变频调速
The speed of standard induction motors can be controlled by variation of the frequency of the voltage applied to the motor. Due to flux saturation problems with induction motors, the voltage applied to the motor must alter with the frequency. The induction motor is a pseudo synchronous machine and so behaves as a speed source. The running speed is set by the frequency applied to it and is independent of load torque provided the motor is not over loaded.
标准的感应电动机可通过改变施加到电动机上的频率和电压控制电动机的旋转速度。由于感应电动机存在磁饱和的问题，施加在电动机上的电压必须随频率的变化而变。感应电动机是准同步电动机，因此是速度的来源。在电动机没有过载的情况下，电动机的旋转速度是由施加在其上的频率决定的，而不是由负载转矩决定的。
1．Vector drives have a mathematical model of the drive in software and by measuring the current vectors in relation to the applied voltage, they are able to maintain a constant field at all frequencies below the line frequency. These drives need to be tuned to the motor and typically include a self tuning algorithm that is enabled at commissioning to determine the component values for the mathematical model. If the motor is replaced, the drive needs to be retuned to learn the characteristics of the new motors.
1. 矢量驱动装置建有软件化的驱动数学模型。通过测量与施加的电压相关联的电流矢量，矢量驱动装置能够在工频以下的所有频率保持恒定的磁场。这些矢量驱动装置需要调节以适应电动机。一般，矢量驱动装置都具有自校正算法。在调试过程中启用这种算法以
确定数学模型的分量值。如果更换了电动机，矢量驱动装置需要重新了解心电动机的特征。
Vector drives come in three major formats, closed loop, open loop and direct torque control. The closed loop controllers were the first vector controllers and are still the best option for accurate control at zero speed. The open loop vector and DTC are suitable for applications requiring good control above 3 – 5 Hz.
矢量驱动装置有以下三种主要类型：闭环控制、开环控制和直接转矩控制。闭环控制装置时最早使用的矢量控制器，并且仍然是零速度精确控制的最好选项。开环矢量控制和直接转矩控制适合于频率在3-5Hz以上的需要良好控制的场合。
Quite a number of modern drives can operate as V/Hz, open loop vector or closed loop vector just by changing a par ameter. – closed loop requires a shaft encoder to give accurate speed feedback.
许多现代驱动装置采用开环矢量或闭环矢量V/Hz控制方式，开环矢量或闭环矢量方式可通过改编参数选择。闭环控制要求加装转轴编码器以获得精确的速度反馈。
The major differentiation between modern VSDs are the enclosure, auxiliary functionality, programming and user interface. Low cost drives are often very poorly filtered and can create major RFI (EMC) issues. Some drives include no filtering and must be installed with external filters, and others include all the filtering required.
现代各种变速驱动（VSD）装置的主要差异在于机壳、辅助功能、程序编制和用户界
面。低成本的驱动装置通常滤波性能差并且会出现射频干扰（电磁兼容性）问题。有些驱动装置没有设计滤波功能，因而必须安装外部滤波装置，而另外一些驱动装置则设计有所需的滤波功能。
DC and AC reactors help to reduce the noise generated by the drive, and to improve the distortion power factor of the drive. 直流和交流电抗器有助于降低驱动装置产生的噪音，并且改善驱动装置的畸变功率因数。Because the drive rectifies the incoming supply, the current waveform is very distorted and so the harmonics are high.由于驱动装置对输入电源进行了整流，电流波形严重扭曲并且产生高次谐波。Low cost drives without the reactors have a very poor power factor. 没有装电抗器的低成本驱动装置的功率因数很差。Most drive manufacturers quote the cosφ as better than 0.95 implying a high power factor. 大多数驱动器装置的制造商报出的cosφ高于0.95。这意味着功率因数很高。While the displacement power factor is high, the distortion power factor can be less than 0.7. 当位移功率因数高时，畸变功率因数可地与0.7。Distortion power factor can not be corrected with capacitors, but can be improved with expensive filters. 畸变功率因数不可通过电容器修正，但可通过昂贵的滤波器改善。There are “active front end” drives or “regenerative” drives that have an inverter stage on the input as well as the output and these can draw sinusoidal current from the supply resulting in a high power factor. “主动前端”或“再生”驱动装置在输入侧和输出侧有倒相级，用于从电源吸取正弦电流，因而达到高的功率因数。It is possible that this technology may become a mandatory requirement at some time in the future.将来某个时候这项技术有可能会强制使用。
Drives are typically used in some form of automation process and so they are now including additional functionality and controls to simplify the automation process. There are a number of programmable inputs and outputs and relays and
most drives also include a PID loop.驱动装置一般都会用于某种形式的自动化过程。因此现在驱动装置都加装额外的功能和多种控制功能，从而简化自动化过程。驱动装置加装了大量的程控输入和输出以及继电器，并且大多数驱动装置都装有PID控制回路。
Vector drives and some V/Hz drives can be set up for speed control or torque control. 矢量驱动装置和某些V/Hz驱动装置可用于速度控制或转矩控制。 Torque control is used in tensioning applications such as paper machines where the master controls a winding drum and the diameter increases as the drum fills up. 转矩控制用于张紧操作，例如卷纸机。主机控制卷筒。当卷筒装满时，纸卷的直径增加。This requires other drive feeding the paper to run at different speeds. 这要求其它纸张输送驱动装置以不同的速度运行。Traditionally, this was achieved by DC machines as they naturally operate in torque mode.传统上，这中操作是通过直流电机实现的，因为直流电动机是以转矩模式运行的。
The speed of standard induction motors can be controlled by variation of the frequency of the voltage applied to the motor.可通过改编施加在电动机上的电压的频率控制 Due to flux saturation problems with induction motors, the voltage applied to the motor must alter with the frequency. The induction motor is a pseudo synchronous machine and so behaves as a speed source. The running speed is set by the frequency applied to it and is independent of load torque provided the motor is not over loaded.
因篇幅问题不能全部显示，请点此查看更多更全内容