RU2259627C2 - Thyristor current regulator - Google Patents

Abstract

FIELD: electrical engineering; various automatic-control devices needing regulation of current or voltage and associated parameters.

SUBSTANCE: proposed device that can be used in electroplating engineering for electrochemical metal deposition and also it can function as welding arc parameter regulator and universal commutator motor speed governor or regulator has thyristor regulating component in primary winding circuit of power transformer whose secondary winding is connected through current sensor to power rectifier, output of the latter being connected to load; low-power transformer whose primary winding is connected to power leads and secondary winding, to input of bridge rectifier; phase-pulse control circuit set up of microelectronic voltage regulator and comparator. Output of microelectronic voltage regulator is connected through integrating circuit to inverting input of comparator which is connected through synchronizing diode to positive lead of bridge rectifier; connected to output of the latter is resistive divider assembled of two resistors whose common point is connected through bias resistor to output of microelectronic voltage regulator; noninverting input of comparator is connected to reference-voltage supply; feedback lead of microelectronic voltage regulator is connected through voltage divider to positive lead of current sensor and the latter is connected through series-interconnected limiting resistor and comparison diode to reference-voltage supply; series-interconnected light-emitting diodes of optocoupler thyristors are connected to comparator output; microelectronic voltage regulator, comparator, and reference-voltage supply are supplied with power through decoupling diode connected to positive lead of bridge rectifier.

EFFECT: enhanced reliability and regulation factor.

1 cl, 2 dwg

Description

The invention relates to the field of electrical engineering and can be used in various automatic control devices where stabilization of current or voltage and, accordingly, other parameters depending on them is required.

It can be used, for example, to power electroplating devices during electrochemical deposition of metals.

It is also possible to use it as a stabilizer of the parameters of the welding arc and a regulator-stabilizer of speed of universal collector motors.

A known control circuit for an AC regulator with inductive load [1] (Thyristors (technical reference), M .: Energy, 1971, p.238, Fig. 9-31) containing a thyristor control element in the primary winding circuit power transformer, step-down transformer for power supply of power (main) thyristors control circuits, phase-pulse control circuit on a single-junction transistor with an RC circuit and an isolation transformer.

The disadvantage of this device is the large power loss in the control circuits of power thyristors, high sensitivity to interference due to the presence of a single-junction transistor, as well as a large initial angle of inclusion (angle of delay) of power thyristors, i.e. their inability to work in diode mode and to obtain maximum power in the load.

Closest to the proposed one is a thyristor DC voltage stabilizer [2] (USSR Author's Certificate No. 748382, class G 05 F 1/56, 1980), containing a thyristor control element in the alternating voltage circuit of a power transformer, to the secondary winding of which a rectifier is connected connected to the output terminals, a phase-pulse control circuit on a single-junction transistor with an RC circuit, the input of which is connected to the terminals for connecting the supply voltage, waiting for a multi-input multivibrator, a threshold key node a resistive current sensor and a voltage divider, the first - the input input of the multivibrator connected to the output of the phase-pulse control circuit, the second - the control input connected through the resistive divider to the output of the rectifier, the third - the locking input is connected through the threshold key node with the resistive current sensor in the output circuit of the rectifier and the output of the multivibrator is connected to the control input of the thyristor regulator, which is made on optocoupler thyristors.

Its disadvantages are a low stabilization coefficient due to the lack of a differential amplifier in the feedback circuit, a large inertia due to the RC filter.

Its disadvantage is also its low reliability, due to the fact that the phase-pulse control circuit is made on a single-junction transistor having a high sensitivity to interference, and the inclusion of optocoupler thyristors is carried out by short pulses after differentiation, the duration of which does not always exceed the phase shift between voltage and current, which leads to omissions half-cycles, magnetization of the magnetic core of the power transformer and a sharp increase in the current of the primary winding.

From [1] p. 238 it is known that with an inductive load the control signal of the thyristor must have a duration equal to the interval of its conductivity. In this stabilizer, this requirement is not fulfilled, and therefore its reliable operation in production conditions is impossible, and far-fetched parameters such as a "soft" network connection only once again emphasize its imperfection.

The objective of the proposed invention is: to increase the stabilization coefficient of the average rectified current, increase reliability by eliminating false positives when working on a load of any nature, including a load with a counter-emf, the ability to adjust the output current from zero to a maximum value.

To perform the tasks thyristor current stabilizer contains:

a thyristor control element in the primary winding circuit of a power transformer, to the secondary winding of which a power rectifier is connected through a current sensor, to the output of which a load is connected,

low-power transformer, the primary winding of which is connected to the terminals for connecting the network, and the secondary winding is connected to the input of the bridge rectifier,

a phase-pulse control circuit made in the form of a microelectronic voltage stabilizer and a comparator.

New in the proposed invention is the presence of a microelectronic voltage stabilizer and comparator.

Wherein:

the output of the microelectronic voltage stabilizer is connected through an integrating circuit to the inverting input of the comparator, which is connected through the synchronization diode to the positive terminal of the bridge rectifier, the output of which is connected by a resistive divider of two resistors, the common point of which is connected through the bias resistor to the output of the microelectronic voltage stabilizer,

the non-inverting input of the comparator is connected to a reference voltage source,

the feedback terminal of the microelectronic voltage stabilizer through a voltage divider is connected to the positive terminal of the current sensor, which is connected through a series-connected limiting resistor and a comparison diode to a reference voltage source,

the serially connected LEDs of the optocoupler thyristors are connected to the output of the comparator, and the microelectronic voltage stabilizer, the comparator and the reference voltage source are supplied through a decoupling diode connected to the positive terminal of the bridge rectifier.

Figure 1 shows the electrical circuit of the thyristor stabilizer, figure 2 - plot voltage and current.

Thyristor current stabilizer contains:

thyristor control element (1, 2) in the primary winding circuit of a power transformer (3), to the secondary winding of which a power rectifier (5) is connected through a current sensor (4), to the output of which a load (6) is connected,

low-power transformer (7), the primary winding of which is connected to the terminals for connecting the network (8), and the secondary winding is connected to the input of the bridge rectifier (9),

a phase-pulse control circuit made in the form of a microelectronic voltage stabilizer (10) and a comparator (11).

Wherein:

the output of the microelectronic voltage stabilizer (10) is connected through an integrating circuit (12) to the inverting input of the comparator (11), which is connected through the synchronization diode (13) to the positive terminal of the bridge rectifier (9), the output of which is connected to a resistive divider (14) of two resistors whose common point is connected through the bias resistor (15) to the output of the microelectronic voltage stabilizer (10),

the non-inverting input of the comparator (11) is connected to a reference voltage source (16),

the feedback terminal of the microelectronic voltage stabilizer (10) through a voltage divider (17) is connected to the positive terminal of the current sensor (4), which is connected through a series-connected limiting resistor (18) and a comparison diode (19) to a reference voltage source (16),

the serially connected LEDs of the optocoupler thyristors (1, 2) are connected to the output of the comparator (11), and the microelectronic voltage stabilizer (10), the comparator (11) and the reference voltage source (16) are supplied through a decoupling diode (20) connected to the positive terminal bridge rectifier (9).

The implementation of the proposed device does not meet fundamental difficulties.

A thyristor current regulator works as follows: at the initial moment, after connecting it to the terminals of the network (8), a voltage close to its maximum value appears at the output of the microelectronic voltage stabilizer (10). As a result, from the output of the integrating circuit (12) to the inverting input of the comparator, a sawtooth voltage begins to arrive at a doubled frequency of the network, synchronized with the network through a synchronization diode (13) at the moment of the transition of zero half-periods of the rectified voltage of the bridge rectifier (9) (see the dotted line in FIG. .2).

In turn, from the output of the microelectronic voltage stabilizer (10) through the bias resistor (15), a bias voltage Ucm, which determines the constant component of the sawtooth voltage, is supplied to the common point of the resistive divider (14).

Since the bias voltage is Ucm. exceeds the reference voltage Uop. supplied to the non-inverting input of the comparator (11), the latter is open and a constant current i sv flows through the LEDs of the optocoupler thyristors (1, 2). 1, 2 (see Fig. 2 g).

This leads to the discovery of optocoupler thyristors dynistors (1, 2) at the beginning of each half-cycle of the mains voltage, similar to counter-parallel connected diodes, and the appearance of the maximum voltage at the output of the power rectifier (5).

A constant current begins to flow through the load (6). A voltage appears at the output of the current sensor (4), which, through a voltage divider (17), is fed to the feedback terminal of the microelectronic voltage stabilizer (10). As soon as this voltage, proportional to the current in the load (6), exceeds the reference voltage of the microelectronic stabilizer (10), the latter is “closed”, and the voltage at its output decreases. This leads to a decrease in bias voltage Ucm. and, accordingly, to reduce the constant component of the sawtooth voltage.

As a result, the sawtooth voltage at the inverting input of the comparator (11) begins to exceed Uon. not at the beginning of the half-cycle, but starting from some angle determined by the position of the voltage divider engine (17) (see Fig. 2c).

Moreover, at the output of the comparator (11), the current through the LEDs i St. 1, 2 optic thyristors (1, 2) has the shape of pulses, the duration of which τ (in) is proportional to the current in the load (6).

When moving the voltage divider motor (17) in the direction of increasing voltage coming from the current sensor (4) to the feedback terminal of the microelectronic voltage stabilizer (10), the latter “closes” more strongly, the voltage at its output decreases, and the bias voltage Ucm. becomes even smaller, and the sawtooth voltage exceeds Uo. only at the very end of the half-period (see Fig.2b).

The duration of the current pulses through the LEDs of the optocoupler thyristors (1, 2) became even less than τ (b) ≪τ (c) and, accordingly, the current in the load became smaller (6).

In order to adjust the current in the load (6) from zero to the maximum value (in the absence of current in the load (6) and, accordingly, the voltage from the current sensor 4, the microelectronic voltage stabilizer (10) cannot be closed), to the feedback circuit In connection with the reference voltage source (16), a voltage is supplied through the comparison diode (19) and the limiting resistor (18), which, at the extreme position of the voltage divider engine (17), which determines the minimum current in the load (6), is sufficient to completely close the microelectronic stabilizer pa voltage (10).

In this case, the output voltage of the latter is minimal, Ucm. small, the sawtooth voltage is less than Uop., the comparator (11) is closed, the optocoupler thyristors (1,2) are closed, the current in the load (6) is zero (see figa).

The increase in current in the load from zero to the specified value is as follows.

When moving the voltage divider motor (17) in the direction of increasing current in the load (6), the voltage supplied from the reference voltage source (16) becomes insufficient to close the microelectronic voltage stabilizer (10). As a result of this, the voltage at the output of the latter increases, the sawtooth voltage partially begins to exceed Uon., The comparator (11) and the optocoupler thyristors (1, 2) open - a current appears in the load (6).

A voltage appears at the output of the current sensor (4), the comparison diode (19) closes, and the device automatically switches to the stabilization mode of the set current.

Compared with the known, the proposed device has a high stabilization coefficient of the average rectified current, when the network voltage and load resistance change, due to the use of a microelectronic voltage stabilizer and comparator with high gain in the feedback circuit.

Compared with the known control signal supplied to the optocoupler thyristors, has a rectangular shape and its duration is equal to the conduction angle of the optocoupler thyristors. All this allows the device to operate without failures at a large inductive load, where the phase angle between the voltage and current can reach a significant value. Counter-parallel connection of optocoupler thyristors and the presence of a control signal throughout the conduction angle on both thyristors allows them to work without failures to the load with the counter-emf.

This is explained by the fact that at any moment during the conduction angle, one or the other optocoupler thyristor can turn on, depending on their anode voltages, i.e. possible reactive energy exchange between the load and the network, and, accordingly, the damping of transients in the load.

In the proposed device, stabilization of the average rectified voltage is possible if voltage is supplied to the feedback circuit from the output of the power rectifier.

The proposed stabilizer, without significant changes in the circuit, can stabilize the current or voltage not only in the primary circuit of the power transformer, but also in the secondary, and stabilization without a transformer is possible.

Claims (1)

A thyristor current regulator containing a thyristor regulating element in the primary winding of a power transformer, to the secondary winding of which is connected a power rectifier, the output of which is connected to a load, a low-power transformer, the primary winding of which is connected to the terminals for connecting the network, and the secondary winding is connected to the input of the bridge rectifier, a phase-pulse control circuit, characterized in that the phase-pulse control circuit is made in the form of a microelectronic stabilizer voltage and a comparator, while the output of the microelectronic voltage stabilizer is connected through an integrating circuit to the inverting input of the comparator, which is connected through a synchronization diode to the positive output of the bridge rectifier, the output of which is connected to a resistive divider of two resistors, the common point of which is connected through the bias resistor to the output of the microelectronic voltage stabilizer, non-inverting input of the comparator is connected to a reference voltage source, microelectro feedback voltage stabilizer through a voltage divider is connected to the positive terminal of the current sensor, which is connected through a series-connected limiting resistor and a comparison diode to a reference voltage source, the LEDs of optocoupler thyristors are connected in series to the output of the comparator, and the microelectronic voltage stabilizer, comparator and reference voltage source are supplied through a decoupling diode connected to the positive terminal of the bridge rectifier.

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