SU884061A1 - Device for regulating electric dc machine excitation current - Google Patents

Description

I

The invention relates to electrical engineering and can be applied to the electric drive of drilling and metalworking machines, excavators, auxiliary mechanisms of rolling mills.

A device is known that contains anti-parallel thyristors, 5 diodes, a capacitor and resistors designed to control alternating currents in an inductive load 1.

The disadvantage of this device is that the current of the power circuit passes not only .. through the thyristors, but through the power diodes, which increases the size and cost of the device. In addition, this device cannot be used to control the current in such a large inductance as the excitation winding of a DC machine, since it does not provide a path to discharge the energy of a magnetic field.

It is also known a device that contains two oppositely connected thyristors connected at one end to the first output of a single-phase AC source 20, and the second end connected to the first output of the excitation winding and a capacitor, the second terminals of which are connected to the second output of the AC source, while controlling thyristor junctions are connected to the outputs of the pulse-phase control systems 2.

A disadvantage of this device is a significant distortion of the form of the supply voltage, since at the time of opening the thyristor there is nothing limited, besides the resistance of the network, the charge current of the capacitors leads to a distortion of the form of the network voltage and to a decrease in the cyclo-resistance of the thyristor. This in turn leads to a decrease in reliability.

The closest to the technical essence of the invention is a device for controlling the excitation current of an electric DC machine, containing an AC source, to which one of the terminals is connected to a pair of anti-switched thyristors connected in parallel to the field winding and a capacitor, switch-on control unit and filter 3 .

The drawbacks of the device are the presence of losses in the permanently activated filter resistance, the inability to use the device to power the excitation winding if there are only alternating current sources without additional rectifiers, the inability to regulate the current without an additional adjustable DC source. field windings as well as control the charge current of the capacitor.

The aim of the invention is to improve the energy performance,

The goal is achieved by introducing into the device a second pair of oppositely connected thyristors, a two-winding choke, the windings of which have a difference of 2-3 times the number of turns, a comparator, two logic gates And, an excitation current sensor and an impedance, and the windings of the chokes are located on the common core and turned on, the second terminal of the first pair of thyristors is connected to the first common point of the second pair of thyristors, and one of the impedance terminals, the second terminal of which together with the second common point The second pair of thyristors inversely connected is connected to the beginning of the winding of the throttle having a smaller number of turns, the end of which, connected to the end of the second winding of the throttle and one of the filter terminals, is connected to one capacitor lead, the second terminal of which is connected through the start current sensor the second winding of the throttles and directly with the AC source and the comparator input, and the output of the excitation current sensor is connected to the input of the switch-on control unit, and its outputs are connected to the pack Aulus yuschimi inputs of the first pair of thyristor directly, and with the control inputs of the second pair of thyristors - via the AND gates, the second inputs of which are coupled to the output of the comparator.

In the device, a third winding can be additionally wound on the choke as the impedance, the number of turns of which is 2-3 times greater than the number of turns of the winding having a greater number of turns, with the start of the additional winding connected to the common point of the first and second pairs .

The comparator in the proposed device contains a transformer, the primary windings of which are the input of a comparator, two diode-bridge circuits, an adjustable resistor, a reference element, a power amplifier and a pulse transformer, the secondary winding of the transformer connected to the AC leads of the first diode-bridge circuit, - DC terminals, which are connected to an adjustable resistor, the moving contact of which and one of the DC terminals of the first diode-bridge circuit

connected to one input of the reference element, the second input of which is connected to the DC output of the second diode bridge circuit, the AC input of which is the second input of the comparator, and the output of the comparison element through the power amplifier is connected to the primary winding of the pulse transformer, the secondary winding of which serves the output of the comparator .

FIG. I shows a block diagram of the proposed device; in fig. 2 - diagram of the logical element And; in fig. 3 is a diagram of a comparator; FIG. 4 is a diagram of a thyristor switch-on control unit.

5 The excitation winding 1 of the electric machine with its end (the beginning is indicated by a point) in series with the excitation current sensor 2 is connected to one output of the AC source | Nick 3, to the second output of which the anode of the first is connected

 the optocoupler thyristor 4 and the cathode of the second op-. thyristor 5. The cathode of thyristor 4 and the anode of thyristor 5 are connected to the anode of the optocoupler thyristor 6, the cathode of the optocoupler thyristor 7 and the first output of impedance 8 (active-inductive), the second output of which is connected to the thyristor 6 of the thyristor 6 and the beginning of the winding 9 with a smaller number of turns, located on one core of 10 drossel with a winding 11, which is connected to the opposite winding 9 and having a number of turns 2-3 times more. The common point of the windings 9 and 11 is connected to the first terminal of the capacitor 12 of the filter 13, consisting, for example, of a series-connected resistor and a capacitor, the second terminal of which is connected

 the second terminal of the capacitor 12 and the second terminal of the source 3. The output of the current sensor 2 is connected to the first input of the thyristor activation control unit 14 to the second inputs of which is supplied

0 voltage The power to the input of the on / off control unit 14 is supplied from the inputs of the AC source 3. The outputs of the switch-on control unit 14 are connected to the first inputs of logic elements 15 and 16 I. The control electrodes of the optocoupler thyristors 4 and 5, and the outputs and inputs of the elements 15 and 16 have a common point with the output of the switch-on control unit 14, with the cathodes of the LEDs of the optocoupler thyristors 4-7 and with the release of the comparator

..17. The second inputs of logic elements 15 and 16 are connected to each other and to the first output of the comparator 17, the first input of which is connected in parallel to the output of the filter 13, and the second input of the comparator 17 to the output terminals of the alternating current source 3.

The outputs of the logic elements 15 and 16 are connected to the anodes of the LEDs of the optocoupler thyristors 6 and 7.

The logical element And (Fig. 2) is assembled on transistors 18 and 19, a diode 20 connected in series with a resistor 21 in the emitter circuit of transistor 19. Resistor 22 in the collector circuit of transistor 18, resistors 23 and 24 have a common point with the base of transistor 18. Resistor 25 is connected between the second input of the element and the common point of the emitter of the transistor 18 and the base of the spring 19.

The output of the resistor 22 included in the collector circuit of the transistor 18 is the first input of the logic element. The second input element is connected to the base of the transistor 18, the resistor 23.

The output of the resistor 26 included in the collector circuit of the transistor 19 is the first output of the element. The second output element - the common point of the cathode of the diode 20 and the resistor 21.

The first input of the comparator 17 (Fig. 3) is the primary winding of the transformer 27, the secondary winding of which is connected to the AC input of the diode-bridge circuit 28. To the second diagonal of this circuit, through a filter 29 consisting of a series-connected resistor and a capacitor, is connected in parallel adjustable resistor 30, one of the conclusions of which is a common point for the comparison element 31 {comparator or Schmitt trigger), power amplifier 32, the primary winding of the pulse transformer 33 and diode-bridge circuit 34. K under The first contact of the comparison element 31 is connected to the contact contact of the resistor 30, the second input of the comparison element 31 is connected to the output of the circuit 34, the output of the comparison element 31 is connected to the input of the power amplifier 32, the output of which is connected to the primary winding of the pulse transformer 33, the secondary winding of which is the output comparator 17.

The thyristors turn-on control unit (Fig. 4) is made in the form of a pulse-phase control system.

The unit consists of a series-connected resistor 35 and anti-parallel-connected diodes 36 and 37, which are connected between the input of a square pulse shaper 38 (for example, a transistor amplifier using composite transistors) and a common point of the shaper 38 and the power amplifier 39. The outputs of the imaging unit 38 are connected to the inputs of the amplifier 39. The outputs of the amplifier 39 are connected to the outputs of the magnetic amplifiers 40 and 41 with internal positive feedback.

The outputs of the magnetic amplifiers 40 and 41 are connected to the input of the pulse amplifiers 42 and 43 of the power (for example, single or three-stage pulse transistor amplifiers). The outputs of amplifiers 42 and 43 are the outputs of node 14. The operating point selection node of magnetic amplifiers of negative coupling with even harmonics and other auxiliary circuits in the diagram (Fig. 4) are not shown.

The device (Fig. 1) works as follows.

When a command arrives at the input of the switch-on control unit, depending on the polarity of the signal of the task, the control wide pulse arrives at the input of the LED of the optocoupler thyristor 4 and the input of the logic element 15 or at the input of the LED of the optocoupler thyristor 5 and at the input of the logic element 16.

As a result, one thyristor is opened, for example, 4, and through the resistance 8, the alternating current voltage from the source 3 output through the thyristor 4, the impedance 8, the winding 9 of the throttles 10 comes in the form of a positive half-wave to the capacitor plate 12, the filter inlet 13 and through the counter included winding 11 droplets 10 on. the winding 1 of the excitation of electric mashiny and to the second input of the filter 13.

The charge current of capacitor 12 is limited by resistance 8, which reduces the distortion of the form of the voltage of the power source. As the capacitor 12 charges, the voltage at the output of the filter 13 rises, i.e., at the first input of the comparator 17. When the capacitor 12 is charged before the voltage close to the voltage at the output of the source 3, the signal at the output of the comparator 17 which goes to the second inputs of logic elements 15 or 16, the output of which, depending on the polarity of the signal, sets the signal.

5 The coincidence of the signals at the two inputs of the elements 15 or 16 leads to the appearance of a signal at their output, which leads to the operation of the optocoupler thyristors 6 or 7 and to the shorting of the resistance 8 and an increase in the charge rate of the capacitor 12. When the voltage on the capacitor 12 becomes close to At the output of source 3, the thyristor current 4 and 6 or 5 and 7 will become less than the holding current and they will close.

5 At the same time, under the action of voltage on the capacitor 12, the current in the winding 1 increases. This current causes the appearance of a signal at the output of the sensor 2 of the excitation current. The resulting excitation current connection acts against Dani's background, decreasing as the excitation current increases, the opening angle of thyristors 4 or 5 in the subsequent half-periods.

During the charging of the capacitor 12, the charge current is also limited by the inductance of the winding. 10. At the same time, when charging the capacitor 12, the core of 10 droplets with one polarity is magnetized, and during the subsequent discharge of the capacitor 12 to the winding 1, the core of the droselsel is reversal with the opposite sign, which significantly reduces the dimensions of the chokes and power losses in its -winding.

During the subsequent working half-periods with the growth or steady-state value of the winding current I of the process, the nature of the process is determined by the value of the residual voltage on the capacitor 12 in my: the beginning of the next working half-period. When the voltage across the capacitor is less than what is required to operate the comparator 17, the opening process of the thyristors proceeds as it was described above. If the capacitor is charged to the control electrodes of the thyristors at the time of arrival of the pulse, before the trigger voltage of the comparator 17 ,. almost simultaneously, transistors 4 and 6 or 5 and 7 are opened and the charging process of capacitor 12 begins, and later on the process described above.

When the setting signal is reduced or reversed, the total signal at the input of the thyristor turn-on control unit 14 changes sign. Therefore, for example, when opening thyristors 4 and 6 in the previous mode, the thyristor 5 opens and the capacitor recharges with the polarity of the previous mode. The capacitor recharge current and distortion of the grid voltage is limited, as already known by the resistance 8 and the inductance of the winding 9. At the same time, the recharge of the condensate 12 occurs at the expense of the energy stored by the winding 1. In this mode, the maximum voltage of the capacitor is higher mains supply voltage, which provides forcing the regimes of 35mov flow recession.

After obtaining the required magnitude and polarity of the excitation winding current, the force is removed by opening the thyristors of opposite polarity.

The logical element works as follows.

- In the absence of signals at the inputs of the logic element I, whose role is played by the outputs of resistors 22 and 23 in the collector circuit j and in the circuit, the base of the transistor 18, the transistors 18 and 19 are locked due to the action of: a positive bias on the nonlinear resistance consisting of the resistor 21 and the diode 20, and the currents of the base terminals of the transistors flowing through the resistors 24 and 25. The operating mode of the transistor 19 is also stabilized by the resistor 26. When only one signal arrives, for example, positive to the first input of the logic element, i.e. the transistor 18, the transistors 18 and 19 remain locked due to the positive displacement described above on the emitter of the transistor 19. When one positive signal is applied to the second input of the logic element, i.e. the base terminal of the transistor 18, a small current is generated chains; resistor 23, base-emitter junction of transistor 18, base-emitter junction of transistor 19, diode 20, resistor 21. Resistance of resistor 21 is 100-300 times less than resistance of resistor 23. Therefore, the voltage across the load is equal to, as before, close to zero.

Only if there are positive signals at both inputs of the element And the transistors 18 and 19 are opened and the signal corresponding to the logical "1." Appears on the resistor 21. In this case, the second input has a high sensitivity.

The comparator circuit (Fig. 3) works as follows.

The voltage proportional to the voltage of the source 3, acting at the secondary output of the isolation transformer 27, is rectified using a diode-bridge circuit 28. The output voltage of the diode-bridge circuit 28 charges the amplitude of the filter capacitor 29, because the resistance the resistor 30 is selected high; a portion of this voltage, determined by the ratio of the arms of the resistor 30, is fed to the first input of the comparison element 31. At the second input of the comparison element 31, a voltage is supplied from the capacitor 12 via the diode circuit 34 (Fig. 1). When these voltages are equalized, the reference element is triggered and its voltage is amplified and, with the help of transformer 33, a pulse is formed from it, which is used to open elements 15 and 16 (Fig. 1).

The pulse-phase control system (Fig. 4) operates as follows.

Claims (3)

With the help of a circuit consisting of a resistor 35 and diodes 36 and 37 of a sinusoidal voltage, the output of the source 3 is formed by a trapezoidal voltage synchronized with the source voltage. This voltage is then transformed into a almost rectangular voltage, also synchronized with the voltage of the power source 3, by amplifying and shaping the power generator 38 and the power amplifier 39. This voltage from the output of amplifier 39 is used to power the working windings of magnetic amplifiers 40 and 41 with internal positive feedback. The pulse width at the output of the magnetic amplifier in each half-period is determined by the algebraic sum of the ampere-turns of the control windings. Therefore, the difference between the reference and feedback signals applied to the first pair of sequentially and oppositely connected control windings of magnetic amplifiers 40 and 41 determines the position of the leading edge of the pulses at the input of the pulse amplifiers 42 and 43. At the same time, the negative half-wave voltage is not used. Positive pulses amplify power with power amplifiers 42 and 43. With this, the steepness of the front edge increases to the required limits. Thus, as a result of the application of the present invention, the adaptive limiting of the capacitor charge current is reduced, the losses in the power supply are reduced, and the shape of the voltage at the power supply output is distorted. In addition, the device circuit has a high noise immunity, speed and, with the exception of Drossel 10, can be performed on standard elements. Claim I. Device for controlling the excitation current of a direct current electric machine, comprising an AC source to which a pair of oppositely connected thyristors is connected by one of the terminals, connected in parallel to the field winding and a capacitor, the switch-on control unit and the filter, In order to improve the energy characteristics, a second pair of opposing thyristors, a double-wound choke, whose windings have a difference of 2-3 times, 2-3 times, are introduced into it omparator, two logical elements And, the excitation current sensor and impedance, with the windings drossel placed on a common core and included counter, the second output of the first pair of thyristors is connected to the first common point of the second pair of thyristors and one of the impedance terminals, the second output of which together with the second common point of the second pair of counter-connected thyristors connected to the beginning of the winding of the throttle having a smaller number of turns, the end of which is connected to the end of the second winding of the throttle and one of the conclusions fi It is connected to one capacitor terminal, the second terminal of which is connected via the excitation current sensor and the excitation winding to the beginning of the second winding of the throttle and directly to the alternating current source and the comparator input, the output of the excitation current sensor being connected to the input of the activation control unit and its outputs connection) with the control inputs of the first pair of thyristors directly, and with the control inputs, the second pair of thyristors through the logic gates And, the second inputs of which are connected with the output of the comparator. 2. The device according to claim 1, characterized in that an additional winding is used as an impedance, a third winding additionally wound on the choke, the number of turns of which is 2-3 times greater than the number of turns of the winding having a greater number of turns, and with its beginning the additional winding is connected to the common the point of the first and second pair of thyristors. 3. The device under item 1 or p. 1 and 2, characterized in that the comparator comprises a transformer, the primary windings of which are the input of a comparator, two bridge diodes, an adjustable resistor, a reference element, a power amplifier and a pulse transformer, the secondary winding of the transformer being connected to the AC leads of the first diode - bridge circuit, the DC outputs of which are connected to an adjustable resistor, the moving contact of which and one of the DC outputs, of the first diode-bridge circuit are connected to the same input One comparison element, the second input of which is connected to the direct current output of the second diode bridge circuit, the AC input of which is the second input of the comparator, and the output of the comparison element through a power amplifier is connected to the dc winding of the pulse transformer, the secondary winding of which serves the output of the comparator. Sources of information taken into account in the examination. 1. USSR author's certificate No. 485429, cl. H 02 R 13/30, 1975. 2.Mitelman M.V., Voinov V.L., Krikun L.I. Modernization of the electric drive of the positioning mechanism.-Sat. "Installation. And adjustment of electrical equipment, No. 9, M., 1976, p. 141. 3. US patent number 3611093, cl. 318-258, H 02 P 5/00, 1970.