外文翻譯--皮帶傳送系統(tǒng)及其牽引系統(tǒng)-預覽頁
【正文】 ull and noload power requirements， empty starting times can be three or four times faster than full load。 Because motor torque 1second a function of voltage， motor voltage must be controlled。 When acceleration is plete， the SCRs, which control the applied voltage to the electric motor， are locked in full conduction, providing fullline voltage to the motor。 the modified motor control system controls motor torque。 The motor systems have a relatively simple design。 DC motor DC motors， available from a fraction of thousands of kW ， are designed to deliver constant torque below base speed and constant kW above base speed to the maximum allowable revolutions per minute(r/min)， with the majority of conveyor drives, a DC shunt wound motor is used。 This system option is expensive in parison to other softstart systems。 the driven impeller, which acts as a centrifugal pump； the driving hydraulic turbine known as the runner and a casing that encloses the two power ponents。 Because the pumping action within the fluid coupling depends on centrifugal forces。 Fixedfill fluid couplings。 Drainablefluid couplings work on the same principle as fixedfill couplings。 Oil from the reservoir is pumped through a heat exchanger to a solenoidoperated hydraulic valve that controls the filling of the fluid coupling。 the system can be electronically intricate。 The casing is fitted with fixed orifices that bleed a predetermined amount of 山東建筑大學畢業(yè)設計外文文獻及譯文 4 fluid into a reservoir。 but the puterbased control system is very plex。 The availability of HVIGBTs has led to the design of a new range of mediumhigh voltage inverter using threelevel NPC topology。 a threelevel neutral point clamped inverter realizes the power section。 The switching states of a threelevel inverter are summarized in Table 1． U． V and W denote each of the three phases respectively； P N and O are the dc bus points。 2． 2 Line side converter For standard applications， a 12pulse diode rectifier feeds the divided DClink capacitor。 end converter can replace the diode rectifier, using the same structure as the inverter。 Fig． 3 includes four curves。 Curve 4 shows the velocity of the controlled belt。 Costeffective and performancedriven conveyor drive system choices for users。1evel inverters used in a 2． 7 km long belt conveyor drives in Chengzhuang Mine indicates that the performance of NPC threelevel inverter using HVIGBTs together with the control strategy of rotor fieldoriented vector control for induction motor drive is excellent for belt conveyor driving system。控制驅動力和加速度扭矩是輸送機的關鍵。 1 帶式輸送機驅動 帶式輸送機驅動方式 全電壓啟動 在全電壓啟動設計中 ， 帶式輸送機驅動軸通過齒輪傳動直接連接到電機。因此 ， 這種方式只用于低功率 ,結構簡單的傳送驅動中。此種控制方式功率可達到 750kW。該方式的電機系統(tǒng)設計相對簡單 ， 但控制系統(tǒng)可能很復雜 ， 因為它們是基于計算機控制的電阻切換。控制山東建筑大學畢業(yè)設計外文文獻及譯文 7 DC 驅動技術一般應用 SCR裝置 ， 它允許連續(xù)的變速操作。流體從葉輪到渦輪 ， 在從動軸產(chǎn)生扭矩。傳遞功率可達幾千千瓦。偶合器的旋轉外殼有溢出口 ,允許液體不斷地從工作腔中流出進入一個分離的輔助腔 ， 油從輔助腔通過一個熱交換器泵到控制偶合器充液量的電磁閥。 勺管控制液力偶合器 也稱為調速型液力偶合器。勺管控制液力偶合器可以應用在單機或多機驅動系統(tǒng) ， 功率范圍為 150kW～ 750kW。 HVIGBT 模塊串聯(lián)可使用在 3. 3kV和 4. 16kV的設備。 三電平中點箝位電壓型逆變器的開關狀態(tài)可歸納于表 1 ， U ， V 和 W 分別表示三相 ， P， N 和 O 是直流母線上的三個點。 輸入端變流器 為 通常使用 12 脈沖二極管整流器給直流環(huán)節(jié)電容器充電 ,在輸入端引入的諧波是很小的。圖 3為測試結果波形。在這些選擇中，可變頻率控制 (VFC)的方法顯現(xiàn)出在將來長距離輸送中帶式輸送機扮演了重
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