SU1171943A1 - Device for controlling induction motor - Google Patents

Abstract

A device for controlling an asynchronous motor with a phase-rotor, containing a rectifier, shunt and thyristor switch in the rotor winding phases, amplifier, comparator, sawtooth generator, control pulse shaper, the outputs of which are connected to control of the control: it uses an electrode, it is connected to a control voltage generator, the outputs of which are connected to the control of a wired winding; to the output of a comparator, the non-inverting input of which is connected to an amplifier, and the inverting input - to a saw-tooth voltage generator, characterized in that, in order to maintain a constant mechanical power when changing the speed of an asynchronous electric motor, a current sensor is inserted into it, a functional converter, I close (O push button, two potentiometers, the current sensor input is connected to the shunt, the output is connected to the input of the functional converter, the output of which is connected to the first potentiometer, the second potentiometer through the locking button to the non-inverting input of the comparator.

Description

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The invention relates to electrical engineering and can be used in controlled electric drives operating with constant shaft power, for example, in electric drives of winding machines of drawing mills. The aim of the invention is to maintain the constancy of the mechanical power when the speed of an asynchronous motor is varied. FIG. 1 shows a block diagram of the device; on .fig. 2 - characteristics of the electric drive and its individual blocks. A device for controlling an induction motor 1 (Fig. 1) with a phase rotor 2, comprising rectifier 3, shunt 4 and thyristor switch 5 in the rotor winding phases, amplifier 6, comparator 7, sawtooth generator 8, control pulse shaper 9, outputs which are connected to the control electrodes of the thyristors 10 of the pulse switch 5, and the input to the output of the comparator 7, the non-inverting input of which is connected to the amplifier 6, and the inverting input - to the sawtooth generator 8, a current sensor 11 brazer 12, closing button 13, two potentiometers 14 and 15, current sensor 11 input is connected to shunt 4, output to input of a functional converter 12, the output of which is connected to amplifier input b and to the first potentiometer 14, second potentiometer 15 is connected via a closing button 13 to the non-inverting input of the comparator 7. The device (Fig. 2) also contains the electromechanical characteristic 16 of the asynchronous electric drive, the static characteristic 17 of the current sensor 11, the static characteristic 18 of the functional converter 12 and rovochnuyu characteristics 19 pulse switch 5. The control apparatus operates as follows.

When the motor 1 is connected to the mains, it starts to accelerate at a predetermined rheostatic mechanical characteristic corresponding to the average resistance value of the switched resistor, the value of which is determined by the duty cycle y. The duty ratio is set by the potentiometer slider 15 with the button 13 closed for acceleration. Selection of the value of y and, accordingly, of the starting torque on the rheostat characteristic is made from the need to avoid looping, wire breaks and satisfactory laying of the first turns of the wire on the spool without slipping.

At the end of the acceleration of the asynchronous motor 1, up to a steady-state speed of knobs From considering the static characteristics in FIG. 2 shows that with increasing

package diameter, increases the torque and current of the rotor of the engine Id. This increases the signal at the output of current sensor 11 (Fig. 2, curve 17), and the control voltage Uy at the output of amplifier 6 decreases along curve 18 (Fig. 2). As a result

this decreases the duty cycle along curve 13 and increases the average value of resistance introduced into the rotor circuit. The rotation speed of the asynchronous motor 1 is reduced in accordance with curve 16 (Fig. 2) so that the tension remains constant. The speed range is determined by the largest package diameter, which is usually doubled. Therefore, the rotation speed of the motor 13 is opened, the high level of the control signal at the inverting input of the comparator 7 is removed and only the control voltage removed from the amplifier output remains. In this case, the asynchronous motor 1 is associated with a mechanical characteristic corresponding to curve 16 (Fig. 2) and set by potentiometer 13, which determines the amount of wire tension required during winding. During the winding process, with an increase in the package diameter under constant tension, the torque and rectified rotor current Id increase. Voltage proportional to the rotor current is removed from shunt 4, amplified by current sensor 11 and fed to the input of a functional converter 12, which performs non-linear conversion of the input voltage so that winding takes place according to characteristic 16 (Fig. 2). From the output of converter 12, the signal enters the comparison circuit at the inverting input of amplifier 6. Through potentiometer 14, characteristic 18 is shifted (Fig. 2) parallel to itself to select the desired tension during wire winding and installed on the control panel. Static characteristic 18 is the dependence of the signal at the output of amplifier 6 on the signal at the input of converter 12, i.e. (Ujp. The control voltage Uy is fed to the inverting input of comparator 7, to another input of which the reference saw voltage is applied From the output of the comparator 7 (Fig. 1) a periodic signal of rectangular shape and positive polarity enters the control pulse driver circuit 9 (Fig. 1) of thyristors 10. The magnitude of the control voltage Uy and determines the duty cycle 7 of tiris operation Hur 10. This is illustrated by the characteristics 18 and 19 in FIG. 2.

1 and the bobbins should be reduced when the bobbin is fully wound also twice

Thus, the introduction of a current sensor with a functional converter makes it possible to ensure the power of the asynchronous electric motor when its speed changes and, thus, to improve the quality of the wire winding due to the constant tension of the wire.

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Claims (1)

A device for controlling an asynchronous electric motor with a phase rotor, comprising a rectifier, a shunt and a thyristor switch in the phases of the rotor winding, an amplifier, a comparator, a sawtooth voltage generator, a control pulse generator, the outputs of which are connected to the control electrodes of the thyristor, and the switch has the input of which is connected to an amplifier, and the inverting one is connected to a sawtooth voltage generator, characterized in that, in order to maintain the constancy of the mechanical when changing the speed of the asynchronous electric _ motor, a current sensor is inserted into it, a <d functional converter, a closing button, two potentiometers, the input of the current sensor L · current is connected to the shunt, the output is to the l input of the functional converter, h the output of which is connected to the input of the amplifier and to the first potentiometer, the second K potentiometer through the closing button - t to the non-inverting input of the comparator. | 1>