RU2079963C1 - Reversible thyristor drive - Google Patents

Abstract

FIELD: automatic-control electric drives and converter engineering. SUBSTANCE: thyristor drive has converter whose output is meant for connecting motor or smoothing reactor and input is connected through current sensor to supply mains; control circuits of converter are connected to pulse-phase control system whose input is connected to regulator unit whose inputs are connected to current sensor, tachogenerator, and speed setting element; it also has logic unit connected to regulator unit and pulse-phase control system; in addition, it is provided with mode-of-operation selecting unit for thyristor set of converter whose inputs are connected to tachogenerator and logic unit and outputs, to inputs of pulse distributor of pulse-phase control system; mode-of-operation selecting unit for thyristor set of converter has two comparators, NAND and NOT gates, and diodes; each comparator has its input connected to inputs of NAND gates and output, to respective NOT gate; outputs of NOT gates are connected to diodes connected in pairs to inputs of pulse distributors of pulse-phase selecting system. EFFECT: improved performance characteristics of thyristor drive. 2 dwg

Description

 The invention relates to electrical engineering, in particular to the field of automated electric drive and converter technology.

 Known reversible DC drive with separation control of the thyristor sets of the converter (see R. Schönfeld and other Automated electric drives. Leningrad. Energoatomizdat, 1985, p. 240 242), containing two sets of thyristors ("forward" and "back"), a motor, a smoothing reactor, two pulse-phase control systems (SIFU), respectively, for controlling sets of thyristors, a logical switching device, current and speed controllers, current and speed sensors.

 The electric drive is widespread, it has well-known advantages, but it has a disadvantage, because of the ripple of the armature current of the motor, the current shape factor increases (which is the ratio of the effective and average current values), which leads to underutilization of the motor in terms of torque and power.

 Of the known solutions, the closest in technical essence is the reversible electric drive of the EPU 2 series (see the catalog "Single-phase unified direct current electric drives EPU 2"; 08.41.10-89, Informelectro, 1989), which is taken as a prototype.

 The electric drive contains a single-phase reversible thyristor converter, a motor, a smoothing reactor, SIFU, a logical switching control device of the converter, a device for linearizing the characteristics (UHL) of the converter in discontinuous current mode, containing a nonlinear link and a positive emf coupling engine, speed controller and knob, speed and current sensors. The speed controller and UHL form a block of ATS regulators.

 Depending on the polarity of the speed-determining signal, the required direction of rotation of the motor is set, UHL provides high dynamic properties of the electric drive in discontinuous current mode, the logic device switches the SIFU pulses to the corresponding set of thyristors ("forward" and "back") when changing the motor current reference. The smoothing reactor is designed to improve the shape of the motor current, improve the use of the motor in torque and power.

 The disadvantage of the electric drive is the underutilization of the motor in terms of torque and power due to the increased form factor of the motor current.

 To improve the use of the engine in terms of torque and power and thereby improve the characteristics of the electric drive is possible by increasing the inductance of the smoothing reactor. This common practice path leads to a sharp increase in the dimensions of the specified reactor, a large consumption of materials, which is a disadvantage of this method.

 The technical result of the proposed solution is the improvement of the characteristics of the electric drive. The technical result is achieved in that a thyristor electric drive containing a two-set thyristor converter, the output of which through a smoothing reactor is connected to the motor, and the input through a current sensor is connected to the supply network, while the control inputs of the converter are connected to a pulse-phase control system, the input of which is connected with the output of the regulator block, the inputs of which are connected to the current sensor, tachogenerator and speed controller; logical device for separate control of sets of thyristors of the converter, depending on the sign of the control signal and the presence of current in the converter, inputs connected to the outputs of the regulator block, and outputs with inputs of the pulse-phase control system, characterized in that a block is selected for selecting the operating mode of sets of converter thyristors, inputs which are connected to the tachogenerator and the outputs of the logic device of the dividing control of the sets of thyristors of the converter depending on the sign the control signal and the presence of current in the converter, and the outputs with the inputs of the pulse distributor of the pulse-phase control system to ensure blocking of the pulse distributor, while the unit for separating the operation mode of the converter thyristor sets contains two comparators, AND-NOT, NOT elements and diodes, the output of each comparators connected to the inputs of the elements AND NOT, their outputs with one output of the corresponding elements NOT, the outputs of which are connected to diodes, the other outputs of which are paired and form the outputs unit, and the inputs of the comparators and other inputs AND NOT its inputs.

 The essence of the invention lies in the fact that improving the characteristics of the electric drive is achieved by improving the use of the motor in torque and power by supplying control pulses simultaneously to all the thyristors of the current set of thyristors, and this is possible only in the case of polarity of the motor counter-voltage, directed against the conductivity of the thyristors specified set of thyristors. This is accomplished by introducing an additional unit for isolating the operation mode of the converter thyristor sets and connecting it to the SIFU pulse distributor, as well as to the logic device and tachogenerator.

In FIG. 1, 2 shows a diagram of the inventive electric drive, where the following notation:
1, 2 sets of thyristors "forward" and "back";
3 reverse thyristor converter;
4 smoothing reactor;
5 engine;
6 current sensor, consisting of a current transformer and a rectifier;
7 pulse phase control system (SIFU);
8 block of ATS registers, for example, current speed regulators;
9 tachogenerator (speed sensor);
10 speed dial;
11 logical separation control device of the thyristor sets of the converter 3, depending on the sign of the control signal and the presence of current in the converter;
12 block allocation mode operation sets of the Converter;
13, 14 comparators;
15, 16 elements "AND NOT";
17, 18 elements are "NOT";
19, 20 group of diodes;
21, 22 threshold elements;
23 sawtooth voltage generator (GPN);
24, 25 diodes;
26 comparator;
27 shaper pulse duration;
28, 29 resistors;
30 35 elements "AND NOT";
36 high-frequency pulse generator;
37, 38 group of pulse transformers "forward" and "back";
39, 40 keys "forward" and "back".

 Elements 21, 22, 24, 25, 28, 29, 30, and 31 form a SIFU antiphase pulse distributor.

 In the proposed device, the kits 1, 2 of the thyristors, forming a reversing converter 3, are interconnected and through a smoothing reactor 4 with the motor 5, as well as with the current sensor 6, the control circuits are connected to the pulse-phase control system 7 (SIFU), which is connected to the unit 8 ATS regulators, the inputs of which are connected to a speed sensor 9, a speed controller 10 and a current sensor 6. The switching of sets 1, 2 is controlled by a logical device 11, the inputs of which are connected to the current sensor 6 and the output of block 8, and the outputs 11 are connected to SIFU 7 and the block 12 for selecting the operating mode of the converter sets, containing comparators 13, 14 connected to the speed sensor 9 and AND-NOT 15, 16 elements connected to NOT 17, 18 elements, the output circuits of which through a pair of diodes 19, 20 are connected to the inputs of the SIFU 7 pulse distributor. In this case, the SIFU 7 consists of comparators 21, 22 and a sawtooth voltage generator 23, connected to the corresponding diodes 24, 25 and a comparator 26 connected to the pulse width former 27, the output of which is connected to the first inputs of AND-NOT elements 30, 31, and the diodes 24, 25 and resistors 28, 29 are connected to the second inputs, while outputs 30 , 31 are connected to the inputs of the AND-NOT 32, 33 elements, the outputs of which are connected to the first inputs of the AND-NOT 34, 35 elements, and a generator of high-frequency pulses 36 is connected to their second inputs, the outputs of the AND-NOT 34, 35 elements are connected to the primary windings pulse transformers 37, 38, which are also connected to a power source Nia through the switches 39, 40, the secondary windings of transformers 37, 38 are connected to the control circuits of the thyristors sets 1 and 2.

 The electric drive operates as follows. (see Fig. 1, 2).

When a reference signal U _{s is} supplied, at the output of the regulators 8, a control signal U _y arrives at SIFU 7, depending on which a certain angle of thyristor regulation α is established. The logical device 11, depending on the sign of the signal U _y, supplies control pulses to one or another set of thyristors 1 (2) of the converter 3. Switching of sets 1 and 2 is carried out by the logical device 11 when the polarity of the signal U _{y is} changed and there is no current in the converter. The output signals from the tachogenerator 9 and the logical device 11 determine the operation of the block 12 allocation mode converter 3. So, for example, when the set of thyristors 1 (set 2 is locked) in the signs of the signals marked by circles, at the outputs 13, 15, 17, respectively, we have signals 1 , 01 and through diodes 19 to the inputs b1, b2 SIFU receives signal 1, blocking the pulse distributor (Fig. 2). As a result, all the thyristors of set 1 receive control pulses and the set operates in a semi-controlled rectifier mode, providing current closure through two thyristors connected in series (the so-called zero-diode effect). This improves the shape of the current in the motor, improves the use of the motor in torque and power. At this time, set 2 is locked, and set 1 is in rectifier mode. However, if at this time the polarity of the emf on the motor will change its sign (there was a plus, but will become a minus), then working set 1 will go into inverter mode (engine braking). In this case, at output 17 we have a signal 0, at the inputs b1, b2 of the pulse distributor, the signals are 0, the latter is not blocked and distributes the pulses in the usual symmetric order. As a result, in set 1, the effect of a zero diode disappears, since this would lead to a shortening of the motor armature. Set 2 works similarly with closed set 1. But in this case, the rectifying mode of the set is ensured with a negative (opposite) polarity of the emf.

 The pulses are connected to the corresponding set of thyristors using a key 39 (40) through pulse transformers 37 (38).

 Thus, the mode separation unit 12 provides, in the rectifier mode of the converter 3, the greatest current utilization of the motor 5, improving the current shape coefficients and the engine utilization coefficient, excluding emergency modes of motor short-circuiting during its braking and reversal.

 The advantage of the proposed drive in comparison with the prototype is the improvement of the characteristics of the drive. Characteristics are improved due to the introduction and corresponding construction of the unit for selecting the modes of the converter 12, which reduces the heating of the motor and improves its use in torque and power.

Claims (1)

A reversible thyristor electric drive containing a two-set thyristor converter, the output of which is connected to the motor through a smoothing reactor and the input is connected to the mains through a current sensor, while the control inputs of the converter are connected to a pulse-phase control system, the input of which is connected to the output of the regulator block, inputs which is connected to a current sensor, a tachogenerator and a speed dial, a logical device for separate control of sets of thyristors of the converter depending from the sign of the control signal and the presence of current in the converter, the inputs connected to the outputs of the regulator block, and the outputs with the inputs of the pulse-phase control system, characterized in that a block for distinguishing the operation mode of the sets of thyristors of the converter is introduced, the inputs of which are connected to the tachogenerator and the outputs of the separate logic device control sets of thyristor sets of the converter depending on the sign of the control signal and the presence of current in the converter, and the outputs with the inputs of the system pulse distributor pulse-phase control to ensure blocking of the pulse distributor, while the unit for separating the operation mode of the converter thyristor sets contains two comparators, elements AND NOT, NOT and diodes, the output of each of the comparators is connected to one of the inputs of the elements AND NOT, their outputs with the inputs of the corresponding elements NOT, the outputs of which are connected to diodes, the other outputs of which are paired together and form the outputs of the block, and the inputs of the comparators and other inputs of the elements AND NOT
its inputs.

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