题目内容
(15分)风力发电作为新型环保新能源,近几年来得到了快速发展,如图所示风车阵中发电机输出功率为100kW,输出电压是250V,用户需要的电压是220V,输电线电阻为10Ω.若输电线因发热而损失的功率为输送功率的4%,试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539142365533.jpg)
(1)在输电线路中设置的升、降压变压器原、副线圈的匝数比.
(2)用户得到的电功率是多少.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539142365533.jpg)
(1)在输电线路中设置的升、降压变压器原、副线圈的匝数比.
(2)用户得到的电功率是多少.
(1)1∶20 240∶11 (2)96kW
试题分析:(1)输电线损失的功率
P损=P×4%=100kW×4%=4kW.
输电线的电流I2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539142511144.png)
升压变电器输出电压U2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153914345426.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153914407623.png)
升压变压器原、副线圈匝数比:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153914470411.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153914548469.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153914922514.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153915000402.png)
电压损失U损=I2R线=20×10V=200V.
降压变压器原线圈端电压U3=U2-U损=4800V.
降压变压器原、副线圈匝数比
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153915062437.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153915140616.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153915499492.png)
(2)用户得到的电功率即降压变压器的输出功率为
P用=P-P损=P(1-4%)=100×96%kW=96kW.
点评:难度中等,处理此类问题,输电线上功率的损耗常作为突破口,求得输送电流之后再由电压见的关系确定其他物理量
![](http://thumb2018.1010pic.com/images/loading.gif)
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