直流电机速度控制SpeedControlofDC Motor中英文资料.docx

1、直流电机速度控制Speed Control of DC Motor中英文资料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 t

2、he load torque is removed ,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 voltag

3、e regulator must also maintain must 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 system, e.g., rolling mills

4、 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 system used. A small speed control system (sometimes known as a velodyne) can employ mechani

5、cal braking, but this is not feasible 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).Regener

6、ative braking is the 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 unwant

7、ed energy is delivered. 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 arran

8、ged to invert to regenerate. Induction 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 vari

9、able speed drives. Eddy current braking 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 rais

10、ed if prolonged braking is applied.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 the armature (usually by a relay, contactor, or thyristor). The field voltage is maintaine

11、d, and braking is applied 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 appl

12、ied to many large AC hoist system where 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 i

13、s satisfactory for all drivers. Its major 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) inst

14、alls 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 to be able to adjust the pressure. The pulse width PWM law are precisely in order to overcome, is in the PW

15、M law which the PAM law this shortcoming 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 meth

16、od then to cause the voltage and the frequency 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

17、harmonic component.Stochastic PWM That 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 peoples inter

18、est. In order to obtain the improvement, 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

19、, various frequencies energy distribution 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 regar

20、ding the carrier frequency is comparing 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 p

21、rovides an analysis, has solved this 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 ma

22、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 decided the inventor the switch, forms the PWM profile. This law embarks from the

23、electric motor angle, regards as 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

24、 divides into the magnetic flux split-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

25、 law output 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 flux feedback, controls the magnetic flux the size and the change speed .Estimates the magnetic flux after the compariso

26、n and assigns the magnetic flux, 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

27、 the electrical machinery pulsation 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 m

28、otor under three-phase coordinate 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 transformatio

29、n, equivalent becomes under the synchronized 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 met

30、hod, realizes to the motor control. 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

31、 magnetic field two components, after 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 th

32、eoretical analysis effect, this is 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 velocit

33、y generator in this kind of vector 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. This approac