US1934231A - Rectifier control system - Google Patents

Description

Nov 7 1933. .1. JONAS RECTIFIER CONTROL SYSTEM Filed July 8, 1952.

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Patented Nov. 7, 1933 FFEQE RECTIFIER CONTROL SYSTEM Julius Jonas, Baden, Switzerland, assignor to Alrtiengesellschaft Brown Boveri & Cie., Baden, Switzerland, a joint-stock company of Switzerland Application July 8, 1932, Serial No. 621,357, and in Germany July 11, 1931 7 Claims.

This invention relates to improvements in electric current rectifying systems and more par-- ticularly to means for applying a potential on the control electrodes of an electric current rectifier of the metallic vapor type in a predetermined sequence.

The operation of electric current rectifiers of the character above indicated may be controlled by controlling the application or" a potential on the control electrodes associated with the anodes of such rectifier. Thus, the impression of a positive potential, relative to the cathode potential of such rectifier, on the control electrodes will permit the associated anodes to pick up an arc, such are is already present in the rectifier, as soon as the potential on such anodes has risen above the cathode potential by more than the amount of the voltage drop in the are from th anodes to the cathode. Impression of a negative potential on a control electrode associated 'viith an anode will prevent such picking up of the are by the anode but, once the arc has been picked up by the anode, cannot cause interruption of the arc until the potential on the anode has dropped below cathode potential plus the arc drop potential. The potential impressed on the control electrodes may either alternating current or direct current or a combination of both. Some means must, however, be provided to cause impression of the positive potential on the control electrodes in sequence at the moment, or just prior to the moment, in the cycle of alternating current supply to the anodes at which the anodes Due to the fact that each of the anodes of a rectifier are generally to up the are once and are to retain ti o arc during a portion of each cycle of the alternating current supply, it is necessary to provide means by which the application of a positive potential on the control electrodes may be obtained in sequence during each cycle of alternating current supply. When only alternating current is applied to the control electrodes, it is possible to obtain such sequential impression of potential on the control electrodes by means of a phase shifting transformer or other static apparatus but when direct current is used as the control potential or as one component thereof, it was heretofore considered necessary to provide switch means of the character of a distributor or other dynamic means which were not desirable in a substantially static system such as a rectifying system. Another disadvantage of such dynamic means was that such means had to be operated in synchronism with the alternating current supply to the rectifier.

It is, therefore, among the objects of the present invention to provide an electric current rectifying system embodying an electric current rectifier of the metallic Vapor arcing type having anodes with associated control electrodes on which diiferent potentials, relative to the oathode potential of the rectifier, are impressed at different times in the cycle or the alternating current supplied to the rectifier to control the operation thereof.

Another object of the invention is to provide an electric current rectifying system embodying an electric current rectifier of the metallic vapor arcing type having anodes with associated control electrodes on which different potentials relative to the cathode potential of the rectifier are impressed by static as opposed to dynamic means. I

Another object of the invention is to provide an electric current rectifying system embodying an electric current rectifier of the metallic Vapor arcing type having anodes with associated control electrodes on which a negative potential is continuously im' ssed from a source of direct current and a positive potential, both potentials being consi ered relative to the oathode potential of the rectifier, is intermittently impressed from a source of alternating current on the control electrodes of a rectifier by static means. 4

A further object of the invention is to provide an electric current rectifying system embodying an electric current rectifier of the metallic vapor arcing type having anodes with associated control electrodes on which a negative potential is continuously impressed from a separate source of direct current and a positive potential is intermittently impressed from a separate source of alternating current potential on the control electrodes of the rectifier, the moments in the cycle of the alternating current supplied to the rectifier at which such potentials are impressed on the control electrodes thereof being controlled in response to the occurrence oi the potential surges in the anode connections of the rectifier.

Objects and advantages other than those above set forth will be apparent from the fol- 105 lowing description when read in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic illustration of one embodiment of the invention in which the control electrodes of an electric current rectifier are continuously connected with the negative terminal of a source of direct current potential and are intermittently connected with the anode connections of an auxiliary rectifier in such manner that the potential surges in the auxiliary rectier, appearing simultaneously in the anode conections of both rectifiers, are impressed in sequence on the control electrodes of the main rectifier.

Fig. 2 is a modified embodiment of the invention in which means are provided for supplying the anodes of an auxiliary rectifier with current from a single phase source rather than from the polyphase source supplying current to the anodes of the main rectifier.

Fig. 3 is a vector diagram illustrating the potential conditions in the means for supplying the auxiliary rectifier from a single phase source by which each of the anodes of such rectifier are supplied with potential of the same value.

Referring more particularly to the drawing by characters of reference, the reference numeral 6 designates a polyphase alternating current transmission line supplied from a suitable source of current (not shown). The line 6 is connected through a transformer comprising a primary winding 7 and a star connected second ary winding 8 to supply potential to a rectifier or the metallic vapor arcing type generally indicated at 9. The rectifier comprises substantially a chamber or tank 12 having a plurality of anodes 13, 14, 15, 16, 17 and 18, extending thereinto and a cathode 19 preferably of vaporizable material such as mercury retained therein. The rectifier is provided with suitable are striking and arc maintaining means such as are well known in the electric current rectifying art and are, therefore, not illustrated or described herein. A conductor 23 connected with the neutral point of the transformer secondary winding 8 forms the negative bus bar and a conductor 24 connected with the cathode 19 of the rectifier forms the positive bus bar of a direct current output line supplying a load herein represented by a resistance 2'7 and an inductance 28.

Control electrodes 33 to 38, inclusive, are severally associated with the anodes for the purpose of controlling the moment in the cycle of the alternating current supply to the anodes at which such anodes may pick up the arc maintained within the rectifier. A negative potential, relative to the potential or" the cathode 19, is continuously impressed on each of the control electrodes from a suitable source such as a battery 41 through a switch 42 and current limiting resistances as at 43 and 44, except when such negative potential is overcome by a positive current potential surge as will be explained hereinafter. The positive terminal of the battery 41 is connected with the cathode 19.

An auxiliary rectifier generally designated by 51 and herein illustrated as being of the same character as the rectifier 9, is connected with the supply line 6 through a transformer comprising a primary winding 52 and a star connected secondary winding 53. It will be understood, of course, that the rectifier 51 may be of the glass enclosed or tube type rather than of the metal enclosed or so-called power type as indicated. The phase sections of the transformer secondary winding 53 are severally connected with the anodes 54 to 59, inclusive, of the rectifier 51 through current transformers each comprising a primary winding 63 and a secondary winding 64. The ratio of the windings 63 and 64 is such that the potentials occurring in the primary Winding 63 are very largely magnified in the winding 64. The cathode 66 of the rectifier 51 is connected through a load resistance 67 which may be of the constant current type, with the neutral point of the transformer secondary winding 53. One terminal of each or" the secondary windings 64 in the auxiliary transformer anode connections is connected to form a common point and such point is connected with a 85 common point formed by the connections of resistances 43. The other terminals of the secondary windings are each connected with one electrode '71 of one of a plurality of spark gaps, the other electrodes 72 of which are each connected with one terminal of the resistances 43, 44. It will be understood that resistances 43 and 44, transformers 63, 64 and spark gaps 71, 72 are illustrated merely as examples and that similar structures are present for each of the control electrodes and the connections of the anodes of the rectifier 51 with the several phase sections of the transformer secondary winding 53. Reference to Fig. 1 of the drawing will show that anode 54 of the auxiliary rectifier is connected 100 as above described with control electrode 33 associated with anode 13 of the main rectifier 9 and thatanode 54 is connected with a phase section of transformer secondary winding 53 advanced relative to the phase section of 105 transformer secondary winding 8 connected with anode 13. It will be understood that phase sections of the transformer secondary windings 3 and 53 in a manner similar to that above described are connected with the anodes and control electrodes associated with each other.

It is well known that each anode of a rectifier carries current onlyfor l/n of a cycle of the alternating current supply line when n is the number of anodes present and that they anode current increases and decreases at a very high rate at the beginning and the end of the firing period for each such anode. Assuming then that an arc has been struck and is being maintained in each of the rectifiers, one method by which the operation of the system may be started is by opening the switch 42 which will disconnect the control electrodes of rectifier 9 from the direct current source 41 and thereby permit the anode therein, at that moment having the highest potential to pick up the arc. It will be understood, however, that rectifiers 9 and 51 are independent structures and that, if it is desired that switch 42 remain closed, the picking up of the arc by one of the anodes in the rectifier 9 130 may be controlled solely by the occurrence of potential surges which cause flash-over of the spark gaps 71, '72 will be apparent from the following. After the arc has been picked up by one or the ano es, the swich 42 is again closed 35 thus imposing a continuous negative potential on all of the control electrodes from the battery 41. Assuming further that anodes 18 and 54 had picked up the arc, being at that moment at the highest positive potential of any of the anodes in either of the rectifiers 9 and 51, respectively, the impression of a negative potential on the control electrode 38, is inc-fiective to interrupt the arc attached to the anode 18.

It will be seen from the drawing that the potential impressed on the anode 54 is advanced relative to the phase position of the potential impressed on the anode 13 and that the transformer 63, 64 connected with the anode 54 is connected with the control electrode 33 asso- 150 ciated with the anode 13. As the current in the circuit of anode 18 decreases, the current will also decrease in the circuit of anode 54. Such current decrease is very rapid and causes a high potential surge in the transformer secondary winding 64 due to the ratio between the windings 63 and 64. Such surge causes flash-over of the spark gap '71, 72 and causes the impression of a positive potential, relative to the potential of cathode 19, on control electrode 33. Anode 13, then having a rising potential impressed thereon higher than the potential then impresed on anode 18, the positive potential on control electrode 33 permits anode 13 to pick up the arc. Anode 55 now picks up the are due to the fact that the potential impressed thereon is rising and is higher than the potential then impressed on anode 54. Anode 55 causes a positive potential surge on control electrode 34 as the end of the firing period of anode 55 is reached thus causing anode 14 to pick up the arc. Actions similar to those above described take place in sequence in the rectifiers and involve a sequential operation of all of the anodes of both rectifiers. The moment in the cycle of the alternating current supply at which the potential surges cause flashover of the arc gaps may be varied by making the transformers 63, 64 adjustable or by pro-,

viding means for shifting the phase of the potentials supplied to the anodes of the rectifier 51 relative to the phase position of the potentials supplied to the rectifier 9 as will be readily understood.

If a single phase electric current supply, rep-- resented by the line '74 in Fig. 2, is to be used to supply the anodes of the auxiliary rectifier 51 such single phase supply may be connected with the anodes of the rectifier 51 to supply substantially polyphase potentials thereto. Anodes 54, 55, 57 and 58 are connected with theline '74 by voltage dividing and phase shifting means such as inductances and resistances connected in series across the line with the anodes connected between such inductances and resistances. It will be seen from the drawing that anodes 54 and 5'7 are connected with the line 7 by inductance '75 and resistance 76 and inductance '17 and resistance '78, respectively. The inductances 75, 7'7 and resistances '76, 78 are preferably of the same dimensions, but the terminals thereof connected with the two conductors of the line '74 are reversed. Anodes and 58 are also connected with line 74 by the series connected inductance 81 and the resistance 82 and inductance 83 and resistance 84, respectively, the inductances and the resistances being preferably of the same dimensions and also connected with the line in reversed order as above. Anodes 56 and 59 are separately connected directly with the conductors of the line. A neutral point for the connection of the cathode 66 is obtained by means of inductances 87 and 88 or by an auto-transformer connected across the line '74. If desired, the line 74 may be connected with the supply line 6 by means of an adjustable phase shifter of any suitable character rather .plying the line 74. The reference characters A, B, C, D, E and F, designate the points of connection of the several anodes with the voltage dividing and phase shifting means or with the line '74 of Fig. 2 and O designates the neutral point of the line, i, e., the point between the inductances 87 and 88 with which the cathode 66 is connected.

Reference to the Voltage vector diagram in Fig. 3 will illustrate how a six phase current is obtained from the single phase line 74. It will be seen that, considering the outer points only, the diagram is substantially hexagonal in shape with the outer points thereof designated by the same reference characters as the points in Fig. 2 at which the anodes are connected to the voltage divided and phase shifting means and the line. The lines FO and O-Qjointly represent the potential across the line '74 and separately represent the potential on the anodes 59 and 56, respectively, considered relative to the potential of the neutral point 0. It will be understood that the several lines of the diagram have been identified "by the same reference characters as are applied to the several elements of the structure shown in Fig. 2. The phase pos tion of the potential impressed on the other anodes of rectifier 51 is obtained by plotting the potentials of the several pairs of inductances and resistances and by taking the resultant potential, of any pair of combined inductance and resistance potentials relative to the neutral point 0. Thus, as an example, the potential of anode 5 1 is represented by the line A-O which is the resultant, relative to the neutral point 0, of the potentials of the inductance 75 and the resistance 76 with which such anode is connected at the point A. It will be seen that polyphase alternating current potentials are thus obtained froma single phase alternating current source and that the potentials impressed on the severai anodes are equal.

Although but two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. 7

t is claimed and desired to secure by Letters Patent: 1

1. In a system for controlling the operation 01" an electric current rectifier of the arcing type comprising a plurality of anodes anda vaporizable cathode, the anodes and the cathode being arranged within a closed chamber, control electrodes associated with the anodes, means for continuously impressing a negative potential" type having anodes and a vaporizable cathode,

means for impressing a potential on the anodes of said electric valve, spark gaps connected with said control electrodes, and means connecting said spark gaps with the anodes of said valve to impress a potential positive with respect to the cathode potential of the rectifier intermittently on said spark gaps responsive to operation of said valve,

2. In a system for controlling the operation of an electric current rectifier of the arcing type comprising a plurality of anodes and a vaporizable cathode, the anodes and the cathode being arranged within a closed chamber, control electrodes associated with the anodes, means for continuously impressing a negative potential relative to the potential of the cathode on said control electrodes, an electric valve of the arcing type having anodes and a vaporizable cathode, means for impressing a potential on the anodes of said valve, spark gaps connected with said control electrodes, and transformers connecting said spark gaps with the anodes of said valve, said transformers being subject to intermittent potential surges responsive to operation of said valve positive with respect to the potential of the cathode of the rectifier to cause flashover of said spark gaps.

3. In a system for controlling the operation of an electric current rectifier of the arcing type comprising a plurality of anodes and a vaporizable cathode, the anodes and the cathode being arranged within a closed chamber, a control electrode associated with each of the anodes of the rectifier, means for continuously impressing a negative potential relative to the potential of the cathode on said control electrodes, an electric valve of the arcing type having anodes and a vaporizable cathode, means for impressing a potential on the anodes of said valve, a spark gap connected with each of said control electrodes, and transformers severally connecting said spark gaps with the anodes of said valve to impress a potential positive with respect to the cathode potential of the rectifier intermittently on said spark gaps responsive to operation of said valve.

4. In a system for controlling the operation of an electric current rectifier of the arcing type comprising a plurality of anodes and a vaporizable cathode, the anodes and the cathode being arranged Within a closed chamber, control elec trodes associated with the anodes, means for continuously impressing a negative potential relative to the potential of the cathode on said control electrodes, an electric valve of the arcing type having anodes and a vaporizable cathode, means for impressing a potential on the anodes of said valve, spark gaps connected with said control electrodes, and transformers connecting said spark gap with the anodes of said valve, the winding ratio of said transformers being such as to cause a potential surge producing flash-over of said spark gaps upon the occurrence of sudden changes in the rate of flow of current through the anodes of said valve.

5. In an electric current rectifying system, an electric current supply line, an electric current rectifier of the arcing type having a plurality of anodes with associated control electrodes, and a vaporizable cathode, a transformer connecting said rectifier with said supply line, an auxiliary electric current rectifier of the arcing type having a plurality of anodes and a vaporizable cathode, means for cyclically impressing a potential on the anodes of said auxiliary rectifier, means for continuously impressing a potential negative relative to the cathode potential of the first said rectifier on the control electrodes thereof, a

spark gap connected with each of the control electrodes, and transformers severally connecting said spark gaps with the anodes of said auxiliary rectifier, the winding ratio of the last said transformer being such as to cause flash-over of said spark gaps connected therewith upon the occurrence of sudden changes in the rate of flow of current through the anodes of said auxiliary rectifier and in response to the cyclical energization of the anodes of the said auxiliary rectifier.

6. In an electric current rectifying system, an electric current supply line, an electric current rectifier of the arcing type having a plurality of anodes with associated control electrodes, and a vaporizable cathode, a transformer connecting said rectifier with said supply line, an auxiliary electric current rectifier of the arcing type having a plurality of anodes and a vaporizable cathode, a transformer connecting the anodes of said auxiliary rectifier with said supply line, means for continuously impressing a potential negative relative to the cathode potential of the first said rectifier on the control electrodes thereof, a spark gap connected with each of the control electrodes, and transformers severally connecting said spark gaps with the anodes of said auxiliary rectifier, the winding ratio and the connection of the last said transformers being such as to cause flash-over of said spark gaps connected therewith upon the occurrence of sudden changes in the rate of flow of current through the anodes of said auxiliary rectifier in response to the energization of the anodes of the said auxiliary rectifier.

7. In an electric current rectifying system, a 110 polyphase electric current supply line, an electric current rectifier of the arcing type having a plurality of anodes with associated control electrodes and a vaporizable cathode, a transformer connecting said rectifier with said supply line, a single phase electric current supply 'line, an auxiliary rectifier having twice the number of anodes as the phases of said polyphase line, means for obtaining a polyphase potential from said single phase line for cyclically impressing 120 potentials on the anodes of said auxiliary rectifier, means for continuously impressing a potential negative relative to the cathode potential of the first said rectifier on the control electrodes thereof, a spark gap connected with each of the 125 control electrodes, and transformers severally connecting the anodes of said auxiliary rectifier with said spark gaps, the winding ratio of the last said transformers being such as to cause flash-over of said spark gaps connected there- 130 with upon the occurrence of potential changes at the anodes of said auxiliary rectifier and in response to the cyclical energization thereof.

JULIUS JONAS.

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