直流电机的介绍_外文翻译.doc

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直流电机的介绍_外文翻译,全文word排版,附英文原文,内容完整,建议电气工程及其自动化专业下载参考。温馨提示:如有任何疑问,请联系值班客服。缺少网用心做好文档,谢谢支持。下面截取文档一部分内容   直流电机的特点是他们的多功用性。依靠不同的并励、串励和他励励磁绕组的组合,他们可以被设计为动态的和静态的运转方式从而呈现出...
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直流电机的介绍_外文翻译

全文word排版,附英文原文,内容完整,建议电气工程及其自动化专业下载参考。

温馨提示:如有任何疑问,请联系值班客服。缺少网用心做好文档,谢谢支持。


下面截取文档一部分内容

   
直流电机的特点是他们的多功用性。依靠不同的并励、串励和他励励磁绕组的组合,他们可以被设计为动态的和静态的运转方式从而呈现出宽广范围变化的伏安特性或速度转矩特性。因为它简单的可操纵性,直流系统经常被用于需要大范围发动机转速或精确控制发动机的输出量的场合。
   
直流电机的总貌如图所示。定子上有凸极,而且由一个或几个励磁线圈励磁。气隙磁通量以磁极中心线为轴线对称分布。这条轴线叫做磁场轴线或直轴。
   
我们都知道,在每个旋转电枢线圈中产生的交流电压,经由一与电枢联接的旋转的换向器和静止的电刷,在电枢线圈出线端转换成直流电压。换向器-电刷组合构成了一个机械整流器,它形成了一个直流电枢电压和一个被固定在空间中的电枢磁势波形。电刷的位置应使换向线圈也处于磁极中性区,即两磁极之间。这样,电枢磁势波的轴线与磁极轴线相差90度,也就是在交轴上。在示意图中,电刷位于交轴上,因为这是线圈和电刷相连的位置。这样,电枢磁势波的轴线也是沿着电刷轴线的(在实际电机中,电刷的几何位置大约偏移图例中所示位置90度,这是因为元件的末端形状构成图示结果与换向器相连)。电刷上的电磁转矩和旋转电势与磁通分布的空间波形无关;为了方便我们可以假设在气隙中有一个正弦的磁通密度波形。转矩可以从磁场的观点分析得到。
   
转矩可以用每个磁极的直轴气隙磁通和电枢磁势波的空间基波分量相互作用的结果来表示。在交轴上的电刷和这个磁场的夹角为90度,其正弦值等于1,对于一台极电机


D.C. machines are characterized by their versatility. By means of various combinations of shunt-, series-, and separately excited field windings they can be designed to display a wide variety of volt-ampere or speed-torque characteristics for both dynamic and steady state operation. Because of the ease with which they can be controlled, systems of D.C. machines are often used in applications requiring a wide range of motor speeds or precise control of motor output.
   
The essential features of a D.C. machine are shown schematically. The stator has salient poles and is excited by one or more field coils. The air-gap flux distribution created by the field winding is symmetrical about the centerline of the field poles. This is called the field axis or direct axis.
   
As we know, the A.C. voltage generated in each rotating armature coil is converted to D.C. in the external armature terminals by means of a rotating commutator and stationary brushes to which the armature leads are connected. The commutator-brush combination forms a mechanical rectifier, resulting in a D.C. armature voltage as well as an armature m.m.f. Wave then is 90 electrical degrees from the axis of the field poles, i.e. in the quadrature axis. In the schematic representation the brushes are shown in quadrature axis because this is the position of the coils to which they are connected. The armature m.m.f. Wave then is along the brush axis as shown. (The geometrical position of the brushes in an actual machine is approximately 90 electrical degrees from their position in the schematic diagram because of the shape of the end connections to the commutator.)
   
The magnetic torque and the speed voltage appearing at the brushes are independent of the spatial waveform of the flux distribution; for convenience we shall continue to assume a sinusoidal flux-density wave in the air gap. The torque can then be found from the magnetic field viewpoint.

The torque can be expressed in terms of the interaction of the direct-axis air-gap flux per pole and space-fundamental component of the armature m.m.f.wave. With the brushes in the quadrature axis the angle between these fields is 90 electrical degrees, and its sine equals unity. For a pole machine