US2075749A - Electric circuit breaker - Google Patents

Description

March 30, 1937. w. PAUL ELECTRIC CIRCUIT BREAKER Filed Aug. l, 1935 /Z LEI/EZ Inventor` William EPaul,

by 77 His A torr'iey.

Patented Mar. so, 193.7`

UNITED STATES PATENT oFElcE 2,075,749' ELECTRIC cracurr BREAKER New York Application August 1, 1935, Serial No. 34,179

Claims.

My invention relates to electric circuit breakers, more particularly to those of the oil-blast type wherein an arc drawn In an insulating or arc extinguishing liquid, such as oil, generates 5 pressure for directing an arc extinguishing blast of said liquid through another arc.

In a well known form of oil-blast circuit breaker relatively movable contact structure, including an intermediate contact, coacts within a so-called'explosion pot forming upon opening of the circuit a pressure generating arc and a main arc. Oil in said pot is forced through the main arc by the pressure generating arc. In

i this design the oil movement for causing inter"- ruptionv of the main arc is generally dependent on separation of the contacts at the main break which is formed subsequent to the pressure generating break. In 'the case of large short circuit currents, excessiverpressure may thus be generated within the explosion pot before being relieved by the oil blast. A Furthermore, a certain time lag in the oil blast occurs since the oil must be accelerated from practically a state of' rest.

The principal object of my invention is the provision of an improved circuit breaker of the aforesaid type which shall initiate movement of liquid from the explosion pot in the direction of the liquid blast prior to formation of themain arc, and more particularly initiate movement of said liquid into the region of said main arc so as to facilitate and hasten the interruption of said main arc by the liquid blast.

In accordance with my invention, a part of the relatively movable contact structure is provided with a passage communicating `or connecting respectively with the regions in which the pressure generating and main arcs' are drawn. Moreparticularly, the contact structure in a pre- 40 ferred form of my invention includes a movable tubular contact, they interior of which is general- 1y in alinement with the aforesaid passage arranged so that upon initial formation of said pressure generating arc liquid from the region thereof is moved through said passage and into said tubular contact prior to formation of the main arc by said tubular contact.

My invention will be more fully set forth Vin the following description referring to the accomv panying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the-drawing, Fig., 1 is an elevational view, partly in section, of one pole of an (Cl. 20o-150) oi1-b1ast.circuit breaker embodying my invention, Fig. 2 is a detailed sectional View of a modified form of a part of the contact structure, and Fig. 3 is a similar view illustrating a modified' form of contact structure embodying my invention.

Referring to Fig. 1, the single pole of the oil blast circuit breaker comprises relatively movable contact structure including a fixed contact I, an intermediate Contact 2 and a movable tubular contact 3. -The contacts I, 2 and 3 are arranged in alinement to make butt contact and vcoact within a so-called explosion chamber or pot 4 which is formed of insulation and provided with a lower throat opening 5 for receiving the tubular contact 3. The explosion pot 4 is suitably secured to the adapter structure 6 which is in turn supported at the lower end of the leadin conductor bushing 1. An insulating shield 8 is secured, as at 9, to the explosion pot, the assembly including an insulating plate I0 which is clamped between the explosion pot and the adapter forming the upper wall of the explosion pot and guide forv the xed contact I. The above structure is immersed in oil or other suitable arc extinguishing liquid as indicated.

The circuit breaker is illustrated in the open circuit position, the circuit being normally completed through the lead-in conductor II, adapter `6, electrical conductors I2 interconnecting the adapter and fixed contact I, intermediate contact 2 and tubular contact 3. The fixed contact I is normally biased by a spring 'I3 to the position shown where it is seated on the insulating plate IIJ. The intermediate contact 2 is likewise biased by a spring I4 seated between an insulating partition I5, in which the intermediate contact is mounted and guided, and the lower end of the intermediate contact so as to biaS contact 2 away from contact I. The lower position of contact 2 is determined by a shoulder I9. Upward or closing movement of the tubular contact 3 causes butt engagement of the contacts 2 and 3 and following movement of the contact 2 against the bias of spring I4 until contacts 2 and I are in engagement to complete the circuit. The spring I3 provides for over-travel of the contact 3.

In the operation of the conventional design opening movement of the tubular contact 3, with the resulting following movement of theusual solid intermediate contact, causes an initial or pressure generating arc between the contacts in the pressure chamber I6 which is in communication with the main arcing chamber l1 through apertures I 5 in the partition I5. The continued opening movement of contact 3, due to the limited following movement of the intermediate contact, causes a break between said con- 5 tacts which forms the main arc. The pressure generated in the pot by the arc in chamber I6 then effects a radial blast of oil into the tubular contact 3 through the main arc, causing extinguishing of the same.

10 Accordingly, it will be noted that no movement of oil into the tubular contact 3 can take place in the case of well known forms of oil blast breakers including an intermediate solid butt contact until separation of the contacts. Furthermore, it will be apparent that due to the inertia Vof the oil body in the region of the-main arc and in the tubular contact 3, instant acceleration of the blast to the desired velocity is notobtained. In the ideal condition movement of oil is well under way for immediate application to the main arc.

For the purpose of initiating such oil movement, the intermediate contact 2 is provided with a longitudinal passage I8 in communication respectively with chambers I6 and I'I and generally in alinement with the passage through the tubular contact 3. The intermediate contact in this form not only utilizes immediately the pressure in the chamber I6 for moving and accelerating oil through the passage I8 and into the tubular contact 3, thereby facilitating acceleration of the oil blast upon separation of contacts 2 and 3, but also directly and immediately relieves high pressures in the chamber I6 generated by arcing during interruption of excess or short circuit currents.

In normal operation, arcing pressure generated in chamber I6 upon separation lof the contacts I and 2 causes immediate flow of oil from said chamber through the alined passages in contacts 2 and 3 thereby accelerating the .oil in the tubular contact 3. Immediately upon separation of the contacts 2 and 3, the high velocity oil and gas iet through the passage I8 further aids the oil blast from the chamber I1 into the tubular contact 3 by reason of the lower pressure existing in the region of the exhaust of the passage I8. This lower pressure resulting from the jet effect, therefore, facilitates acceleration of the radial oil blast from the region adjacent the main are into the tubular contact 3.

It will likewise be apparent that since initial high pressure in the chamber I6 may be relieved -directly through the intermediate and tubular contacts, the explosion pot throat opening at 5 need not be as large as in previous designs. Accordingly, the oil within the explosion pot may be used mainly for the eiective oil blast with a minimum leakage at the throat for pressure relief.

00 For a given interrupting capacity it, therefore, follows that a smaller explosion pot may be used.

An important factor in the interruption of power currents is gas formation. The amount of gas generated by a power arc depends, among 5 other things, on the length of the arc and duration of the arc. Since a comparatively short arc in the chamber I6 is effective to generate the required pressure and since initial movement of the oil through the intermediate contact greatly 70 facilitates acceleration of the oil blast through the arc formed upon separation of contacts 2 and 3, it will be apparent that the arcingtime is very brief duo to the fast application oi. the oil blast. The resulting gas formation is therefore low.

75 Referring more particularly to Fig. 2, there is shown a form of intermediate contact particularlyl adaptable for operating conditions wherein a wide range of current values must be dealt with. For example, very light currents at high voltage may generate insucient pressure for an effective oil blast, whereas a short circuit current on the same line may generate high pressures which might blow up the breaker unless relieved.

To this end an intermediate contact 2 is provided, as in the previous case, with a longitudinal passage I8 which is controlled by valve 20. 'I'he valve is normally biased by a spring 2i into seating engagement with the upper portion of the contact at 22 and is provided with a hollow stem 23 guided within the passage I8'. As illustrated, the passage I8' is enlarged to provide for the spring 2| and is in communication with the passage to the valve stem through the lateral ports 24. The intermediate contact 2' is normally biased into following engagement with the contact 3 by the spring I4.

The operation of the intermediate contact shown by Fig. 2 is believed to be clear, the valve 22 remaining seated under the bias of spring `2l for building up more pressure in the pot 4 when light currents are being interrupted, and opening to relieve the pressure and accelerate the oil blast in the manner above explained in response to vhigher currents.

In Fig. 3 there is shown a modied form of contact structure wherein the intermediate contact 2" is provided with an enlarged contact portion 25 having lateral passages 26 which merge to form a passage communicating with the interiors of the explosion pot 4 and the tubular contact 3 respectively. The contact arrangement is essentially the same as that in Fig. 1, the intermediate contact 2 being arranged to engage in butt contacten upper xed contact (not shown). In this case the pressure generated by the initial arc, which instantly sets up iiuid pressure in all parts of the explosion pot, initiates acceleration of the liquid blast into the tubular contact 3 from the lower part of the explosion pot. By this arrangement practically no gas formed by the initial arc is mixed with the accelerated oil blast. The tubular contact 3, as illustrated, is provided with ports 3' which likewise serve to decrease the resistance to quick acceleration of the oil blast.

It should be understood that my invention is not limited to specic details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing Iromvthe spirit of my invention.

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

1. An electric circuit breaker of the oil-blast type comprising an explosion pot, relatively movable contact structure including xed, intermediate and tubular contacts coacting in said pot and arranged to form two breaks in series, the arc at one of said breaks creating pressure within said pot for driving a blast of arc extinguishing liquid through the arc at the other break, Said intermediate contact having a passage generally in registry with said tubular contact for transmitting pressure from said pot to the interior of said tubular contact prior to separation of said intermediate and tubular contacts.

2. An electric circuit breaker of the oil blast type comprising relatively movable contact structure arranged upon opening of the circuit to form a pressure generating arc and a main arc. said contact structure including a contact member having a passage freely communicating respectively in the open circuit position with both regions in whichv said arcs are drawn,v the coacting contact structure also having a passage `ii in registry with the aforesaid passage in the closed circuit position for permitting initial acceleration o! oil therethrough.

3. An electric circuit breaker of the oil blast type comprising an explosion pot; relatively movl0 able contact structure arranged to coact within said pot including a iixed contact, an intermediate contact and a movable tubular contact arranged to form in said pot upon opening movement oi said tubular contact a pressure generat- 15 ing arc and a main arc. said intermediate contact having a passage therethrough communicating respectively with the region 'in which said pressure generating arc is drawn and the interior of said tubular contact.

20 4. An electric circuit breaker of the oil blast type comprising an explosion pot. an insulating partition having apertures therein' dividing said pot into a pressure generating chamber and a main arcing chamber, a xed contact disposed in said pressure generating chamber, a tubular contact movable into said main arcing chamber, and an intermediate contact mounted in said partition for engaging both said ilxed and tubular contacts, said intermediate contact having a passage therethrough independent of the apertures in said partition communicating respectively with said pressure generating chamberv and main arc-y ing chamber and in general alinement with the passage through said tubular contact.

5. An electric circuit breaker of the oil blast type comprising relatively movable contact structure arranged upon opening of the circuit to form a pressure generating arc and a main arc, said contact structure including a contact member having a passage therethrough communicating respectively with the regions in which said arcs are drawn, and a pressure actuated valve for normally closing said passage except when the pressure in the region of said pressure generating arc exceeds a predetermined value.

WILLIAM E. PAUL.

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