SU1339855A1 - D.c.electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used to control DC motors. The aim of the invention is to increase the quality of drive control. The electric drive contains a forming link 13 with an operational amplifier and a resistor-capacitor feedback circuit. The current amplitude fixing unit 17 of the core includes an analog-digital converter 18 and memory blocks 19 and information changers 20, three comparators 21, 22 and 23 with sensors 24, 25, 26 of the response level. In this electric drive, forced oscillations of the power circuit current are reduced in a wide frequency range. 5 il. with Z5 LZZl-J (/) FIG.

Description

I. in the circuit with forcing 1 in the circuit without forcing. The invention relates to the field of electrical engineering and can be used in electric drives of direct current.

The aim of the invention is to improve the quality of drive control.

FIG. 1 shows a functional electrical circuit of a direct current drive; Fig. 2 is a graph showing the change in current i of an electric motor with a cyclic pulsating load on the shaft as a function of time (quasi steady state); in fig. 3 is a graph of the change in motor current under cyclic shock load on the shaft (quasi-steady mode); in fig. 4 is a graph of changes in the ratio of the currents of the engine core to one and the two-fold integrating systems of the subordinate regulation as a function of the ripple frequency of the load f; in fig. 5 is a graph of current-to-current ratio

of the parameter cf, which characterizes the constant time of the forcing element at a frequency of f 4 Hz.

The direct current drive comprises an electric motor 1 connected to converter 2 and series-connected frequency controller 3, intensity setpoint 4, PI controller 5 speed of rotation in 1SH controller 6 current connected to converter 2 input, first switching element 7, the shunt capacitor 8 of the feedback circuit of the PI controller of the rotation frequency 5, series-connected tachogenerators 9 and the voltage sensor 10, whose output is connected to the feedback input of the PI controller of the rotation frequency 5, the current meter 11 and the current sensor 12, the output of which is connected to the feedback input of the pi current regulator 6, are connected.

The actuator also contains a forming link 13 with an operational amplifier and a resistor-capacitor feedback circuit, including a parallel-connected capacitor 14 and a second switching element 15, the third switching element 16 connected in series, and a current amplitude-fixing unit 17, including an analog-to-digital converter 18 and blocks 19 and 20 of memory and change of information, three comparators 21-23 with setting devices 24-26 of the trigger level, i two triggers 27 and 28, and a start and braking control unit 29 having two inputs and two the output, one of which is connected to the control input of the third switching element 16, the free output of which is connected to the output of current sensor 12, the output of the current amplitude fixing block 17 of the core is connected to the comparator inputs, the outputs of the first 27 and second 28 flip-flops are connected to the control inputs

respectively, the first 7 and second 15 switching elements, the first and second inputs of the starting and braking unit 29 are connected to the outputs, respectively, of the setting device 3 rotational speed

and voltage sensor 10, the outputs of the first 21 and second 22 comparators are connected to the first inputs of the first 27 and second 28, respectively, triggers, the second inputs of which are connected to the output of the third comparator 23 and the second output of the starting and braking unit 29.

The drive works as follows.

The motor 1 is powered by a thyristor converter 2. The values of the converter voltage are determined by the setpoint of the rotation speed setting 3, and the acceleration rate is set by the intensity setting 4. When started, the current regulator 6 provides the acceleration of the engine with a constant maximum torque on the shaft. A feedback signal is provided to the input of current sensor 12 from

meter 11 current box

Before the start of the start-up process is completed, during the course of the start-up and braking control unit 29, there is no signal and the third switching element 16 turns off

input circuit analog-digital converter 18.

After the motor 1 is accelerated to a predetermined rotational frequency by the signal from the output of block 29, the third switching element 16 connects the current amplitude block 17 to the current sensor 12. The electric motor operates in the quasi-established mode of forced oscillations. In this case, the current of the core will change along the curve (Fig. 2) under the action of a pulsating moment on the shaft or along curves (Fig. 3) in case a periodic shock moment is applied to the shaft.

The rotational speed controller 5 supplies a setting voltage to the input of the control system of the converter 2 and receives a feedback signal from the tachogenerator 9 via the voltage sensor 10.

To minimize electric power losses during long-term operation in a quasi-steady state, the circuit continuously compares the magnitude of the current magnitude 1, with a given optimal value of the extremum I and the corresponding change

structure of links of the regulation system. For this purpose, the output signal of current sensor 12 is supplied via a third switching element 16 to a block 17 for recording the amplitude of the current box cor.

The optimum value of the extremum of the current 1 "is determined by calculating the condition of limiting the loss of electric power and ensuring the specified value of the first harmonic of the frequency of rotation of the engine. In the absence of rigid constraints on the amplitude of the pulsations of the angular velocity of the electric drive (Li), it is advisable to take the value of I equal to the amplitude of current oscillations in a single-integrating system of subordinate regulation, adjusted according to the modular optimum.

t mcftl

 1 +

where Mg is the amplitude of the static moment on the shaft; C, is the moment coefficient; f - magnetic flux; t - constant time

current loop contouring; I - the angular frequency

load.

If for the permissible value of the deviation of the angular velocity, the inequality

  t.Aop ",",

where ay, and 4U) - - amplitudes of harmonics

 tn Z rm

angular velocity in

m

ST

Fg +

 . I

one and twice integrating SAR, then the corresponding value of the optimum amplitude of the current is -gg

dt of condition

. / 1 +

. Met p

t.opt-S „F

„“

1 + 64TfSl

Q g

2o and 25

35

g

50

-gg

„“

l

Adjusters 24 and 25 give settings for the optimum value of the current extremum 1 p, respectively, to the first and second comparators 21 and 22, and the setpoint of the setpoint 25 somewhat exceeds the setpoint of the setter 2D.

Due to the fact that the signal from the trigger 28 is removed from the inverse output, when 1 1 there is a voltage on the control electrode of the second switching element 15, the capacitor 14 is bridged and the boost link 13 becomes proportional.

If, with an increase in the load on the shaft or the frequency of the pulsating moment or the pulse frequency of the cyclic shock, the amplitude of the core current exceeds 1 by a certain value set by the setting device 24, the trigger trigger 27 of the comparator 21 is activated. This is applied to the control electrode of the first switching element 7 .

The capacitor 8 is shunted, the regulator -5 becomes proportional. In accordance with FIG. 4, in the zone of the most common frequencies of 1-5 Hz or more, the magnitude of the core current decreases significantly. If during further operation condition 1 Irn.onr occurs again and the signal exceeds the setpoint of the setpoint 25, a voltage appears at the output of the comparator 22, at the inverse output of the trigger 28 and accordingly at the control electrode of the second switching element 15 the signal disappears into the circuit a capacitor 14 is introduced. The link 13 becomes forcing, which leads to a decrease in the current amplitude of the core in accordance with the curve in FIG. five.

If during the operation of the mechanism, when the amplitude of the torque on the shaft of the electric drive or its frequency decreases, the amplitude of the core current decreases to the value set by the setting device 26, a signal is generated at the output of the third comparator 23, which returns the triggers 27 and 28 to their original states. A capacitor 8 is reintroduced into the circuit, and a capacitor 14 is shunted. The third switching element 16 disables the input unit 17 fixing the amplitude of the current box. The circuit returns to its original state. Similar switchings occur in the circuit when the drive is stopped, when the setpoint 3 rotational speed is shifted to the zero position. After the termination of deceleration of the electric motor 1, at the output of the control and start braking unit 29, a signal O is generated, which returns the triggers 27 and 28 to the initial state.

The proposed electric drive reduces the forced oscillations of the power circuit current in a wide frequency range, which ensures a reduction in the IQ loss of the mutation element connected between the output of the current sensor and the input of the current amplitude fixing box of the core, three comparators with setters for leveling, two triggers and a block

15 control of starting and braking, having two inputs and two outputs, one of which is connected to the control input of the third co-switching element, output of the current amplitude fixing unit

The 2Q core is connected to the inputs of the comparators, the outputs of the first and second triggers are connected to the control inputs of the first and second switching elements, respectively, the first and second

25 inputs of the control unit for starting and braking are connected to the outputs respectively of the rotational frequency adjuster and the voltage sensor; the outputs of the first and second comparators are connected to

30 first inputs, respectively, of the first and second triggers, the second inputs of which are connected to the output of the third comparator and the second output of the control unit for starting and braking.

electricity in the engine and converter.

Claims (1)

Invention Formula A DC motor that contains a motor connected to the converter and connected in series with a rotational frequency adjuster, an intensity adjuster, a PI speed regulator, and a PI current regulator connected to the converter input, the first switching element, a shunt capacitor in the feedback circuit PI frequency controller, serially connected tachogenerator and voltage sensor, the output of which is connected to the feedback input of the PI frequency controller, in series with unity current meter and current sensor, characterized in that, in order povsheni quality control, it boosts administered link with a resistor-capacitor feedback circuit and connected between the output of the tick sensor and the feedback input of the PI current controller, the second switching element shunting the forcing feedback feedback circuit capacitor, the current amplitude lock core block, the third com 0} 1 / g.2 Fig.Z 125 75 Hz FIG A g 3 5 fig. five V Editor L. Gratilllo Compiled by V. Trofimenko Tehred L. Serdyukova Proofreader A. Obruchar Order 4243/54 Circulation 659 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4