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The article presents the developing condition of PWM and SVPWM first.Then the theory of SVPWM is discussed in detail.The SVPWM is based on the thought of magnetic chain tracking.It makes the ideal magnetic chain circle of three-phased sysmmetry electric motor supplied by three-phased sysmmetry sine wave voltage for basis,uses the practical magnetic chain vector formed by the different switch modes of three-phased inverter to track the basic magnetic chain circle.During the course of tracking,the inverter changes the switch modes properly to form the PWM waves.Then the modulation wave of SVPWM is analyzed in detail.The modulation wave of SVPWM is implicit,but the analogous modulation wave in A-B-C axis needs to be calculated in order to expose the internal relation of SVPWM and SPWM.That is to show the implicit modulation wave of SVPWM. SVPWM actually is a transformed SPWM ruly sampled by the modulation wave which is injected by the zero prefaces based on space vectors.

本文首先对脉宽调制技术的发展现状进行了综述，在此基础上分析了电压空间矢量脉宽调制技术的发展现状；接着对空间电压矢量脉宽调制技术的基本原理进行了详细的分析和推导，SVPWM是基于磁链追踪的思想，它以三相对称正弦波电压供电下三相对称电动机定子理想磁链圆为基准，由三相逆变器不同开关模式下所形成的实际磁链矢量来追踪基准磁链圆的，在追踪的过程中，逆变器的开关模式作适当的切换，从而形成PWM波；然后详细分析了电压空间矢量脉宽调制技术的调制波，虽然SVPWM法的调制波是隐含的，但是为了揭示SVPWM法与SPWM法的内在联系，需要求出SVPWM在A-B-C坐标系上的等效调制波，也就是将SVPWM的隐含调制波显化；SVPWM实质是一种基于空间矢量在三相正弦波中注入了零序分量的调制波进行规则采样的一种变形SPWM。

Placing the switch in the test position illuminates the indicator lights, and placing the switch in the dim position dims them.

将开关置于测试位照亮指示器灯光，驾驶舱指示器系统的灯光可通过中央面板上的&灯光&开关来调暗或测试。

The main products are: timer; counter; photoelectric switch; close switch; temperature controller; solid-state relay; security screens, etc..

主要产品有：计时器；计数器；光电开关；接近开关；温度控制器；固态继电器；安全光幕等。

Switch force and inadequate displacement of elastic bending switch rail is one of the key parameters in the design of turnout.

随着列车提速和客运专线的建设，道岔的设计也由静态设计向动态设计转变，弹性可弯尖轨及心轨的扳动力及不足位移是道岔设计中的关键问题。

The design techniques of multi-channel field distortion switch were studied and a 200kV/100kA ring rail electrode switch was designed and tested.

成功设计和研制了200kV/100kA环型轨道式场畸变开关和200kV激光触发多级多通道开关，达到了国内先进水平。

Obviously,uses electricity between the rail switch handle and the signal handle locks the relation to obtain the interconnection relations,also not both distance limit far and near,also not rail switch number how many influence.

显然，在道岔握柄和信号握柄间用电锁器联系取得联锁关系，既不受两者距离远近的限制，也不受道岔数多少的影响。

Locks the contact through side rail switch electricity to control opposite party signal electromagnetism to lock the electric circuit which the electricity locks,realizes the semaphore interconnection between the semaphore and the rail switch as well as.

通过一方道岔电锁器的接点控制对方信号电磁锁器电锁的电路，以实现信号机和道岔间以及信号机相互间的联锁。

The electricity locks the interconnection separately supposes the electricity on the rail switch and the signal handle to lock,the electricity locks on has the contact separately on behalf of the rail switch and the signal position.

电锁器联锁分别在道岔和信号握柄上设电锁器，电锁器上有接点分别代表道岔和信号位置。

The camber near the switch point changes rather slowly, while it changesrapidly at certain distance range from switch rail.

建议尖轨轨头非工作边的刨切曲线采用缓和曲线和圆曲线的组合线型，在尖轨理论尖端至圆曲线之间，为一曲率渐变的缓和曲线，在尖轨尖端附近矢度变化较慢，而在距尖轨一定范围时，矢度变化较快。

Pay attention to keeping the switch of electric actuator in line with the switch of the valve when installing.

安装时，注意使执行器的开关与阀门的开关一致。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了