5-电力变压器

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以前，变压器 的最高电压为 1000kV，最 大容量为 3×1000MVA， 这台变压器安 装在日本变电 站。 2008年底，50 00KV输变电
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系统投入运 行，在山西 到湖北的一 段电网。尽 管是短短的 5
由于电力作为能源，可以从能源产地将煤炭、石油、天 然气或核能等转换成电力后，很方便地通过变压器由输 电线路将电能输送到需要动力能源的地方。电力输送比 其他形式的能源输送都更简单、方便。 电力为经济的发展，提供了可靠的、不间断的能源。 可以说国民经济的各行各业和人民生活都离不开电力。 一般情况下，能源基地和需要动力能源的地方会有一 定的距离，为了经济地远距离地输送电力，必须将发电 机电压提高到输电电压，而在电力用户处，再将输电电 压降低到用户使用的电压，升高和降低电压的设备是变 压器．
各种电压的变换就要用到变压器
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Categories of transformer 变压器的分类
Air cored Transformer 空芯变压器
Ferrite core transformer
铁氧磁芯变压器
Laminated iron core transformer 叠层铁芯变压器
V = p Vs
N N ps
So if we had a 240V supply connected to the primary, and let us say 200 turns of wire on the primary, and 100 turns of wire on the secondary, and put these figures in to the equation:VS = 240 200VS VS
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Of course no piece of equipment is 100% efficient, and the losses in a transformer will be covered later in this section, but to understand the theory, we will consider that our transformer is perfect. In our ideal transformer the formula is:当然不可能有100%的转换率，有一定的损失，以后的课程将讨论。为了方便理解我们先讨论理想变 压器。
Power Transformer 电力变压器
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General of Transformers
For a number of reasons, from time to time, we need a different voltage from the one available to us. Here in China normal domestic supplies are 220V. hand operated electric tools are very often 110V for safety reasons. China’s transmission system is at high voltage, and this voltage must be brought down to 380V 3 phase for industry, and to 220V for domestic use. To accomplish these changes in voltage we use Transformers. 介于各种各样的原因，我们需要各种不同的的电压一满足我们的 需要。中国的民用电压为220V ，但其他国家的手动工具的电压微 110V ，所以我们需要变压器来变压。 Transformers are electromagnetic devices, and use the principle that an alternating current in a coil will induce an alternating current in another coil. Transformers cannot work on DC, the supply must be an alternating one. 变压器是种磁电转换装置，其原理是通有交流电的线圈在另一线 gao yu ping 2 圈中感应出交流电。直流电是不能工作在变压器上。
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Offshore platform voltage class
• • • • • • • CACT平台标准电压： 34.5KV 13.8KV 4.16KV 600V 480V 208-120V • • • • • • Some 平台标准电压： 13.8KV 6.3KV/3.3KV 600V 400V 230V
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Where:VS VP NS NP
= Voltage in the secondary winding. = Voltage in the primary winding. = Number of turns of wire in the secondary winding. = Number of turns of wire in the primary winding.
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Step up transformers.
It has already been said that if there are more turns of wire on the secondary, than on the primary, the secondary winding would be at a higher voltage than the primary. Does this mean we are getting more energy out than we are putting in? 正如我们说所如果次级线圈的匝数多于初级线圈的匝数，则次级电压要高于 初级电压。是否我们在次极上能得到比初级多的能量？
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Transformer ratio 变压器的比率（简称变压比）
• It is very often more convenient to quote a transformer’s ratiomer means that if it’s input is 240V then the output will be 120V, and equally if the input to the same transformer was reduced to 110V, the output would be 55V because it still maintains it’s ratio of 2 : 1 with the primary always quoted first.
1882年高纳德(Gaulard)和吉伯斯(Gibbs)的交流供电系 统，获得英国专利。他们用一种叫做“第2发电机”(具有 开口铁心，是变压器的前身)的设备来升高和降低电压。
第一台闭合铁心变压器，在铁心柱外有绕组的变压器，是 1884年9月16日由德利、伯拉锡和济拍劳斯基在匈牙利的 干茨工厂制造出来的，这台变压器是单相变压器，容量为 1400VA，电压比为120/72V，频率为40Hz(见下图)，并在 他们的专利申请中首次使用“变压器”这一术语。 1885年在布达佩斯展览会上展出了这台设备。 美国人威斯汀豪斯(Westinghouse)买了几台高纳德和 吉伯斯的交流电压变换设备及其专利、开始重新进行机械 和电气设计。1886年第1台用于交流照明系统的变压器投 入使用并获得成功，随后这一项技术得到迅速的发展。 1890年AEG(原德国通用电气公司)工厂的多里弗多布 罗夫斯基发明了三相变压器。
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Categories of transformer 变压器的分类
• Single phase transformer Three phase transformer
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step down and step up transformer
• Transformers have two coils , the supply voltage is fed into ‘the Primary’ coil, and the new transformed voltage is taken from the ‘secondary’ coil. A transformer which gives a lower voltage than the supply voltage is known as a step down transformer, while a transformer which gives a higher voltage output is called a step up transformer. • 变压器有两个线圈，电源进入初级线圈，次级线圈输出 不同电压的电源。如果初级电压高于次级电压的变压器 称为降压变压器。反之，称为升压变压器。
100 200 = 24000 120V
12
= 24000 = 200
Question
a transformer has 500 turns on it’s primary winding, and is connected to a 240V 50Hz supply. What would be the voltage in the secondary winding if there are 7500 turns of wire on it? 一个变压器初级线圈是500匝240伏50赫兹，如果次级线圈是7500 匝 求次级电压是多少？