機械專業(yè)外文翻譯----直流電動機調(diào)速控制(存儲版)
【正文】 電氣制動的方式。其他類型的調(diào)節(jié)器也提供輸出功率，溫度調(diào)節(jié)器必須保持爐內(nèi)的溫度恒定，也就是說，即使?fàn)t內(nèi)的溫度散失也必須保持爐溫不變。 （ 3） 能耗制動 （ 4） 反接制動 回饋制動雖然并不一定是 最經(jīng)濟的方式，但卻是最好的方式。在大型系統(tǒng)中，散熱問題是很重要的，因為如果長時間制動，軸、軸承和電機的溫度就會升高。在可控情況下，這種制動方法對所傳動裝置都是使用的。要將轉(zhuǎn)速增加到較高值，可以增大 U 或減小 Φ 。電樞電流由一個晶閘管控制，該晶閘管又由加在它們極上的脈沖控制。在 所示拖動系統(tǒng)中，當(dāng)晶閘管處于斷開狀態(tài)時，其陽極電勢等于電機反電動勢。當(dāng)電感能量消失（ D 點），電樞電流為零，電壓恢復(fù)到它的正常水平，這個暫態(tài)過程最后穩(wěn)定在 E 點。在該波形中，晶閘管在 A點觸發(fā)，一直到 B 點電源電壓低于電樞反電動勢時導(dǎo)通。速度參考信號與電樞電壓信號極性相反，以確保施加的都是負(fù)反饋。而且，回饋制動不能用于電機；在這種系統(tǒng)類型中，電機電樞可以通過電氣制動靜止（例如，當(dāng)晶閘管門極脈沖反向時，電阻可通過一個繼電器或其他裝置連接到電樞上）。要將轉(zhuǎn)速降為零，或者 U=0 或 Φ =∞ 。能耗制動應(yīng)用在許多大型交流升降系統(tǒng)中，制動的職責(zé)是反向和延長。由晶閘管換流器而來的廉價變頻電源的出現(xiàn)在變速裝置感應(yīng)電機應(yīng)用中引起了巨大的變化。 可行的各種電氣制動方法有： （ 1） 回饋制動。 例如，電機速度調(diào)節(jié)器要能在負(fù)載轉(zhuǎn)矩變化時仍能保持電機轉(zhuǎn)速為恒定值。derstro168。 A temperature regulator must maintain the temperature of, say, an oven constant despite the heat loss in the oven. A voltage regulator must also maintain the output voltage constant despite variation in the load current. For any system to provide an output, ., speed, temperature, voltage, etc., an error signal must exist under steadystate conditions. Electrical Braking In many speed control systems, ., rolling mills, mine winders, etc., the load has to be frequently brought to a standstill and reversed. The rate at which the speed reduces following a reduced speed demand is dependent on the stored energy and the braking system used. A small speed control system (sometimes known as a velodyne) can employ mechanical braking, but this is not feasible with large speed controllers since it is difficult and costly to remove the heat generated. The various methods of electrical braking available are: (1) Regenerative braking. (2) Eddy current braking. (3) Dynamic braking. (4) Reverse current braking(plugging) Regenerative braking is the best method, though not necessarily the most economic. The stored energy in the load is converted into electrical energy by the work motor (acting temporarily as a generator) and is returned to the power supply system. The supply system thus acts as a”sink”into which the unwanted energy is delivered. Providing the supply system has adequate capacity, the consequent rise in terminal voltage will be small during the short periods of regeneration. In the WardLeonard method of speed control of DC motors, regenerative braking is inherent, but thyristor drives have to be arranged to invert to regenerate. Induction motor drives can regenerate if the rotor shaft is driven faster than speed of the rotating field. The ad
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