US2866149A - Device for rapid voltage regulation in contact converters provided with switching coils - Google Patents

Description

Dec. 23, 1958 A. BRANDT 2,856,149 VOLTAGE DEVICE FOR RAPID REG TION IN CONTACT CONVERTERS PROVIDED WITH TCHING COILS Filed March 9, 1956 5 Sheets-Sheet 1 Dec. 23, 1958 A. BRANDT 2,856,149

DEVICE FOR RAPID VOLTAGE REG TION IN CONTACT CONVERTERS PROVIDED WITH TCHING C OILS Filed March 9, l 5 Sheets-Sheet 2 Dec. 23, 1958 A. BRANDT R 2,866,149

DEVIcE FOR RAPID VOLTAGE REGULATION IN CONTACT CONVERTERS PROVIDED WITH SWITCHING COILS Filed March 9, 1956 3 Sheets-Sheet 5 DEVKCE FKIDR RAPID VQZLTAGE REGULATION IN CGNTACT CGNVERTERE; PRGVIDEID WITH Sii/KTCHTNG Uilllhfi Armand Brandt, Wettingen, Eiwitzeriand, assignor to Akitiengeseiischait Brown, ldoveri & Cie, Eaden, Switzerland, a joint-stock company Application March 9, 1956, Serial No. 570,513

Claims priority, application Switzerland March 18, 1955 7 Claims. (Ell. 321-43) The present invention concerns an arrangement for rapid voltage regulation in contact converters provided with switching coils.

The delivered direct voltage of the contact converter can be regulated, as known, in a simple manner by varying the duration of the connection interval of the contact currents. The variation of the connection interval is effected in known manner by varying either the direct current magnetization or the alternate current polarization of the switching coils. In both cases, the intensity of the step current in the disconnecting point is influenced together with the variation of the duration of the connection interval, which leads to difliculties with regard to the correct adjustment of the parallel circuit impulses to the current step. Besides, both the duration of the connection interval and the intensity of the step current at i the time of disconnection are, in this arrangement, dependent on the phase position of the A.-C. polarization of the switching coils with regard to the position of the contact switching times, so that the parallel circuit impulse must always be readjusted with each variation of the phase position, in view of the current-less interruption of the contacts. The above mentioned disadvantages are eliminated by the practicing of the principles of the present invention.

The invention consists in that two current-limiting coils are provided which are connected in parallel and polarized with direct current, and in that they are so connected by means of valves or rectifiers with the polarization windings of the switching coils that the latter are magnetized alternately by rectangular currents whose positive half-waves are limited by one coil and whose negative half-waves are limited by the other coil, and in that one limiting coil has an additional winding which is traversed by a current proportional to the difference between the actual value and the nominal value of the quantity to be regulated, so that the amplitude of one-half wave of this rectangular cur rent is so changed that the duration of the connection interval of the contact currents is influenced in a regulating sense, while the amplitude of the half-wave with the opposite polarity remains unchanged.

The limiting coils thus become by this measure regulating coils, which makes it possible to eiiect the regulation conssiderably faster than would be possible with sector regulators, for example. Besides, the arrangement does not require any moving parts or contacts, which circumstance is of advantage for the safety of the operation.

The invention is illustrated in detail by means of an embodiment shown in the accompanying drawings, in which:

Figs. 1 and 2 show the wiring of the arrangement; and Figs. 3 to 5 show operating diagrams.

Fig. 1 shows a contact converter in a three-phase bridge connection. The contact converter transformer is designated at 1, the switching coils for the production of the low-current intervals at 2 and 3, and the contacts of the converter at 4 and 5. The switching coils are each equipped, in known manner, with a polarization winding 2355,1349 Patented Dec. 23, 1958 2i and 31 respectively. The polarization windings of the switching coils of phase and counterphase are fed in parallel over current-limiting coils 8, 9. Fig. 1 shows only the current-limiting coils for the phase R. For each of the phases S and T there are also provided two such limiting coils. Each current-limiting coil has two cores 1 and II, each of which is provided with a working winding a. The working windings are so connected in series that the two cores are oppositely magnetized.

As core material there is used a type of iron having a pronounced magnetization break, for example, nickel iron. The two cores of the current-limiting coils are both wound with a D.-C. polarization winding b. The polarization windings b of all coils are connected in series, and are fed with direct current over a control resistance 18. One current-limiting coil 9 of each phase is also provided with a regulating winding c, which encloses both partial cores. The windings c of these current-limiting coils, acting as regulating coils 9, are connected in series and are fed with a clifierential voltage which is proportional to the deviation of the converter current from its nominal value. To this end, a voltage is produced at the resistance 12 over a D.-C. converter circuit 6, consisting of the D.-C. magnetized coil with feed transformer 16, the valves or rectifier-s 7 and the smoothing reactor or choke 13, which voltage is proportional to the converter current, and is compared with a fixed voltage at the resistance 14. The ditlerential voltage which thus represents directly a measure of the deviation of the actual value from the nominal value or": the direct current of the converter, exists at the terminals of the coil windings 0, connected in series in such a way that when the nominal value of the converter current is exceeded-that is, with positive differential vol agethe polarization of the regulating coils 9, caused by the windings b, is reduced, while it increases when it is lower than the nominal valuethat is, with negative differential voltage. The working windings a of the coils and 9 are connected over valves or rectifiers 16 with the inlets of the polarization windings 21 and 31 respectively of the switching coils, in such a way that after each halfwave the polarization windings of the switching coils are communicated from one current-limiting coil to the other. This has the result that one of the half-waves is limited by the coil 8 in the polarization winding of the switching coil and remains unchanged in its amplitude, while the half-waves with opposite polarity are limited by the regulating coil 9 and can be varied in their amplitude.

Fig. 3 shows the magnetization curves of the currentlimiting coils. The two cores of the coils are polarized with direct current corresponding to the ampere windings AWg. The current in the working windings eiiects an increase or" the magnetization by AW in one of the cores. Since the two cores have the same dimensions and the same number of turns, and the two hatched areas must be equal, the resulting circulation is increased by Delta AW. With increasing AW+ and AW, Delta AW increases likewise. 1f the current in the working windings is an alternating current, the Delta AW pulsates between the value 0 and a maximum value with double the mains frequency. To compensate the ampere windings Delta AW, the current-limiting coils are provided with a feedback .winding d, which is fed over valves 11 in bridge connection from a shunt 15'.

Due to the broken magnetization curve of the currentlimiting coils, the amplitude of the alternating current in the working windings is limited corresponding to the value of the AWg, and'its current curve is approximately rectangular. By varying the direct current polarization by means of the regulating Winding c, the

amplitude of the alternating current can be regulated in the working windings of the limiting coils.

The method of operation of the above described arrangement is represented schematically in Fig. 4.

Fig. 4a shows the course of the current i,, of a converter contact with practically complete modulation, as well as the current i in the polarization winding of the corresponding switching coil.

Fig. 4b shows the same with a highly readjusted direct voltage, that is, with a lower contact current i At the connection point A (Fig. 4a) the switching coil is polarized by the amount I' In Fig. 5, which represents the magnetization curve of the switching coil, the connection is eitected in the magnetized state P of the switching coil. With increasing current i the switching coil is magnetized by 1 the contact current 1 up to the point P where the switching coil is in the saturated state. This point P corresponds to the point B in Fig. 4a. While the switching coil shows a high inductivity in the region P P which limits the current to a low value (connecting step current), this inductivity decreases in jumps with increased magnetization, and has practically no more influence on the contact current i until the magnetization of the switching coil, returning over the point P has reached the point P with decreasing contact current in the point C (Fig. 4a). At this moment the switching coil suddenly becomes inductive and limits the current to a small value i (disconnecting step current). Since the switching coil has been polarized, in this time interval, corresponding to the current i the zero passage of the current occurs only in the point P'S (Fig. 5), corresponding to the point D in Fig. 4a. In the intervals AB and CD the entire current reversal voltage of the converter is therefore above the switching coil (hatched areas); in the interval BC, however, the voltage above the coil is very low. If the amplitude of the polarization i of the switching coil is reduced by the regulating coil 9 in the connecting point of the converter contact, the duration of the connection step increases according to Fig. 4b; the direct voltage delivered by the converter diminishes and correspondingly also the direct current of the converter. This reverse regulation of the direct current occurs, for example, if the actual value tapped over the voltage divider 112 exceeds the nominal value for the direct current of the converter to be regulated, which is tapped at the voltage divider 114, so that the winding of the regulating coil reduces the action of the po larization winding b. But if the actual value drops below the nominal value, the polarization of the regulating coil 9 is increased by the AW of the regulating winding 0, so that the amplitude of the polarization current of the switching coil is also increased. Thus the duration of the connecting step decreases, the direct voltage increases and the direct current is adjusted to the nominal value. Since the polarization current is limited during the disconnecting step by the coil 8, the amount of the step current Delta 1 remains unchanged, because the point is fixed in Fig. 5.

The above described device regulates the direct voltage delivered by the converter in such a way that the delivered direct current remains constant within certain limits, as it is desired, for example, in electrolytic plants. But the device can also be so designed that the voltage is regulated to a constant value. in this case, the voltages at the resistance 14 would be compared directly with the direct voltage delivered by the converter.

Fig. 2 shows another embodiment where the direct current converter circuit is connected directly to the regulating winding 0 of the regulating coils so that the comparison between actual and nominal values can be made in the regulating coil itself.

I claim:

1. Device for rapid voltage regulation in contact converters provided with switching coils, the switching coils of each phase of the converter having two current-limiting coils which are connected in parallel and polarized with direct current, said current-limiting coils having cores of a magnetic material with a pronounced magnetization break and being connected to their associated switching coils by valve means so that the switching coils are magnetized alternately by square-wave currents whose positive half-waves are limited by one coil and whose negative half-waves are limited by-the other coil; means for varying the amplitude of one-half of the rectangular currents so that the duration of the connection intervals of the contact current is influenced in a regulating sense while the amplitude of the half-wave of opposite polarity remains unchanged comprising an additional winding on one of the current-limiting coils which is traversed by a current proportional to the difference between the actual and the nominal value of the quantity to be regulated.

2. Arrangement according to claim 1, characterized in that each of the current-limiting coils is provided with two cores of an iron having a pronounced magnetization break.

3. Arrangement according to claim 2, characterized in that each of the two cores has a working winding which is so connected in series that the two cores are oppositely magnetized, and in that a polarization winding is provided which embraces both cores.

4. Arrangement according to'claim 3, characterized in that the two cores have an additional feed-back winding which embraces both cores and which is fed over valves with a pulsating direct current of double mains frequency, proportional to the alternating current in the working windings.

5. Arrangement according to claim 1, characterized in that the variation of the amplitude of one half-wave of the rectangular current is effected in dependence on the diflerence between the actual value and the nominal value of the direct current delivered by the contact converter;

6. Arrangement according to claim 1, characterized in that the variation of the amplitude of the half-wave of the rectangular current is effected in dependence on the difference between the actual value and the nominal value of the direct voltage delivered by the contact converter.

7. A device for rapid voltage regulation of a contact converter provided with switching coils comprising a pair of current-limiting coils associated with each phase of the contact converter, said current-limiting coils having cores of a material with a pronounced magnetic break, a source of electrical power causing said current-limiting coils to produce rectangular half-wave voltages, an auxiliary coil positioned about the core of one of said current-limiting coils, means for producing a current proportional to the diiference between the actual and the nominal value of the quantity to be regulated, said auxiliary coil being connected to said current producing means so that the magnetization component produced in the core will affect the magnitude of the voltage produced by the associated current-limiting coil, and valve means connecting the current-limiting coils to the switching coils so that the switching coils are magnetized alternately by square wave currents whose positive half-waves are limited by one coil and whose negative half-waves are limited by the other coil.

References Cited in the file of this patent UNl-TED STATES PATENTS 2,568,140 Belamin Sept. 18, 1951 2,756,381 Rolf July 24, 1956 FOREIGN PATENTS 113,439 Sweden Mar. 13, 1945

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