SU1764042A1 - Control method for mixed active-reactive loading of relay-pulse regulating device - Google Patents

Abstract

The invention relates to a converter technique and can be used in electrical technology installations, in particular in electric welding devices. The essence of the invention: when current passes through zero, the thyristors are turned on, with the on state of which the output voltage varies along the lower quantization level, and then with an adjustable time delay in the interval until the voltage passes through zero, the thyristors turn on, with the on state of which output the voltage varies across the top quantization level. After this, the thyristors, with the on state of which the output voltage varies along the lower quantization level, are re-enabled during the half-period with adjustable time delay in the interval from the time the voltage passes through zero to the time current passes through zero, thereby achieving the goal . Positive effect: by changing the angle ar from the highest value to zero, the control range is expanded by closing the adjustment characteristic. 2 Il. (Ls

Description

The invention relates to a converter technique and can be used in electrical technology installations, in particular in electric welding devices.

The closest in technical essence is a method of controlling an alternating voltage relay-pulse control device, in which during each half-cycle of the adjustment cycle the thyristors, with the switched on state of which, the load voltage varies according to the lower quantization level, at the moment the current passes through zero , and thyristors, when enabled

the states of which the load voltage varies according to the upper quantization level are switched on with an adjustable time delay on the interval until the voltage passes through zero. The disadvantage of this method is the presence of an uncontrollability range under active-inductive load, which degrades the control properties of the device.

The purpose of the invention is to expand the range of regulation.

When the current passes through zero, the thyristors turn on, with the on state of which the output voltage changes

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on the lower quantization level, and then with an adjustable time delay on the interval until the voltage passes through zero, the thyristors are switched on, with the on state of which the output voltage varies on the upper quantization level. After this, the thyristors, with the switched on state of which the output voltage varies along the lower quantization level, are reapplied during a half-period with an adjustable time delay in the interval from the time the voltage passes through zero to the time the current passes through zero. goal.

In figure 1 (a, b, c) given the scheme of devices that implement this method; 2 shows time diagrams of the voltage It and the current n of the load and the primary current I.

The devices contain a source of alternating voltage 1, a transformer 2, an active-inductive load 3, a thyristor switch 4 of anti-parallel thyristors 5, 6, when switched on, the output voltage varies along the lower quantization level, the thyristor The main key 7 of the counter-parallel thyristors 8, 9 in Fig. 1, a, 8, 9, 10, 11 in Fig. 1, b, with the switched on state of which, the output voltage varies along the upper quantization level. At time 11 (see Fig. 2), the thyristor 5 is turned on with the polarity of the supplying alternating voltage in FIG. 1, a, b and the secondary voltage of the transformer in FIG. 1, c shown without brackets. In this case, the electromotive force (EMF) in the windings of the transformer has the direction shown in Fig. 1 by a solid arrow. At time ta, determined by the angle of regulation a. , include the thyristor 8 in figs, 1, a, b, or thyristors 8, 10 in fig, 1.6, where The EMF direction is such that when the thyristor 8 is turned on in Fig. 1, a, or thyristors 8, 10 in Fig. 1, b, the thyristor 5 is turned off, which corresponds to the transition from the lower level of quantization of the output voltage to the upper level, i.e. The instantaneous values of UH and I increase in where the ratio of the amplitude of the lower quantization level to the amplitude of the upper level. At time t3, the power supply the voltage changes polarity and the current with active-inductive load keeps the same direction until time ts. In the known control method, changing the control angle "1, change the average value for the half-period of the output voltage. The disadvantage of this method is that when going from the value of a, which is infinitely small (less for real thyristors, by the time they were turned on), to a value equal to the average values of the output voltage and current decreases abruptly, since in the first case the change 1) n and 1H in the interval ta-ts is determined by the upper level of quantization, and in the second case - by the lower level. Thus, in the adjustment characteristic of a known method, there is a discontinuity (range of deregulation), which becomes significant at low cos p.

In the proposed control method, this gap is eliminated due to the transition to the lower quantization level in the interval. At the time point ta, the polarity of the supply voltage in Fig. 1, a, b, or secondary for example of a transformer in Fig. 1, becomes what it is shown in brackets. This polarity corresponds to the direction of the EMF shown in FIG. 1 with a dotted arrow, which means that the EMF is directed in the conducting direction for the thyristor 5 and non-conducting for the thyristor 8 in FIG. 1, a, b and thyristors 8, 10 on figure 1, b. At time t4, determined by the angle of control cti, the thyristor 5 is turned on again for half a period, which causes the thyristor 8 to be turned off in FIG. 1, a, and in or the thyristors 8, 10 in FIG. 1.6, and the transition to the lower level of quantization, i.e. the instantaneous UH and I values are reduced by a factor of 1/6. The control in the second half period of adjustment is carried out similarly to the control in the first half period. By varying the angle oa, from the highest value to zero, the control range is expanded by closing the gap in the adjustment characteristic.

Claims (1)

The invention The method of controlling the device of the relay-pulse control of the alternating voltage with active-inductive load, in which during each half-cycle of the regulation cycle the thyristors, at the switched on state of which the load voltage varies along the lower quantization level, are included in the moment of current passage through zero, and thyristors, in the on state of which the load voltage varies according to the upper quantization level, are switched on with an adjustable time delay in the interval up to the moment of voltage passing through zero, characterized in that, in order to improve the adjusting properties of the device, thyristors, with the on state of which the load voltage Q varies according to the lower quantization level, re-enable with adjustable time delay in the interval from the moment the voltage passes through zero to the time current passes through zero w L: -: q4 k .. .. J --s   l- -Ch-a-l-ll / TGUL n 1 -J 3 t5. „.. (-) P 9 ±. J I Li four -k - j : Tl j