外文翻譯直流電機(jī)速度控制精品

1、speed control of dc motorregulator systemsa regulator system is one which normally provides output power in its steady-state operation.for example, a motor speed regulator maintains the motor speed at a constant value despite variations in load torque. even if the load torque is removed ,the motor m

2、ust provide sufficient torque to overcome the viscous friction effect of the bearings. other forms of regulator also provide output power; 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 must ou

3、tput voltage constant despite variation in the load current. for any system to provide an output, e.g., speed, temperature, voltage, etc, an error signal must exist under steady-state conditions.electrical brakingin many speed control system, e.g., rolling mills mine winders, etc., the load has to b

4、e 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

5、with large speed controllers since it is difficult and costly to remove the heat generated. the various methods of electrical braking avaiable are:(1) regenerative braking.(2) eddy current braking.(3) dynamic braking.(4) reverse current braking(plugging).regenerative braking is the best method, thou

6、gh 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

7、supply system has adequate capacity, the consequent rise in terminal voltage will be small during the short periods of regeneration. in the ward-leonard method of speed control of dc motors, regenerative braking is inherent, but thyristor drives have to be arranged to invert to regenerate. induction

8、 motor driver can regenerate if the rotor shaft is driven faster than speed of the rotating field. the advent of low-cost variable variable-frequency supplies from thyristor inverters have brought about considerable charges in the use of induction motors in variable speed drives. eddy current brakin

9、g can be applied to any machine, simply by mounting a copper 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 prolonged braking is applied.in

10、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 the armature (usually by a relay, contactor, or thyristor). the field voltage is maintained, and braking is applied down to the

11、lowest speed. induction motors require a somewhat more complex arrangement, the stator windings being disconnected from the ac supply and reconnected to a dc supply. the electrical energy generated is then dissipated in the rotor circuit. dynamic braking is applied to many large ac hoist system wher

12、e the braking duty is both severe and prolonged. any electrical motor can be brought to a standstill by suddenly reconnecting the supply to reverse the direction of rotation (reverse current braking). applied under controlled conditions, this method of braking is satisfactory for all drivers. its ma

13、jor disadvantage is that the electrical energy consumed by the machine when braking is equal to the stored energy in the load. this increases the running cost significantly in large drives.equal pulse width pwm law vvvf (variable voltage variable frequency) installs in the early time is uses pam (pu

14、lse amplitude modulation) to control, its inventor part which the technology realizes but only can output the frequency adjustable square-wave voltage not 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 shortcomi

15、ng development comes the simplest one kind. it is each pulse width equal pulse row took the pwm wave, through a change pulse row cycle may the frequency modulation, the change pulse width or the duty factor may adjust the pressure, uses the suitable control method then to cause the voltage and the f

16、requency coordination change. is opposite in the pam law, this method merit simplified the electric circuit structure, enhanced the input end power factor, but simultaneously also has in the output voltage besides the fundamental wave, but also contains the big harmonic component.stochastic pwm that

17、 time the high efficiency transistor mainly for the bipolarity daring ton triode, the carrier frequency generally 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 impro

18、vement, the stochastic pwm method arises at the historic moment. its principle is the stochastic change turn-on frequency causes the electrical machinery electromagnetism noise to be limited to approximately the belt white noise (in linear frequency coordinate system, various frequencies energy dist

19、ribution is even), although the noise a decibel number has not always changed, but weakens greatly take the fixed turn-on frequency as the characteristic colored noise intensity. because of this, even if in igbt by widespread application today, has had to limit regarding the carrier frequency is com

20、paring the low frequency the situation, stochastic pwm still had its special value; on the other hand explained eliminates the machinery and the electromagnetism noise best method enhances the operating frequency blindly, the stochastic pwm technology was precisely provides an analysis, has solved t

21、his kind of question brand-new mentality.spatial voltage vector control pwm 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 machinery air gap the ideal circula

22、r 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 decided the inventor the switch, forms the pwm profile. this law embarks from the electric motor angle, regards as

23、the inventor and the electrical machinery a whole, inscribes the polygon to approach the circle the way to carry on the control, causes the electrical machinery to obtain the peak-to-peak value constant circular magnetic field (sine magnetic flux).the concrete method divides into the magnetic flux s

24、plit-ring type and the magnetic flux closed loop type. the 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 output ratio-voltage sine-wa

25、ve modulation enhances 15% close, sum of the harmonic current effective value smallest. the magnetic flux closed loop type introduces the magnetic flux feedback, controls the magnetic flux the size and the change speed .estimates the magnetic flux after the comparison and assigns the magnetic flux,

26、according to the error decided has the next voltage vector, forms the pwm profile. this method has overcome the magnetic flux split-ring method insufficiency, when has solved the electrical machinery low speed, the stator resistance affects the major problem, reduced the electrical machinery pulsati

27、on and the noise. but because has not introduced the torque the adjustment, the system performance has not had the fundamental improvement.vector control pwmthe vector control also called the magnetic field direction detection control, its principle is asynchronous motor under three-phase coordinate

28、 system stator current ia, ib and ic , through the three-phase/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, equivalent becomes under the s

29、ynchronized revolving coordinate system direct current im1 and it1 (im1 is equal to the direct current motor exciting current; it1 is equal to the armature electric current which is proportional with the torque), then the imitation direct discharge motive control method, realizes to the motor contro

30、l. its essence is the motor equivalent is the direct current motor, separately to the speed, the magnetic field two components carries on the independent control. through the control rotor flux linkage, then the decomposition stator current obtains the torque and the magnetic field two components, a

31、fter coordinate transformation, realization orthogonal or decoupling control.but, because the rotor flux linkage accurately observes with difficulty, as well as the vector transformation complexity, causes the actual control effect often with difficulty to achieve theoretical analysis effect, this i

32、s the vector control technology in the practice insufficiency. in addition, it must directly or indirectly obtains the 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 generator in this kind of vecto

33、r control system, this gives many application situations to bring inconveniently obviously.the analytical functions of the armature 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.

34、this approach is different from the method of equivalent 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 different.brushless dc motor (bldcm) wit

35、h permanent excitation, in which electrical commutator is used instead of mechanical, has not only the same good characteristics of speed control as traditional dc motor, but also the good characteristics of ac motor. brushless dc motors have found wide application due to their high power density an

36、d ease of control. moreover, the machines have high efficiency over wide speed range. recently it has been quickly developed.scm control of permanent magnet brushless dc motor speed control system applicable to electric bicycles, and other low-power work. redundant power and can return to collapse.

37、the system has good speed performance, high power factor, energy saving, small size, light weight, and other advantages.according to the permanent magnet brushless dc motor control of the pwm pulse width, speed sensor and passed through eighth speed digital dynamic display of speed, through hardware

38、 and software support, for the entire system design requirements.brushless dc motor driveideal torque productionas stated earlier, a brushless dc motor generally describes a motor having a trape-zoidal back emf. for this case, the phase currents are rectangular pulses, sometimes loosely identified a

39、s squarewave currents. while (8.3) can be used to describe torque production for this motor, it is easier to understand this configuration graphically as shown in fig. 8-2, where the three phases have been labeled a, b, and c respectively.in the figure, the back emf shapes, i.e ., the back emfs divi

40、ded by speed, are trape-zoids having 2/3 duty cycle. that is, for each 180!ae the back emf shape is constan over 120!ae. the current associated with each back emf is composed of rectangula pulses having a 2/3 duty cycle, where the nonzero portions of the pulses are aligned with the flat areas of the

41、 respective back emf shapes and the polarity of the current matches that of the back emf. following (8.2), the constant torque produced is shown at the bottom of the figure. over each 60!ae segment, positive current flows i one phase, negative current flows in another, and no current flows in the th

42、ird phase. the letters below the constant torque line signify the two phases carrying current, with the overbar denoting negative current flow or flow out of a phase. every 60!ae where the back emf in a phase makes a transition, the current in one phase remains unchanged, while the current in anothe

43、r goes to zero, and the current in the thirdbecomes nonzero. over 360!ae, there are six transitions or commutations before the sequence repeats. as a result, this motor drive is often called a .six step drive.dc motor speed control the basis of all methods of dc motor speed control is derived from t

44、he equations:eu=e+iarathe terms having their usual meanings. if the iara drop is small, the equations approximate to uoru/ thus, control of armature voltage and field flux influences the motor speed. to reduce the speed to zero, either u=0 or =. the latter is inadmissible; hence control at low speed

45、 is by armature voltage variation. to increase the speed to a high value, either u is made very large or is reduced. the latter is the most practical way and is known as field weakening. combinations of the two are used where a wide range of speed is required.直流電機(jī)速度控制調(diào)節(jié)系統(tǒng)調(diào)節(jié)系統(tǒng)是一類(lèi)通常能提供穩(wěn)定輸出功率的系統(tǒng)。例如，電機(jī)速

46、度調(diào)節(jié)器要能在負(fù)載轉(zhuǎn)矩變化時(shí)仍能保持電機(jī)速度為恒定值。即使負(fù)載轉(zhuǎn)矩為零，電機(jī)也必須提供 足夠的轉(zhuǎn)矩來(lái)克服軸承的粘滯摩擦影響。其它類(lèi)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(shuō)，即使?fàn)t內(nèi)的熱量散失也必須保持爐溫不變。一個(gè)電壓調(diào)節(jié)器必須也保持負(fù)載電流值變化時(shí)輸出電壓恒定。對(duì)于任何一個(gè)提供一個(gè)輸出，例如速度、溫度、電壓等的系統(tǒng)，在穩(wěn)態(tài)下必定存在一個(gè)誤差信號(hào)。電氣制動(dòng)在許多速度控制系統(tǒng)中，例如軋鋼機(jī)，礦坑卷?yè)P(yáng)機(jī)等這些負(fù)載要求頻繁地停頓和反向運(yùn)動(dòng)的系統(tǒng)。隨著減速要求，速度減小的比率取決于存儲(chǔ)的能量和所使用的制動(dòng)系統(tǒng)。一個(gè)小型速度控制系統(tǒng)（例如所知的伺服積分器）可以采取機(jī)械制動(dòng)，但

47、這對(duì)大型速度控制器并不可行，因?yàn)樯岷茈y并且很昂貴?？尚械母鞣N電氣制動(dòng)方法有：（1）回饋制動(dòng)。（2）渦流制動(dòng)。（3）能耗制動(dòng)。（4）反向（接）制動(dòng)。回饋制動(dòng)雖然并不一定是最經(jīng)濟(jì)的方式，但卻是做好的方式。負(fù)載中存儲(chǔ)的能量通過(guò)工作電機(jī)（暫時(shí)以發(fā)電機(jī)模式運(yùn)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(dāng)了一個(gè)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(shí)回饋過(guò)程中最終引起的端電壓升高會(huì)很少。在直流電機(jī)速度控制沃特-勒奧那多法中，回饋制動(dòng)是固有的，但可控硅傳動(dòng)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(chǎng)的速度，感應(yīng)電機(jī)傳動(dòng)裝置可以反饋。有晶閘管換流器而來(lái)的廉價(jià)變頻電源的出現(xiàn)在變速裝

48、置感應(yīng)電機(jī)應(yīng)用中引起了巨大的變化。渦流制動(dòng)可用于任何機(jī)器，只要在軸上安裝一個(gè)銅條或鋁盤(pán)并在磁場(chǎng)中旋轉(zhuǎn)它即可。在大型系統(tǒng)中，散熱問(wèn)題很重要的，因?yàn)槿绻L(zhǎng)時(shí)間制動(dòng)，軸、軸承和電機(jī)的溫度就會(huì)升高。在能耗制動(dòng)中，存儲(chǔ)的能量消耗在回路電阻器上。用在小型直流電機(jī)上時(shí)，電樞供電被斷開(kāi)，接入一個(gè)電阻器（通常是一個(gè)繼電器、接觸器或晶閘管）。保持磁場(chǎng)電壓，施加制動(dòng)降到最低速。感應(yīng)電機(jī)要求稍微復(fù)雜一點(diǎn)的排布，定子繞組被從交流電源上斷開(kāi)，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(dòng)應(yīng)用在許多大型交流升降系統(tǒng)中，制動(dòng)的職責(zé)是反向和延長(zhǎng)。任何電機(jī)都可以通過(guò)突然反接電源以提供反向的旋轉(zhuǎn)方向（反接制動(dòng)）來(lái)停機(jī)。在

49、可控情況下，這種制動(dòng)方法對(duì)所有傳統(tǒng)裝置都是適用的。它主要的缺點(diǎn)就是當(dāng)制動(dòng)等于負(fù)載存儲(chǔ)的能量時(shí)，電能被機(jī)器消耗了。這在大型裝置中就大大增加了運(yùn)行成本。等脈寬pwm法 vvvf(variable voltage variable frequency)裝置在早期是采用pam（pulse amplitude modulation）控制技術(shù)來(lái)實(shí)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法的這個(gè)缺點(diǎn)發(fā)展而來(lái)的，是pwm法中最為簡(jiǎn)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(guò)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(dāng)控制方

50、法即可使電壓與頻率協(xié)調(diào)變化。相對(duì)于pam法，該方法的優(yōu)點(diǎn)是簡(jiǎn)化了電路結(jié)構(gòu)，提高了輸入端的功率因數(shù)，但同時(shí)也存在輸出電壓中除基波外，還包含較大的諧波分量。隨機(jī)pwm  在上世紀(jì)70年代開(kāi)始至上世紀(jì)80年代初，由于當(dāng)時(shí)大功率晶體管主要為雙極性達(dá)林頓三極管，載波頻率一般不超過(guò)5khz，電機(jī)繞組的電磁噪音及諧波造成的振動(dòng)引起了人們的關(guān)注。為求得改善，隨機(jī)pwm方法應(yīng)運(yùn)而生。其原理是隨機(jī)改變開(kāi)關(guān)頻率使電機(jī)電磁噪音近似為限帶白噪聲（在線性頻率坐標(biāo)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(kāi)關(guān)頻率為特征的有色噪音強(qiáng)度大大削弱。正因?yàn)槿绱?，即使在igbt已被廣泛應(yīng)用的今天，對(duì)于

51、載波頻率必須限制在較低頻率的場(chǎng)合，隨機(jī)pwm仍然有其特殊的價(jià)值；另一方面則說(shuō)明了消除機(jī)械和電磁噪音的最佳方法不是盲目地提高工作頻率，隨機(jī)pwm技術(shù)正是提供了一個(gè)分析、解決這種問(wèn)題的全新思路。 空間電壓矢量控制pwm   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(jī)氣隙的理想圓形旋轉(zhuǎn)磁場(chǎng)軌跡為目的，用逆變器不同的開(kāi)關(guān)模式所產(chǎn)生的實(shí)際磁通去逼近基準(zhǔn)圓磁通，由它們的比較結(jié)果決定逆變器的開(kāi)關(guān)，形成pwm波形。此法從電動(dòng)機(jī)的角度出發(fā)，把逆變器和電機(jī)看作一個(gè)整體，以內(nèi)切多邊形逼近圓的方式進(jìn)行控制，使電機(jī)獲得幅值恒定的圓形磁場(chǎng)(正弦

52、磁通)。  具體方法又分為磁通開(kāi)環(huán)式和磁通閉環(huán)式。磁通開(kāi)環(huán)法用兩個(gè)非零矢量和一個(gè)零矢量合成一個(gè)等效的電壓矢量，若采樣時(shí)間足夠小，可合成任意電壓矢量。此法輸出電壓比正弦波調(diào)制時(shí)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(gè)電壓矢量，形成pwm波形。這種方法克服了磁通開(kāi)環(huán)法的不足，解決了電機(jī)低速時(shí)，定子電阻影響大的問(wèn)題，減小了電機(jī)的脈動(dòng)和噪音。但由于未引入轉(zhuǎn)矩的調(diào)節(jié)，系統(tǒng)性能沒(méi)有得到根本性的改善。 矢量控制pwm   矢量控制也稱(chēng)磁場(chǎng)定向控制，其原理是將異步電動(dòng)機(jī)在三相坐標(biāo)系

53、下的定子電流ia，ib及ic，通過(guò)三相/二相變換，等效成兩相靜止坐標(biāo)系下的交流電流ia1及ib1，再通過(guò)按轉(zhuǎn)子磁場(chǎng)定向旋轉(zhuǎn)變換，等效成同步旋轉(zhuǎn)坐標(biāo)系下的直流電流im1及相當(dāng)于直流電動(dòng)機(jī)的勵(lì)磁電流；it1相當(dāng)于與轉(zhuǎn)矩成正比的電樞電流），然后模仿對(duì)直流電動(dòng)機(jī)的控制方法，實(shí)現(xiàn)對(duì)交流電動(dòng)機(jī)的控制。其實(shí)質(zhì)是將交流電動(dòng)機(jī)等效為直流電動(dòng)機(jī)，分別對(duì)速度、磁場(chǎng)兩個(gè)分量進(jìn)行獨(dú)立控制。通過(guò)控制轉(zhuǎn)子磁鏈，然后分解定子電流而獲得轉(zhuǎn)矩和磁場(chǎng)兩個(gè)分量，經(jīng)坐標(biāo)變換，實(shí)現(xiàn)正交或解耦控制。但是，由于轉(zhuǎn)子磁鏈難以準(zhǔn)確觀測(cè)，以及矢量變換的復(fù)雜性，使得實(shí)際控制效果往往難以達(dá)到理論分析的效果，這是矢量控制技術(shù)在實(shí)踐上的不足。此外它必須直

54、接或間接地得到轉(zhuǎn)子磁鏈在空間上的位置才能實(shí)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(yīng)用場(chǎng)合帶來(lái)不便。無(wú)刷直流電機(jī)是近年來(lái)迅速發(fā)展起來(lái)的一種新型電機(jī),它利用電子換相代替機(jī)械 換相,既具有直流電動(dòng)機(jī)的調(diào)速性能,又具有交流電機(jī)結(jié)構(gòu)簡(jiǎn)單、運(yùn)行可靠、維護(hù)方便等。而且體積小、效率高,在許多領(lǐng)域已得到了廣泛的運(yùn)用。單片機(jī)控制的永磁無(wú)刷直流電動(dòng)機(jī)調(diào)速系統(tǒng)適用于電動(dòng)自行車(chē)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(diǎn)。根據(jù)永磁無(wú)刷直流電動(dòng)機(jī)的特性實(shí)施脈寬pwm控制，并通過(guò)轉(zhuǎn)速傳感器測(cè)量轉(zhuǎn)速通過(guò)數(shù)碼管動(dòng)態(tài)顯示出其轉(zhuǎn)速

55、，通過(guò)軟硬件的配合使用，實(shí)現(xiàn)了整個(gè)系統(tǒng)的速度控制的要求。無(wú)刷直流電動(dòng)機(jī)驅(qū)動(dòng)器 ideal torque production理想的扭矩生產(chǎn)：as stated earlier, a brushless dc motor generally describes a motor having a t如前所述，直流無(wú)刷電機(jī)一般描述了電機(jī)具有trape - zoidal back emf.zoidal反電勢(shì)。 for this case, the phase currents are rectangular pulses, some對(duì)于這種情況下，相電流矩形脈沖，有時(shí) loosely identified as squarewave currents.松散確定為squarewave電流。 while (8.3) can be used to describe torq雖然可以用來(lái)描述扭矩production for this motor, it is easier to understand this configuration graph