电力绞车的控制外文翻译、中英文翻译、外文文献翻译

1 英文原文 Electrical Winch Controls by Tom Young The form of motor control we all know best is the simple manual station with up and down pushbuttons. While these stations may still be the perfect choice for certain applications， a dizzying array of more sophisticated controls is also available. This article addresses the basic electrical requirements of the motors and user interface issues you will need to address before spcifying， building or buying winch controls. begin with， the manual control stations should be of the hold-to-run type， so that if you take your finger off of the button the winch stops. Additionally， every control station needs an emergency stop (E-stop) that kills all power to the winch， not just the control circuit. Think about it if the winch isnt stopping when it should， you really need a failsafe way to kill the line power. Its also a great idea to have a key operated switch on control stations ， especially where access to the stations is not controlled. Safe operation by authorized personnel must be considered when designing even the simplest manual controls. Controlling Fixed Speed Motors The actual controlling device for a fixed speed winch is a three phase reversing starter. The motor is reversed by simply switching the phase sequence from ABC to CBA. This is accomplished by two three-pole contactors， interlocked， so they cant both be closed at the same time. The NEC requires both overload and short circuit protection. To protect the motor from overheating due to mechanical overloads a thermal overload relay is built into the starter. This has bi-metallic strips that match the heating pattern of the motor and trips contacts when they overheat. Alternatively， a thermistor can be mounted in the motor winding to 2 monitor the motor temperature. Short circuit protection is generally provided by fuses rated for use with motors. A separate line contactor should be provided ahead of the reversing contactor for redundancy. This contactor is controlled by the safety circuits: E-stop and overtravel limits. This brings us to limit switches. When you get to the normal end of travel limit the winch stops and you can only move it in the opposite direction (away from the limit). There also needs to be an overtravel limit in case， due to an electrical or mechanical problem， the winch runs past the normal limit. If you hit an overtravel limit the line contactor opens so there is no way to drive off of the limits. If this occurs， a competent technician needs to fix the problem that resulted in hitting the overtravel limit. Then， you can override the overtravels using the spring return toggle switch inside the starter as opposed to using jumpers or hand shooting the contactors. Variable Speed Requirements Of course， the simple fixed speed starter gets replaced with a variable speed drive. Heres where things start to get interesting! At the very least you need to add a speed pot to the control station. A joystick is a better operator interface， as it gives you a more intuitive control of the moving piece. Unfortunately， you cant just order any old variable speed drive from your local supplier and expect it to raise and lower equipment safely and reliably over kids on stage. Most variable speed drives wont ， as they arent designed for lifting. The drive needs to be set up so that torque is developed at the motor before the brake is released， and (when stopping) the brake is set before torque is taken away. For many years DC motors and drives provided a popular solution as they allowed for good torque at all speeds. The large DC motors required for most winches are expensive， costing many times what a comparable AC motor costs. However， the early AC drives were not very useful， as they had a very limited speed range and produced low torque at low speeds. More recently， as the AC drives improved， the low cost and plentiful availability of AC motors resulted in a transition to AC drives. There are two families of variable speed AC drives. Variable frequency inverters are well known and readily available. These drives convert AC to DC， then convert it back to AC with a different frequency. If the drive produces 30 Hz， a normal 60 Hz motor will run at half speed. In theory this is great， but in reality there are a couple of problems. First， a typical 60 Hz motor gets confused at a line frequency below 2 or 3 Hz， and starts to cog (jerk and sputter)， or just stops. 3 This limits you to a speed range of as low as 20:1 hardly suitable for subtle effects on stage! Second， many lower cost inverters are also incapable of providing full torque at low speeds. Employing such drives can result in jerky moves， or a complete failure to lift the piece exactly what you dont want to see when you are trying to start smoothly lifting a scenic element. Some of the newer inverters are closed loop (obtain feedback from the motor to provide more accurate speed control) and will work quite well. The other family of AC drives is flux vector drives. These units require an encoder mounted on the motor shaft allowing the drive to precisely monitor the rotation of the armature. A processor determines the exact vector of magnetic flux (thus flux vector drive) required to rotate the armature the next few degrees at a given speed. These drives allow an infinite speed range， as you can actually produce full torque at zero speed. The precise speed and position control offered by these drives make them a favorite in high performance applications. PLC-based controls provide system status as well as control options. This screen give the operator full access to Carnegie Halls nine stage floor lifts. PLC Based Systems A PLC is a programmable logic controller. First developed to replace the relay based industrial control systems of the 50s and 60s ， these controls are at home in rugged， industrial environments. These are modular systems with a great variety of I/O modules allowing semi-custom hardware configurations to be assembled easily at a reasonable price. These include position control modules， counters， A/D and D/A converters and all sorts of solid state or hard contact closure outputs. The great variety of I/O components and the modular nature of the PLC make this an effective way to build custom and semi-custom control systems. The greatest drawback to PLC systems is the lack of really great displays to tell you what they are doing or to help you program them. Monochrome and medium resolution color displays are the norm， as the primary use for these components in on a factory floor. One of the first major PLC systems used in a large entertainment venue is the 4 complex lift and wagon system at the original MGM Grand (now Ballys) in Las Vegas. Several manufacturers offer standard PLC-based systems and a host of semi-custom acoustic banner， shell， and lift control systems is also available. The ability to build custom systems from standard building blocks is the greatest strength of PLC-based controls. High End Controllers The most sophisticated rigging controllers go well beyond speed， time， and position control. They include the ability to write complex cues， record profiled moves， and manage multiple cues running at once. Many of the larger opera houses are moving toward point hoist systems， where there is a separate winch for each lift line (the rigging equivalent of dimmer per cir cuit). When multiple winches are used to carry a single piece， the winches must be perfectly synchronized， or the load can shift so that an individual winch can become dangerously overloaded. The control system must be able to keep selected winches in synch or provide a rapid， coordinated stop if a winch is unable to stay in synch with the others. With a typical top speed of of each other 240 fpm and a requirement to keep the winches within a 1/8 ， you have less than three milliseconds to recognize a problem， attempt to correct the errant winchs speed ， determine that youve failed and initiate a coordinated stop of all the winches in the group. This takes a lot of computing， fast I/O， and well-written software. There are two very different approaches to large rigging control systems. Originally， a single console was used， with the usual problem of where it should be located for the operators optimum view. Unfortunately this can change not only from show to show， but also from one cue to the next. This dilemma has been partially addressed by using video cameras at different locations in conjunction with 3D screen graphics that allow the operator to view the expected rigging motion three dimensionally from any viewpoint. This allows the operator to view the on screen movement of the rigging from a viewpoint that matches his actual view of the stage， or the actual view of a closed circuit camera. For complex moves with inter-related pieces this makes the control and understanding of what is happening much simpler. The other approach is a distributed system， with several portable consoles. This allows different operators to control different aspects of the rigging， in the same manner we have done with manual sets. A dramatic example of this approach is used by the Royal Opera at Covent Garden， where there are ten consoles controlling a total of 240 motors. Each console has five playbacks， and is set up so that each motor is assigned to a single console. One operator and console could control everything， but frequently one console may be running stage lifts， another the onstage rigging， and a third is being used backstage to move stored drops. 5 Cutting-edge portable consoles allow multiple operators to control the action from the best vantage points and provide 3D displays. Reprinted from PROTOCOL， the Journal of the Entertainment Services and Technology Association () Fall 2003 issue. 2003 ESTA. Conclusion The tremendous variety of rigging control systems currently available ranges from the pushbutton station to complex multi-user computerized control system. When shopping for rigging control systems you generally get what you pay for. The most important features are safety and reliability. These are features with real value， and you should expect to pay a fair price for this security. Work with an established manufacturer who can show you working installations and who will put you in contact with users who have requirements similar to yours. 中文译文 6 电力绞车的控制 对于电动机的控制，我们所知道的最好的方式就是使用由许多点动式按钮组成的简单的手工操作台。而这种操作台在某些应用方面可能仍 然是个不错的选择，如一些令人头痛的复杂的控制也可以用。这篇文章讲述了，在你设计、组建或是购买绞车控制器之前，你必须对电动机的基本电气设备和你将需要寻址的用户接口命令进行编址。 首先，手动控制台应该是手动控制型的，因此，如果你把你的手指移开按钮，绞车就会停车。另外，每个控制工作站都需要配备紧急制动闸，紧急制动闸可以切断绞车的所有电源，而不仅仅是控制电路的。仔细想想看，如果绞车在该停车时，它却没有停下来，你就确实需要一种故障保障的方法去切断线路的电源。在控制工作台上设置一个关键操作开关，也是一个非常好 的主意，特 别是在通向工作站的线路不能控制时，就可以用那个开关来控制。 (在设计控制台时，即使是最简单的手工控制台，也要考虑设置由专门人员操作的安全操作按键。 ) 控制定速电动机 对于一台定速绞车的实际控制设备是一台三相起动器。电动机的转向被反向，是通过简单的开关控制相序从 A-B-C 变换到 C-B-A。这些动作被完成，是通过两个三磁极式电流接触器，而且它们是互锁的，所以，它们不可能被同时关闭。 NEC 公司要求同时拥有过载和短路保护装置。为了保护电动机免受由于机械过载引起的过热的影响，在起动器内要安装热量过载延迟装置。当热量过 载延迟装置过热时，它所拥有的双金属长条断开电动机的电源。除此外，还可以选择一台电热调节器可以用缠绕的方式安装在电动机上，它可以用于监控电动机的温度变化。对于短路保护，我们一般是通过电动机常用的熔断器来实现的。 一台独立的线性电流接触器，被配置的电流接触器应该超过主回路的电流接触器，从而达到冗余的目的。这台电流接触器是由安全电路来控制的，如：紧急制动和越程极限。 我们可以使用限位开关来实现上述的操作。当你到达正常的行程极限位置末端时，绞车就会停车，并且你只能够向相反的方向移动绞车 (即远离极限位置的方向 )。这里 也需要一个越程限制以防万一，由于电气的或者机械的问题，而使绞车的运行超过正常的极限位。如果你碰到越程限制器，线形电流接触器就会打开，因此，绞车将无法被驱动超过这个极限位置。如果上述情况发生，就需要请专业的技术人员来检查导致碰到越程限制器的具体原因。然后，你就能够用起动器内部的弹力恢复拨动开关来处理越程的问题，而不是使用跳闸器或是手工切断电流接触器。 变速的必要条件 当然，简单的定速起动器被变速驱动器所取代。这就使事情开始变得有趣起来了！至少，你需要在控制操作台上增加一个速度表盘。操纵杆是一个较好的操作接口， 由于它使你对部件的移动有一个更直观的控制。 不幸的是，你不能仅仅从你的本地控制台去发命令控制老式的变速驱动器，此外，你不能希望它在初始阶段，就能安全而可靠的提升与下放设备。大多数的变速驱动器不能实现上述的要求，因为它们并不是设计用来做提升工作的。驱动器需要设置成在制动器松开之前，就能够在电动机上产生扭矩，并且，当停车时，即在扭矩撤销之前，制动器将先动作。 7 许多年来，直流电动机和驱动器提供了一些普遍的解决方案，如它们在各种速度时都具有良好的力矩特性。对于大多数的绞车所需求的大型直流电动机是很贵的，那要比同类型 的交流电动机贵得多。虽然，早期的交流驱动器不是非常有用，如它们有一个非常有限速度适用范围，而且仅产生低速小扭矩。如今，随着直流驱动器的发展，低成本而且大量可用的交流电动机的出现，导致了一场交流驱动的革命。 变速交流驱动器有两个系列。变频转换器已经家喻户晓，而且的确很容易使用。这些驱动器将交流转换成直流，然后，再把它转换回交流，转换后的交流已经是不同频率的。如果驱动器产生 30Hz 的交流，一台正常的 60Hz 的电动机将以一半的速度运行。从理论上说，这非常好，但是，在实际中，这将会有很多的问题。首先，一台典型的 60Hz 的电动机在线性频率低于 2Hz 或是 3Hz 的区域会出现误差，并且，开始嵌齿 (即急推，猛拉 )，或是停车。这将限制你的速度范围低于 20： 1，几乎不适应于运行阶段的细微调节。其次，许多低成本的转换器也不能够在低速时提供额定扭矩。使用这些驱动器，将导致急速移动，或是对于提升部件完全的失效，准确地说，当你试图去平稳的提升一台科学仪器时，你不愿看到这样的情况。一些新型的变极器是闭环系统 (从电动机获得反馈，提供更加准确的速度控制 )，并且使电动机将会工作的相当好。 交流驱动器的另一个系列是流量矢量型驱动器。这些元器件要求在 电动机的主轴上安装编码器，使用这些编码器会使驱动器可以准确地监控电机电枢的旋转。处理器测定了准确的磁性流量的矢量值，这些值要求使电枢在给定的速度下旋转。这些驱动器允许有无穷大的速度，因此，你实际能够在零速度时就产生额定扭矩。这些驱动器所提供的准确的速度和位置的控制，使这些驱动器在高性能应用方面受到欢迎。 (基于 PLC 的控制器提供有系统状态和控制选项。这个屏幕展示给操作者全面的访问卡内基霍尔德的九层电梯提升的控制面板。 ) 基于 PLC 的系统 一台 PLC 的全称是可编程序逻辑控制器。首先， PLC 的控制器发展到取代了 基于五六十年代的工业控制系统的继电器，它们工作在室内的恶劣的工业环境中。这些是模块化的系统，它们具有大量的各种各样的 I/O 模块。这些模块化的系统可以很容易的实现把半自定义的硬件配置组装起来，而这样得到的配置的价钱也很合理。这些模块包括：位置控制模块，计数器， A/D 和 D/A 转换器，以及各种实体状态或是物理接触闭式输出模块。大量不同类型的 I/O 元器件和 PLC 的模块属性使得它成为一条有效的途径去组装自定义和半自定义的控制