农业电气化专业英语试卷

1、LOGO农业电气化专业英语试集团文件发布号：（9816-UATWW-MWUB-WUNN-INNUL-DQQTY-专业英语词汇potential difference电位差 frequency domainSinusoidal AC Circuit正弦交流电路Three-Phase Circuit平衡三相电路D/A = Digital-to-Analog数模变换 On-State Losses 通态损耗 Power ElectronicTechnology电力电子技术transformer 变压器 synchronous motor同步电动机permanent magnet 永久磁铁 horse

2、shoe magnet马蹄形磁铁exciting voltage 励做电压 performance characteristics 工作特性audio signal 声频信号 instruction 指令electric powersystem电力系统nominal frequency额定频率distribution system 配电系统二、英译汉1. Modern powersystems are usuallylarge-scale,geographicallydistributed, and withhundreds tothousands ofgenerators operating

3、 inparallel andsynchronously.They may vary in size andstructure fromone to another, but they all have the same basic characteristics：transmit power over significant distances to consumersspread over a wide area. This requires a transmission system comprising subsystems operating at different voltage

4、 levels. 现代电力系统通常是规模大，地域分布广，具有成百上千并列同步运 行的发电机组。2. In spite of the initial widespread use of DC systems, they were almost completely superseded by AC systems. By 1886, the limitations of DC systems were becoming increasingly apparent. They could deliver power only a short distance from generators. To

5、 keep transmission power losses (I2R) and voltage drops to acceptable levels, voltage levels had to be high for long-distance power transmission. Such high voltages were not acceptable for generation and consumption of power; therefore, a convenient means for voltage transformation became a necessit

6、y.3. Most people can formulate a mental picture of a computer, but computers do so many things and come in such a variety of shapes and sizes that it might seem difficult to distill their common characteristics into an all- purpose definition. At its core, a computer is a device that accepts input,

7、processes data, stores data, and produces output, all according to a series of stored instructions.4. Whereas the copper disk will rotate in the same direction as the rotating magnetic field, it will never reach the same speed as the rotating magnet, because if it did, there would be no relative mot

8、ion between the two and therefore no current induced in the copper disk. The difference in speed between the rotating magnetic field and the copper disk is known as slip, which is essential to the operation of an induction motor.5. Switches including the diodes are assumed to be ideal and unidirecti

9、onal, that is, they have zero on-state losses, zero off-state losses, zero switching losses and unrestricted voltage or current carrying capabilities. Switching devices in a practical design example must be selected with these desired characteristics in mind. Inductors, capacitors and transformers a

10、re assumed to be ideal.6. Power losses in the power electronic converters are comprised of the switching losses and the parasitic losses. The parasitic losses account for the losses due to the winding resistances of the inductors and transformers, the dielectric losses of capacitors, the eddy and th

11、e hysteresis losses. The switching losses aresignificant and can be managed. They can be further divided into three components: (a) the on-state losses, (b) the off-state losses and the losses in the transition states.7. The other kind of signal is a digital signal. A digital signal is one that can

12、take on values within two discrete ranges. Such signals are used to represent ON-OFF or YES- NO information. An ordinary household thermostat delivers a digital signal to control the furnace. When the room temperature drops below a preset value, the thermostat switch closes turning on the furnace. O

13、nce the room temperature rises high enough, the switch opens turning off the furnace. The current through the switch provides a digital representation of the temperature variation： ON equals "too cold" while OFF equals "not too cold”.8. A signal-processing system is an interconnection

14、 of components and devices that can accept an input signal or a group of input signals, operate on the signals in some fashion either to extract or improve the quality of the information, and present the information as an output inthe proper form at the proper time.9. Analyzing AC circuit usually re

15、quires three steps.(1) ) Transform the circuit to the phasor or frequency domain.(2) Solve the problem using circuits techniques (nodal analysis, mesh analysis, superposition theorem etc.).(3) Transform the resulting phasor to the time domain.10. A typical three-phase system consists of three voltag

16、e sources connected to loads by three or four wires(or transmission lines). A three-phsQzsystem is equivalent to"ba three single-phase circuits. The voltage sources can be either wye-connected as shown in Fig.1-23 (a) or delta-connected as in Fig. 1-23 (b).11. Fig. 12 shows the voltage across a

17、n element (represented by a rectangular block) connected to points a and b. The plus (+) and minus (一) signs are used to define reference direction or voltage polarity. The uab can be interpreted in two ways： point a is at a potential of uab volts higher than point b; the potential at point a with r

18、espect to point b is uab. It follows logically that in general uah = -ulM2 .三、汉译英1. The increasing need for transmitting large amounts ofpower over longer distance created an incentive to use progressively high voltage levels.日益增长的对远距离大容量功率输送的需求导致所使用的电压水 平不断提高。2. The series of instructions that tell

19、 a computer how to carry out processing tasks is referred to as a computer program, or simply a ,'program. 告诉计算机如何执行处理任务的一系列指令被称为计算机程序， 简称为程序。3. Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C).电荷是构成物质的原子的电气属性，其量纲为库仑。原题： 1. Electrical lo

20、ads can be of three types： impedance load, AC voltage sink load or AC current sink load. Examples of impedance load are electromagnetic ac relays, electromagnetic pick up and lift equipments. The load comprises of a large value inductor. Examples of ac voltage sink are the constant speed drives for inducti