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变频器与传动

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驱动器世界（下）

2008-6-24 15:07:01　中国传动网翻译　供稿

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无刷伺服驱动器

    无刷伺服驱动器有交流无刷和直流无刷两种。反馈设备决定了是用直流还是用交流，自从规定了控制方案，反馈设备可以是Hall传感器、编码器或是分析器中的任意一个。当具备Hall传感器反馈时，三相无刷电机会在某一时刻由三个线圈中的两个供以动力。
    一个机械旋转过程有六个不同的交换部分，在每一个交换部分，都会应用直流供电。DC应用的数量，将与运行的电机速度直接成比例。因此，DC无刷在这里比较适用。当电机线圈在持续工作的情况下，并应用正弦波时，则应用AC无刷。自从电机拥有三相正弦反电动势起，其将由三相驱动电流波供以动力，并获得“额外转矩”。针对相同转矩重新获项，与直流无刷驱动相比，交流刷驱动要求的电流要小一些。

    针对此原因，交流无刷包装非常流行。此外，其有可能适用于更小型的电机。该控制设计降低了转矩波动并提供了很好的低速运转环境。
    无刷电机设计用于提供一个优化的扭矩每次封装尺寸并提高了扭矩到惯量的比率，还提供了快速的增量，精确的定位。
    无刷技术的优势包括高速，包装体积小、扭矩高，惯量低（更快的加速度）。当然，还有在使用过程中的长期可靠的维护周期。这也是为什么它们被应用在机器人、包装、电子组装、半导体设备、纺织、切割、印刷或标签行业，甚至是在移动网上执行。当然也有其它应用。

对照比较

    变频器控制目前可达500hp.
    该技术被充分应用在开路可调速应用中。表1对各种闭环驱动技术进行了比较。矢量驱动器的速度可高达800hp。这些可被用在可调速应用中，用于改善速度控制或是用于定位应用。
    商用的无刷驱动通常能达到15hp, 用户定制设计可达60hp, 专业设计可提供更高的马力。无刷伺服驱动的优势就是它在小型包装中的快速定位能力。在选择驱动包装时，适当的定型选择、加速力矩、包装尺寸和惯性匹配都必须考虑。
    表1 驱动技术比较

直线驱动

    首先，让我们先定义一个直线电机。想象一个旋转马达被切割打开，就会出现一个扁平的线性电机。无论产品是旋转的还是线性的，可以应用相同的电动机械原理。
    例如，一个永磁直流旋转电机与永磁直线电机相似，一个交流感应鼠笼式电机与一个感应直线电机相似。相同的电磁力量，既在旋转电机上产生“扭矩”，又可在直线电机中产生“动力”。直线电机与旋转电机应用相同的控制和编程定位控制器。
    在发明直线电机之前，仅有的办法就是制造直线过程，利用气压或水压缸，利用滚珠螺杆或带子和滑轮，将旋转运动转化成旋转运动。
    有时，选择另一个过程技术或许是一个更好的选择。但是每一个应用都应被应用。
    直线电机的优势包括有：很高的加速度、高速和低速应用、小冲程和长冲程及亚微米位置精度。

原文下载

original text

The World of Drives

By John Mazurkiewicz Baldor Electric

   Brushless servo drives
    Brushless servos are available as either DC brushless or AC brushless. The feedback device determines whether it is considered DC or AC, since this dictates the control scheme. The feedback device may be either Hall sensors, encoders, or resolvers.
    With Hall sensor feedback, the three–phase brushless motor is powered by energizing two of the three motor windings at a time.
    There are six different commutation sections for one mechanical revolution, and within each commutation section, a DC level of power is applied. The amount of DC applied, is directly proportional to the desired operating motor speed. Thus the term “DC brushless”. When a sinusoidal waveform is applied on the motor windings on a continuous basis, the term “AC brushless” is used. Since the motor has a three phase sinusoidal back–emf, and it is being powered by a three phase driving current waveform, “extra torque” is available. Or re–phrasing, for the same torque （compared to a “DC brushless” drive）, the “AC brushless” drive will require less current.
    For this reason, the AC brushless packages are popular. In addition, it may be possible to use a smaller sized motor. This control scheme reduces torque ripple and provides good low speed operating conditions.
    Brushless motors are designed to provide an optimized–torque–per–package size and improve the torque–to–inertia ratio. They also offer rapid incrementing and accurate positioning.
    Advantages of brushless technology include higher speed capability, higher torques in a smaller package, much lower inertia （thus much faster acceleration capability）, and of course, long reliable maintenance free life in applications. That’s why they are used in robotics, packaging, electronic assembly, semiconductor equipment, textile, cutting, printing or labeling which may even be performed on a moving web. Many other applications of course exist.
    Comparison
    Inverter controls are presently available through 500 hp
    This technology works adequately in open loop adjustable speed applications. Table 1 presents a comparison of the various closed loop drive technologies. Vector drives are available up through 800 hp These can be used in adjustable speed application for improved speed control, or in a positioning application.
    Commercially available brushless drives typically range through 15 hp, custom designs range to 60 hp, and specialty designs provide higher hp. The advantage of brushless servos would be the rapid positioning capability, in a smaller package size. For proper sizing and selection, acceleration torque, package size, and inertia matching, all should be considered when selecting a drive package for the application.
    Linear drives
    First of all let’s define a “linear” motor. Imagine that a rotary motor is cut open and unrolled. The result is a flat linear motor. The same electromechanical principles apply – whether the product is rotary or linear.
    For example, a permanent magnet DC rotary motor is similar to a permanent magnet linear motor; and an AC induction squirrel cage motor is similar to an induction linear motor. The same electromagnetic force that produces “torque” in a rotary motor also produces “force” in a linear motor. The linear motor uses the same controls and programmable position controllers as rotary motors.
    Prior to the invention of linear motors, the only way to produce linear motion was to use either pneumatic or hydraulic cylinders or to translate rotary motion into rotary motion using ball screws or belts and pulleys.
    Sometimes these other linear motion technologies may be a better choice. But each application has to be investigated.
    Advantages of linear motors include high acceleration, low speed and high speed capability, small strokes and long strokes, and sub–micron position accuracy.

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