冲断开。

有趣的是发现新型功率半导体器件的出现,增长他们的力量评级,改善他们的特点是不断推动电力电子和电机驱动技术。

我只想说,如果设备进化会停止在可控硅层面,电力电子技术将会停滞在原始阶段的不可救药。

B
Only a few define statements can ba made in comparing these devices since a number of properties must be considered simultaneously and because the devices are still evolving at a rapid pace.However,the qualitative observations given in Table 3-1 can be made.
It should be noted that in addition to the improvements in these devices,new devices are being investigated.The progress in semiconductor technology will undoubtedly lead to higher power ratings,faster switching speeds,and lower costs.On the other hand,the forced-commutated thyristor,which was once widely used in circuits for controllable switch applications,is no longer being used in new converter designs with the possible exception of power converters in multi-MV A ratings.This is a pertinent example of how the advances in semiconductor power devices have modified
converter design.
只有几个定义语句可以英航在比较这些设备,因为许多属性必须同时考虑,因为设备仍在快速发展。

然而,表3 - 1中给出的定性观察。

应该指出的是,除了这些设备的改进,新设备正在接受调查。

半导体技术的进步无疑将导致更高的评级,更快的开关速度,并降低成本。

另一方面,forced-commutated晶闸管,曾广泛应用于电路可控开关应用,不再是被用于新的转换器设计可能除了multi-MV A电力转换器的评级。

这是一个相关的例子半导体电力设备的进步转换器设计修改。

UNIT 3 A
Diodes and phase converters constitute the largest segment of power electronics that interface to the electric utility today.The history of these converters extends nearly one hundred years,and often defined as classical power electronics.Before the advent of solid-state diodes and thyristors,which are invariably used presently,gas-filled glass-bulb devices such as mercury-arc rectifiers,phanotrons,and thyratrons,and ignitrons were dominant in the early part of this century.Then,during World War 2,saturable-core magnetic amplifiers were introduced.This class of converters mainly conversion 50/60 Hz AC to DC(rectification),but a select group can also function for DC to AC conversion (inversion).The efficiency of the converters is high because of soft switching,accompanied with low conduction loss.
二极管和相位转换器构成最大的电力电子接口的部分电力。

这些转换器扩展了近一百年的历史,而且经常定义为古典电力电子。

出现之前的固态二极管和晶体闸流管,总是使用目前,充气玻璃灯泡设备如汞弧整流器、phanotrons,和闸流管,引燃管是在本世纪初占统治地位。

然后,在二战期间,饱和铁芯磁放大器。

这类转换器主要转换50/60 Hz交流到直流(整流),但选择组还可以为DC AC转换函数(反演)。

转换器的效率很高,因为软切换,伴随着低传导损耗。

B
The voltage and currents in a power circuit are frequently not pure sine waves.The line voltages usually have a satisfactory wave-shape but the currents are sometimes badly distorted.The distortion maybe caused by magnetic saturation in the core of a transformer,by the switching action of thyristors.Harmonic voltage and currents are usually undesirable,but in some ac circuits they are also unavoidable.Harmonics are created by nonlinear loads,such as electric arcs and saturated magnetic circuits.
It is important to know how a circuit responds to harmonics.In linear circuits composed of resistors,inductors, capacitors,and transformers,the various harmonics act independently of each other.The fundamental and each harmonics behave as if the others were not here.In solving such a circuits for a particular harmonic, the voltages sources of the other harmonics, including that of the fundamental, are replaced by a short-circuit,.Then , the totalrms current in each branch is equal to the algebraic sum of the effective fundamental current and the effective values of the individual harmonic currents.
In AC circuits, the fundamental current and fundamental voltage together produces a fundamental power. This fundamental power is the useful power that causes a motor to rotate and an arc furnace to heat up. The product of a harmonic voltage times the corresponding harmonic current also produces a harmonic power. The latter is usually。