1、<p>　　長江大學工程技術(shù)學院</p><p>　　畢業(yè)設計（論文）外文翻譯</p><p><b>　　直流電機速度控制</b></p><p>　　Bruce Trump著，郭成譯</p><p><b>　　1 調(diào)節(jié)系統(tǒng)</b></p><p>　　調(diào)節(jié)系統(tǒng)

2、是一類通常能提供穩(wěn)定輸出功率的系統(tǒng)。</p><p>　　例如，電機速度調(diào)節(jié)器要能在負載轉(zhuǎn)矩變化時仍能保持電機速度為恒定值。即使負載轉(zhuǎn)矩為零，電機也必須提供足夠的轉(zhuǎn)矩來克服軸承的粘滯摩擦影響。其它類型的調(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，即使爐內(nèi)的熱量散失也必須保持爐溫不變。一個電壓調(diào)節(jié)器必須也保持負載電流值變化時輸出電壓恒定。對于任何一個提供一個輸出，例如速度、溫度、電壓等的系統(tǒng)，

3、在穩(wěn)態(tài)下必定存在一個誤差信號。</p><p><b>　　2 電氣制動</b></p><p>　　在許多速度控制系統(tǒng)中，例如軋鋼機，礦坑卷揚機等這些負載要求頻繁地停頓和反向運動的系統(tǒng)。隨著減速要求，速度減小的比率取決于存儲的能量和所使用的制動系統(tǒng)。一個小型速度控制系統(tǒng)（例如所知的伺服積分器）可以采取機械制動，但這對大型速度控制器并不可行，因為散熱很難并且很昂貴。&

4、lt;/p><p>　　可行的各種電氣制動方法有：</p><p><b>　　（1）回饋制動。</b></p><p><b>　　（2）渦流制動。</b></p><p><b>　　（3）能耗制動。</b></p><p>　?。?）反向（接）制動。&

5、lt;/p><p>　　回饋制動雖然并不一定是最經(jīng)濟的方式，但卻是做好的方式。負載中存儲的能量通過工作電機（暫時以發(fā)電機模式運行）被轉(zhuǎn)化成電能并被返回到電源系統(tǒng)中。這樣電源就充當了一個收容不想要的能量的角色。假如電源系統(tǒng)具有足夠的容量，在短時回饋過程中最終引起的端電壓升高會很少。在直流電機速度控制沃特-勒奧那多法中，回饋制動是固有的，但可控硅傳動裝置必須被排布的可以反饋。如果軸轉(zhuǎn)速快于旋轉(zhuǎn)磁場的速度，感應電機傳動裝置

6、可以反饋。有晶閘管換流器而來的廉價變頻電源的出現(xiàn)在變速裝置感應電機應用中引起了巨大的變化。</p><p>　　渦流制動可用于任何機器，只要在軸上安裝一個銅條或鋁盤并在磁場中旋轉(zhuǎn)它即可。在大型系統(tǒng)中，散熱問題很重要的，因為如果長時間制動，軸、軸承和電機的溫度就會升高。</p><p>　　在能耗制動中，存儲的能量消耗在回路電阻器上。用在小型直流電機上時，電樞供電被斷開，接入一個電阻器（通常

7、是一個繼電器、接觸器或晶閘管）。保持磁場電壓，施加制動降到最低速。感應電機要求稍微復雜一點的排布，定子繞組被從交流電源上斷開，接到直流電源上。產(chǎn)生的電能繼而消耗在轉(zhuǎn)子回路中。能耗制動應用在許多大型交流升降系統(tǒng)中，制動的職責是反向和延長。</p><p>　　任何電機都可以通過突然反接電源以提供反向的旋轉(zhuǎn)方向（反接制動）來停機。在可控情況下，這種制動方法對所有傳統(tǒng)裝置都是適用的。它主要的缺點就是當制動等于負載存儲的

8、能量時，電能被機器消耗了。這在大型裝置中就大大增加了運行成本。</p><p>　　3 等脈寬PWM法 </p><p>　　VVVF(Variable Voltage Variable Frequency)裝置在早期是采用PAM（Pulse Amplitude Modulation）控制技術(shù)來實現(xiàn)的，其逆變器部分只能輸出頻率可調(diào)的方波電壓而不能調(diào)壓。等脈寬PWM法正是為了克服PAM法的這

9、個缺點發(fā)展而來的，是PWM法中最為簡單的一種。它是把每一脈沖的寬度均相等的脈沖列作為PWM波，通過改變脈沖列的周期可以調(diào)頻，改變脈沖的寬度或占空比可以調(diào)壓，采用適當控制方法即可使電壓與頻率協(xié)調(diào)變化。相對于PAM法，該方法的優(yōu)點是簡化了電路結(jié)構(gòu)，提高了輸入端的功率因數(shù)，但同時也存在輸出電壓中除基波外，還包含較大的諧波分量。</p><p><b>　　4 隨機PWM </b></p>

10、;<p>　　在上世紀70年代開始至上世紀80年代初，由于當時大功率晶體管主要為雙極性達林頓三極管，載波頻率一般不超過5kHz，電機繞組的電磁噪音及諧波造成的振動引起了人們的關(guān)注。為求得改善，隨機PWM方法應運而生。其原理是隨機改變開關(guān)頻率使電機電磁噪音近似為限帶白噪聲（在線性頻率坐標系中，各頻率能量分布是均勻的），盡管噪音的總分貝數(shù)未變，但以固定開關(guān)頻率為特征的有色噪音強度大大削弱。正因為如此，即使在IGBT已被廣泛應用

11、的今天，對于載波頻率必須限制在較低頻率的場合，隨機PWM仍然有其特殊的價值；另一方面則說明了消除機械和電磁噪音的最佳方法不是盲目地提高工作頻率，隨機PWM技術(shù)正是提供了一個分析、解決這種問題的全新思路。 </p><p>　　5 空間電壓矢量控制PWM </p><p>　　空間電壓矢量控制PWM（SVPWM）也叫磁通正弦PWM法。它以三相波形整體生成效果為前提，以逼近電機氣隙的理想圓形旋

12、轉(zhuǎn)磁場軌跡為目的，用逆變器不同的開關(guān)模式所產(chǎn)生的實際磁通去逼近基準圓磁通，由它們的比較結(jié)果決定逆變器的開關(guān)，形成PWM波形。此法從電動機的角度出發(fā)，把逆變器和電機看作一個整體，以內(nèi)切多邊形逼近圓的方式進行控制，使電機獲得幅值恒定的圓形磁場(正弦磁通)。 </p><p>　　具體方法又分為磁通開環(huán)式和磁通閉環(huán)式。磁通開環(huán)法用兩個非零矢量和一個零矢量合成一個等效的電壓矢量，若采樣時間足夠小，可合成任意電壓矢量。此法

13、輸出電壓比正弦波調(diào)制時提高15％，諧波電流有效值之和接近最小。磁通閉環(huán)式引入磁通反饋，控制磁通的大小和變化的速度。在比較估算磁通和給定磁通后，根據(jù)誤差決定產(chǎn)生下一個電壓矢量，形成PWM波形。這種方法克服了磁通開環(huán)法的不足，解決了電機低速時，定子電阻影響大的問題，減小了電機的脈動和噪音。但由于未引入轉(zhuǎn)矩的調(diào)節(jié)，系統(tǒng)性能沒有得到根本性的改善。 </p><p>　　6 矢量控制PWM </p><

14、p>　　矢量控制也稱磁場定向控制，其原理是將異步電動機在三相坐標系下的定子電流Ia，Ib及Ic，通過三相/二相變換，等效成兩相靜止坐標系下的交流電流Ia1及Ib1，再通過按轉(zhuǎn)子磁場定向旋轉(zhuǎn)變換，等效成同步旋轉(zhuǎn)坐標系下的直流電流Im1及相當于直流電動機的勵磁電流；It1相當于與轉(zhuǎn)矩成正比的電樞電流），然后模仿對直流電動機的控制方法，實現(xiàn)對交流電動機的控制。其實質(zhì)是將交流電動機等效為直流電動機，分別對速度、磁場兩個分量進行獨立控制。通

15、過控制轉(zhuǎn)子磁鏈，然后分解定子電流而獲得轉(zhuǎn)矩和磁場兩個分量，經(jīng)坐標變換，實現(xiàn)正交或解耦控制。但是，由于轉(zhuǎn)子磁鏈難以準確觀測，以及矢量變換的復雜性，使得實際控制效果往往難以達到理論分析的效果，這是矢量控制技術(shù)在實踐上的不足。此外．它必須直接或間接地得到轉(zhuǎn)子磁鏈在空間上的位置才能實現(xiàn)定子電流解耦控制，在這種矢量控制系統(tǒng)中需要配置轉(zhuǎn)子位置或速度傳感器，這顯然給許多應用場合帶來不便。</p><p>　　無刷直流電機是近年

16、來迅速發(fā)展起來的一種新型電機,它利用電子換相代替機械 換相,既具有直流電動機的調(diào)速性能,又具有交流電機結(jié)構(gòu)簡單、運行可靠、維護方便等。而且體積小、效率高,在許多領域已得到了廣泛的運用。</p><p>　　單片機控制的永磁無刷直流電動機調(diào)速系統(tǒng)適用于電動自行車等小功率的工作情況。并能將多余的電能回潰。該系統(tǒng)具有調(diào)速性能好、功率因數(shù)高、節(jié)能、體積小、重量輕等優(yōu)點。</p><p>　　根據(jù)永

17、磁無刷直流電動機的特性實施脈寬PWM控制，并通過轉(zhuǎn)速傳感器測量轉(zhuǎn)速通過數(shù)碼管動態(tài)顯示出其轉(zhuǎn)速，通過軟硬件的配合使用，實現(xiàn)了整個系統(tǒng)的速度控制的要求。</p><p>　　7 Ideal Torque Prod直流電機速度控制</p><p>　　所有直流電機速度控制的基本關(guān)系都可以由下式得出：</p><p><b>　　E∝Φω</b><

18、;/p><p><b>　　U=E+IaRa</b></p><p>　　各項就是它們通常所指的含義。如果IaRa 很小，等式近似為U∝Φω或ω∝U/Φ。這樣，控制電樞電壓和磁通就可以影響電機的轉(zhuǎn)速。要將轉(zhuǎn)速降為零，或者U=0或者Φ=∞。后者是不可能的，因此只可通過電樞電壓的變化來減低轉(zhuǎn)速。要將轉(zhuǎn)速增加到較高值，可以增大或者減小Φ。后者是最可行的方法，就是我們通常所知的弱

19、磁場。在要求速度調(diào)解范圍寬的場合可綜合使用這兩種方法。</p><p>　　Speed Control of DC Motor</p><p>　　By Bruce Trump</p><p>　　1 Regulating system</p><p>　　Control system is a kind of usually offe

20、r a stable output power system.</p><p>　　For example, motor speed regulator can load torque changes in can still keep motor speed for a constant value. Even if the load torque is zero, motor must also provid

21、e enough torque to overcome bearing viscous friction effects. Other types of regulator also provide power output, temperature regulator must be kept inside the furnace temperature constant, that is, even inside the furna

22、ce temperature and heat loss must be kept constant. A voltage regulator must also keep load current value change o</p><p>　　2 Electric braking</p><p>　　In many speed control system, e.g., rollin

23、g 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 syste

24、m 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. <

25、;/p><p>　　The various methods of electrical braking avaiable are:</p><p>　　Regenerative braking.</p><p>　　Eddy current braking.</p><p>　　Dynamic braking.</p><p&

26、gt;　　Reverse current braking(plugging).</p><p>　　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 wo

27、rk 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 capaci

28、ty, the consequent rise in terminal voltage will be small during the short periods of regeneration. In the Ward-Leonard me</p><p>　　Eddy current braking can be applied to any machine, simply by mounting a co

29、pper or aluminium disc on the shaft and rotating it in a magnetic field. The problem of removing the heat generated is severe in large system as the temperature of the shaft, bearing, and motor will be raised if prolonge

30、d braking is applied.</p><p>　　In dynamic breaking, the stored energy is a resistor in the circuit. When applied to small DC machines, the armature supply is disconnected and a resistor is connected across t

31、he armature (usually by a relay, contactor, or thyristor). The field voltage is maintained, and braking is applied down to the lowest speed. Induction motors require a somewhat more complex arrangement, the stator windin

32、gs being disconnected from the AC supply and reconnected to a DC supply. The electrical energy generated</p><p>　　Any electrical motor can be brought to a standstill by suddenly reconnecting the supply to re

33、verse the direction of rotation (reverse current braking). Applied under controlled conditions, this method of braking is satisfactory for all drivers. Its major disadvantage is that the electrical energy consumed by the

34、 machine when braking is equal to the stored energy in the load. This increases the running cost significantly in large drives.</p><p>　　3 Equal pulse width PWM law </p><p>　　VVVF (Variable Volt

35、age Variable Frequency) installs in the early time is uses PAM (Pulse Amplitude Modulation) to control, its inventor part which the technology realizes but only can output the frequency adjustable square-wave voltage not

36、 to be able to adjust the pressure. The pulse width PWM law are precisely in order to overcome, is in the PWM law which the PAM law this shortcoming development comes the simplest one kind. It is each pulse width equal p

37、ulse row took the PWM wave, through a cha</p><p>　　4 Stochastic PWM </p><p>　　That time the high efficiency transistor mainly for the bipolarity Daring ton triode, the carrier frequency genera

38、lly did not surpass 5kHz, the vibration which the electrical machinery winding electromagnetism noise and the overtone created has aroused people's interest. In order to obtain the improvement, the stochastic PWM met

39、hod arises at the historic moment. Its principle is the stochastic change turn-on frequency causes the electrical machinery electromagnetism noise to be limited to appro</p><p>　　5 space voltage vector PWM c

40、ontrol</p><p>　　Spatial voltage vector control PWM (SVPWM) also calls the magnetic flux sine PWM law .It take the three-phase profile whole production effect as the premise, take approaches the electrical ma

41、chinery air gap the ideal circular rotary field path as the goal, has the actual magnetic flux with the inventor different switch pattern to approach the base director circle magnetic flux, by theirs comparison result de

42、cided the inventor the switch, forms the PWM profile. This law embarks from the electric </p><p>　　The concrete method divides into the magnetic flux split-ring type and the magnetic flux closed loop type. T

43、he magnetic flux split-ring law synthesizes an equivalent voltage vector with a two non-vanishing vector sum null vector, if the sampling time enough is small, may synthesize the random voltage vector. When this law outp

44、ut ratio-voltage sine-wave modulation enhances 15% close, sum of the harmonic current effective value smallest. The magnetic flux closed loop type introduces the magnetic f</p><p>　　6 Vector Control PWM</

45、p><p>　　The vector control also called the magnetic field direction detection control, its principle is asynchronous motor under three-phase coordinate system stator current Ia, Ib and Ic , through the three-p

46、hase/two phase transformation, equivalent becomes under two static coordinate systems alternating current Ia1 and Ib1, again through presses the rotor magnetic field direction detection revolving transformation, equivale

47、nt becomes under the synchronized revolving coordinate system direct current I</p><p>　　But, because the rotor flux linkage accurately observes with difficulty, as well as the vector transformation complexit

48、y, causes the actual control effect often with difficulty to achieve theoretical analysis effect, this is the vector control technology in the practice insufficiency. In addition, It must directly or indirectly obtains t

49、he rotor flux linkage to be able to realize the stator current decoupling control in space position, needs to dispose the rotor position or the velocity generato</p><p>　　The analytical functions of the arma

50、ture reaction of permanent magnet brushless DC motor with concentrated coils are proposed by using the method of image, concerning with the configuration of these machines. This approach is different from the method of e

51、quivalent distributed current sheet and more suitable for the electric machines, which have concentrated coils and deeper slots. Under different control mode, the analytical functions of the armature reaction are differe

52、nt.</p><p>　　Brushless DC motor (BLDCM) with permanent excitation, in which electrical commutator is used instead of mechanical, has not only the same good characteristics of speed control as traditional DC

53、motor, but also the good characteristics of AC Motor. Brushless DC motors have found wide application due to their high power density and ease of control. Moreover, the machines have high efficiency over wide speed range

54、. Recently it has been quickly developed.</p><p>　　SCM control of permanent magnet brushless DC motor speed control system applicable to electric bicycles, and other low-power work. Redundant power and can r

55、eturn to collapse. The system has good speed performance, high power factor, energy saving, small size, light weight, and other advantages.</p><p>　　According to the permanent magnet brushless DC motor contr

56、ol of the PWM pulse width, speed sensor and passed through eighth speed digital dynamic display of speed, through hardware and software support, for the entire system design requirements.</p><p>　　7 DC Motor

57、 Speed Control </p><p>　　The basis of all methods of DC motor speed control is derived from the equations:</p><p><b>　　E∝Φω</b></p><p><b>　　U=E+IaRa</b><

58、/p><p>　　the terms having their usual meanings. If the IaRa drop is small, the equations approximate to </p><p><b>　　U∝Φω</b></p><p><b>　　or</b></p><

59、;p><b>　　ω∝U/Φ</b></p><p>　　Thus, control of armature voltage and field flux influences the motor speed. To reduce the speed to zero, either U=0 or Φ=∞. The latter is inadmissible; hence contro

60、l at low speed is by armature voltage variation. To increase the speed to a high value, either U is made very large or Φ is reduced. The latter is the most practical way and is known as field weakening. Combinations of t