US2242946A - Electric discharge apparatus - Google Patents

Description

May 20, 1941. J. L 2,242,946 ELECTRIC DISCHARGE APPARATUS Filed April 13. 1939 [at 1 mm 6511M! PaZeztia Z 9 wnwssses; INV.ENTOR 597%. Jafiazzlzes f /k.

Patented May 20, 1941 UNITED STATS OFFICE ELECTRIC DISCHARGE. APPARATUS Application April 13, 1939, Serial No. 267,629 In Germany June 2, 1938 12 Claims.

The invention relates to a rectifier arrangement in which a load is connected through two antiparallel connected discharge paths to an alternating current source and in which the load current is to be regulated by selective determination of the ignition timepoint of the discharge paths. The invention is applicable for the different lmown types of arc discharge paths in which the timepoint for the ignition of the are between the main electrodes of the discharge paths may be selectively determined by the impressing of potential on control electrodes, particularly control grids. The invention is of particular significance for grid controlled mercury vapor discharge vessels.

The basis of the invention is the problem of operating a rectifier arrangement with two anti- .parallel connected discharge paths in such manner that the control electrodes or the control grids of both discharge paths are electrically connected with each other so that the two control electrodes of the double discharge path are connected in the control circuit as a single control electrode or a single control grid of an individual discharge path. In accordance with the invention, this problem is solved by connecting impedances, the magnitude of which depends on the polarity of the potential impressed upon them, between the control conductor common to the two discharge paths and the main electrodes of the double discharge paths by the operation of which the potential of the control electrodes of both discharge paths is brought to the potential of the cathode of the discharge path that at any time has potential of positive polarity impressed thereon. The essence of the invention thus consists in the introduction of an auxiliary circuit which operates with impedances, the magnitude of which depends upon the polarity of the potential and which provides that the potential of the control electrodes of the double discharge path, which are directly electrically connected with each other, shall be varied in synchronism with the alternating current potential feeding the double discharge path in such manner that the potential of these control electrodes at any time is equal to the potential of principal electrode of the double discharge path on which the alternating potential of negative polarity is impressed. The potential of the common control electrode of the double discharge path is, accordingly, periodically reversed and thereby in spite of the conductive connection of the control electrodes of the two discharge paths with each other, it is possible to selectively determine at any time, by a control potential introduced in the usual manner in the control circuit, the ignition timepoint of that discharge path on which the potential with positive polarity of the alternating potential is impressed.

The impedance, the magnitude of which depends upon the polarity of the potential in accordance with the invention is connected between the common control conductor of the double discharge path and at least one of the two poles of the double discharge path. The impedance preferably comprises a rectifier element in the form of a dry rectifier or a small hot cathode rectifier. For the connection of this rectifier, there are difierent possibilities which will be explained in detail with reference to the following description of the exemplary embodiment illustrated in the drawing, in which Figure 1 is a diagrammatic representation of a control circuit and apparatus embodying my invention, and

Figs. 2, 3 and 4 are diagrammatic views illustrating modifications of my invention.

In Figure 1, a load I is connected through a double discharge path 2 with two anti-parallel connected arc discharge paths to an alternating current source. The two discharge paths of the double discharge path 2 may be arranged in a common vessel in which at any time an anode of one discharge path is connected with the cathode of the other discharge path conductively.

.However, as is assumed in the circuit shown in 'a dry rectifier 5 is connected between the conductor 4 and the lower pole of the double discharge path, while the upper pole of the double discharge path: is connected through an impedance 6 with the control conductor. This impedance is so dimensioned that it is small with reference to the impedance of the dry rectifier 5 in the reverse conducting direction. At 1, a control potential is inserted betweenthe control conductor 4 and the connection point of the impedance 6 with the dry rectifier 5 which at any time within the half waves applied to the two discharge paths at the timepoint of the intended ignition produces a potential variation from negative to positive values. This control potential may, for example, be an alternating potential of double frequency or a pulsating direct'current potential which is derived from any kind of a control potential source, for example, an inverter.

The operation of the circuit illustrated in Figure 1 is as follows: If a timepoint is selected at which the alternating potential applied to the double discharge path 2 is positive at the upper pole, this alternating potential acts on the dry rectifier in the direction from the anode to cathode and because of the rectifying effect of the dry rectifier 5, the control conductor 4 is connected with the lower pole of the double discharge path 2. Accordingly, the control con ductor 4 assumes the potential of that pole of the double rectifier path which at this instant is connected to the negative pole of the alternating potential source 3. In the next half wave, the lower pole of the double discharge path 2 has impressed thereon the alternating potential source 3. The alternating potential acts on the rectifier 5 contrary to its conductive direction. This signifies that now the control conductor A is brought substantially to the potential of the upper pole of the double discharge path 2; since the impedance 6, as stated above, is so dimensioned that it is small compared to the back impedance of the rectifier 5. The functioning of the auxiliary circuit of Fig. 1 is thus such that the control conductor 4 obtains a periodically alternating changing potential and indeed at any time a potential of that pole of the double discharge path 2 which is the cathode of the discharge path passing the current. By the control potential introduced at I, the ignition timepoint within the two half waves of the alternating potential source 3 may then be selectively determined in any desired manner.

In lieu of the impedance 6 in Fig. 1, a second rectifier may be used. This has the advantage that the current flowing in the auxiliary circuit 5, 6 for any length of time is considerably decreased. In Fig. 2, this circuit is illustrated. The construction of the circuit is, with regard to the load I of the double discharge path 2 and the alternating current source 3, the same as Fig. 1. The auxiliary circuit for periodically varying the potential of the control electrodes of thetwo discharge paths comprises, in this case, of two rectifiers 8 and 9 which are connected to the secondary winding of an auxiliary transformer I I with the transformation relationship 1:1} Between the connection-point of the two rectifiers 8 and 9, and the zero-point of the transformer In, another loading impedance II may be connected. The zero points of the two windings of the transformer I0 are conductively connected to fix the potential of the secondary circuit of transformer II] with reference to the main circuit I, 2, 3. The position of this connecting point is in itself immaterial; for example, the primary and secondary winding of the transformer I!) may, for example, also be connected with each other at one end. The auxiliary circuit comprises ,in the arrangement according to Fig. 2, a branch rectifier arrangement and the negative pole of this rectifier arrangement is connected with the control conductor 5 of the double discharge path 2'.

In Fig. 3, a further exemplary embodiment is illustrated, which differs from the arrangement according to Fig. 2 in that the two rectifiers 8 and 9 have their cathodes connected together and not their anodes as shown in the circuit according to Fig. 2. For the rest, the auxiliary circuit com-prises here also a two path rectifier which is supplied by transformer IE and a loadin resistor II. Since in this case, however, the negative pole of the rectifier arrangement is connected to the zero point of the secondary winding of the transformer Ii), this point must be connected to the control conductor 4 of the double path discharge path. correspondingly, the connecting point is connected between the rectifiers 8 and 9 and the zero point of the primary Winding of the transformer It. The advantage of the circuit according to Fig. 3

resides in the fact that the two rectifiers 8 and I 9 may be formed into a two path rectifier with a common discharge vessel. At this point, a hot cathode rectifier common in the trade with two anodes and a common cathode may be used. As compared to the dry rectifiers, the advantage is attained that the rectifier paths in the back direction have a practically unlimited large resistance.

The control potential serving for determining the ignition timepoint is introduced in the two circuits of Figs. 2 and 3, as well as in the circuit of Fig. 1 at I in the connecting conductor between the control conductor 4 and the auxiliary circuit. As has already been mentioned, the control potential comprises either of an alternating potential of double the frequency or of a pulsating direct current potential, which changes from a negative to a positive value at the desired timepoint at any time within the two half waves. In Figs. 1-3, the control potential may also be added in the two branches of the rectifier paths.

In Fig. 4, another exemplary embodiment is illustrated which differs from the other exemplary embodiments in that as control potential, a transformer is used, the primary winding of which is connected to the feeding alternating current source, while the control potential for the two half waves of the double discharge path are derived from two secondary windings of this transformer. For the rest here also a load I is connected through the double discharge path 2 to an alternating current source 3. The auxiliay circuit for the periodic variation of the 'potential of the common control conductor 4 comprises a two path rectifier arrangement which is fed by a transformer l8 and which has the two discharge paths 8 and 9. The loading'impedance ll of the two path rectifier arrangement is connected between the control conductor 4 and the common cathodes of the two rectifier paths 8 and 9 just as in the circuit according to Fig. 3. The control transformer I2 is connected to the alternating current source feeding the main circuit. Its two secondary windings I3 and M are connected in the two branches of the two-path rectifier arrangement 8I I. The ignition time. point of the discharge paths of the double discharge path 2 is determined by the variation of the phase of the control transformer I2. This transformer may, for this purpose, be constructed either as a rotation transformer or its primary winding may be connected to one of the. known circuits for varying the phase position of a given alternating potential. The control transformer I2 may for the rest also be used in lieu of the control potential I in the exemplary embodiment of Figs. 1 and 2. Its two secondary windings should be connected in Fig. 2 between the rectifiers 8 and 9 and the two terminals of the secondary winding of the transformer It).

In the circuit of Fig. 4, an inductance with a resistance connected in parallel thereto is added in addition to a'lo-ad 1, thereby exception is given to the fact that in a load which is simultaneously a consumer for operating current and wattless current, preferably the inductance is bridged by a resistance to cut down potential peaks. The high frequency oscillations arising from the disconnection of the inductance may also be maintained remote with the aid of a filtering chain of the double discharge path. If the discharge path becomes extinguishing when the ignition potential is below the ignition value, high potential peaks and oscillations of high frequency are impressed on the inductance. Because of the symmetry of the grid arrangement between the anodes and the cathodes of the double discharge path, the grid tends to assume an intermediate potential between that of the oppositely connected anodes. This signifies that the grid has a positive potential with reference to the cathode of the discharge path capable of passing current and this discharge path is ignited. A certain control is thereby made possible. The disturbances by high frequency oscillations may be suppressed either by the above named parallel resistance or by connecting a resonant circuit parallel to the discharge path.

I claim as my invention:

1. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, an anode and a cathode for each discharge path, a control conductor common to the two discharge paths, a rectifier, means for connecting the rectifier between the control conductor and one of the anodes, a bilateral impedance, and means for connecting the bilateral impedance between the control conductor and the other anode.

2. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, a plurality of main electrodes comprising an anode and a cathode for each discharge path, a control conductor common to the two discharge paths, a rectifier having an anode and a cathode, means for connecting the cathode of the rectifier to the control conductor, means for connecting the anode of the rectifier to the anode of one of the discharge paths, a bilateral impedance small compared to the back impedance of the rectifier, and means for connecting the bilateral impedance between the control conductor and the anode of the other discharge path.

3. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, an anode and a cathode for each discharge path, a control conductor common to the two discharge paths, a pair of rectifiers connected in opposition having a common terminal and a pair of end terminals, means for connecting the common terminal to the said control conductor, and means connecting one of the end terminals to one of the anodes and the other end terminal to the other of the anodes.

' 4. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, an anode and a cathode for each discharge path, a control conductor common to the two discharge paths, a pair of oppositely connected rectifiers having a common terminal and a pair of end terminals, means for connecting the common terminal to said control conductor, a transformer having a primary and a secondary winding, means for connecting the primary winding across the discharge paths, and means for connecting the end terminals of the pair of rectifiers to the secondary winding.

5. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, a :control conductor common to the two discharge paths, a two-path rectifier, each rectifier path having an anode and a cathode, a transformer having a primary and a secondary winding, each of said windings having terminal taps and a zero point, an impedance, means for connecting the two rectifier anodes together to the control conductor and to one end of the impedance, means for connecting the other end of the impedance to the zero-points of the transformer windings, means for connecting the rectifier cathodes to the terminal taps of the secondary winding and means for connecting the primary winding across the discharge paths.

6. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, a control conductor common to the two discharge paths, a two-path rectifier, each rectifier path having an anode and a cathode, a transformer having a primary and a secondary winding, each of said windings having terminal taps and a zero-point, an impedance, means for connecting the rectifier cathodes together to the zero-point of the primary winding and to one end of the impedance, means for connecting the other end of the impedance to the control conductor and to the zero-point of the secondary winding, means for connecting the rectifier anodes to the terminal taps of the secondary winding, and means for connecting the primary winding across the discharge paths.

7. Device for the selective determination of the ignition timepoint of two discharge paths which are connected in antiparallel and through which a load is connected to an alternating current source, a control conductor common to the two discharge paths, a two-path rectifier, each rectifier path having an anode and a cathode, a transformer having a primary and a secondary winding, each of said transformer windings having terminal taps and a zero-point, an impedance, means for connecting the rectifier cathodes together to the zero-point of the primary winding and to one end of the impedance, means for connecting the other end of the impedance to the control conductor and to the zero-point of the secondary winding, phase shift means having a pair of secondary windings, means connecting one of the rectifier anodes through one of the secondary windings of the phase shift means to one of the terminal taps of the transformer secondary winding, means for connecting the other rectifier anode through the other secondary winding of the phase shift means to the other terminal tap of'the transformer second-' ary winding, and means for connecting the transformer secondary winding across the discharge paths.

8. Device according to .claim 1, characterized by the fact that in the control conductor a control alternating potential is connected, the frequency of which is twice the frequency of the alternating potential feeding the double discharge path.

9. Device according to claim 3, characterized by the fact that in the control conductor a control alternating potential is connected, the frequency of which is twice the frequency of the alternating potential feeding the double discharge path.

10. Device according to claim 5, characterized by the fact that in the control conductor a control alternating potential is connected, the frequency of which is twice the frequency of the alternating potential feeding the double discharge path.

11. In combination, an electric discharge device for controlling the supply of power from a source to a work circuit, the said discharge device having a pair of discharge paths connected in anti-parallel and a control electrode common to both of said discharge paths, a rectifier and a bilateral impedance connected in series circuit relation across said discharge paths, and means for impressing a control potential between the a J OHANNES FALK.

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