US2134572A - Electric circuit breaker - Google Patents

Description

Oct. 25, 1938. w. E, PAUL ELECTRIC CIRCUIT BREAKER Filed May 27, 1937 Insulation Patented occas, 1938 ELECTRIC CIRCUIT BREAKER William E. Paul, Schenectady, General Electric Company,

' New York N. Y., assignor to a corporation of iApplication May 27, 1937, Serial No. 145,057

` 15 Claims.

My invention relates to electric circuit breakers, more particularly to high voltage circuit breakers of the oil blast type wherein pressure generated by arcing at one part of the circuit is utilized for directing a blast .of arc-extinguishing fluid through an arc at another part of the circuit. g It has been proposed in ircuit breakers of the aforesaid type that the contact structure be arranged so that two arcs in series are progressively formed. The first orpressure generating arc has a substantially constant length and is utilized to cause a blast of oil or other arc-extinguishing liquidat the subsequently formed main arc for interrupting the same. With this arrangement there may be difficulty in interrupting with equal facility comparatively small and 'heavy short circuit currents by reason of the substantially xed length of the pressure generating arc. This is due to the fact that insumcient pressure may be generated for interrupting a low current arc, assuming of course that the contact separation is suitable for large currents.

Another limiting factor in this design is thatthe speed of operation is somewhat retarded by the movement or fwipe of the contact structure prior to actual arc formation and the interrupting action of the blast. That is, a certain wipe takes place even before formation of the pressure generating arc, and a subsequent wipe or following action of the contacts occurs prior to formationof the main arc which is subject to the oil blast. Where the interruption of high voltage alternating current power circuits within two or three cycles is required, theseiactors are very important in determining the ultimate operating speed of the breaker.

The principal object oi my invention is the provision of anrimproved high voltage circuit breaker of the oil blast type that is emcient and reliable particularly as regards arc interruption throughout the entire rated interrupting range of the breaker, and is also capable of high speed circuit interruption.

My invention. `will be more fullyv set forth in the following description referring to the ach1 companying 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, the single figure thereof is an elevational view, partly in section and partly diagrammatic,v of ahigh voltage eleca tric circuit breaker embodying the present invention.

(Cl. 20G-150) 'Ihe circuit breaker i S PATENT OFFICE llustrated is of the high voltage oil-blast type and comprises an insulating casing or iibre cylinder i forming a pressure-confining chamber containing a suitable arc-extinguishing liquid 2, such as oil for example, in 5 which are immersed the relatively movable contacts.

fixed or terminal contact The breaker contact structure comprises a 3y electrically connected at 4 to the metallic terminal housing 5, a pivoted arcing contact 6 normally biased by a spring 'i into contact engagement with the fixed contact 3, a stationary intermediate contact 8 electrically connected at 9 to the intermediate contact t, and

a movable rod contact l0 which is guided for reciprocal movement through the bottom plate li of the breaker casing. in the open-circuit posi The breaker as shown is tion, the contacts t and lil being insulated from each other by the insulating oil in the casing. The contact rod I0 is suitably operated position,

wherein it engages in between its closed circuit butt contact the intermediate contact t, and the open circuit position by an operating cated at i2.

The power circuit is position of the breake structure 4 5, coacting mechanism generally indicompleted in the closed r through the terminal contacts 3 and S, inter-J mediate contact structure 3--Q, and the contact rod lil which is suitably connected to the other terminal. the circuit, an arc is insulating oil between thereby generating pre When the rod immediately formed in the lil is lowered tc open the contacts ti and lil, ssure depending on the arc current within the breaker casing.

'I'he upper part of the a. pressure relief passa casing i is provided with ge i3 within which the pivoted contact 6 is located so as normally to close the, passage. arc pressure builds Accordingly, when sumcient up within the lower part of the casing, the contact t is pivoted clcckwise circuit at that point. C is released through the against the bias of spring i thereby opening the oncur-rently a blast of oil chimney-like passage it to exhaust into the upper housing t where it is collected and subsecluently returned tothe arc chamber.

Accordingly, the

arc formed 'between the contacts 3 and t is traversed by a high velocity oil blasty and the circuit It will be apparent that l may be adjusted so the tension of the spring that the contact t will open only when the desired arc pressure is geri-s eratecl within the casin g. ln this manner even terrupted since the are pressure is substantially is interrupted at that point.

confined until it builds up to the desired blast value. Interruption of the arc at the contact 6 necessarily extinguishes the series arc at the contacts 8, l so that an isolating gap in oil between these contacts is effective to prevent re-establishment of arcing. The contact 6 therefore may return to its initial position under bias of the spring ll.

In order, however, to prevent premature closing of the contact G a suitable retarding device, generally indicated at I4, is operatively connected to the contact S through a pivoted lever i 5 and an insulating link I6 connected at Il to an extension of the contact 6. Any suitable retarding or escapement device may be employed, a dash-pot i8 being illustrated by way of example. When the contact S is opened the dash-pot plunger is raised without resistance, the opposite stroke, however, retarding the reclosing movement of the Contact 6. En this manner, the arc gases etc., tending to decrease the dielectric strength of the oil, can escape from the region of the contacts S-i t before reclosure of contact S, thereby minimizing the possibility or" reignition of the arc.

In the case of heavy short circuit currents the arc pressure, particularly where the arc is lengthened as by looping under the iniiuence of magnetic forces, may be so great as to damage the breaker. For the purpose of controlling the arc pressure in the case of heavy currents, there is provided means for short-circuiting the initial part or" a heavy current arc, thereby shortening the same, so that the pressure is correspondingly decreased. To this end a conducting sleeve or ring is iixed with respect to and surrounds the contact portion of the intermediate contact 8. lThe member i 9, which is larger in diameter than the contact rod lil so that no actual contact is made between the two, is provided with laterally disposed pressure relief vents and in the present instance is electrically connected to the contact Ei.

it shall be understood that the conducting ring is not necessarily electrically connected to the contact il and that under certain conditions a small insulating gap may separate the same. A heavy current are by reason of the magnetic forces tending to cause looping or bowing will shift laterally to the surrounding conductor and strike between the lower edge of the member I9 and the contact rod i0 as indicated at I9', thereby shortening the length of the arc and decreasing the arc pressure correspondingly. In the case of light currents, the arc tends to strike directly between the contacts 8 and l0 so as to utilize the maximum arc length for building up the blast pressure. s

It will be apparent that the conducting ring l 9 may be formed in any suitabe manner, such as for example like asquirrel cage, the spacing between the bars in this case serving as pressure relief openings for the gas pressure generated when the contacts separate. This gas pressure may otherwise produce an abnormal accelerating effect on the rod I0.

A further device is preferably also employed for regulating the arc pressure due to heavy load or short-circuit currents. This comprises a current responsive control mechanism generally indicated at 2l for determining the length of stroke of the contact rod l0 under certain conditions. Since the arc pressure is dependent inter alia on the length of the arc, the opening travel of the contact l0 is shortened as the current increases.

To this end the contact l0 which is'operatedD in a manner presently described by the iioating lever 22 of the operating mechanism l2 is connected in series with a conductor loop 23. The opposite sides of the loop are secured with respect to a pair of insulating jaws 24 and 25 ,pivotally connected at 26. The 'jaw 24 is secured to a fixed mounting at 2l, and the relatively movable jaw 25 is operatively connected by means of a link 28 to a slidably mounted stop member 29 adapted to coact with the lower end of the Contact rod I0. A compression spring 30 bearing between a fixed guide 3l and the jaw 25 tends to maintain the conducting loop in a compressed position as indicated.

When the floating lever 22 is rotated under bias of the main operating spring 32 so as to cause downward or opening movement of the contact l0 the current traversing the circuit creates magnetic forces tending to expand the loop 23 in a manner well known in the art. The tensionof the spring 30 bears a predetermined relation to the magnitude of the current so that only in response to moderately heavy currents is the stop member 29 moved by the magnetic forces acting against the bias of spring 30.

Assuming now that a moderately heavy load current is to be interrupted, the loop 23 is expanded by the magnetic forces so as to slide the stop member 29 a short distance toward the right as viewed so that the step 29 is beneath the 5 insulating end portion l0' of the contact rod. The opening stroke of the contact is thereby reduced by a predetermined amount and the arc correspondingly shortened. If a heavy short circuit is involved the member 29 will be moved so that the step 29" is beneath the Contact end l0', thereby further shortening the arc.

It will be apparent that any desired number of steps may be used in this connection, or as a simple alternative the stop member may be wedge-shaped so as to limit the arc length more closely with respect to the current to be interrupted.

Referring more particularly to the operating mechanism I2 which may be of any suitable high speed trip-free type, the floating lever 22 is pivotally connected at one end to the armature 33 of a tripping magnet 33 and at the other end is connected to the contact rod l0 through a link 34. The central part of the lever coacts through a guide member 35 with an operating arm 36 of a suitable power device.

It will therefore be apparent that the lever 22 can be pivotally rotated about its pivotal connection with the armature 33' to cause upward or circuit-closing movement of the rod I0 when the arm 36 of the power device is rotated clockwise.

The guide member 35 comprises a cylinder guided for vertical reciprocal movement at 3l and at 38. For the purpose of allowing a limited amount of wipe between the power device and the operating mechanism the cylinder 35 has mounted therein a. spring buffer arrangement 39 for coacting with the roller 40 of the power device.

The cylinder 35 is connected to the lever 22 through a pin and slot connection 4I-42, the slot 42 in the lever 22 being slightly elongated 'for permitting pivotal movement of the lever with respect to the tripping magnet 33. A cornpression spring 43 acting between the guide 35 and lever at 43 is utilized for biasing the lever toward thel right so as to center the magnet end of the lever during the resetting operation. At the end of the operating stroke the spring buler 39 takes up the additional wipe of the mechanism formerly assumed by the contact structure.

In this manner the connections between the floating lever 22, which is directly controlled by Athe tripping magnet 33, and the movable contact structure can be rigid so that opening of the circuit immediately upon release of the iioating lever is effected by the spring 32.

The operation of the tripping magnet 33 is well known in the art and can be readily understood from the drawing, the tripping coil M for causing release of the armature 33' from the permanent magnet 33 being energized from the conventional line current transformer at M.

The operation of the mechanism I2 is as follows: In the open circuit position shown the magnet 33 is' reset so that the armature 33 constitutes a iixed pivot for the oating lever 22. When the power device at 36 is actuated, the guide member 35 is raised and the lever 22 rotated clockwise about the armature 33' against the bias of spring 32 so as to close the breaker at the contacts 8-I0. When the breaker is tripped in response to overload or short-circuit, the tripping coil 44 of the magnet releases the armature 33' so that floating lever 22 is rotated rapidly about its central pivot at 4i in counterclockwise direction by the opening spring 32. Resetting of the mechanism is effected by simply lowering the arm 3B of the power device so that the armature 33 again engages the magnet. It will be apparent that the mechanism is tripfree in operation since at any time duringthe closing stroke the spring 32 is effective to rotate the lever 22 about its central pivot pin upon' release of the armature 33.

The wip-e" connection at 39 it will be noted is between the power device and the lever 22 so that release of the armature 33 is effective to cause instant separation of the coacting butt contacts ill-ld which have no wipe contact. Accordingly, the pressure-generating arc is instantly formed after the tripping impulse and the pressure created for interrupting the arc is generated at the earliest possible moment.

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 from the spirit of my invention.

What l claim as new and desire to secure by Letters Patent -of the United States, is:

l. An electric circuitbreaker of the oil blast type comprising a pressure-confining casing containing an arc-extinguishing liquid and relatively movable contact structure adapted to form two breaks in series in said-liquid including a movable pivoted contact normally biased toward closed circuit position, said pivoted contact normally closing "a pressure relief passage in said casing, an intermediate relatively fixed contact and a second movable contact coacting with said xed contact, the arc pressure generated in said casing at the break between said fixed and second movable contact being utilized to open said biased contact and drive an arc-extinguishing liquid blast through said passage and the arc at that point.

2. An electric circuit breaker oi the oil blast type comprising a pressure-confining casing containing an arc-extinguishing liquid and relatively movable contact structure immersed in said liquid including a movable contact normally biased toward closed circuit positiori,'means for generating arc pressure in said casing for causing' opening of said biased contact and an arc-extinguishing liquid blast through the arc at that point, and retarding means for delaying reclosure of said movable contact after extinction of said are.

3. An electric circuit breaker of the oil blast type comprising a pressure-confining casing containing an arc-extinguishing liquid, relatively movable contact structure adapted to form two breaks in series in said liquid including a movable contact normally biased to closed circuit position, an intermediate relatively iixed contact .electrically connected to said biased contact and a movable rod contact coacting with said fixed contact, the are pressure generated at the break between said xed and. rod contacts being utilized to open said biased contact and drive an arcinterrupting liquid blast through the arc at "that point, and a retarding device operatively con` nected to said biased contact for permitting free opening movement thereof and for retarding reclosure thereof for decreasing the possibility of reestablishment of arcing betweenv said xed and rod contacts. t

4. An electric circuit breaker of the oil blast type comprising a pressure-confining casing containing anew-extinguishing liquid, said casing being vertically positioned and having a chimneylike exhaust passage at the upper part thereof,A and relatively movable contact structure adapted 1 to form two breaks in series in substantially Vertical alinement in said liquid including a movable contact normally biased to lclosed circuit position, said contact being .positioned in said passage so as to close the same in said closed circuit position, and means at one of said breaks for creating arc pressure in the lower part of 4 said chamberl for opening said biased contact and driving an arc-extinguishing liquid blast through said passage and the arc at that point.

5. An electric circuit breaker of' the oil blast type comprising a pressure-confining casing having an exhaust Ipassage and containingan arcextinguishing liquid, and relatively movable contact structure adapted to form two breaks in series in said liquid including a pivoted Contact normally biased toward closed circuit position and locatedi-in said exhaust passage to close the same, opening of said pivoted contact forming a break in the circuit substantially transversely of said passage, a relatively fixed rigidly mounted contact electrically connected to said pivoted contact, and a movable rod contact adapted to abut said xed contact, opening movement of said rod contact causing instantly a break at said l fixed Contact for generating in said chamber are pressure for opening said biased contact and driving an arc-extinguishing liquid blast through said passage and the arc at said first-named break.

6. An electric circuit breaker of the oil blast type comprising relatively movable contact structure adapted to form two breaks in series in an arc-extinguishing liquid, means ier directing the pressure generated at one of said breaks so as to dii cause a blast oi said liquid at tl'ieotlier break for interrupting the circuit, and means for controlling the arc pressure at said generating break including conducting structure substantially surrounding said generating break adjacent the point of :formation thereof sc that a heavy current are is short cireuited in part by said conducting structure so as to shorten said arc.

7. in oil circuit breaker including relatively movable contact structure Asepa rable in an arcarc-extinguishing liquid, said Contact structure adapted to form a pressure-generating break for causing an 'arc-interrupting liquid blast, and means for controlling the arc pressure comprising a conducting cylinder electrically connected to a part of said contact structure and substantially surrounding the arc at the point oi initial formation thereof, said cylinder being open at one end for receiving another part of said contact structure and being in spaced concentric relation thereto so that said arc is short circuited in part by said conducting cylinder at comparatively large arc currents.

9. An electric circuit breaker of the oil blast type comprising a xedcontact and a relatively movable rod vcontact positioned within a pressureconfining casing and immersed in an arc-extinguishing liquid, a conducting cylinder connected to said fixed contact so as-to surround in concentric relation the contact end of said rod contact in closed circuit `position, said cylinder having pressure relief openings and being spaced from said Contact rod so as to short circuit the enclosed part of the arc at comparatively heavy arc currents.

10. An electric circuit breaker comprising relatively movable contact structure, and electromagnetic means responsive to the magnitude ci" the current to be interrupted for determining the degree of separation ci said contact structure.

11. An electric circuit breaker comprising nxed and relatively movable contacts arranged to form two breaks in series, the arc pressure generated upon separation of said contacts at one of said breaks being utilized for interrupting the circuit at the other of said breaks, and means coacting with the movable contact structure at said pressure generating break responsive to the magnitude of the current to he interrupted for limiting uthe opening stroke of said Contact structure so as to decrease the arc pressure at comparatively high currents.

l2. An electric circuit breaker comprising relatively movable contacts, the arc pressure generated upon separation of said contacts being utilized for interrupting the circuit, and electromagnetic means responsive to the magnitude of the current to be interrupted for blocking the separation of said contact structure at a predetermined point.

13. An electric circuit breaker comprising relatively movable contact structure, the arc pressure generated upon separation of said contact structure being utilized for interrupting the circuit, and arc pressure control means including a conductor in series with the circuit normally positioned in the form of a compressed loop, resilient means biasing said loop toward Said compressed position and a member adapted to coact with said contact structure for limiting the degree of separation thereof, said member being operatively connected to said loop so that expansion of said loop in response to comparatively large currents causes movement of said member toward a position for limiting the aforesaid contact separation.

14. An electric circuit breaker comprising relatively movable contact structure adapted to coact in substantially non-yielding engagement for facilitating quick separation thereof and means for effecting high speed separation of said contact structure including an operating member having a non-yielding operative connection with a movable part oi said structure,means for biasing said member to open circuit position, a tripping device directly connected to said member for restraining the member in closed circuit position, actuating means for moving said member against said biasing means to closed circuit position, and resilient means interposed between said actuating means 'and said member for permitting a limited over-travel of said actuating means upon contact engagement.

l5. An electric circuit breaker comprising relatively movable contacts, a iloating lever operatively connected at one end to the movable contact, a tripping device coacting With the opposite end of said lever, said lever being pivotally mounted with respect to s'aid device and movable contact, actuating means coacting with said lever intermediate the ends thereof for' closing said movable contact, a reciprocally guided resilient connection between said lever and actuating means, said lever having a limited lateral movement with respect to said guided connection for permitting rotation'about said tripping device, and spring structure for biasing said lever to- Ward open circuit`position about said guided connection in response to actuation of said tripping device.

WILLIAM E. PAUL.

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