执行器附件和相关标准
ACTUATOR ACCESSORY & RATING TERMS

　　工作循环 - 电动执行器电击连续运行或“循环”的能力 - 100%工作循环。比100%小意味着执行器电击有能力断断续续运行，正如多数应用那样。例如，25%工作循环意味着每运行1分钟，就需要3分钟不运行。通常只有当遇到需要额外工作负载时，工作循环才会大于25%，如阀门处于节流状态或驱动大型蝶阀的应用场合。
　　Duty Cycle - The capability of an Electric actuator motor to operate or "cycle" continuously - a 100% Duty Cycle. Ratings less than 100% mean that the actuator motor is capable of intermittent operation, as is the case with most actuation applications. For example, a 25% Duty Cycle means that for each 1-minute of operation, 3-minutes of non-operation is required. Duty cycles greater than 25% are generally needed only when additional work loads are encountered, such as valve modulation or in actuation of larger butterfly valves.

　　限位开关 - 是应用在电动执行器或气动执行器上的一种电气开关，用以提供信号指示阀门循环已经完成。在电动执行器里，主要限位开关用来控制阀门的开启和关闭位置。辅助限位开关可能用来完成其他功能如启动或停止泵的运行。限位开关多数情况下是机械式，并靠控制杆或压杆进行物理接触激发的。接近开关则是靠电气激发，不需要物理接触，可以用于某些计算机或微处理器控制的应用场合。
　　Limit Switches - Electrical switches which may be applied to either electric or Pneumatic actuators to supply a signal that the valve cycle has been completed. In Electric actuators, the primary limit switches are used to control the open and closed position of the valve. Auxiliary limit switches may be used to perform other functions such as starting or stopping a pump. Limit switches are most often mechanical and are activated by physical contact with either a lever or plunger. Proximity switches are electrically tripped without physical contact and may be used with certain computer or micro processor controls.

　　NEMA标准 - 美国全国电气制造商协会有关电气部件外壳的标准。最常用到的用于电动执行器和电气附件外壳的NEMA标准是NEMA 4和NEMA 4X。
　　NEMA Rating - National Electric Manufacturers Association standard for rating electrical component enclosures. The most commonly used NEMA ratings for electric actuator and electrical accessory enclosures are NEMA 4 and NEMA 4X.

　　NEMA 1: 一般用途 - 用于室内，没有异常的应用环境，主要是保护部件不会被接触到。
　　NEMA 1: General Purposes - for indoor use without unusual service conditions, primarily to protect components from contact.

　　NEMA 2: 防滴水 - 用于室内，保护级别为有限数量的落水或污垢。
　　NEMA 2: Drip proof - for indoor use with degree of protection against limited amounts of falling water or dirt.

　　NEMA 3: 防雨水 - 用于室外，保护不受风吹灰尘、雨水和冰雹及结冰的破坏。
　　NEMA 3: Rain tight - for outdoor use with protection from windblown dust, rain and sleet, and undamaged by ice formation.

　　NEMA 4: 防水和防尘 - 用于室内外，保护不受风吹灰尘、雨水或直接软管浇水冲刷环境。
　　NEMA 4: Watertight and Dust tight - for indoor/outdoor use with a protection from windblown dust, rain or hose directed wash down environments.

　　NEMA 4X: 防水和防尘 - 与NEMA 4相同，但还具有耐腐蚀性能。
　　NEMA 4X: Watertight and Dust tight - same as NEMA 4 with addition of corrosion resistance.

　　NEMA 7: 防爆（等级I，分区1，组A, B, C, D）- 设计要求当安装在设计规定的环境组别内时，即使发生内在爆炸也不会造成外部危害。组A = 大气中含有乙炔；组B = 大气中含有氢； 组C = 大气中含有乙醚蒸汽，乙烯，或环丙烷；组D = 大气中含有汽油，乙烷，石脑油，苯，丁烷，丙烷，酒精，丙酮，不纯苯，漆，溶剂蒸汽，或天然气。
　　NEMA 7: Explosion Proof (class I, division 1, groups A, B, C, D) - designed to contain an internal explosion without causing an external hazard when installed in a designated environment group. Group A = atmospheres containing acetylene; Group B = atmospheres containing hydrogen; Group C = atmosphere containing ethyl-ether vapors, ethylene, or cyclopropane; Group D = atmospheres containing gasoline, hexane, naphtha, benzene, butane, propane, alcohol, acetone, benzol, lacquer, solvent vapors or natural gas.

　　NEMA 9: 防爆（等级II，分区1，组E, F, G）- 粉尘点燃保护外壳设计用于防止粉尘的进入和点燃粉尘在外壳外部或周围大气的加热能力。组E = 大气中含有金属粉尘，包括铝，镁，它们的合金，具有类似危险特性的其他金属；组F = 大气中含有炭黑，煤或焦炭粉尘；组G = 大气中含有面粉，淀粉，或谷物粉尘。
　　NEMA 9: Explosion Proof (class II, division 1, groups E, F, G) - Dust-ignition-proof enclosures designed to prevent both entrance of dust and external heating capable of igniting dust on the enclosure or in the surrounding atmosphere. Group E = atmospheres containing metal dust including aluminum, magnesium, their commercial alloys, and other metals of similar hazardous characteristics; Group F = atmospheres containing carbon black, coal or coke dust; Group G = atmospheres containing flour, starch, or grain dust.

　　定位器 - 可附加在电动或气动执行器，对阀门位置从开启到关闭进行自动调节控制。电气位置调节装置靠2电流的比较进行工作，一个来自于输入信号，一个来自于执行器。气动定位器根据来自外部控制源的输入信号对气源进行增加，减少和平衡。输入信号是靠3至15 psi气动信号，或4至20毫安电-气信号而产生。
　　Positioner - Attachment for either electric or Pneumatic actuators which provides automatic modulating control of the valve position from open to closed. Electric positioners work by comparison of 2-currents, one derived from the input signal and one from the actuator. Pneumatic positioners increase, decrease and balance the air supply according to an input signal from an external control source. Input signals are generated by either a 3 to 15 psi pneumatic signal, or a 4 to 20 milliamp electro-pneumatic signal.

　　电磁阀 - 一种电-磁驱动的阀门，能够实现对气动执行器的气源进行电气控制。电磁阀接线到手动开关或任何电控制器。双作用执行器需要一个4通电磁阀，弹簧复位执行器需要一个3通电磁阀以实现恰当的气源控制。作为电气装置，可提供各种NEMA标准的电磁阀。
　　Solenoid Valve - An electro-magnetically operated valve which enables electrical control of air supply to a pneumatic actuator. Solenoids are wired to a manual switch or any electric controller. Double Acting actuators require a 4-way solenoid, Spring-Return actuators require a 3-way solenoid for proper air control. As electrical devices, solenoid valves are available in various NEMA ratings.