电气专业英语课后练习翻译讲述.doc

PART1 U1T1、 n 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 2T1、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