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  • 变换器

    Electrical transformers mounted on a utility pole, used for voltage regulation in power transmission.

    Power loss in long transmission lines is related to the magnitude of the current. Specifically, the power loss can be decreased by decreasing the magnitude of the current.
    ::长输电线断电与电流的强度有关,具体来说,可以通过降低电流的强度来减少电流的断电。

    The amount of power passed through transmission lines can be calculated by multiplying by current. The same power can be transmitted using a very high voltage and a very low current as with a low voltage and high current.
    ::通过输电线路输送的电量可以通过电流乘以乘以来计算。同样的电能可以使用非常高的电压和非常低的电流来传输,与低的电压和高的电流一样。

    Since power companies do not wish to waste power as it is transmitted to homes and businesses, they deliberately 'step up' the voltage and reduce the current before transmitting the power over extended distances. That type of power transmits well without great loss of but it cannot be used in household appliances. It becomes necessary to convert it back ('step down') to low voltage and high current for household use. That is the job of electrical transformers – those big gray barrels you see on power poles.
    ::由于电力公司不想浪费电力,因为电力被传送到家庭和企业,它们故意“加快”电压,降低电流,然后将电流传送到远方。 这种电能在没有重大损失的情况下传播得很好,但不能用于家用电器。 有必要将电能转换为低电压(“降低 ” ) 和高电流,供家庭使用。 这是变压器的工作 — — 你在电线杆上看到的那些大灰色桶。

    Transformers
    ::变换器

    When we move a wire through a , a force is exerted on the charges in the wire and a current is induced. Essentially the same thing happens if we hold the wire steady and move the magnetic field by moving the . Yet a third way of causing relative motion between the charges in a wire and a magnetic field is to expand or contract the field through the wire.
    ::当我们通过电线移动电线时,电线电线的电荷会受到压力,电流也会被诱发。基本上,如果我们保持电线稳定,通过移动电磁场移动磁场,同样的事情也会发生。然而,电线电线和磁场之间产生相对运动的第三个方法是通过电线扩大或收缩电场。

    When a current begins to flow in a wire, a circular magnetic field forms around the wire. Within the first fractional second when the current begins to flow, the magnetic field expands outward from the wire. If a second wire is placed nearby, the expanding field will pass through the second wire and induce a brief current in the wire.
    ::当一个电流开始在一条电线中流动时,一个圆形磁场围绕电线形成。当电流开始流动时,在第一小秒内,磁场从电线向外延伸。如果在附近放置第二小条电线,扩大的电场将穿过第二小条电线,并在电线中引起一小串电流。

    Sketch illustrating current flow and magnetic field interactions in a transformer setup.

    Consider the sketch above. When the knife switch is closed, current begins to flow in the first and therefore, a magnetic field expands outward around the wire. When the magnetic field expands outward from the wire on the right side, it will pass through the wire in the second circuit. This relative motion between wire and field induces a current in the second circuit. The magnetic field expands outward for only a very short period of time and therefore, only a short jolt of current is induced in the second circuit. You can leave the knife switch closed and the current will continue to flow in the first circuit but no current is induced in the second circuit because the field is constant and therefore there is no relative motion between the field and the wire in the second circuit. When the knife switch is opened, the current in the first circuit ceases to flow and the magnetic field collapses back through the wire to zero. As the magnetic field collapses, it passes through the wire and once again we have relative motion between the wire in the second circuit and the magnetic field. Therefore, we once again have a short jolt of current induced in the second circuit. This second jolt of induced current will be flowing in the opposite direction of the first induced current. We can produce an alternating current in the second circuit simply by closing and opening the knife switch continuously in the first circuit. 
    ::考虑上面的草图。 当刀切开关关闭时, 电流开始在第一个电路中流动, 因此, 磁场会向外扩展。 当磁场从右侧的电线向外扩展时, 它会在第二个电路中穿过电线。 电线和字段之间的相对运动在第二个电路中引出电流。 磁场向外扩张的时间很短, 因此, 第二电路中只能导出一小点电流。 您可以离开刀开关, 电流将继续在第一个电路中流动, 但是第二电路中不会发生电流, 因为电磁场是固定的, 因此在第二个电路中, 磁场和电线之间没有发生相对的电流。 当打开刀开关时, 第一个电路的电流将停止流, 磁场的电流会回流到零。 当磁场坍塌时, 电流在第二个电路和磁场的电线之间再次发生相对的移动。 因此, 我们再次在第二个电路中会有一个短的电流在第二个电流流中, 。 第二次电流的电流的第二个电流将不断的电流将持续向向向向向向向回流中, 。

    Obviously, a transformer would have little use in the case of DC current because current is only induced in the second circuit when the first circuit is started or stopped. With AC current, however, since the current changes direction 60 times per second, the magnetic field would constantly be expanding and contracting through the second wire. 
    ::显然,变压器在DC洋流的情况下用处不大,因为电流只在第一场电路启动或停止时在第二场电路中诱导。 然而,由于AC洋流每秒60次改变方向,磁场将不断扩张,并通过第二场电线收缩。

    A transformer is a device used to increase or decrease alternating current voltages. They do this with essentially no loss of energy. A transformer has two coils, electrically insulated from each other as shown in the sketch. One coil is called the primary coil and the other is called the secondary coil . When the primary coil is connected to a source of AC voltage, the changing current creates a varying magnetic field. The varying magnetic field induces a varying EMF in the secondary coil. The EMF induced in the secondary coil is called the secondary voltage and is proportional to the primary voltage. The secondary voltage also depends on the ratio of turns on the secondary coil to turns on the primary coil.
    ::变压器是用来增加或减少交替电流电压的装置。 它们基本上不会失去能量。 变压器有两圈, 如素描所示, 电绝缘。 一个卷被称为主线圈, 另一卷称为二次线圈。 当主线圈与电压源连接时, 变化的电流会产生一个不同的磁场。 不同的磁场在二次电流中诱发了不同的电磁场。 二级电流中诱发的电磁场被称为次电压, 与主电流成比例。 二级电流也取决于二级电流的旋转率, 以打开主电流。

    A Step-Up And Step-Down Transformer With Primary And Secondary Coils Labeled.

    @$$\begin{align*}\frac{\text{secondary voltage}}{\text{primary voltage}} &= \frac{\text{number of turns on secondary}}{\text{number of turns on primary}}\\ \frac{V_S}{V_P} &= \frac{N_S}{N_P}\end{align*}@$$
    ::@ $\ begin{ align}\ frac} text{ 主要电压} {\ frac\ text} =\ frac\ text{ 次要电压} =\ text{ 翻转次数} =\ frac{ V_ S_ V_ P} =\ frac{ N_ S\\ n_ P_ end} ALign} 翻转次数 =$

    If the secondary voltage is larger than the primary voltage, the transformer is called a step-up transformer . If the voltage out of the transformer is smaller than the voltage in, then the transformer is called a step-down transformer .
    ::如果二次电压大于一次电压,变压器就称为递升变压器。如果变压器的电压小于电压,那么变压器就称为递降变压器。

    In an ideal transformer, the electric power put into the primary equals the electric power delivered by the secondary.
    ::在一个理想的变压器中,电力投入到初级电源中,等于由二级电源输送的电能。

    @$$\begin{align*}V_PI_P = V_SI_S\end{align*}@$$
    ::@ $\ begin{ ALIGN} @ V_ PI_ P = V_ SI_ S\ end{ ALIGIN} $

    The current that flows in the primary depends on how much current is required by the secondary circuit.
    ::初级电流的流量取决于二级电路需要多少电流。

    @$$\begin{align*}\frac{I_S}{I_P}=\frac{V_P}{V_S}=\frac{N_P}{N_S}\end{align*}@$$
    ::@$\ begin{ align} frac{ I_ SI_ Pfrac{ V_ PV_ Sfrac{ N_ PN_ Send{ align} $

    Example  
    ::示例示例示例示例

    A particular step-up transformer has 200 turns on the primary coil and 3000 turns on the secondary coil.
    ::一种特定的升级变压器在主螺旋上有200个开关,在二级螺旋上有3000个开关。

    1. If the voltage on the primary coil is 90.0 V, what is the voltage on the secondary coil?
      ::如果主螺旋上的电压是90.0V,二级螺旋上的电压是多少?
    2. If the current in the secondary circuit is 2.00 A, what is the current in the primary coil?
      ::如果二次电路中的电流是2.00 A,主线圈中的电流是什么?
    3. What is the power in the primary circuit?
      ::主电路的动力是什么?
    4. What is the power in the secondary circuit?
      ::二级电路的动力是什么?

     

    1. @$\begin{align*}\frac{V_P}{V_S}=\frac{N_P}{N_S} \qquad \frac{90.0 \ V}{V_S}=\frac{200}{3000} \qquad V_S=\frac{(90.0 \ V)(3000)}{(200)}=1350 \ V\end{align*}@$
      ::@ $\ begin{ legin{ legn{ rac{ V_ PV_ Sfrac{ N_ PN_ S}\ qqquad\ frac{ 90.0\ VV_ Sfrac{ (90.0 \ V)( 3000)\ (200)\\\ 1350\ V\ end{ ALign} \ qqquad V_ Sfrac{ (90.0 \ V)( 3000)\ (200)\\/1350\ V\ end{ ALign}
    2. @$\begin{align*}\frac{I_S}{I_P}=\frac{N_P}{N_S} \qquad \frac{2.00 \ A}{I_P}=\frac{200}{3000} \qquad I_P=30.0 \ A\end{align*}@$
      ::@$\ begin{ legin{ legn{ I_ SI_ Pfrac{ N_ PN_ n_ S}\ qquad\ frac{ 2. 00\ AI_ Pfrac{ 200\\ 3000}\ qqquad I_ P=30.0\ A\ end{ align}
    3. @$\begin{align*}P_P = V_PI_P = (90.0 \ V)(30.0 \ A) = 2700 \ W\end{align*}@$
      ::@$\ begin{align}}P_P = V_PI_P = (90.0 \ V) (30.0 \ A) = 2700 \ W\ end{align$ = (90.0 \ V) (30.0 \ A) = 2700 \ W\ end{align$ ) </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> <span class="x-ck12-mathEditor" data-contenteditable="false" data-edithtml="" data-math-class="x-ck12-math" data-mathmethod="inline" data-tex="P_S%20%3D%20V_SI_S%20%3D%20(1350%20%5C%20V)(2.00%20%5C%20A)%20%3D%202700%20%5C%20W"> @$\begin{align*}P_S = V_SI_S = (1350 \ V)(2.00 \ A) = 2700 \ W\end{align*}@$
      ::@$\ begin{ legin{ p_ S = V_ SI_ S = (1350 \ V) (2. 00 \ A) = 2700 \ W\ end{ end{ ALign$ = (1350 \ V) = 2,00 \ A) = 2,700 \ W\ end{ end{ laign$ $ 。 </span> </li> </ol> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <p id="x-ck12-NDVmOTI3ZGYxOGRmYWRlYzkwMjkyZGJjYTcwOTk1NzA.-0ho"> <span style="font-weight: 400;"> Launch the AC Transformer simulation below to visualize how we use a transformer to “step down” the high voltage on a residential power line:   </span> <br/> <span style="color: green; "> ::启动下面的AC变压器模拟, 以直观地显示我们如何使用变压器“降低”住宅电线的高电压: </span> </p> <div class="x-ck12-video-object" id="x-ck12-sgq"> <div class="iframe-wrapper ck12-no-annotation"> <iframe data-artifactlang="en" frameborder="0" height="225" id="x-ck12-MTUwNDI5MTkwNDcwNg.." longdesc="Learn%20about%20how%20high-voltage%20alternating%20current%20%28AC%29%20electricity%20generated%20by%20a%20power%20station%20is%20converted%20into%20low-voltage%20AC%20electricity%20for%20your%20home." name="192167" src="https://flexbooks.ck12.org/flx/show/interactive/http%3A//www.ck12.org/embed/%23module%3Dlauncher%26artifactID%3D1916732%26nochrome%3Dtrue%3Fhash%3D6a1687567566ec81eefe342962007372" style="max-width: 100%;" title="video" width="620"> </iframe> </div> </div> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <h3> Further Reading <br/> <span style="color: green; "> ::继续阅读 </span> </h3> <ul id="x-ck12-M2VkYjY1NGE1NDE4ZjA2OGY5ZWVmYjk1MDQ0ZGY2OTA.-n6b"> <li> </li> </ul> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <h3> Summary <br/> <span style="color: green; "> ::摘要 </span> </h3> <ul id="x-ck12-NjgyOGUyOTVhY2Q5MjdkYjE1ZGI2ZWRlMjhhZjdmMTM.-ful"> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> When a current begins to flow in a wire, a circular magnetic field forms around the wire. <br/> <span style="color: green; "> ::当电流开始在铁丝中流动时,电线周围形成一个圆形磁场。 </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> Within the first fractional second when the current begins to flow, the magnetic field expands outward from the wire. <br/> <span style="color: green; "> ::当水流开始流动时,磁场从电线向外扩张。 </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> If a second wire is placed nearby, the expanding field will pass through the second wire and induce a brief current in the wire. <br/> <span style="color: green; "> ::如果第二根电线被放置在附近,扩大的电场将穿过第二根电线,并诱发电线中的短流。 </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> A transformer is a device used to increase or decrease alternating current voltages. <br/> <span style="color: green; "> ::变压器是一种用于增减交替电流电压的设备。 </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> A transformer has two coils, electrically insulated from each other. One coil is called the primary coil and the other is called the secondary coil. <br/> <span style="color: green; "> ::变压器有两个线圈, 电绝缘。 一个称为主线圈, 另一个称为第二线圈。 </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> The varying magnetic field induces a varying EMF in the secondary coil. <br/> <span style="color: green; "> ::不同的磁场在二级圆圈中诱发了不同的EMF。 </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> The EMF induced in the secondary coil is called the secondary voltage and is proportional to the primary voltage. The secondary voltage also depends on the ratio of turns on the secondary coil to turns on the primary coil. <br/> <span style="color: green; "> ::二级电线圈诱发的电磁放大系数称为二级电压,与一级电压成比例,二级电压还取决于二级电线圈的转动比率,即第一级电线圈的转动比率。 </span> </li> </ul> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <p class="x-ck12-indent" id="x-ck12-ejk"> <span class="x-ck12-mathEditor" data-contenteditable="false" data-edithtml="" data-math-class="x-ck12-math" data-mathmethod="inline" data-tex="%5Cfrac%7B%5Ctext%7Bsecondary%20voltage%7D%7D%7B%5Ctext%7Bprimary%20voltage%7D%7D%3D%5Cfrac%7B%5Ctext%7Bnumber%20of%20turns%20on%20secondary%7D%7D%7B%5Ctext%7Bnumber%20of%20turns%20on%20primary%7D%7D"> @$\begin{align*}\frac{\text{secondary voltage}}{\text{primary voltage}}=\frac{\text{number of turns on secondary}}{\text{number of turns on primary}}\end{align*}@$
      ::@ $\ begin{ ligin{ leger}\ frac\ text{ 二级电压{ text{ 主要电压} _frac\ text{ 二次的转弯次数} < text{ 初级的转弯次数}\ end{ ALign} ?

      Review
      ::回顾

      1. A step-down transformer has 7500 turns on its primary and 125 turns on its secondary. The voltage across the primary is 7200 V.
        1. What is the voltage across the secondary?
          ::二级的电压是多少?
        2. The current in the secondary is 36 A. What current flows in the primary?
          ::中学的当前是36A。 小学的当前流动是多少?

        ::二级电压为 7200 V。 二级电压是 7200 V 。 二级电压是 多少? 二级电流是 36 A 。 初级电流是什么?
      2. The secondary of a step-down transformer has 500 turns. The primary has 15,000 turns.
        1. The EMF of the primary is 3600 V. What is the EMF of the secondary?
          ::小学的EMF是3600 V。 中学的EMF是什么?
        2. The current in the primary is 3.0 A. What is the current in the secondary?
          ::小学的水流是3.0 A. 中学的水流是什么?

        ::递减变压器的二级是500转。 一级是15,000转。 初级的EMF是3600 V。 二级的EMF是什么? 初级的当前是3. 0 A。 二级的当前是什么?
      3. An ideal step-up transformer’s primary coil has 500 turns and its secondary coil has 15,000 turns. The primary EMF is 120 V.
        1. Calculate the EMF of the secondary.
          ::计算二级的EMF。
        2. If the secondary current is 3.0 A, what is the primary current?
          ::如果二流电流是3.0A,主要电流是什么?
        3. What power is drawn by the primary?
          ::原主的力量是什么?

        ::理想的逐步升级变压器的主要螺旋有500个旋转,其二级螺旋有15,000个旋转。 主要的EMF是120 V. 计算二级的EMF。 如果二级电流是3.0 A,那么主要电流是什么? 初级电流是什么?

      Explore More
      ::探索更多

      Use this resource to answer the questions that follow.
      ::使用此资源回答下面的问题 。

       

      1. What type of transformer is used at the power station where the electric power is generated?
        ::在发电的发电站使用何种变压器?
      2. What type of transformer is used at power sub-stations? 
        ::电源分站使用哪种变压器?
      3. What type of transformer is used inside cell phone chargers?
        ::何种变压器在手机充电器中使用?