【正文】 s amount and density and the torque in proportion to input 10 speed. Because the pumping action within the fluid coupling depends on centrifugal forces. the output speed is less than the input speed. Referred to as slip. this normally is between 1% and 3%. Basic hydrokiic couplings are available in configurations from fractional to several thousand KW. Fixedfill fluid couplings. Fixedfill fluid couplings are the most monly used softstart devices for conveyors with simpler belt profiles and limited convex/concave sections. They are relatively simple,lowcost,reliable,maintenance free devices that provide excellent soft starting results to the majority of belt conveyors in use today. Variablefill drain couplings. Drainablefluid couplings work on the same principle as fixedfill couplings. The coupling39。s design. Due to the advances in conveyor drive control technology, at present many more reliable. Costeffective and performance driven conveyor drive systems covering a wide range of power are available for customers39。由圖看出，曲線 1 顯示受控帶速，帶速呈 S 形曲線形狀，曲線 3 分別表示電流和扭矩，曲線 4 顯示帶張力。 PWM調(diào)制器 該調(diào)制器實際上是把空間矢量調(diào)制概念擴展到三電平逆變器。在中性點箱位時，該相在 o 狀態(tài)，這時根據(jù)相電流極性的正負，或者是 S2U 導(dǎo)通或者是 S3U 導(dǎo)通。高壓 IGBT(HVIGBT)的出現(xiàn)使得應(yīng)用三電平中性點箱位原理的中高壓逆變器設(shè)計有了更大的應(yīng)用范圍。VFC 設(shè)備是一個電力電子控制器，首先把 AC 整流成 DC，然后利用逆變器，再將 DC 轉(zhuǎn)換成頻率、電壓可控的 AC. VFC 驅(qū)動采用矢量控制或直接轉(zhuǎn)矩控制 (DTC)技術(shù) ，能根據(jù)不同的負載采用不同的運行速度?？勺兂湟阂毫ε己掀骺墒褂迷谥写蠊β瘦斔拖到y(tǒng)中，功率可達到數(shù)千千瓦口這種驅(qū)動無論在機械，或在電氣上都是很復(fù)雜的，其驅(qū)動系統(tǒng)成本中等。這種連接產(chǎn)生的動力決定于液力偶合器的充液量 ，扭矩正比于輸入速度。當今，控制系統(tǒng)的大多數(shù)是定制設(shè)計來滿足傳送系統(tǒng)的特殊規(guī)格繞線轉(zhuǎn)子電機適合于需要 400kVV 以上的系統(tǒng)。 降壓啟動 隨著傳送驅(qū) 動功率的增加，在加速期間控制使用的電機扭矩變得越來越重要?？刂乞?qū)動力和加速度扭矩是輸送機的關(guān)鍵。一個高效的驅(qū)動系統(tǒng)應(yīng)該能順利的運行，同時保持輸送帶張緊力在指定的安全極限負荷內(nèi)。由于電機扭矩是電壓的函數(shù)，電機電壓必須得到控制，一般用可控硅整流器 (SCR}構(gòu)成的降壓啟動裝置，先施加低電壓拉緊輸送帶，然后線性的增加供電電壓直到全電壓和最大帶速。 直流 (DC)電機 大多數(shù)傳送驅(qū)動使用 DC 并勵電機，電機的電樞在外部連接。因在流體偶合中輸出速度小于輸入速度，其間的差值稱為滑差，一般為 1%3%。 勺管控制液力偶合器 也稱為調(diào)速型液力偶合器。 VFC 驅(qū)動能根據(jù)給定的 S 曲線啟動或停車，實現(xiàn)自動跟蹤啟動或停車曲線。這種逆變器目前可以實現(xiàn)從 2. RV到 4. 16kV 全范圍的應(yīng)用。為了保證中性點電壓平衡，在 o 點被注入的平均電流應(yīng)該是零 。其基本原理是三電平 PWM 調(diào)制器使用兩個參考波認 Ur1 和 Ur2，但只使用一個三角波。從圖中可以發(fā)現(xiàn)，帶張力的波動范圍很小，所有檢測結(jié)果顯示出帶式輸送機驅(qū)動系統(tǒng)令人滿意的特性。 choices[1]. 1 Analysis on conveyor drive technologies 1. 1 Direct drives Fullvoltage starters. With a fullvoltage starter design, the conveyor head shaft is directcoupled to the motor through the gear drive. Direct fullvoltage starters are adequate for relatively lowpower, simple Profile conveyors. With direct fullvoltage starters. no control is provided for various conveyor loads and. depending on the ratio between full and noload power requirements, empty starting 8 times can be three or four times faster than full load. The maintenancefree starting system is simple, lowcost and very reliable. However, they cannot control starting torque and maximum stall torque。s impellers are mounted on the AC motor and the runners on the driven reducer highspeed shaft. Housing mounted to the drive base encloses the working circuit. The coupling39。 the driving hydraulic turbine known as the runner and a casing that encloses the two power ponents. Hydraulic fluid is pumped from the driven impeller to the driving runner, producing torque at the driven shaft. Because circulating hydraulic fluid produces the torque and speed, no mechanical connection is required between the driving and driver power produced by this coupling is based on the circulated fluid39。 performance. A efficient drive system should be able to provide smooth, soft starts while maintaining belt tensions within the specified safe limits. For load sharing on multiple drives. torque and speed control are also considerations in the drive system39。圖 3 為測試結(jié)果波形。對相加結(jié)果的頻率信號積分，然后產(chǎn)生單位矢量 (cosθ e 和 sinOθ e )，最后通過矢量旋轉(zhuǎn)器產(chǎn)生電壓 V’角θ控制 PWM 調(diào)制器。例如，當開關(guān) S1u 和S2u 閉合時， U 相處于狀態(tài) P(正母線電壓 )，反之，當開關(guān) S3u 和 S4U 閉合時， U 相處于狀態(tài) n(負母線電壓 )。 2 使用 IGBT 的中性點箱位三電平逆變器 由于串聯(lián)器件電壓均分容易，器件每次開關(guān)的 dv/dt 低以及輸出端出色的諧波品質(zhì)，三電平電壓型逆變器在大功率傳動應(yīng)用中變得越來越流行。 VFC裝置為感應(yīng)電機提供變化的頻率和電壓，產(chǎn)生優(yōu)良的啟動轉(zhuǎn)矩和加速度。為了控制單機傳動系統(tǒng)的啟動轉(zhuǎn)矩，必須監(jiān)測 AC電機電流給電磁閥的控制提供反饋 。由于循環(huán)流體產(chǎn)生扭矩和速度，在驅(qū)動軸和從動軸之間不需要任何機械連接。該方式的電機系統(tǒng)設(shè)計相對簡單，但控制系統(tǒng)可能很復(fù)雜，因為它們是基于計算機控制的電阻切換。因此，這種方式只用于低功率，結(jié)構(gòu)簡單的傳送驅(qū)動中。如今，較大的輸送帶和多驅(qū)動系統(tǒng)需耍更大的功率，比如 3 驅(qū)動系統(tǒng)需耍給輸送帶 750KW(成莊煤礦輸送機驅(qū)動系統(tǒng)的要求 )。為了負載分配在多個