SU1539951A1 - Reversible asynchronous electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in a reversible automated asynchronous electric drive in devices for moving tape media. The aim of the invention is to increase energy performance and speed. The reversible asynchronous electric drive contains a three-phase electric motor 1, a speed regulator 2, a current regulator 3, a module 4, a zero-organ 5, a logic element AND 6, an amplifier 7, a controlled key element 8, a generator 9 of the reference voltage, a setting device 10 , logical element EXCLUSIVE OR 11, threshold elements 12,13, galvanic isolation unit 14, triac 15, rotational speed sensor 16, capacitor 17, saturating choke 18, three-phase bridge rectifier 19, current sensor 20, rotational frequency setting device 21 and switch 22 characters. The use of two voltage regulators - a triac 15 and a bridge rectifier 19 with a key element 8 - and their interconnected control system by reducing the negative sequence currents in a single-phase capacitor solution and keeping the average value of the rectified current at a constant level improve energy indicators electric drive. Voltage regulation at the carrier frequency at the same time allows to increase the speed of the rotational speed control system of the electric motor 1. 3 sludge.

Description

element 6, amplifier 7, controlled key element 8, reference voltage generator 9, sensor 10, logic EXCLUSIVE OR 11, threshold elements 12, 13, galvanic isolation unit 1, triac 15, rotational speed sensor 16, capacitor 17, a saturable choke 18, a three-phase bridge rectifier 13, a current sensor 20, a rotational speed setting device 21, and a switch 22 of characters. Use in the device of two voltage regulators - a triac 15

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and a bridge rectifier 19 with a key element 8 - and their interconnected control system, by reducing the negative sequence currents in the capacitor solution oflHo0a3HqM and keeping the mean value of the rectified current at a constant level, improve the electric performance of the electric drive. Regulation of the voltage at the carrier frequency in this case allows to increase the speed of the system for controlling the frequency of rotation of the motor. one . 3 il.

The invention relates to electrical engineering and can be used in a reversible automated asynchronous electric drive in devices for moving tape media.

The purpose of the invention is to increase energy. hetichny indicators and speed.

Fig. 1 shows a functional diagram of a reversible asynchronous electric drive; Fig. 2 shows voltage diagrams; fig.Z mechanical characteristics of the drive.

The reversible asynchronous electric drive contains a three-phase electric motor 1, a regulator 2 of the rotation frequency, a current regulator 3, a k module, a zero-organ 5, a logic element AND 6, an amplifier 7, a controlled key element 8, a generator of the reference voltage, setting device 10, logical element EXCLUSIVE OR 11, first and second threshold elements 12 and 13, galvanic isolation unit 11, triac 15, rotational speed sensor 16, capacitor 17, saturating throttle 18, three-phase bridge rectifier 19, current sensor 20, setting device 21 speeds and shifters sign 22 Tel.

One terminals of the first and second phases of the stator winding of the electric motor 1 are directly, and one terminal of the third phase of the stator winding is connected via terminals of the triac 15 to the terminals for connection to the mains.

One terminal of the third phase of the stator winding of the electric motor 1 through a series-connected capacitor 17 and a saturated choke 18

connected to one output of the second phase of the stator winding of the electric motor 1. The first and second inputs of the speed regulator 2 are connected to the outputs of the rotational speed setting device 21 and the rotational speed sensor 16 of the electric motor 1. The inputs of the three-phase bridge rectifier 19 are connected to other outputs of the stator phases the motor windings 1, and the outputs of the three-phase bridge rectifier 19 are shunted by series-connected controlled key element 8 and current sensor 20. The output of current sensor 20 is connected to a first input of a character switch 22, the output of which is connected to the first input of current regulator 3, the second input of which is connected to the input of the second threshold element 13 and connected to the output of rotation speed regulator 2. The output of the regulator J, the current through the first threshold element 12 is connected to the first input of the EXCLUSIVE OR logic element, the second input of which is connected to the second input of the switch 22 characters, to the input of the galvanic isolation unit and connected to the output of the second threshold element 13 - The output of the regulator 3 current through module 4 module is connected to the first input of the zero-body 5 whose second input is connected to the output of the generator 9 of the reference voltage, the third input of the zero-body 5 is designed to provide a reference signal, and the output of the zero-body 5 is connected to th input of the AND gate 6 whose output is connected through an amplifier 7 to a control input of the key element 8. The output of gate XOR. 1 1 is connected to the second input of the logic element AND 6. The outputs of the galvanic isolation unit 1 are connected to the control circuits of the simulator 15.

The rotational speed sensor 16 consists of a two-channel measuring element 23 and a frequency-voltage converter 24.

Reversible asynchronous electric drive works as follows.

The rotational speed control of the asynchronous motor 1 is made by varying the voltage, which is controlled by the pulse-width modulation of the mains voltage at the carrier frequency.

A speed control system with feedbacks on the stator circuit current and engine speed. The measurement of the rotational speed is carried out using the rotational speed sensor 16. Depending on the direction of rotation, the pulses are produced at one of the outputs of the two-channel measuring unit 23. These pulses are fed to the converter 24, where they are converted into voltage. The voltage at the output of converter 24 is directly proportional to the input frequency, and its sign is determined by the channel of the passage of pulses. This voltage in the form of a negative speed feedback signal is supplied to the rotational frequency controller 2, where it is compared with the rotational frequency setting signal 21 and a correction signal is generated. The reverse of the engine 1 and its transition to the anti-switching mode are carried out as a function of the error signal from the output of the speed regulator 2. Depending on the sign of the error, the second threshold element 13 is transferred from one state to another, in accordance with which the control voltage of the triac 15 is applied to or is removed from the galvanic isolation unit 14. The speed error signal from the output of the speed regulator 2 enters the current loop and regulates its change.

In modes close to stationary, the signal error in speed - the value of

0

U -; constant and determines the current value of the stator motor circuit.

The current is controlled by pulsed parametric voltage control at the carrier frequency (Fig. 2B). The average value of the voltage on the switching interval / -

U, p. -L- U sinoi; i 1,2n

(one)

where Usin -.- the average value of the sinusoidal voltage on the i-th interval of switching J

amplitude value of mains voltage; angle,

key closure duration on i-th period of carrier frequency |

- - the duration of the carrier frequency period.

If there is no voltage regulation, 5 then for a sufficiently large carrier frequency, equation (1) can be written

in the form of i

Of U sinot,

i.

0 where silt U is the equivalent value of the voltage amplitude; const; WITH - angular frequency, t - time.

For a three-phase bridge circuit, in the case of a symmetrical three-phase voltage system, the amplitude of the rectified voltage (current) ripple is 5.7% of the average value. These pulsations can be neglected and the current feedback signal can be used to stabilize voltages.

If triac 15 is turned on, a three-phase symmetrical voltage system is applied to the windings of the motor 1. In stationary modes of operation in the circuit: a three-phase bridge rectifier 19 key element 8, almost constant current flows. At the same time, the error signal is

0

five

0

five

C d U. with current regulator 3 value constant. This signal is pre-rectified by block 4 of the module and fed to a null organ 5, where it is converted into a pulse-width signal (Fig. 26). As a sweep signal Up, a ramp is used from the output of the reference voltage generator 9 (Fig. 2a).

To ensure a proportional relationship between the control voltage and Ucf. - | d uy | and the duration of the pulses dc at the output of the null organ 5 uses the voltage Ucw of the voltage applied to the third input of the null organ 5 (Fig. 2a, b). The signals from the zero-organ 5 through the logic element And 6 are fed to the amplifier 7 made on the basis of the operational amplifier. Here they are amplified in power and in the form of a bipolar voltage are applied to the key element 8, with which the phase voltages are modulated. With a symmetric three-phase system, the voltages in phases B and C will be shifted with a shift in phase A (Fig. 2c).

If triac 15 is disconnected, the windings of the motor 1 are turned on for single-phase voltage with an additional phase shifting capacitor 17. The power supply system of the motor 1 in this case is asymmetrical (fig.2d, f, e) and corresponds to reverse phase rotation.

signal control .-., duration of conductivity

The reduction in the asymmetry of the currents in the phases of the motor 1 is achieved by the high-speed current loop, the key element 8 of which operates at a carrier frequency much higher than the frequency of the network. The deviation of the current from the specified leads to a change

and. accordingly, the key

element 8 (Figg). In this case, the voltages U, Uft, Uc in the phases of the motor (fig.2d, e, h) are modulated in such a way as to maintain the symmetrical nature of the flow of currents in the motor windings. The first harmonics of the phase voltages (see curves, designation of the power line, in Fig.2d, e, g) have a significantly better phase and amplitude distribution among themselves than the original unmodulated voltages.

Thus, due to the compensating effect of the current loop, the phase voltages are modulated so that the corresponding system of phase currents is close to symmetrical.

When the engine 1 is operating in a closed system, as the load torque M increases, the speed error increases and, accordingly, the activation time of the key element 8. For

ten

15

20

thirty

35

40

45

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by pulse-width voltage regulation, a family of artificial characteristics of engine 1 is formed, each of which characterizes an established mode of operation. In this case, the dependences (Z) of the rotational speed W on the moment of load M for the closed-in-speed control system are located in the zone between the characteristics (L) of the open-loop system (Fig. 3).

The stiffness of the mechanical characteristics of Z is significantly higher than the natural characteristics of the asynchronous motor, which allows for an adjustment range (10-20): 1.

To increase the speed of the current loop and eliminate overshoot, logic elements AND 6 and EXCLUSIVE OR 11 are used. Taking into account the inversion of the signals by the operational amplifiers of current and frequency regulators 3 and rotation frequency, the current overload control signal is formed and the signs of their output voltages coincide. What corresponds to a combination of logic levels (O or 1) of the signals of the threshold elements 12 and 13. In this case, using the logic element EXCLUSIVE OR 11, a signal is forbidden for the passage of zero-o pulses Gana 5 via the AND gate 6 and is formed Tokova pause.

Since the switching frequency of the key element 8 is significantly higher than the network frequency, this makes it possible to increase the drive speed, since the key element 8 reduces the uncontrollability interval of the triac 15 due to faster interruption of the active-inductive current of the asynchronous motor 1.

Since the rectified value of the motor current 1 is controlled, the sign switch 22 is used to match the signs, voltages from the outputs of the speed controller 2 and the current sensor 20. The voltage sign from the current sensor 20 changes simultaneously with the motor moving work in backward or reverse mode. In order to limit the currents through the triac 15, at the moment of its switching on, a saturating choke 18 is introduced into the capacitor 17 circuit.

91

Thus, the introduction into the stator circuit of the engine 1 of the second power regulator (bridge rectifier 19 and key element 8) and the system of interconnected control of voltage regulators, in which one of them creates a direct or inverse sequence of alternating phases, the other adjusts the magnitude of the voltage by its pulse-width modulation, which makes it possible to significantly improve the power ones. This is achieved by reducing the negative-sequence currents in a single-phase capacitor mode by keeping at a constant level the average value of the rectified current in modes close to stationary. As a result, despite the stress asymmetry, the magnetic field remains close to circular. This increases torque and reduces engine losses. In addition, the regulation of the voltage at the carrier frequency makes it possible to reduce the uncontrollability interval and increase the speed of the speed control system.

Claims (1)

Invention Formula A reversible asynchronous electric drive containing a three-phase electric motor, one terminals of the first and second phases of the stator winding of which are directly, and one terminal of the third phase of the stator winding are connected to the power supply terminals via a simulator, the third phase terminal of the stator winding of the electric motor is connected to one the output of the capacitor, the galvanic isolation unit, the outputs of which are connected to control circuits of the triac, the rotation frequency regulator, the first and second inputs of which are connected to the outputs, respectively, of the speed sensor and the motor speed sensor, characterized in that, for the purpose of increasing power and speed indicators, a saturable choke, a three-phase bridge rectifier, a control key element, a current sensor, a sign switch, a current regulator, two threshold elements, a logic element EXCLUSIVE OR, a logic element AND, a force, 0, the module module, the reference voltage generator and the null organ, another capacitor lead through a saturable choke is connected to one end of the second phase of the stator winding of the electric motor, the three-phase bridge rectifier inputs are connected to Other terminals of the stator winding phase of an electric motor, a positive output of a three-phase bridge rectifier 20 A Resistively connected key element and a current sensor are connected to the negative output of a three-phase bridge rectifier, the output of the current sensor is connected to the first input of the sign switch, the output of which is connected to the first regulator input current, the second input of which is connected to the input of the second threshold element and connected to the output of the frequency regulator rotation, the output of the current controller through the first threshold element is connected to the first input of the EXCLUSIVE OR logic element, the second input of which is connected to the second input of the sign switch, the input of the galvanic isolator and connected to the output of the second threshold element, the output of the current regulator is connected to the first input zero through the module -organ, the second input of which is connected to the output of the reference voltage generator, the third input of the zero-organ is intended to supply a reference signal, and the output of the zero-organ is connected to the first input of the logic element I, the output to orogo via an amplifier connected to the control input of the key element, the logic element output coupled to an exclusive OR logic gate second input I. but .Ј1Л1п ппаш1Ш1 I L N G $ tt "JNp dffi w jfl H-flfhx , tfr fЈ Editor A. Ogar Fig.z Compiled by S.Pozdnukhov Tehrel M.Hodanich Proofreader E.Lonchakova / jttk