农业电气化专业英语试卷

农业电气化专业英语试

卷

集团文件发布号：（9816-UATWW-MWUB-WUNN-INNUL-DQQTY-

专业英语

一、词汇

potential difference 电位差 frequency domain 频域

Sinusoidal 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 Electronic Technology 电力电子技术

transformer 变压器 synchronous motor 同步电动机

permanent magnet 永久磁铁 horseshoe magnet 马蹄形磁铁

exciting voltage 励磁电压 performance characteristics 工作特性

audio signal 声频信号 instruction指令

electric power system电力系统

nominal frequency 额定频率 distribution system 配电系统

二、英译汉

1.Modern power systems are usually large-scale,

geographically distributed, and with hundreds to thousands of generators operating in parallel and synchronously. They may vary in size and structure from one to another, but they all have the same basic characteristics：

transmit power over significant distances to consumers spread over a wide area. This requires a transmission system comprising subsystems operating at different voltage 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were almost completely superseded by AC systems.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 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 necessity.

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, 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 motion 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 i ncluding the diodes are assumed to be ideal and

unidirectional, 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 are assumed to be ideal.

6.Power losses in the power electronic converters are

comprised of ①the switching losses and ②the 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