SU1598223A1 - Device for compensating for reactive power of induction installation - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to improve the accuracy of compensation. The device contains a counter-parallel-connected diode 1 and a thyristor 2, a compensating capacitor 3, a synchronizing transformer 4, a driver of 16 pulses, a pulse transformer 17. The presence of counters 13,14 and the supply of pulses with a frequency F to one of them and F / ₂ allows, when comparing the number of pulses, to accurately capture the moment of maximum of the mains voltage, which ensures the inclusion of a thyristor without a current surge. 1 il.

Description

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The invention relates to electrical engineering and can be applied in induction heating and smelting plants, in the metallurgical and engineering industries.

The purpose of the invention is to improve the accuracy of compensation.

FIG. 1 shows a block diagram of the device; in fig. 2 - voltage plots on the elements of the device circuit, which show its operation.

The device contains a diode 1, a thyristor 2, a compensating capacitor 3, a clock transformer k, rectifier 5, amplifier 6, diodes 7 and 8, filling generator 9, counter trigger 10, elements 11 and 12, counters 13 and 11, block 15 comparison, pulse shaper 1b, pulse transformer 17, synchronization trigger 18, with the primary of MotKa 19 of the synchronizing transformer connected to a chain of counter-parallel-connected diode 1 and thyristor 2 and a compensating capacitor 3 connected in series to them Weaving 20 synchronizing transformer through rectifier 5 and the amplifier is connected to the first inputs of the elements 11 and 12, and the ends of the second secondary winding 21 through the diodes to the second inputs of the elements I.

The device works as follows.

The power supply voltage (Fig. ..2a). Through diode 1, the capacitor 3 is charged with that indicated in FIG. 1-polarity, the same voltage is supplying for the synchronizing transformer g From the first secondary winding 20 of this transformer, the voltage through the rectifier 5 is fed to the input of the amplifier b (operating in the mode

threshold gain), which generates rectangular pulses, the shape of which is shown in FIG. 2 b.

From the output of the amplifier, the signals arrive at the first inputs of the elements 11 and 12. From the second secondary winding 21 of the synchronizing transformer, the voltage rectified by the diodes 7 and 8 (Fig. 2c, d) goes to the second inputs of the elements 11, respectively.

and 12.

The source of high-frequency pulses is the filling generator 9, which operates continuously (Fig.),

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the frequency of its operation is chosen based on the required accuracy of the device and is limited by the permissible frequency of the element base.

From the output of the generator 9, pulses with a frequency f are fed to the third input of the element I and to the counting input of the trigger 10. From the output of the trigger 10, pulses with a frequency of f / 2 (Fig. 2 e) are fed to the third input of the element I 12. Thus, through the element And 12 pulses with a frequency f / 2 during the time determined by the duration of the pulses from amplifier 6 at its first input, and in the half-period determined by the presence of a signal at the second input, will be fed to the input of counter 13 (Fig. 2), and through the element And 11 pulses with a frequency f also during the time determined by the duration pulses from amplifier 6 at its first input, and into the next half-period, determined by the presence of a signal at its second input, will be fed to the input of the counter I l (Fig. 2 h).

The signals of the counters 13 and 1 are fed to the input of the comparator unit 15, and when the state of the counter I t is equal to the state of the counter 13, a signal is generated at the output of the comparator 15 (Fig. 2 and), which in turn is fed to the input of the imager 1b pulses. The shaper is limited in duration through a pulse transformer to the control electrode of thyristor 2. The leading edge of the pulse exactly corresponds to the maximum mains voltage, which ensures that the thyristor switches on without a current surge.

The synchronization trigger provides zeroing of the counters 13 and 1 after the 45 formation of the leading edge of the pulse, as well as synchronous switching on of the device when the start signal arrives (the counting starts from the beginning of the positive sinusoid due to the connection of the cathode of the diode 7 and the trigger input 18) 18

Thus, due to the fact that the thyristor starting impulse is formed at the moment when the voltage on the capacitor and in the network are equal and, oppositely directed, the switching on of the compensating capacitor will occur without a transient process.

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The reliability of the proposed device as compared with the known one is characterized by a higher accuracy of the corresponding half-cycle of the mains voltage, and in the proposed device the degree of synchronization accuracy is determined by the frequency of the filling generator operation and can reach 0.5 el. hail and more. In addition, the accuracy of the device does not deteriorate with the deviation of the amplitude of the supply voltage and its frequency, which follows from the principle of its operation.

Claims (1)

Invention Formula A device for compensating the reactive power of an induction installation, containing a chain of a series-connected compensating capacitor and an oppositely connected diode and a thyristor, to the control electrode of which the secondary winding of the pulse transformer is connected, to the primary winding of which the output of the pulse former is connected to the primary winding synchronizing transformer having two secondary windings, one  of which has a midpoint output, characterized in that, in order to improve the accuracy of compensation, a device, an amplifier, two diodes, a filling generator, a counting trigger, two AND elements, two counters, a comparison unit and a syncro trigger 10 are added to the device. first secondary winding of a synchronizing transformer through a series-connected rectifier and amplifier connected to the first inputs of both elements, And, 15 the middle point of the second secondary winding is grounded, and its ends are connected to the second through diodes the inputs of the elements I, the output of the filling generator is connected to the third input of the first element 20 and directly, and to the third input of the second element I through a counting trigger, the outputs of both elements I are connected to the first inputs of the counters, the outputs of which are connected 25 to the inputs of the comparison unit connected to the input of the pulse driver, the output of which is connected to the first input of the synchronization trigger, the second input of which is connected to the 30 second input of the second element I, and the output to the second inputs of the counters. g Uh g g U, to one t (t i