US2738442A - Ignitron control - Google Patents

Description

March 1956 P. M. G. TOULON 2,738,442

IGNITRON CONTROL Filed Dec. 12, 1950 I INVENTOR j PIERRE MARIE GABRIEL TOULON lei-- $24 L E *1 w BY WWW 26 ATTORNEY United States Patent IGNITRON CONTROL Pierre M. G. Toulon, New York, N. Y., assignor, by direct and mesne assignments, of seventy-five per cent to Products and Licensing Corporation, New York, N. Y., a corporation of Delaware, and twenty-five per cent to Nelson Moore and William D. Hall, as joint tenants Application December 12, 1950, Serial No. 2665704 6 Claims. (Cl. 315-483) The present invention relates to a new system for controlling the passage of current in tubes provided with a liquid cathode, and more particularly of the type generally designated as ignitrons. It is well known that arcing between the anode and cathode of such ignitrons may be initiated by passing a pulse of relatively high current from a starting electrode immersed in the cathode and called igniter to the cathode.

The classical technique for releasing this high current in the igniter electrode consists of utilizing an ionic tube with a control grid (thyratron), that is inserted between the igniter electrode and the cathode.

In the usual constructions, however (rectification of current, changing of frequency), one normally utilizes a great number of ignitrons at the same time, and the necessity of providing each one of them with a thyratron tube constitutes a very major problem. The structural complications, clumsiness, and price of the overall arrange ment make it rapidly prohibitive.

The major object of the present invention is, accordingly, the provision of a system which, through the utilization of a single thyratron, permits the priming, in turn, of a great number of ignitrons.

According to the present invention, the igniter electrode of each of a plurality of ignitrons is connected to its respective cathode across the secondary of a transformer, and in series with an inductance coil. This transformer is preferably characterized by an extremely tight coupling between the secondary and the primary thereof. Such a transformer may be manufactured by winding the wire of the primary coiling and that of the secondary coiling side by side along their entire length so that the flux produced by these two coilings are practically identical. For this purpose, two insulated wires may be employed, these wires being wound simultaneously on a magnetic core. The first of these wires serves as primary and the second serves as secondary. If a relatively large capacitor should be discharged through the primary winding so formed, a very strong instantaneous current immediately follows in the secondary. An inductance coil placed in series with the secondary, and which has, preferably, an air-gap so constructed that there is a substantial leakage inductance, effects a prolonging of the duration of the secondary impulse which facilitates the formation of the cathodic spot. The duration of the most advantageous discharge has been recognized experimentally as of the order of 1/ of a second.

To discharge a condenser into each transformer primary, according to the invention, a single thyratron tube is employed Whose grid is rapidly carried to a positive voltage at the desired instant in order to thereby render it conductive. The control of the thyratron grid potential can be obtained by a static process, or by a mechanical device.

The present invention contemplates apparatus utilizing, in combination the single thyratron, a synchronized dis- 'tributor and special transformers such as have been described above, whereby by properly synchronizing the firing of a single thyratron with a voltage distributor coupled thereto, a relatively large number of ignitrons may be fired in sequence.

According to the variant of the invention, use may be made of as many transformers of the type described above as there are ignitrons to feed; the primaries of these transformers are connected to commutator sectors insulated from each other and placed in a circle, and a brush is rotated on these sectors, driven by a synchronized motor. The discharging current of the condenser is then passed through this brush to giving the overvoltage necessary for the priming of the igniter.

The objects and the method of construction of my invention may be better understood by reference to the following description and accompanying drawings, in which:

Figure 1 illustrates the winding of a special transformer, preferably utilized in the instant invention, in which the coupling between the primary and the secondary is extremely tight, and

Figure 2 illustrates one embodiment of the present invention in which a single thyratron is utilized to prime 2. hexaphased rectifier.

All the figures are givenmerely by way of indication in order to understand better the object of the invention. They do not possess any restrictive or limitative character as far as the scope of my invention is concerned.

In order to simplify the set-up of the ignitrons, it is evidently very desirable to be able to insulate the priming circuit from the principal circuit.

In accordance with the invention, and as has been described above, a special insulating transformer is uti' lized which permits a very high current to pass through the igniter during a very short space of time by ensuring its electrical insulation with relation to the circuit which furnishes the energy. With conventional transformer winding arrangements one cannot prevent the leakage of the coil from being very high and the coupling between primary and secondary from being very loose. Such structures are not acceptable in effecting the priming of the ignitron tubes. I have observed, in fact, that it is futile to make use of a very highly charged condenser of very great capacity since the secondary does not take very high instantaneous currents, inasmuch as the circuit of the igniter constitutes a short circuit which prevents the variation of the flux from being produced in the core.

In order to avoid such inconveniences I utilize a new method of construction of transformers which consists of winding the primary coil and the secondary coil at the same time.

In Figure l, the numeral 1 represents a core of magnetic material upon which my special magnetic circuit on which transformer is wound; numeral 2 represents the primary coiling and numeral 3 the secondary coiling.

As one can see, the two primary and secondary Wires are coiled at the same time in such a way that the flux covered by one is the same as the flux covered by the other. The coupling is thus extremely high, so that when a condenser is discharged into the primary everything occurs as if it were discharged into the secondary.

In the example shown in Figure l, the ratio of transformation is unity. In order to reduce the power of the capacity it may be better to choose another ratio, for instance, a ratio of 2 or 3 or 4. To obtain this latter result two, three, or four primary wires may be wound at the same time as the secondary wires (the sections of the conductors being in inverse ratio to their number), and the different coils thus individually created may be connected in series.

Theabove described isolating transformer presents the very great advantage of permitting priming to be eifected, no matter what the position of the ignitron in the set-up.

In particular, it permits the priming of six ignitrons of a rectifier construction installed in a voltage doubler.

This transformer shows, in addition, the remarkable property of permitting the utilization several times per cycle, of the same thyratron in order to prime a plurality of different ignitrons.

According to the present invention, therefore, a single thyratron is utilized in order to prime, in turn, a plurality of ignitrons.

Figure 2 represents the application of this principle to the priming of a hexaphased rectifier with a voltage doubler. In this figure, the numeral 4 designates a threephase feeding system, and the numerals 5, 6, 7, 8, 9, 10, respectively designate the six ignitrons that are to be primed in turn.

The cathodes of three of these tubes 5, 6, 7, constitute the positive pole of a continuous current distribution system, while the three anodes of the three other tubes 8, 9, 10, constitute the negative pole. The utilization circuit is represented as an induction motor 11, the circuit serving to regulate the terminal voltage of motor 11 with a view to varying its speed. Field coil 12 provides the motor field excitation which excitation is effected at a constant power by means of a small separate rectifier 13.

A single releaser thyratron 14 provides, in accordance with the instant invention, the priming of the six ignitrons 10 inclusive. A capacitor 15 and a resistance 25 are also connected to the anode of thyratron 14. The thyratron 14 is fed by means of a high voltage supply furnished by the rectifiers 17 and 18, which continually recharge the condenser 16. An undulating charge current passes across the primary of a transformer 19, which thus supplies to the secondary thereof a voltage of an equal frequency at six times the frequency of the feeding network system 4. The secondary voltage of transformer 19 is applied to the grid of the thyratron 14, and thus insures a periodic deblocking of the tubes. The discharge of the condenser 15, across the thyratron 14, is effected in turn, in the primary of one or the other of the transformers, 23, according to the invention. The selection of the particular transformer 23 concerned is obtained by means of a brush 20, rotating on a distributor constituted by the independent insulated sectors 21. The brush 20 is driven by a small synchronized motor 22, fed also by the system 4.

The functioning of the device is easily explained: the alternating voltage equal to six times the frequency of the system, supplied by the transformer 19, periodically releases the priming of the thyratron 14. At the moment when each impulse of current is produced, the brush 20 is on one of the sectors 21, and the primary of the corresponding transformer thus inducts into the secondary a very strong instantaneous current. A small coil 24, placed in series with the secondary, prolongs the flux of the current for a sufiicient space of time to insure the ionization of the cathode and to prime the ignitron. This operation lasts a very short time, about of a second, so that the brush has practically had no time to rotate.

At the end of ,6 to of a second, the condenser 15 is recharged, and the brush 20 has come into position with a new sector 21.

The grid of thyration 14 becomes again positive and the thyratron 14 is released a second time. But the discharge of the condenser 15 is then introduced into the primary of another transformer 23, so that it is another ignitron which is primed, and so on. 1

By diverting the harmonic voltage applied to the grid of the thyratron 41 (by means of an artificial line 26, for instance), one can regulate the priming phase of each ignitron with relation to the feeding system, and thus one succeeds in regulating the mean value of the current which circulates in the induction motor 11.

The set-up that has just been described is of a rectifier with an output voltage that can be regulated. It can be utilized in the discharging of accumulator batteries with a constant voltage or intensity, in the feeding of motors of variable speeds, in all the problems of control or telecontrol, etc. or again in the control of magnetic plungers provided with current for electrolysed vats and in a general fashion for all electrochemical appliances, etc. It may also be used for the control of the excitation of large alternators, or again for the constitution of very powerful magnetic fields (cyclotron), etc.

The principle of the invention that has just been described is capable of being generalized and applied to a multitude of problems.

Instead of making only a rectifier, one can also make a converter based on the same principle. By periodically varying the phase of the priming system to a fairly fast rhythm, one succeeds in creating an undulating current of the same rhythm.

In order to engender an alternating current, two ignitron and thyration groups, similar to those which have been described, may be placed in opposing directions and are controlled alternatively. By installing several similar groups and by controlling them with a diversion of a suitable phase, one may succeed in constructing on the same principle the distribution of multiphased currents with variable frequency. The commutators of the various groups are then driven by a small motor with a variable speed instead of the synchronized motor described above and the frequency of the circuit of utilization may be chosen at will by acting on the speed of this motor. Such generators are particularly interesting from the point of view of feeding synchronized motors of variable speeds.

The invention is not limited to the field of converters or rectifiers, in which is effected a periodic regular priming of the tubes. It applies also to arrangements in which the priming is only effected for a limited time. Such arrangements are generally found in the construction of spot welding machines, for instance, or again for telecontrol, the maneuvering of electromagnets, etc.

In a general fashion, the invention may be applied to all problems in which the priming circuits of the thyratrons should be insulated, and in particular to any application necessitating the simultaneous use of several ignitrous.

While I have described and illustrated specific forms of my invention it will be clear that variations thereof may be resorted to without departing from the true scope of the invention as defined in the appended claims.

What I claim and desire to secure by Letters Patent of the United States is:

1. In a system for controlling the firing of a plurality of isolated arc discharge devices each having an igniter element, a single thyratron, a circular commutator device having a plurality of sectors and a brush successively contacting each of said sectors, circuit means coupling each of said sectors to the igniter of each of said tubes respectively, circuit means coupling said thyratron to said brush, drive means rotating said brush, and means operatively connected for controlling the firing of said thyratron at a frequency related to the speed of rotation of said brush.

2. The system of claim 1 in which said means coupling each of said sectors to said igniters comprises a plurality of heavily coupled transformers, the primary and secondary windings of said transformers being wound together, each of said secondaries being respectively coupled between the igniter and cathode of one of said are discharge devices, one end of each of said primaries being respectively coupled to one of said sectors, the other ends of each of said primaries being coupled in parallel to said thyratron.

3. An electrical power system comprising a plurality of arc discharge devices each of which has a cathode and an igniter element, means isolating each of said are discharge devices from one another comprising a plurality of transformers coupled respectively to each of said discharge devices, the secondaries of each of said transformers being respectively coupled between the igniter and cathode of a single discharge device, each of said transformers having a primary closely coupled to its respective secondary, a single thyratron, and distributing means connected for successively coupling said single thyratron to different ones of said primaries.

4. The system of claim 3 in which said thyratron has first and second conduction elements and a grid, said distributing means comprising a mechanical commutator having a plurality of sectors electrically isolated from one another and a brush making successive contact with each of said sectors, one end of each of said primaries being respectively coupled to one of said sectors, each of the other ends of said primaries being coupled, in parallel, to one conduction element of said thyratron, the other conduction element of said thyratron being coupled to said brush.

5. The system of claim 4 including means moving said brush over said sectors at a predetermined rate of speed, and trigger means coupled to the grid of said 6 thyratron and so constructed and arranged that the ire quency of elfective operation of said trigger means being dependent upon the number of said sectors and the speed of said brush.

6. The system of claim 3 in which said means coupling said thyratron to difierent ones of said primaries includes a capacitor coupled between said thyratron and each of said primaries, means for charging said capacitor, and means for successively firing said thyratron to discharge said capacitor therethrough each time said thyratron is coupled to a different one of said primaries.

References Cited in the file of this patent UNITED STATES PATENTS 2,008,675 Bangratz July 23, 1935 2,169,031 Slepian Aug. 8, 1939 2,193,914 Alexanderson Mar. 19, 1940 2,289,119 Herskind July 7, 1942 2,494,747 Drugmand Jan. 17, 1950 2,515,985 Casanova July 18, 1950 2,568,587 Macgeorge Sept. 18, 1951

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