机械 外文翻译 外文文献 英文文献 直流电动机调速控制.docx

1、机械 外文翻译 外文文献 英文文献 直流电动机调速控制Speed Control of DC MotorAbstract Conditioning system is characterized in that output power to maintain stability. Different speed control system can use a different brake system, high starting and braking torque, quick response and quick adjustment range of degree require

2、ments of DC drive system, the use of the electric braking mode. Depends on the speed control of DC motor armature voltage and flux. To zero speed, or U = 0 or = . The latter is impossible, it only changes through the armature voltage to reduce speed. To speed to a higher value can increase or decrea

3、se the U .Keyword DC Speed Feedback BrakeRegulator 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 remo

4、ved, the motor must 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

5、maintain the output 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 systems, e.g., rolling mills, mine winders, etc.

6、, 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 th

7、is 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

8、 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 delivere

9、d. Providing the 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 rege

10、nerate. Induction motor drives can regenerate if the rotor shaft is driven faster than speed of the rotating field. The advent of low-cost variable-frequency supplies from thyristor inverters have brought about considerable changes in the use of induction motors in variable speed drives.Eddy current

11、 braking can be applied to any machine, simply by mounting a copper or aluminum 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, bearings, and motor will be raised if prolonged braking is appl

12、ied.In dynamic braking, the stored energy is dissipated in 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 a

13、pplied down to the 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 A

14、C hoist systems where the braking duty is both severe and prolonged.DC Motor Speed ControlThe basis of all methods of DC motor speed control is derived from the equations:the terms having their usual meanings. If the IaRa drop is small, the equations approximate to or。Thus, control of armature volta

15、ge 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 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 an

16、d is known as field weakening. Combinations of the two are used where a wide range of speed is required.A Single-Quadrant Speed Control System Using ThyristorsA single-quadrant thyristor converter system is shown in Fig.1.For the moment the reader should ignore the rectifier BR2 and its associated c

17、ircuitry (including resistor R in the AC circuit), since this is needed only as a protective feature and is described in next section.Fig.1 Thyristor speed control system with current limitation on the AC sideSince the circuit is a single-quadrant converter, the speed of the motor shaft (which is th

18、e output from the system) can be controlled in one direction of rotation only. Moreover, regenerative braking cannot be applied to the motor; in this type of system, the motor armature can suddenly be brought to rest by dynamic braking (i.e. when the thyristor gate pulses are phased back to 180o, a

19、resister can be connected across the armature by a relay or some other means).Rectifier BR1 provides a constant voltage across the shunt field winding, giving a constant field flux. The armature current is controlled by a thyristor which is, in turn, controlled by the pulses applied to its gate. The

20、 armature speed increases as the pulses are phased forward (which reduces the delay angle of firing), and the armature speed reduces as the gate pulses are phased back.The speed reference signal is derived from a manually operated potentiometer (shown at the right-hand side of Fig.23.1), and the fee

21、dback signal or output speed signal is derived from the resistor chain R1 R2, which is connected across the armature. (Strictly speaking, the feedback signal in the system in Fig.23.1 is proportional to the armature voltage, which is proportional to the shaft speed only if the armature resistance dr

22、op, IaRa, is small. Methods used to compensate for the IaRa drop are discussed in Reading Material.)Since the armature voltage is obtained from a thyristor, the voltage consists of a series of pulses; these pulses are smoothed by capacitor C. The speed reference signal is of the opposite polarity to

23、 the armature voltage signal to ensure that overall negative feedback is applied.A feature of DC motor drives is that the load presented to the supply is a mixture of resistance, inductance, and back EMF Diode D in Fig.1 ensures that the thyristor current commutates to zero when its anode potential

24、falls below the potential of the upper armature connection, in the manner outlined before. In the drive shown, the potential of the thyristor cathode is equal to the back EMF of the motor while it is in a blocking state. Conduction can only take place during the time interval when the instantaneous

25、supply voltage is greater than the back EMF.Inspection of Fig.2 shows that when the motor is running, the peak inverse voltage applied to the thyristor is mush greater than the peak forward voltage. By connecting a diode in series with the thyristor, as shown, the reverse blocking capability of the

26、circuit is increased to allow low-voltage thyristor to be used.References:Fig.2 Illustrating the effect of motor back EMF on thePeak inverse voltage applied to the thyristorFig.3 Armature voltage waveformsThe waveforms shown in Fig.2 are idealized waveforms as much as they ignore the effects of arma

27、ture inductance,commutator ripple,etc.Typical armature voltage waveforms are shown in Fig.3.In this waveform the thyristor is triggered at point A, and conduction continues to point B when the supply voltage falls below the armature back EMF.The effect of armature inductance is to force the thyristo

28、r to continue to conduct until point C,when the fly-wheel diode prevents the armature voltage from reversing. When the inductive energy has dissipated (point D), the armature current is zero and the voltage returns to its normal level, the transients having settled out by point E.The undulations on

29、the waveform between E and F are due to commentator ripple.References1.Landau ID(1999)From robust control to adaptive control.Control Eng Prac 7:111311242.Forssell U,Ljung L(1999)Closed-loop identification revisited. Automatica 35:121512413.Soderstrom T,Stoica P(1989)System identification.Prentice H

30、all,Cambridge,UK4.Horng JH(1999)Neural adaptive tracking control of a DC motor.Information Sci 118:1135.Lyshevski SE(1999)Nonlinear control of mechatronic systems with permanent-magnet DC motors.Mechatronics 9:5395526.Yavin Y,Kemp PD(2000)Modeling and control of the motion of a rolling disk:e?ect of

31、 the motor dynamics on the dynamical model.Comput Meth Appl Mech Eng 188:6136247.Mummadi VC(2000)Steady-state and dynamic performance analysis of PV supplied DC motors fed from intermediate power converter.Solar Energy Mater Solar Cells 61:3653818.Jang JO,Jeon GJ(2000)A parallel neuro-controller for

32、 DC motors containing nonlinear friction.Neurocomputing 30:2332489.Nordin M,Gutman P(2002)Controlling mechanical systems with backlasha survey.Automatica 38:1633164910.Wu R-H,Tung P-C(2002)Studies of stick-slip friction,pre-sliding displacement,and hunting.J Dyn Syst 124:11111711.Ogata K(1990)Modern control engineering.Prentice Hall,Englewood Cli?s,NJ12.Slotine E,Li W(1991)Applied nonlinear control.Prentice Hall,Englewood Cli?s,NJ13.Lee PL(1993)Nonlinear process control:applications of gen-eric model control.Springer,Berlin Heidelberg New York直流电动机调速控制摘要 调节系统的特征在于