题目内容
某交流发电机输出功率为5×105 W,输出电压为1.0×103 V,已知输电线的总电阻R =" 40" Ω,在输电线上损失的电功率等于输电功率的5%,用户使用电压U="380" V.输电所使用的变压器均为理想变压器。
(1)画出输电线路的示意图.(标明各部分的符号)
(2)求所用升压和降压变压器的原、副线圈的匝数比各是多少?
(1)画出输电线路的示意图.(标明各部分的符号)
(2)求所用升压和降压变压器的原、副线圈的匝数比各是多少?
(1)见解析(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155750074395.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155749872406.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155750074395.png)
试题分析:(1)输电线路的示意图如图所示.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557503089890.jpg)
(2)由功率的公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155750480451.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155750667734.png)
输电线的损耗的功率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557508861202.png)
由损失的功率 P损=I22R可得输电线的电流为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557510421082.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557512761042.png)
所以升压变压器的匝数比为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241557515101021.png)
降压变压器的匝数比为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155751666810.png)
点评:掌握住理想变压器的电压、电流及功率之间的关系,本题即可得到解决.
![](http://thumb2018.1010pic.com/images/loading.gif)
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