SU985915A1 - Adjustable dc electric drive with periodic load - Google Patents

Description

(54) ADJUSTABLE DC ELECTRIC DRIVE WITH PERIODIC LOAD

The invention relates to electrical engineering, in particular, to adjustable DC electric drives operating with variable load, having a constant and harmonic component, for example, electric drives of centrifugal vibromodules, swinging mechanisms of crystallizers. A valve electric drive containing a direct current motor, valve converters for powering the core circuits and driving the motors, speed and current controllers for the core, and a motor drive control system are known. The disadvantages of this electric drive are significant ripple of current and frequency of rotation of the electric drive, which leads to the need to increase the power of the installed engine and to the deterioration of product quality. An electric actuator is also known, which additionally contains a rotation angle converter of the mechanism shaft into a sinusoidal signal, the output of which is connected to the input current regulator of engine 2. This electric system reduces fluctuations in engine speed, however, current ripples in the core are not eliminated. In addition, a valve actuator with a subordinate regulation of the core current and rotation frequency is known, which contains a periodic signal generator, a unit for calculating the root-mean-square velocity deviation, an analyzer of oscillation of the drive parameters, a self-tuning unit for the phase and waveform signal H. However, this drive has a control system. The closest to the invention according to the technical essence is an electric drive comprising an electric motor, a thyristor converter of the power supply of the motor circuit, a series-connected current regulator, a regulator of the motor rotation frequency, an inverter power supply converter of the motor winding, and an angle converter into a sinusoidal signal , the input of which is connected to the shaft of the eccentric mechanism j offset blocks and frequency sensors connected to the inputs of the corresponding regulators increments, the current core and the excitation current k. A disadvantage of the known electric drive is the manual control of the phasing units, as a result of which the ripple current and speed are compensated only for a certain fixed speed. At a different drive speed, the setting of the phasing unit must be changed. This makes it difficult to operate the drive, and if it is necessary to change the rotation frequency in software mode (for example, in vibromodule electric drives), the compensation of current oscillations of the core and rotation frequency at frequencies other than fixed | for which the phasing blocks are tuned) becomes impossible which is reflected in the quality of the speed control. The purpose of the invention is to improve the quality of electric drive control. The goal is achieved by the fact that two displacement units, three scaling units, a multiplication unit, two demodulators and a rotation angle converter are inserted into a cosine signal, the output of which through the first demodulator is connected to the first input of the multiplication unit, the second input of which is through the first scaling unit. connected to the output of the rotational speed sensor, and the output to the inputs of the second and third scaling units, the outputs of which are connected respectively to the input of the rotational speed regulator and the input An excitation pulse, while the output of the angle converter into a sinusoidal signal is connected to the inputs of the rotational frequency and excitation controllers through the second demodulator and displacement blocks, the formation at the inputs of the rotational frequency and excitation regulators of the signal proportional to the cosine of the angle of rotation of the output shaft sine wave provides the corresponding phase shift of the compensating effect, and multiplying the cosine wave signal by a signal proportional to the output shaft rotation frequency The output from the output of the drive speed sensor provides automatic change of the phase shift of the compensating effect in 1 {) function of change of the rotation frequency of the electric drive. The electric drive contains a DC motor 1, the measles of which is powered by a valve, for example thyristor, converter 2, and its excitation winding 3 is powered by a thyristor converter L. These converters have a system. 5 and 6 of the pulse-phase control, Electric | WD also contains a rotational frequency controller 7 with a limitation unit 8, a core current regulator 9 and a regulator 10 excitation. The rotational frequency sensor 11, current sensors 12 and 13 are used in the feedback circuits core, voltage sensor 1 and excitation sensor 15. At the input of the speed controller, the intensity setting device 16 is turned on. The motor 1, through a gearbox 17, on which the output shaft 18 of which an eccentric 19 is mounted, drives the mechanism 20 into reciprocating motion. With the shaft 18, the angle converters 21 and 22 are connected into a sinusoidal and cosine wave (as converters 21 and 22 used, for example, a rotating transformer). The rotation angle converter 21 through demodulator 23 and the first bias unit 2 (consisting, for example, of a resistor with a voltage source connected to it) is connected to the inputs of the speed regulator 7, and through the second bias unit 25 to the regulator inputs torus 10 excitation. The rotation angle converter 22 into a cosine signal is connected via a demodulator 26 to a first input of multiplication unit 27, the second input of which is connected via a first scaling unit 28 to a rotational speed sensor 11. The output of the multiplication unit 27 through the second scaling unit 29 is connected to the input of the speed regulator 7 and through the third scaling unit 30 to the input of the excitation controller 10. The drive works as follows. When the shaft 18 with the eccentric 19 is rotated, the mechanism 20 is driven in a reciprocating motion. On the shaft 18, a load moment acts cyclically. The torque of the engine is M Mn + Hg-sin t .cp, where Hn is a constant component of the moment; Mq is the amplitude value and frequency of the variable component of the moment; time; , current and motor magnetic flux; K.- constructive engine constant. In order to maintain a constant current of the motor i 1c const, the motor flow Cp must be changed according to the order M + Ma-S4n5lt LL (L: KM-IH) This is achieved by supplying two exclusion signals from the converters 21 and 22 of the steering angle to the input of the excitation controller 10 The first correction signal is generated by the angle converter 21 into a sinusoidal signal and through the demodulator 23 and the displacement unit 2 supplies from the input of the rotational frequency controller 7, and through the offset unit 25 to the input of the excitation controller 10 The second correction signal is generated the rotation angle pickup 22 into a cosine signal and feed through demodulator 26 to a block 27 p of the multiplication unit, where it is multiplied with the signal of the rotation speed sensor 11 supplied through the scaling unit 28 to the second input of the multiplying unit. The resulting signal from the output of the multiplying unit through the block 29, the scaling is fed to the input of the speed regulator 7, and through the third scaling unit 30 to the input of the excitation controller 10. Corrective signals are supplied to the additional inputs of the regulators and 10. The introduction of the second correction signal is equivalent to the phase shift of the first correction signal. Moreover, the phase shift depends on the pulsation frequency SI (frequency of shaft shaft 18) and changes automatically as a function of frequency. This is explained as follows. In steady state operation (52 d? T / dt, where OS. Is the angle of rotation of shaft 18, the sum of correction signals supplied to the input of excitation controller 10 from converters 21 and 22 through demodulators 23 and 26, after conversion in blocks 28- 30 scaling, 25 displacement block and multiplication block 27 are equal to Uj. Color centers where (c is a constant voltage to compensate for a constant momentum, is formed using an offset unit 25; the maximum voltage value at the output of the demodule tori 23 and 26; Uqg- voltage at the output of the frequency sensor 11 is rotated ; K and Kg are the transmission coefficients of the first 28 and third 30 scaling units; The output voltage of the rotational speed sensor is determined by the following COOT: - Adhesive –MWD de CHz - transmission coefficient of the rotational speed sensor 11; Cr - transmission ratio of the gearbox 17. Using the well-known formulas for the recording of isusoidal quantities, the expression l), taking into account (2), is represented as Ug Uf, 1-Uo, -A-sin (nt-bCf) j (3) .a.cl4lbM.Ssj). The expression (h) indicates that the sum correction signal supplies the input of the excitation controller 10 with a phase leading phase tf, the value of which automatically changes as a function of the frequency of rotation of the SI shaft 18, This signal is compensated. 985911 sirut inertia of the controller 10 excitation.

In order to compensate for the effect of the harmonic component of the motor flux on the rotational speed, one should keep in mind 5 the law of the voltage variation of the valve converter 2.

 n ,, con5t From the equality ,, E./NE-HH., (.-.,.

we find, u -; - InIa -; gmf7.

Cdd C

. To implement this law of voltage variation of converter 2, the elements of the circuit 23, 2528, 30 act in analogy with the elements 23, 2k, 26-29.

The required phase of the total correction signal supplied to the input of the rotational frequency controller 7 is adjusted by setting the transmission coefficients of the scaling units 28 and 29, and the correction signal supplied to the input of the controller 10 is adjusted by setting the coefficients of the scaling units 28 and 30,

The combined effect of the two channels of forming the required laws for changing the magnetic flux of the motor .1 and the voltage of the converter 2 ensures an effective reduction of current and rotation frequency fluctuations.

The invention eliminates the manual adjustment of the phase of the compensating signal when the speed changes and thereby improves the speed and accuracy of the transition from one speed to another. When synchronizing speeds and synchronizing the work of several centrifugal vibromodules forming a vibroblock and controlled from one software device, the use of such electric drives improves interconnects the vibromodules, improves the harmonic composition of the vibrations generated by the vibroblock, and reduces the associated energy cal losses.

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Claims (3)

1. Lebedev E.D. and others. Control of valve electric drives of direct current. M., Energie, 1970, with. 76-83. 2. German Patent No. 1282YO, cl. 21 from 62/05, 1969. 3. USSR author's certificate N ° 729797, cl. H 02 R 5/00, 1977. k. USSR Author's Certificate No. 555525, cl. H 02 R 5/06, 1971.