SU1365333A1 - Frequency-controlled electric drive of load-handling mechanism - Google Patents

Abstract

The invention relates to electrical engineering and can be used in thyristor asynchronous electric AC drives of lifting mechanisms with a wide range of speed control. The aim of the invention is to increase the energy and dynamic performance by reducing the braking torque during the transition from one rotational speed to another and increasing the overload capacity. In the structure of an electric drive containing a thyristor frequency converter, an asynchronous electric motor, a control unit 17, threshold elements 16, a shift register 8, stepwise and smoothly variable frequency generators 19 and 18, by introducing a frequency converter 20 - voltage, block 28 definition of phase EMF, adders 21, 35, 37-39, proportional-integral controller 36, supra-meters 29-31, controllable switches 10-12, systems 13-15 pulse-phase control, current sensors 22- 24 and voltages 25-27 increase energy and ynamic indices for frequency regulation by reducing the braking torque of the motor when changing from one frequency to another rotation and increased overload capacity motor. 2 Il. c (o

Description

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The invention relates to electrical engineering and can be used in thyristor asynchronous electric drives of alternating current of lifting mechanisms with a wide range of speed control.

The aim of the invention is to increase the energy and dynamic performance by reducing the braking torque during the transition from one rotational speed to another and increasing the overload capacity.

Figure 1 shows the block diagram of the variable frequency drive of the lifting mechanism; in figure 2

timing diagrams explaining the formation of the control input signal of the pulse-phase control system.

The frequency-controlled electric drive of the lifting mechanism contains an asynchronous motor 1 connected by phase windings to the output of a frequency converter with a direct connection 5 composed of three groups of three-phase thyristor bridges 2-4, the control circuits of which are connected to the outputs of the formers 5-7 of the thyristor control pulses an annular shift register 8, the output of which is connected to the first inputs of the thyristor control drivers 5-7, the second inputs of which are connected to the first, second and tr Each of the outputs of the control unit 9 and with the control circuits of the first, second and third controlled switches 10-12, respectively, and the third inputs of the thyristor control drivers 5-7 are connected to the outputs of the first 13, second 1A and third 15 pulse systems -phase control, n threshold elements 16 connected by inputs to the outputs of the commander 17, and outputs k of the threshold elements 16 are connected to the inputs of the master oscillator 18 of a variable frequency, and the outputs nk of the threshold elements 16 are connected to the inputs of the master generator the torus 19, the step-variable-frequency output of the nth threshold element 16 is connected to the input circular shift register 8, the outputs of the oscillators 18 and 19 are connected to the host controller 9 inputs and the inputs of the converter 20 frequency - voltage, the output of which is connected to the second

the input of the second adder 21, the sensors 22-24 of the phase currents and the sensors 25-27 of the phase voltages of the electric motor 1 are connected to the inputs of the block 28 for determining the phase EMF, the outputs of which are connected to the inputs of rectifiers 29-31 and the first inputs of the controlled switches 10-12 directly and with the second inputs of these controlled switches through inverting amplifiers 32-34, the outputs of rectifiers 29-31 are connected to the inputs of the first adder 35, the output connected to the first input of the second adder 21, the output of which is connected to the input proportional integral integral controller 36 EMF module, the output of proportional-integral regulator 36 module EMF is connected to the first inputs of the third 37, fourth 38 and fifth 39 adders, the second inputs of which are connected to the outputs of the controlled switches 10-12, and the outputs to the inputs of systems 13-15 pulse-phase control.

FIG. 2 shows: a - output

control node 9 signal; B - output signal of the block 28 for determining the phase EMF; 6- output signal invert

power amplifier 32; g, 3 - U

in J and CC.

control signals SIFU 13, Uyper-output voltage proportional-integral controller 36 module

5 emf.

The frequency-controlled electric drive of the lifting mechanism works as follows. The electric drive provides single-zone frequency control of the rotational speed of the asynchronous motor 1 (down from the nominal value). The rated speed of the motor is achieved at

Its operation at the mains frequency, with each thyristor three-phase bridge 2-4 including one pair of anti-parallel thyristors connected to different phases of the mains supply. The command to operate the drive in the specified mode (switch mode) is given when the nth threshold element 16 is turned on when the control unit 17 is set to the extreme

g position The order of switching on the pairs of anti-parallel thyristors in bridges 2-4 is sampled depending on the combination of signals at the inputs of the thyristor control pulses 5-7 from the control node 9 and on the ring shift register 8 switched each time it triggers (nl) - ro of the threshold element 16, i.e. each time the induction motor I switches into nominal speed mode. The outputs of the control unit 9 determine the duration of the operation of the cathode and anode groups of the thyristors in the three-phase thyristor bridges 2-4 in the rectifying mode. The output signals of the pulse-phase control systems (SIFU) 13-15 are blocked in this mode. When the knob of the command device 17 is set to the position corresponding to the switching of the threshold elements 16 from (n-1) -th to (k + l) -ro, the output frequency of the converter is determined by the master oscillator 19 of the step-varying frequency. When translating the command device 17 to the position corresponding to the inclusion of the K-th threshold element 16, the operation of the master oscillator 19 of the step-variable frequency is blocked and the master oscillator 18 of the smooth variable frequency is switched on.

When the output frequency of the converter is changed, the voltage setting of the EMF of the electric motor 1 is changed according to the law, ensuring the constancy of the overload capacity of the electric motor 1. This function is performed by the frequency-voltage converter 20, which provides a linear relationship between its input frequency and output voltage. The phase electromotive unit voltage electromotive unit 28 of the motor 1, based on the input signals from the current sensors 22-24 and voltage sensors 25-27, calculates the instantaneous values of the phase electromotive voltage of the electric motor by the expression

If

 Dt

iFR - L -j--,

1, R

L

where zf. - phase voltage; current in phase;

active phase resistance inductance dissipation phase.

Rectifiers 29-31 and adder 35 approximately calculate the EMF module of electric motor 1 as a result of the six-pulse rectification of the instantaneous values of the phase EMF of electric motor 1.

ten

15

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Adder 21 carries negative feedback modulo the EMF of the engine 1, which provides stabilization of the magnitude of the module EMF of the engine. The error from the output of the adder 2 is fed to the input of the proportional-integral regulator module EMF 36. The output signal of the proportional-integral regulator 36 is changed so as to maintain a constant module EMF of the motor I, which maintains the flow rate of the asynchronous engine 1 in static modes . The bi-polar input voltages of the SIFU control 13–15, determined by the triac's opening thyristor angles, are formed on adders 37–39 as the sum of the output voltage of the proportional-integral regulator 36 and the signals proportional to the phase EMF of the engine 1. Timing diagrams (FIG. .2) the principle of forming the control input signal of a SIFU of one of the phases of the converter is explained. The corresponding output signal of the control unit 9 (Fig. 2a), which enters the input of the thyristor control pulse generator 5, allows the cathode to operate, and

20

25

thirty

five

zero - the work of the anode group of the thyristors of the three-phase bridge 2 of this output phase of the converter. The same signal goes to the control input of the corresponding switch 10. When the control signal of the switch 10 is zero, the calculated instant-0 is fed to the input of the adder 37 and the motor emf is at its single-phase value, and the opposite is the sign and the output of the inverting amplifier 32, Let at time t, be given the resolution

five

0

five

on the operation of the anodic group of thyristors of a three-phase bridge 2, the voltage intended for controlling SIFU 13 looks as shown in Figure 2d (here also shown is the output voltage U-jptr of the proportional-integral controller of the EMF module 36) the end of the conduction interval of the anode group Ua decreases, the opening angles of the thyristors increase, which provides an improvement in the operation of the drive in the inverter mode. At time tj, permission is granted for the operation of the cathode group of the thyristors of the three-phase bridge 2 and the control voltage, and arriving at the corresponding input of SIFU 13, has the form shown in fig.2d. At the moments when the output frequency of the master oscillator 1 9 changes in a discrete frequency, the duration of the output signals of node 9 can be strongly changed, controlling both downwards and downwards with a constant value of the output signal of the proportional-integral controller 36. This can lead to an increase in current electric motor 1 and the possibility of large braking torques. Let the output frequency of the master oscillator 19 change at the time t and increase the duration of the output signal of the control unit 9 (Fig. 2a). In this case, the control voltage of SIFU 13 (FIG. 2d) is further reduced by increasing the negative value of the calculated motor EMF (-Ef) fed to the adder 37, the opening angles of the thyristors increase, which leads to a decrease in current and, consequently, braking torques asynchronous motor 1. Thus, the input voltages of the control SIFU 13 are formed so as to reduce the influence of the internal feedback of the motor on the emf on its current. The SIFU 13-15 transforms the input signals in a sequence of thyristor opening pulses that are applied to the third inputs of the transducer thyristor control thyristors 5-7.

Thus, the proposed electric load-lifting mechanism, by introducing a frequency-voltage converter, a phase electromotive voltage detection unit, controllable inverter amplifiers, SIFU, current sensors and voltage sensors, has higher energy and dynamic performance compared with the known technical solutions, as it allows the engine to reduce braking torques when changing from one rotational speed to another and increase the overload capacity of the engine.

Claims (1)

Invention Formula Frequency-controlled electric lifting mechanism, contains five 0 a three-phase asynchronous electric motor connected by the output of phase windings Q by the output of a frequency converter with a direct connection made up of three groups of three-phase thyristor bridges, thyristor control pulse drivers, connected by their outputs with control circuits of three-phase thyristor bridge groups, ring shears - a dummy register, the output of which is connected to the first inputs of the thyristor control pulse driver, which sets the oscillators to smoothly and stepwise frequency, the outputs of which are connected to the inputs of the control unit, the outputs of which are connected to the second inputs of the thyristor control pulse drivers, n threshold elements connected by inputs to the outputs of the controller, the outputs of the k threshold elements are connected to the inputs of the master oscillator 5 variable frequencies, inputs (nk) threshold elements connected to the inputs of the master oscillator of a stepwise variable frequency; the output of the nth threshold element is connected to the input of an annular shift register, characterized in that, in order to increase the energy physical and dynamic parameters due to a decrease in braking moments during the transition from one rotational frequency to another and increasing overload capacity, a frequency-voltage converter, a phase EMF determination unit, five totalizers, an emf proportional-integral controller, three pulse-voltage systems were introduced phase control, three rectifiers, three controllable switches, three inverting amplifiers, phase current sensors and phase voltage sensors, thyristor control pulse driver These inputs, their second inputs are connected to the control circuits of the three controlled switches, respectively, the outputs of the phase current sensors and the phase voltage sensors are connected to the inputs of the phase EMF unit whose outputs are connected to the rectifier inputs and the first inputs of the controlled switches directly and to the second inputs of controlled switches through inverting amplifiers, the outputs of the connectors are connected to the inputs 0 five 0 five 0 55 the first adder, the output of which is connected to the first input of the second adder, the frequency converter inputs - voltage is connected to the outputs of master oscillators smoothly and stepwise variable frequency, and the frequency converter output voltage is connected to the second input of the second adder, the output of which is connected to the input proportional -integral controller of the module ZDS, the first inputs of the third, fourth and fifth adders are combined and connected to the output of the proportional-integral regulator of the EMF module, the second inputs of the third, fourth and fifth adders are connected to the outputs of the first, second and third controlled switches, the third inputs of the thyristor control pulse drivers are connected to the outputs of the corresponding pulse-phase control systems The inputs of which are connected to the outputs of the third, fourth and nth adders, respectively, FIG.