農業(yè)電氣化專業(yè)英語試卷

1、專業(yè)英語一、詞匯potential difference 電位差 frequency domain 頻域Sinu soidal AC Circuit 正弦交流電路Three-Phase Circuit 平衡三相電路 D/A = Digita-to-Analog數(shù) 模變換 On-State Losses 通態(tài)損耗Power Electro nic Techn ology 電力電子技術tran sformer變壓器 syn chro nous motor 同步電動機permanent magnet 永久磁鐵 horseshoe magnet 馬蹄形磁鐵 exciting voltage 勵磁電壓

2、performance characteristics 工作特性 audio signal 聲頻信號 instruction 指令electric power system 電力系統(tǒng)nominal frequency 額定頻率 distribution system 配電系統(tǒng)二、英譯漢1. Modern power systems are usually large-scale, geographically distributed, and with hundreds to thousands of generators operating in parallel and synchrono

3、usly. They may vary in size and structure from one to another, but they all have the same basic characteristic：stransmit power over significant distances to consumers spread over a wide area. This requires a transmission system comprising subsystems operating at different voltage levels.現(xiàn)代電力系統(tǒng)通常是規(guī)模大

4、，地域分布廣，具有成百上千并列同步運行的發(fā) 電機組。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 In spite of the initial widespread use of DC systems, they were almost completely superseded by AC systems.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 keep transmission po

5、wer 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 necessity.3. Most people can

6、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, processes data, stores

7、 data, and produces output, all according to a series of stored instructions.4. Whereasthe 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 motion between the two and

8、 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 unidirectional, that is, they hav

9、e 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 are assumed to be ideal.

10、6. Power losses in the power electronic converters are comprised of the switchi ng losses and the parasitic losses. The parasitic losses acco unt for the losses due to the winding resistances of the inductors and transformers, the dielectric losses of capacitors, the eddy and the hysteresis losses.

11、The switching losses are significant 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 tran siti on states.7. The other kind of signal is a digital signal. A digital signal is one that can take on values wit

12、hin two discrete ranges. Such signals are used to represent ON-OFF or YE-SNO 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. Once the room temper

13、ature 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 of components

14、 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 in the proper form at the proper time.9. Analyzing AC circuit usually requires three

15、steps.(1) Transform the circuit to the phasor or frequency domain.(2) Solve the problem using ucabircuitusbatechniques (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 voltage sources

16、connected to loads by three or four wires(or transmission lines). A three-phase system is equivalent to 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.l-2 shows the voltage across an element (represent

17、ed by a rectangularblock) connected to points a and b. The plus (+) and minus (-) 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 respect to point b is

18、uab. It follows logically that in general uabuba .三、漢譯英1. The increasing need for transmitting large amounts of power over longer distance created an incentive to use progressively high voltage levels. 日益增長的對遠距離大容量功率輸送的需求導致所使用的電壓水平不斷2. The series of instructions that tell a computer how to carry out

19、 processing tasks is referred to as a computer program, or simply a "program." 告訴計算機如何執(zhí)行處理任務的一系列指令被稱為計算機程序，簡稱為 程序。3. Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C). 電荷是構成物質的原子的電氣屬性，其量綱為庫侖。原題：1. Electrical loads 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 induction