RU2067351C1 - Ac electric drive - Google Patents

Abstract

FIELD: control systems of machines, machine-tools, automated industrial and domestic sewing machines. SUBSTANCE: ac drive has uncontrollable rectifier 12 and is provided with carrier-frequency generator whose output is connected to third input of third three-input adder 19, two flip-flops 13, 20, inverter 14, two AND gates 15, 16, and two controlled switches 8, 9 with four inputs and three outputs; first, second, and third inputs of first controlled switch 8 are connected to three like-polarity outputs of scaling-distributing device 7 whose fourth, fifth, and sixth outputs are coupled with first, second, and third inputs of second controlled switch 9; input of first flip-flop 13 is connected to output of master oscillator 17 and its output is connected to second input of second AND gate 16 and through inverter 14, to first input of first AND gate 15 whose second input is connected to output of second flip-flop 20 whose input is connected to output of third adder 19 and output, to first input of second AND gate 16. Output of each AND gate is coupled with fourth input of like-polarity controlled switch 8 (9). First, second, and third outputs of first controlled switch 8 are connected with like-polarity control inputs of self-contained inverter 10 whose fourth, fifth, and sixth control inputs are connected to first, second, and third outputs of second controlled switch 9. EFFECT: improved design. 2 dwg

Description

 The invention relates to the field of electrical engineering and can be used in control systems of machines, machine tools, in automated industrial and household sewing machines.

 The electric drive is an AC drive in which a three-phase asynchronous squirrel-cage induction motor is used as an actuating element.

 Currently, frequency-controlled electric drives are known, for example, the electric drive described in [1]. The specified electric drive contains a frequency control circuit including a first adder, limiter amplifier (UO), a second adder, an autonomous inverter control system (IMS), autonomous inverter (AI), a voltage control circuit, including a series-connected functional converter (FP), a third adder, an electric motor stator current regulator (RT), a control system a rectifier (SUV), a controlled rectifier, from the output of which the signal enters the second input of the autonomous inverter and, through the current sensor, to the second input of the third adder. A self-contained inverter controls an asynchronous electric motor, the output of which is connected through the speed sensor to the second inputs of the first and second adders, and the output of the limiter amplifier is connected to the input of the functional converter.

 The disadvantage of this electric drive is the small range of speed regulation, since the maximum value of the output adjustable frequency does not exceed 40 of the frequency of the supply network, as well as the large size and weight due to the presence of a rectifier control system and a controlled rectifier in the drive, which regulate the power supply voltage of the autonomous inverter.

 Of the known AC electric drives, the closest in technical essence is the electric drive described in 2. The specified electric drive contains a frequency control circuit including a series-connected input adder (operational amplifier K1), a correction device (zener diodes in the feedback of amplifier K2), an inverter control system, autonomous inverter, voltage control circuit, containing series-connected module isolation unit (amplifier K3 and diodes 10, and 2D), third adder (amplifier K4 Tel), a rectifier control system controlled rectifier, whose output signal is fed to the second input of the third adder. The input of the module selection unit is connected to the output of the correction device. A self-contained inverter controls an induction motor, the output of which is connected through a speed sensor to the first and second adders.

 The disadvantages of such an electric drive are relatively large dimensions and weight with low reliability, which is determined by the presence in the circuit of the rectifier control system and a controlled rectifier that regulate the supply voltage of the autonomous inverter.

 The purpose of this invention is to simplify the design, reduce weight and dimensions and increase the reliability of the electric drive by combining the functions of frequency and voltage control in one unit.

 The goal is achieved in that in an AC electric drive containing an electric motor with a speed sensor mounted on its shaft, connected to the output of an autonomous inverter, the power input of which is connected to the output of the rectifier, a speed controller connected to the first input of the first two-input adder, the second input of which is connected with the output of the speed sensor, and the output through the correction device is connected to the first input of the second two-input adder, the second input connected to the output of the speed sensor, and the output with the input of the control system of an autonomous inverter, composed of a master oscillator and a distribution and distribution device, connected in series, a module separation unit, input connected to the output of the correction device, and output with the first input of the third three-input adder, the second input of which is connected to the current sensor through the rectifier output, the rectifier is made uncontrollable and the carrier frequency generator is introduced, the output connected to the third input of the third three-input adder, a trigger, an inverter, two AND elements and two controlled keys with four inputs and three outputs, while the first, second and third inputs of the first controlled key are connected to the three outputs of the same switchgear, the fourth, fifth and sixth outputs of which are connected to the first , by the second and third inputs of the second controlled key, the input of the first trigger is connected to the output of the master frequency generator, and the output is connected to the second input of the second element And through an inverter with the first input of the first element And, the second the course of which is connected to the output of the second trigger, the input connected to the output of the third adder, and the output to the first input of the second element And, the output of each element And is connected to the fourth input of the same managed key, the first, second and third outputs of the first managed key are connected to the same control inputs autonomous inverter, the fourth, fifth and sixth control inputs of which are connected to the first, second and third outputs of the second managed key. The frequency of the signal from the carrier frequency generator is at least an order of magnitude higher than the maximum possible frequency of the signal of the master oscillator of the autonomous inverter control system.

In FIG. 1 shows a block diagram of an AC electric drive, where:
1 speed dial;
2 first two-input adder;
3 corrective device;
4 second two-input adder;
5, a control system for an autonomous inverter containing a master oscillator 6, for example, a microcircuit 541GG1 and a switchgear 7;
8 and 9 are controlled keys with four inputs and three outputs (made, for example, in the form of three transistors, the bases of which are interconnected and are the fourth input, the emitters of each transistor are the first, second and third inputs, respectively, and connected to the corresponding outputs of the distribution devices, and collectors are the first, second and third outputs connected to a stand-alone inverter);
10 autonomous inverter;
11 asynchronous electric motor;
12 rectifier (made according to the scheme of a three-phase diode bridge with smoothing capacitors);
13 trigger;
14 inverter, for example, chip 564LN2;
15 and 16 logical elements And, for example, chip K555LI1;
17 reference frequency generator
18 block selection module;
19 third three-input adder;
20 trigger;
21 speed sensors, for example, a tachogenerator;
22 current sensor, for example, a shunt.

 The AC electric drive comprises an asynchronous electric motor 11 with a speed sensor 21 mounted on its shaft, connected to the output of the autonomous inverter 10, the power input of which is connected to the output of the rectifier 12, the speed controller 1, the output connected to the first input of the first two-input adder 2, the second input of which is connected with the output of the speed sensor 21, and the output through the correction device 3 is connected to the first input of the second two-input adder 4, the second input connected to the output of the speed sensor 21, with the output ohm with the input of the control system of an autonomous inverter 5, made up of a master oscillator 6 and a switchgear 7 connected in series, an allocation unit 18 of the module, connected to the output of the correction device 3 by the input and the first input of the third three-input adder 19, the second input which through the current sensor 22 is connected to the output of the uncontrolled rectifier 12, the carrier frequency generator 17, the output connected to the third input of the third three-input adder 19, two triggers 13 and 20, in ertor 14, two elements And 15 and 16 and two managed keys 8 and 9 with four inputs and three outputs, while the first, second and third inputs of the first managed key 8 are connected to the three outputs of the same switchgear 7, fourth, fifth and the sixth outputs of which are connected with the first, second and third inputs of the second managed key 9, the input of the first trigger 13 is connected to the output of the master frequency generator 6, and the output is connected to the second input of the second element And 16 and through the inverter 14 with the first input of the first element And 15, tue The second input of which is connected to the output of the second trigger 20, the input connected to the output of the third adder 9, and the output with the first input of the second element And 16, the output of each element And 15 and 16 is connected to the fourth input of the same managed key, respectively 8 and 9, the first, second and the third outputs of the first managed key 8 are connected to the same control inputs of the autonomous inverter 10, the fourth, fifth and sixth control inputs of which are connected to the first, second and third outputs of the second managed key 9.

 Electric AC operates as follows.

 A signal proportional to the set speed from the setter 1 is fed to the first two-input adder 2, where it is algebraically summed with the signal of the speed feedback sensor 21 and fed to the input of the correction device 3, from where to the second two-input adder 4 and the module selection unit 18. To the second input two-input adder 4 receives a signal from the speed sensor 21, providing compensation for feedback on the counter-EMF of the engine in order to obtain the absolute slip value at the output of adder 2. The signal from the output of the adder 4 is fed to the input of the master oscillator 6 of the control system of the autonomous inverter 5. From the master generator 6, which generates clock pulses with a repetition rate proportional to the signal at the output of the adder 4 (output 1, Fig. 2), the signal is fed to the input switchgear 7 of the autonomous inverter control system 5. At each of the six inputs of the switchgear 7, a logical “1” appears alternately. Depending on the position of the logical "1", the switchgear produces a combination of control pulses of the autonomous inverter 10 (output 2 7 of Fig. 2). A stand-alone inverter 10, powered by an uncontrolled rectifier 12, controls the operation of the asynchronous motor 11. From the output of the module selection unit 18, the signal is fed to the first input of a three-input adder 19, to the second and third inputs of which signals from a current sensor 22 and a carrier frequency generator 17 are received. the input of the second trigger 20 is a sequence of pulses of constant frequency (output 8, Fig. 2) with a duty ratio proportional to the required voltage on the motor 11. The pulses of the signal from the output of the first trigger 13 (output 9, Fig. 2) have a frequency half that of the signals of the master oscillator 6 of the control system of an autonomous inverter. Logical signals "1" coming from the output of the first trigger 13 (output 9, Fig. 2) to the second input of the second element And 15 and from the inverter 14 (output 10, Fig. 2) to the first input of the first element And 15 are set to the outputs of the elements And 15 and 16 alternately the state of the logical "1", which corresponds to the passage during this time of the carrier frequency signals from the output 5 of the second trigger 20 with a duty ratio proportional to the required voltage on the motor (outputs 11 and 12, Fig. 2). Using the controlled keys 8 and 9, the signals from the output of the switchgear 7 of the control system of the autonomous inverter 5 are filled with pulses of the carrier frequency of the variable duty cycle, supplied to the fourth inputs of the controlled keys 8 and 9 only for a time corresponding to the set at the outputs of the elements And 15 and And 16 logical units (output 13 18, Fig. 2). The power switches of the autonomous inverter 10 controlling the asynchronous motor 11 are switched in accordance with the signals of the carrier frequency pulses of the controlled keys 8 and 9 for a limited period of time necessary only to reproduce the signal proportional to the error between the driving action and the signal from the motor speed sensor (output 13 18, Fig. 2), which ensures low heating of the power transistors of the autonomous inverter 10 and increased reliability of the AC electric drive. Thus, by making the rectifier in the AC drive uncontrollable and introducing the carrier frequency generator 17, trigger 20, inverter 17, two I 15 and 16 elements and two controlled keys 8, 9 into the electric drive, the design is greatly simplified, weight and dimensions are reduced, and its reliability is increased by eliminating the rectifier control system and the controlled rectifier. This ensures a small heating of the power transistors of the autonomous inverter, since the power transistors are switched by the carrier frequency pulses of the controlled keys 8 and 9 only for a limited period of time necessary to reproduce the signal proportional to the error between the driving action and the signal from the motor speed sensor.

 The functions of the rectifier control system and the controlled rectifier are performed by an uncontrolled rectifier introduced into the electric drive, a carrier frequency generator, a trigger and two controlled keys having small dimensions and weight.

 As a result of reducing the number of elements that control the high voltages present in the rectifier control system, which are excluded in the proposed electric drive, ensuring small heating of the power switches of the autonomous inverter by introducing a second trigger, an inverter, and two And elements with appropriate connections, the reliability of the electric drive is significantly increased. At the same time, elements operating at high voltage and having a relatively high cost are excluded, which leads to a reduction in the cost of the entire electric drive.

Information sources
1. V.V. Moskalenko. Automated Electric Drive, 1986, p. 239, Fig. 4. 32 a.

 2. A. S. Sandler, R. S. Sarbatov. Automatic frequency control of induction motors, 1974, p. 153, fig. 5 14.

 3. Yu. K. Rozanov. Fundamentals of power conversion technology, 1979, p. 323, fig. 5 10, p. 179, fig. 3 15.

 A. G. Alekseenko et al. Application of precision analog microcircuits, p. 142, fig. 5.17.

Claims (1)

 An AC drive containing an electric motor with a speed sensor mounted on its shaft, connected to the output of a stand-alone inverter, the power input of which is connected to the output of the rectifier, a speed controller, connected to the first input of the first two-input adder, the second input of which is connected to the output of the speed sensor, and the output through the correction device is connected to the first input of the second two-input adder, the second input connected to the output of the speed sensor, and the output to the input of the control system a stand-alone inverter, made up of a master oscillator and a switchgear, connected in series, a module isolation unit, connected to the output of the correction device by an input and an output with the first input of the third three-input adder, the second input of which is connected to the output of the rectifier through a current sensor, the fact that the rectifier is made uncontrollable and a carrier frequency generator is introduced, with an output connected to the third input of the third three-input adder, two trigs a unit, an inverter, two AND elements and two managed keys with four inputs and three outputs, the first, second and third inputs of the first managed key connected to the three outputs of the same switchgear, the fourth, fifth and sixth outputs of which are connected to the first, the second and third inputs of the second managed key, the input of the first trigger is connected to the output of the master frequency generator, and the output is connected to the second input of the second element And through an inverter with the first input of the first element And, the second input is the second is connected to the output of the second trigger, the input connected to the output of the third adder, and the output to the first input of the second element And, the output of each element And is connected to the fourth input of the same managed key, the first, second and third outputs of the first managed key are connected to the same control inputs of the autonomous inverters, the fourth, fifth and sixth control inputs of which are connected to the first, second and third outputs of the second managed key.

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