US1359222A - Current-interrupter for electric circuits - Google Patents

Description

C. E. BENNETT.

CURRENT INTERRUPTER FOR ELECTRIC CIRCUITS.

APPUCATION FILED MAY 19, 1919.

1 $359,222. Patented Nov. 16,1920.

2 SHEETS-SHEET ,I.

} an meadow CHHRZES E, BENNETT 3%, M sum/" C. E. BENNETT.

CURRENT INTEHRUPTER FOR ELECTRHJ CIRCUITS.

APPLICATION FILED MAY19| I919.

Patented Nov. 16, 1920.

2 suns-sun 2.

tain'ed b UNITED PATENT OFFICE.

CHARLES E..BENNETT, OF ATLANTA. GEORGIA, ASSIGNOR OF ONE-HALF TO MAR- SHALL P. MAXWELL; O1

ATLANTA, GEORGIA.

- CUERENT-INTERBUPTER FOR ELECTRIC CIRCUITS.

Specification of Letters latent.

Patented Nov. 16, 1920.

Application filed May 19, 1919. Serial No. 298,273.

To (LU whom it may concern Be it known that l, UHAnLns E. BENNETT, a citizen of the United States of America, residing in the. city of Atlanta, county oi Fulton, andSt-ate of Georgia, have invented a. certain new and useful improvement in Current-Internlpters for Electric (in-nits. of which the following is a specification.

My invention relates to current interruir ters for electric circuits. and particularly to a. high-spced-gap device applicable to the protection of electrical apparatus from injury due either to line surges (:r to high treqnency current imposed thereon.

In the acconr ranying drawings- Figures 1 and 2 are diagrammatic repre sent-ations of installations in which my invention is embodied in different forms.

In the form shown in Fig. 1 the transformer or other equipment 5 to be protected is connected through a choke coil or inductance 6 to the line 7. Shunted around this coil and in multiple with it is a small gap 8 and a. condenser 9 in series therewith on the equipment side of the gap. A ground line 10 is connected to the terminal 11,here shown as a sphere, spaced from the gap horns-12 and 13 predetermined distances. usually unequal, dependent upon the volt age of the line 7. The spacing between the horns at the gap 8 is very slight, say to s an inch, and thespi cing between the horn 12 and the ground terminal 11 is less than the spacing between the horn 13 and the terminal 11. A current breaker 14 arranged in the ground line 10 may be of any suitable construction.

If a surge or over-voltage occurs on the line 7 at normal low frequency an are forms at once between the horn 13 and the terminal 11, and the current discharged through the ground line 10 and quickly broken at 14.

Should a transient high frequency po' tential, even of low voltage, be imposed upon the line, the choke coil 6 prevents its flow to the transformer 5, and builds up a local high potential in the circuit through the coil 6, condenser 9 and gap 8, with the result that the current arcs across gap 8. The are thus formed at the gap 8 is mainthe normal line current, and rising in t e horns 12 and 13 breaks the dielectric strength of the air adjacent the sphere 11, jumps from horn 12 to terminal.

11, and the current passes from horn 13 to the ground. line 10, where it broken at 1 1.

Should the frequency of the transient potential be extremely high the current .will build up a very high potential on a few end turns of the coil (5, thereby inducing in the remaining turns a still higher poten tial which tends to form an zu'cncross the gap 8 through the condenser 9.

At normal frequency the condenser 9 is of high impedance between lhc point 15 and the horn 12. This make. it possibie' .to set the horns close together so that the gap 8 may be very small without danger of a potential flow or arc-over between the horns. In the event of a current of high frequency imposed upon the line, however, the current. passes the condenser and arcs the gap This lowers the potential at the horn 12 to a. voltage corresponding to that of the ground line 10, which is determined by that of the automatic circuit breaker 14. Inasmuch as the gap 8 is very small as compared to that between the horn 13 and ground terminal 11, an arc is established at 8 followed immediately by its rise and jump from the horn 12 to the ground terminal 11, the discharge over the ground line 10 being shortly broken at 14.

The particular construction of the apparatus arranged in accordance with the diagram is of no particular moment. Thus the terminals of the horns 12 and 13 may be spherical, hemi spherical or pointed, as may prove most advantageous. Similarly the terminals at the ga 8 may be hemi-sphcrical or otherwise. he constructions of the condenser 9 and of the choke coil 6 possess no unusual features.

The arrangement indicated in Fig. 2 involves the same general principles, but affords a still reater safe-guard for the equipment 5. he connection to the equipment is here made from the choke coil 6 at a point 16 midway between the ends of its turns. At one end the coil is connected to the line 7. Shuntcd around this coil is the'gap 8 in series with a condenser 9 connectedat 17 to the opposite end of the choke coil 6. From a point intermediate the condenser 9 and thegap is a lead 18, which is carried through a main condenser 19 to the ground line 10 at the point 20 above the automatic circuit breaker 14.

With this arrangement the operation is as follows: When a high frequency current is imposed on the line 7 it attempts to pass through the coil 6 to the transformer 5, but is choked by the coil and builds up a magnetic flux which induces a higher voltage in all of the turnsan auto transformer efiect similar to that occurring in the construction first described. This builds up a local high potential in the circuit through the coil 6, condenser 9, gap 8, and back to line 7. As the gap 8 is very short, approximately a to 1} of an inch, the induced high potential current arcs this gap and the high frequency current on the line now flows across the gap and through the main condenser 19 to ground line 10. Inasmuch as the condenser 19 is of such construction that it will allow the normal current of the power line to flow therethrough, this current maintains the arc established by the momentary high, frequency current and the hot arc which results rises on horns 13-12 until it is transferred to the terminal 11, whereupon the current passes directly into the ground line 10 ani is broken at the interrupter 14, thus reestablishing normal conditions on the line.

The main condenser 19 is so constructed that the voltage drop thereover is such that the gap 8 may be made extremely short since at low frequency of the line the potential difference between the horns 12 and 13 will not be sufficient to cause an arc to form.

In addition to the features above referred to it should be borne in mind that the gap between the horns l2 and 13 and between the horns in the ground terminal 11, as well as the condensers 9 and 19 may be so adjusted that the device will respond with accuracy to any frequency near the natural period of the transformer or other equipment pro tected by this high speed gap. In other words, every transformer, or the like, has some relative ratio of capacity to its indu tance and the natural period is the point at which these two are'equal, so that resonance occurs. Any of the harmonics of this natural period become damaging to the equipment. Therefore, if the high speed gap be so constructed and arranged that the inductance of the choke coil and auxiliary condensers respond to'any given setting, practically absolute protection of the equipment is secured. This functioning is similar to that of the tuning up of a wireless outfit, the capacity remaining constant but varying the indu'tame until resonance is secured. The present apparatus possesses the highlydesi able characteristics that its gaps may be set selectively with relation to anormal line current, and the resonance of the equipment which it is designed to protect, and will operate to disahargethe line of any overvoltage or high frequency current imposed thereon at any predetermined frequency or harmonics that may endanger the equip ment.

The arrester 14 may be of any suitable construction, such for instance as that dis 7 sociated with but spaced from the gap terminals, an automatic current interrupter in the ground connection, a ca acity in series with the gap in the linegan an inductancc lay-passing the gap and condenser in the line.

2. An electric circuit having therein a horn gap, :1 ground connection terminal associated with but spaced unequal distances from the gap terminals, an automatic current interrupter in the ground connection, a capacity in series with the gap in the line and an inductance by-passing the gap and condenser in the line.

3. An electric circuit having therein a horn gap, at ground connection terminatessociated with but spaced from the ap terminals and arranged closer to the horn on the. condenser side of the gap, an automatic current interrupter in the ground connection, a capacity in series with the gap in the line and an inductance by-pas'sing the gap and condenser in the line.

4. An electric circuit having therein a horn gap, a ground connection terminal associated with but spaced from the gap terminals, an automatic current interrupter in the ground connection, a capacity in series with the gap in the line, and an inductance by-passing the gap and condenser in the line, together with a capacity by-passing the ground terminal at the gap and connecting the ground line to the power line between the gap and the capacity in the line.

5. An electric circuit having therein a horn gap, a ground connection terminal associated with but spaced from the gap terminals, an automatic current interrupter in the ground connection, a ca acity in series with the gap in the line, and an inductance lay-passing the gap and con-denser in the line, the line connection being madet'o the inductance intermediate the ends of the coil-.

In testimony whereof I have signed my name to this specification.

CHARLES E. BENNETT.

Images