US2644913A - Surge suppressor - Google Patents

Description

July 7 7, 1953 W. G. STONE SURGE SUPPRESSOR Filed Aug. 16, 1949 INVENTOR;

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Patented July 7, 1953 UNITED STATES OFFICE I 2;c44,91-s- I v .SQURGE'SUPPRESSOR I aims Stone-Oak Ridge,"Tenn'., assignor, by -mesne assignments, to the United-States of America as represented by :the United nStates vAtomic.Energyiilommissiun Application August s, 1949,;seriamo;110,487

. 1 -My invention relates to surge suppressors and more'particularly to a device'for suppressing electric surges, and transients 'frorn surges and is especially useful in suppressing the sparking of calutrons. s

In the use of electromagnetic equipment, such as calutrons, for refining'uranium, or other "materials, high voltages are required for the electrodes which accelerate the particles or ions in the separating and sorting operations. During the-operation of such equipment, sparking at the electrodes may take place asoften'as'ten times per second during good operation and oftener during poor operation. This maybeinherent in-the operation of this type of equipment; but since it tends to discharge the 'entirecapacityof the electrodes-and lines, and the'capacit'ors-of the supply cubicle, it oftenresults-intheufailure of insulators and cables as well as the consumption of considerable amounts of power. Closing down these units for insulator-or cable replacements results in expensive time consuming maintenance, and removes the units from use for a substantial portion of Y the available time, th us -limiting their service and output. a

Numerous attempts have been made to reduce sparking and to protect the system from the harmful results thereof. lVIost of these attempts have proved to be costly and elaboratewhile failing to meet the problem. Asone-possible arrangement, the high voltage leads may be lengthened and coiled to produce one turn transformer primaries. A closed loop or tube may be inserted therein so that the inductive efiectbetween them Will have the result of producing transformers with short circuited secondaries, but that arrangement may require considerable additional space with longer leads. Such an arrangement might be expensive and only partially successful.

Applicant with a knowledge of all these defects in and objections to the prior art has for an object of his invention the provision of a surge suppressor which is easily installed and maintained and which effectively reduces the harmful effects of surges.

Applicant has as another object of his invention the provision of a surge suppressor which is cheap to produce or replace and which will occupy a minimum of space while effectively reducing surges and their harmful eiTects.

Applicant has as a further object of his invention the provision of a surge suppressor which protects insulators and cables from failure or break down resulting from surges in high voltage lines.

1 Claim. (Cl. 315- 248) Applicant'has as 'a still further object 'of his invention the provision =of 'a. surge suppressor Whichis-safe to handle'and which maybe operated overrelatively'long periods of time without either replacement or maintenance.

Applicant has as'an additional object of his inventionthe provision'of a surge suppressor-capable of reducing the-effectof thetransients of some"leader strokes'so that they-do not result incompletebreakdownandsparking.

Other obj ects 'and'advantages of my invention will appear from the following specification and accompanying drawings and the novel features thereof will be particularly pointed out in the annexed claim.

'In the drawings, Fig. "1 is a plan view of my improved'surge suppressorpositioned about a-high voltage lead or conductor. Fig. 2 is a crosssectional view'of my improved-surgesuppressor taken along-the lines 2- 2 of Fig. 1. Fig. 3 is'the'same suppressor, partlyin'section; indicating the direction of the magnetic field :and induced currents therein. Fig.4 is-a graphofcharacteristic curves formy improved surge suppressor where current perunitvolumeis plottedagainst timefor different changing currents.

Gne'difiicuIty involved in the use of high voltages, *as heretofore indicated, is that of large surges of current due to short' circuits and "sparking. A surge may result in a relatively lon transient. The high frequencies and high voltages "present in-the transient result in insulator and "cable failures. A transient also may cause the apparatus to be inoperable for a period of time equal to-the time of thetr-ansient. The present inventionacts 'like a transformerwith a short circuitedisecond-ary 'to suppress the surge and shorten the time of the resulting transient.

A spark or shorting are normally starts with what is called a leader stroke which. may consist of a thin line of ionized gas providing a conducting path of limited current carrying capability. In the normal case secondary emission and ionizing collisions progressively lower the resistance of the path and the current rises rapidly until a dead short is established and the current is limited only by the electrical constants of the system. This dead short may endure for milliseconds after currents capable of sustaining the are have ceased, due to the dense cloud of ions and electrons in the gap. By providing this surge suppressor adjacent to the gap it is observed that leader strokes are many times not followed by arcs. This is attributed to current starvation which results from the drop in voltage at the arc 3 and the high impedance at the suppressor. In. such cases the disturbance is over in a. small fraction of a microsecond.

Referring to the drawings in detail, l desist-- hates the body of my improved surge suppressor which is generally of doughnut configuration. The body is tubular and is preferably made of some inexpensive material, such as glass, although any other suitable non-conducting material may be employed. The space in the tubular body I of the suppressor is evacuated and some gas having a low ionization potential and which will produce large ion currents may be fed into the chamber. Applicant prefers to use hydrogen gas and maintains it under a pressure of from 4 to 10 microns in the chamber, although this may be found difficult with hydrogen. To aid in initial ionization of the hydrogen gas some material such as radium chloride in a very small quantity may be enclosed in the chamber since it is helpful in providing a certain initial ionization for the hydrogen gas. After the hydrogen reaches the proper pressure, as indicated above, the body l of the surge suppressor is sealed completing the doughnut configuration. The larger the diameter of the tubular body I of the doughnut, the lower the threshold rate of change of current which would be required to fire or activate the suppressor. Further, the smaller the doughnut hole through the body, the better the will be determined by the conditions under which it is to operate.

With the suppressor encircling one conductor or cable 2 of the high voltage leads, it is in a position to suppress or limit high voltage surges. For instance, a surge indicated by the arrow in Fig. 3 causes the gas in the suppressor to ionize due to high frequencies associated with the surge. With the surge moving in the conductor or cable in the direction indicated by the arrow, a magnetic field of circular configuration is set up about the cable 2, as is well understood from the fundamental concept of a current flowing through a wire. This field cuts the walls of the body portion I, but does not induce a current therein, since the material of the body is a non-conductor. In addition, it passes around the chamber or tubular portion of the body l as is indicated by the designation on the drawings, where the crosses indicate the tails of the arrows and the dots indicate the heads of the arrows, thus establishing the direction of the flux. Since the radium chloride produces some initial ionization in the hydrogen gas of the suppressor, the device is near the point where substantial currents may be caused to flow by further ionization, as is indicated by the characteristic curves of Fig. 4. The setting up of this magnetic field in the suppressor causing it to out through the gaseous chamber thereof produces currents very much like those produced by cutting a metallic conductor and such currents flow in a circular path such as is indicated by the arrows a and b. This causes the gaseous medium to act as a short circuited conductor and the flux set up by the currents travelling in paths a and b reacts upon the magnetic field from the cable 2 initiated b the surge therein, and tends to reduce the effect and duration of that surge. In short, the gaseous medium of the chamber in body I acts as a closed loop which produces the effect of a single conductor in a one turn secondary transformer which has been short circuited upon itself. This short circuited secondary through transformer action upon the cable I, which is in effect the primary, tends to resist any change in the magnitude of the current flowing therethrough and tends to obliterate the effect of surges.

Some portion of the effectiveness of this suppressor appears to result from the non-linear character of the impedance it presents. This may be due to the marked difierence in reflection from a non-linear impedance. Furthermore this suppressor has substantially no effect on low or medium level impulses in the cable, whatever their frequency components. It may therefore be used on communication lines for lightning protection or for any similar use.

Having thus described my invention, I claim:

A surge suppressor of the character described comprising a tubular body of substantially circular configuration defining a continuous chamber, said body being of non-conducting material, hydrogen gas maintained in said chamber at less than atmosphric pressure, means for partially ionizing said gas, and a conductor disposed within the body and spaced therefrom whereby surges above a predetermined magnitude in the conductor increase ionization of said gaseous medium and suppress said surges.

WALLACE G. STONE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,531,301 Metzger Mar. 31, 1925 1,658,568 Moore Feb. '7, 1928 FOREIGN PATENTS Number Country Date 324,101 Great Britain Jan. 17, 1930

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