电气工程专业英语unt2

,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,电气工程及其自动化专业英语,主编 杨勇 邓秋玲,Unit 2 Power Electronics,2.1 Introduction,2.2 Power Semiconductor Devices,2.3 Power Electronic Converters,2.4 Further Reading:Electronic Filters,2.1 Introduction,New Words and Expressions,solid-state adj. 固态的 computation n. 计算；估计,integration n.结合；整合；dynamic adj.动态的；n.动力学；mercury-arc医汞弧 valve n. 阀；真空管；semiconductorn.物半导体 switchingn. 开关；转换；,diode n. 二极管 inverter n. 反用换流器逆变器；thyristorn. 半导体闸流管；硅可控整流器,inverter thyristor 晶闸管逆变器；可控硅逆变器,transistorn. 晶体管；晶体管收音机；半导体收音机,transmissionn. 播送；传送；信息；传动装置,substantial adj. 结实的；重大的 n. 本质；,2.1 Introduction,New Words and Expressions,fluorescentfl:resnt lamp ballast 荧光灯镇流器,mercury n. 水银；汞 thermionic adj. 物热电子的；HVDC transmission system 高压直流输电系统,induction motor 感应电动机,vacuum n. 真空； adj. 真空的；vt. 用真空吸尘器清扫,dissipate v. 驱散；rectifier n. 纠正者；整流器,triggered adj. 触发的 thyratronartrn n. 电闸流管 ignitron n. 引燃管；放电管,cycloconverter n. 周波变换器；双向离子变频器,triac n. 电三端双向可控硅开关元件,a scope of一个范围 spectrumn. 谱，光谱；能谱；,2.1 Introduction,text,Power electronics is the application of solid-state elec-tronics for the control and conversion of electric power.,It also,refers to, a subject of research in electrical engineering which,deals with,design, control, comput-ation and integration of nonlinear, time varying energy processing electronic systems with fast dynamics,.,Note：refers to指的是;,此句译成：电力电子技术是电气工程研究课题之一，主要对具有快速动态响应的非线性、时变能源处理的电子系统进展设计、控制、计算和集成。,2.1 Introduction,text,Power electronic converters can be,found wherever there is a need,to change voltage, current or frequency of electric power, as shown in Fig.2.1, Fig.2.2 and Fig.2.3.,The,power range,of these converters,is from,some mill-iwatts (as in a mobile phone),to,hundreds of megawatts in a high voltage direct current (HVDC) transmission sys-tem,.,Note：found wherever there is a need用在那些需要.的场合，对电压、电流或电能的频率进展转换时，就要用到电力电子转换器。,Note：power range is from.to 这些转换器的功率范围从毫瓦特如移动 的功率到高压直流输电系统的数百兆瓦。,2.1 Introduction,text,With “classical electronics, electrical currents and voltage are used to carry information, whereas with power electronics, they carry power. Thus, the main metric 主要指标of power electronics becomes the efficiency.,Note,：评价,电力电子的主要性能指标是效率。,2.1 Introduction,text,Applications of power electronics,range in size,from,a,switched mode power supply,in an alternating current (AC) adapter, battery chargers, fluorescent lamp ballasts,through,variable frequency drives and direct current (DC) motor drives used to operate pumps, fans, and manufactur-ing machinery,up to,gigawatt-scale high voltage direct current power transmission systems used to interconnect electrical grids.,Note,：,range in size:,按大小排列.此句译为：按大小排列，从AC适配器中的开关电源、电池充电器、荧光灯镇流器、到变频驱动和水泵、风机、机床的DC电机驱动，再到用于电网互连、具有千兆瓦规模的高压直流电力传输系统，都能发现电力电子技术的应用。,2.1 Introduction,text,Then in 1948 the invention of the bipolar junction transistor by Shockley all at once 突然；同时reduced the cost and size while increasing the efficiency of transistors beginning a revolution in semiconductor electronics.,Shortly after, in the 1950s, semiconductor power diodes became available and started replacing vacuum tubes. Then in 1956 the silicon controlled rectifier (SCR) was introduced by General Electric marking the point where semiconductor power electronics really began.,Note：标志着半导体电力电子技术的真正开场：,2.1 Introduction,text,Power electronics started with the development of mercury arc rectifier. Invented by Peter Cooper Hewitt in 1902, the mercury arc rectifier was used to convert AC into DC. In 1933 selenium 硒rectifiers were invented.,In 1947 the bipolar point-contact transistor 双极点接触型晶体管was invented by Walter H Brattain and John Bardeen under the direction of 在的领导之下,William Shockley at the Bell Telephone Laboratory.,Note： started with 开场于；,mercury arc rectifier 汞弧整流器.,2.1 Introduction,text,In 1960s the switching speed of bipolar junction tran-sistors (BJTs) allowed for 允许DC/DC converters to be possible in high frequency, with the metal oxide semi-conductor field effect transistor (MOSFET) introduced in 1960.,In 1976 power MOSFET becomes commercially availa-ble. Then in 1982 the insulated gate bipolar transistor (IGBT) was introduced.,Note,：,commercially available,市场上能买到的,2.1 Introduction,text,The capabilities and economy of power electronics system,are determined by,the active devices that are available. Their characteristics and limitations are a key element in the design of power electronics systems.,Formerly, the mercury arc valve, the high-vacuum and,gas-filled,diode,thermionic rectifiers, and triggered devices such as the thyratron and ignitron,were widely used in,power electronics.,Note,：,are determined by,取决于；,Note,：,gas-filled,充气的；,thermionic rectifiers,热离子整流器,2.1 Introduction,text,As the ratings of solid-state devices improved,in both voltage and current-handling capacity, vacuum devices have been nearly entirely replaced by solid-state devices.,The first high power electronic devices were mercury-arc valves. In modern systems the conversion,is per-formed with,semiconductor switching devices such as diodes, thyristors and transistors,as pioneered by,R. D. Middlebrook and others beginning in the 1950s,Note,：,is per-formed with,用.执行，实现,；,as pioneered by,由.开创的。,2.1 Introduction,text,.,In contrast to,electronic systems,concerned with,transmission and processing of signals and data, in power electronics substantial amounts of electrical energy are processed,.,An AC/DC converter (rectifier) is the most typical pow-er electronics device found in many,consumer electronic devices, e.g. television sets, personal computers, battery chargers, etc.,Note,：,In contrast to,与.相比,；,concerned with涉及,此句译为：电力电子处理大量的电能。,Note,：,consumer electronic devices,消费电子用品。,2.1 Introduction,text,The power range is,typically,from,tens of watts,to,several hundred watts. In industry a common applica-tion is the variable speed drive (VSD) that is used to control an induction motor.,The,power range,of VSDs,starts from,a few hundred watts,and end at,tens of megawatts.,Power electronic devices may,be used as,switches, or as amplifiers.,2.1 Introduction,text,An ideal switch is,either open or closed,and so dissipates no power; it withstands an applied voltage and,passes no current, or,passes any amount of current with no voltage drop,.,Semiconductor devices used as switches can,appro-ximate this ideal property,and so most power electronic applications,rely on,switching devices on and off, which makes systems very efficient as no power is wasted in the switching devices.,Note： either open or closed 或翻开或关闭；passes any amount of current with no voltage drop 流过电流而不引起压降。,2.1 Introduction,text,By contrast,in the case of,the amplifier, the current through the device varies continuously according to a controlled input.,Power electronics,makes up a large part,of engin-eering and has,close connections with,many,areas,of physics, chemistry, and mechanics. It establishes a rapidly expanding field in electrical engineering and a scope of its technology covers a wide spectrum.,Note,：,in the case of,就.来说；,Note：makes up a large part 占.大局部；,close connections with与. 有严密联系。,2.2 Power Semiconductor Devices,New Words and Expressions,wafern. 圆片；晶片,SCRn. 可控硅整流器,GTOn. 门极可关断晶闸管,MCTn. MOS控制晶闸管,IGBTn. 绝缘栅双极型晶体管,BJTn. 双极结型晶体管,FETn. 场效应管,semiconductorn. 半导体,freewheelingn. 惯性滑行 adj. 惯性滑行的；随心所欲的 v. 轻快地行动,forward-bias正向偏置,2.2 Power Semiconductor Devices,New Words and Expressions,kiloamperesn. 千安培,leakagen. 漏，泄漏；漏损量；渗漏物,switch n. 开关；转换，转换器；vt. & vi. 转变，转换,reverse-biased反向偏置,silicon-controlled可控硅,MOSFETn. 金属氧化层半导体场效应晶体管,gigahertzn. 千兆赫,enhancement n. 增强；增加；提高；改善,drawbackn. 缺点；不利条件；障碍,withstandvt. 承受，经得起；对抗 vi. 对抗；经得起,breakdownn. 崩溃；损坏，故障；分解；垮，衰竭,Diodes, thyristors and transistors are the,essential com-ponents,of the power electronic applications. Today, the single,wafer,diodes are able to,block,more than 9kV over a wide temperature range.,At the same time, thyristors withstand more than 10kV. These devices,conduct,up to 5kA,. The levels of 6kV and 0.6kA,are approachable,by power transistors.,2.2 Power Semiconductor Devices,TEXT,Note： essential components 根本元件,关键部件；, block 阻断,Note,：,conduct,导电；,are approachable,可接近。,A comparative diagram,of power ratings and switching speeds of the controlled semiconductor electronic de-vices is given in Fig.2.4.,2.2 Power Semiconductor Devices,TEXT,2.2.1 Diodes,As shown in Fig.2.5(a), diodes are the,main build-ing blocks,of rectifiers, rectifier sections of AC and DC converters, their,freewheeling paths, and multiple control electronic units.,That is why,a diode is the most commonly used ele-ctronic device in the modern power electronic sys-tems.,2.2 Power Semiconductor Devices,TEXT,Note,：,main build-ing blocks,主要构件；,freewheeling paths,续流路径,The rectifier diode has a smaller,voltage drop,in the,for-ward-bias, state. The forward bias characteristic of the power diode is approximately linear, which means that the voltage drop,is proportional to,the Ohmic resistance and current.,The maximum current in the forward bias,depends on,the PN-junction area. Today, the rated currents of power dio-des approach kiloamperes.,2.2 Power Semiconductor Devices,TEXT,Note：, forward-bias:正向偏置;,At turn on, the diode can,be considered as,an ideal switch because it opens rapidly,compared to,transients in the circuit. In most of circuits, the,leakage current,does not have,a significant effect on,the circuit and thus the diode can,be considered as,a switch.,In the case of,reverse-biased voltage, only a small lea-kage current flows through the diode.,2.2 Power Semiconductor Devices,TEXT,Note：,be considered as,可看作；,leakage current,漏电流；,Note：,In the case of,， 就反向偏置电压而言。,This current,is independent of,reverse voltage until the,breakdown voltage,is reached. After that, the diode voltage,remains essentially constant,while the current increases dramatically. Only the resistance of the exter-nal circuit limits the maximum value of the current.,Simultaneous large current and large voltage in the breakdown operation of the diode must be avoided.,2.2 Power Semiconductor Devices,TEXT,Note： is independent of 与.无关；, breakdown voltage击穿电压；, remains essentially constant 根本上不变。,2.2.2 Thyristors and GTOs,As shown in Fig.2.5(b), rectifier thyristors,known as,silicon-controlled rectifiers (SCRs) are commonly used in adjustable rectifier circuits, especially in high power units,up to,100 MVA.,Their frequency capabilities are not high,being,lower than 10 kHz.,2.2 Power Semiconductor Devices,TEXT,Note：,known as,被称为是,所谓；,up to,高达,，作后置定语，修饰high power units.,If positive voltage,is applied,without gate current, the thyristor constitutes the,state of forward blocking,. A low-power pulse of gate current,switches the thyristor to the on-state,.,The output characteristic of a conducting thyristor in the forward bias,is very similar to,the same curve of the diode with a small leakage current. Thus, the thyristor assumes very low resistance in the forward direction.,2.2 Power Semiconductor Devices,TEXT,Note：,switches .to .,切换到，转到，转变成,；,is very similar to,与.很相似，,很接近.,Once turned on, the thyristor remains in this state after the end of the gate pulse while its current is higher than the,holding level,.,If the current drops below the holding value, the device,switches back to,the non-conducting region.,Switching off by gate pulse is impossible. Therefore, using the same arguments,as for,( 至于,关于),diodes, the thyristor can,be represented by,the idealized switch.,2.2 Power Semiconductor Devices,TEXT,Note：,Once turned on,一旦导通；,holding level,保持级；,switches back to,转回到。,When a thyristor is supplied by AC, the moment of a thyristor opening should be adjusted by,shifting,th,e control pulse,relative to,the starting point of the posi-tive alternation of,anode voltage,. This delay is called the firing angle .,The output characteristic of SCR in the,reverse bias,is very similar to,the same curve of the diode with a small leakage current.,2.2 Power Semiconductor Devices,TEXT,Note：,在交流情况下使用晶闸管时，它的导通时刻可以通过相对于,阳极电压,变为正的起始点移动控制脉冲来调节.,With negative voltage between,anode and cathode, this,corresponds to,the,reverse blocking,state.,If the maximum reverse voltage exceeds the permissible value, the leakage current rises rapidly,as with,diodes, leading to breakdown and,thermal destruction,of the thyristor.,Besides the rectifier thyristors, the,gate turn-off thyrist-ors,(GTOs) are produced as shown in Fig.2.5(c).,2.2 Power Semiconductor Devices,TEXT,Note：,as with,如同，和-一样；,thermal destruction,热破坏。,These devices have two adjustable operations: they can be,turned on or off,by the current gate pulses.,The GTO thyristor turns on,similarly to the SCR thyri-stors, i.e. after the current pulse will,be applied to,the gate electrode. To turn it off, a powerful negative curr-ent control pulse must be applied to the gate electrode.,A switching frequency range of a GTO thyristor is a few hundred hertz to tens kilohertz.,Note：,similarly to the SCR thyristors,和SCR相似,。,2.2 Power Semiconductor Devices,TEXT,Their on-state voltage (23V) is higher than that of SCR.,Because of their,capability of handling,large voltages (up to 5kV) and large currents (up to a few kiloamperes at 10MVA), the GTO thyristors are,more,convenient to use,than,the SCR thyristors,in applications where,high price and high power are allowed,.,Note：由于GTO具有处理高电压高达5千伏、大电流达几千安培，容量可达10MVA的能力，GTO在那些高本钱的大功率场合使用，比SCR更为便利。,2.2 Power Semiconductor Devices,TEXT,2.2.3 Power MOSFETs and IGBTs,As shown in Fig.2.5(d), (e),metal-oxide-semiconductor field-effect transistor (MOSFET),is a voltage-controll-ed metal-oxide semiconductor field-effect transistor.,The advantages of the MOSFETs are as follows:,high switching capability that is the operational frequencies reach gigahertz; simple protection circuits and voltage control; normally,off device,when,the enhancement mode is used,; and easy paralleling to increase the current values.,2.2 Power Semiconductor Devices,TEXT,The drawbacks of the MOSFETs,are as follows,: relatively low power handling capabilities, less than 10kVA, 1000V, and 200A; and relatively high (more than 2V) forward voltage drop.,In contrast to,MOSFETs, bipolar junction transistors (BJTs) have some advantages.,Both BJTs and MOS-FETs have the technical parame-ters and characteristics,that complement each other,.,2.2 Power Semiconductor Devices,TEXT,Note：,are as follows,如下,Note：,BJT和MOSFET的技术参数及特性成为互补。,2.2 Power Semiconductor Devices,TEXT,BJTs have lower conduction losses in the,on,-,state, espe-cially at larger blocking voltages, but they have longer switching times. MOSFETs are much faster, but their on-state conduction losses are higher.,Therefore,attempts were made,to,combine,these two types of transistors,on the same silicon wafer to,achieve better technical features,.,为了得到更好的技术性能，人们尝试将两者组合在同一硅片上。,These investigations,resulted in,the development of the insulated gate bipolar transistor (IGBT) as shown in Fig.2.5(f), which is becoming the,device of choice,in most of new power applications.,IGBTs have the highest power capabilities up to 1700-kVA, 2000V, 800A.,Because of the less resistance than the MOSFET, the heating losses of the IGBT are lower too.,Note：,device of choice,选择的装置。,2.2 Power Semiconductor Devices,TEXT,Their forward voltage drop is 23V, that is higher than that of a bipolar transistor but lower than the MOSFET has.,Due to the negative,temperature coefficient, when a temperature is raised, the power and heating decrease therefore the device withstands the overloading and operates in parallel well,.,Note：,temperature coefficient,温度系数；此句译为：由于IGBT属于负温度系数半导体材料，当温度上升时，功耗和热量会随之降低，所以能过载运行，且适合并联。,2.2 Power Semiconductor Devices,TEXT,The reliability of the IGBTs is higher than that of the field-effect transistors (FETs),thanks to,the absence of a,secondary breakdown,.,They have relatively simple voltage controlled gate driver and low gate current. Unfortunately, IGBTs,are not suitable for,high frequency,supply sources,.,Note：,thanks to,由于,2.2 Power Semiconductor Devices,TEXT,Note：,supply source：,电源。遗憾的是IGBT不适合于高频电源.,2.3 Power Electronic Converters,New Words and Expressions,interactionn. 互相影响；utilityn. 功用，效用；公用事业 topologyn. 拓扑构造 commutation n. 交换；折算；,rectifier n. 整流器 invertern. 逆变器,magnitude n. 巨大，重要；chopper n. 斩波器,domesticadj. 家庭的 virtually adv. 实际上；controllability n. 可操纵性；adequate adj. 足够的；适当的；,electromechanicaladj. 电动机械的；机电的；电机的,vehicle n. 车辆；交通工具；传播媒介，媒介物,householdn. 家庭； adj. 家庭的，；日常的,insufficientadj. 缺乏的；不够的,2.3 Power Electronic Converters,New Words and Expressions,cope with对付；stringent adj. 严格的；迫切的,alternatelyadv. 轮流地，交替地；交互,sinkvi. 淹没；下落； vt. 使下沉；使下垂,regeneration n. 正反响,autonomousadj. 自治的；有自主权的,quadrantn. 四分之一圆；扇形体；象限仪,shuntv. 使转轨；使分流；转向一边；避开 n. 转轨；分流器,unifyvt. 使联合；使一样；使一致；统一,replenish vt. 补充；重新装满；把装满,specify vt. 指定；详述 vi. 明确提出，详细说明,polarity n. 极性,2.3 Power Electronic Converters,Text,Interaction between,the utility supply,and,the load depends on the topology of the power system, which,converts,the,line feed,into,the load power.,The availability of excellent fast,commutation devices,and advancements in digital technology have driven a rapid power converter development. The four main classes of power electronic converters are depicted in Fig.2.6. They are:,- AC/DC converters,called rectifiers that convert input AC voltage U,s,to DC with adjustment of output voltage U,d,and current I,d, as shown in Fig.2.6(a);,Note：,line feed,线路馈电;,commutation devices,整流装置,2.3 Power Electronic Converters,Text,-,DC/AC converters,called inverters that produce out-put AC voltage U,s,of controllable magnitude and frequ-ency,from input DC voltage U,d, as shown in Fig.2.6(b);,-,AC/AC converters,called frequency converters and changers that establish AC frequency, phase, magnitude, and shape, as shown in Fig.2.6(c);,-,DC/DC converters,called choppers that change DC voltage and current levels using the switching mode of semiconductor devices, as shown in Fig.2.6(d).,2.3 Power Electronic Converters,Text,2.3.1 Rectifiers and Inverters,AC/DC converters,serve as,rectifiers. They convert AC to DC in a number of industrial, domestic, agricultural, and other applications.,Rectifiers are used,as,stand-alone units,feeding single and multiple DC loads and,as,input stages of AC systems because of their virtually unlimited output power and fine controllability.,Note：,serve as,充当， 担任；,Note：,stand-alone units,独立单元。,2.3 Power Electronic Converters,Text,Their speed of response is usually adequate to handle electromechanical transients occurring in motor drives and power suppliers.,AC/DC,line-commutated converters,or, as they also called,converters with natural commutation or passive rectifiers, are the most usual choice for applications, where a single-phase and three-phase supply is availa-ble.,Note：,AC/DC电网换流换流器，亦称为自然换流换流器或无源换流器。在单相或三相电源的场合，通常选择电网换流换流器。,line-commutated converters:,电网换流换流器：借助于电网电压来实现换流，不需要器件具有门极可关断能力。,2.3 Power Electronic Converters,Text,This is due to simplicity of the circuits requiring a mi-nimum number of active and passive components. Thyristors are the main line-commutated power switches.,The term “line-commutated describes the type of com-mutation, i.e. the transfer of current from one conducting element to the