US2822449A

US2822449A - Circuit breaker with combined magnetic and air blasting devices for arc extinction

Info

Publication number: US2822449A
Application number: US622983A
Authority: US
Inventors: Thommen Hans
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1955-11-24
Filing date: 1956-11-19
Publication date: 1958-02-04
Anticipated expiration: 1975-02-04
Also published as: DE1002841B; CH336109A; FR1160575A

Description

Feb. 4, 1958 H. THOMMEN 2,822,449

CIRCUIT BREAKER WITH COMBINED MAGNETIC AND AIR BLASTING DEVICES FOR ARC EXTINCTION Filed Nov. 19, 1956 INVENTOR Ha. n5 777cm 2?? e )7 ATTORNEYS United States PatentO CIRCUIT BREAKER WITH COMBINED 'MAGNETIC zTkllzlvDcTlggllq BLASTING DEVICES FOR ARC EX Hans Thommen, Baden, Switzerland, assignor' to Aktiengesellschaft Brown, Boveri &' Cie', Baden, Switzerland, a joint-stock company Application November 19, 1956, Serial No.- 622,983-

Claims priority, application Switzerland November 24, 1955 7 Claims. (Cl. 200-447) This invention relates to electric switches for heavy duty high and low voltage power supply systems-and in particular to switches of the type wherein special means are provided for extinguishing the are which is drawn between the contacts of the switch upon their separation. One such means is known as magnetic blasting and is constituted by a coil which when energized produces a magnetic field which causes the are formed between the contacts to be driven by motor action into blasting chambers where the arc is extended by partition walls defining the chambers and finally separated. It has been known to energize the coil by the current to be disconnected and during the disconnection so that the magnetic blasting effect depends upon-the intensity of the current.

It may occur that the blasting effect istoo small when the current is too Weak so that the arc will not be drawn into the blasting chambers with adequate force although with weak currents the arc itself is weaker and istherefore interrupted more easily. There is thus formed a boundary zone where the disconnection lasts longer than required.

It has been recommended in switches operated at higher voltages to provide also an additional arc blasting effect by the use of compressed air. The are extinction effect is thereby also improved and the use of compressed air has the added advantage that when interrupting relatively weak currents, the blasting effect is adequate because the force produced by the compressed air is independent of the current to be switchedoff. In the known constructions both the magnetic and compressed air produced blasting effects have been applied to the same contact means on the switch or circuit breaker. However, the compressed air blasting component in such an arrangement has the disadvantage that the construction of the contact is not adapted to the particularities of the compressed air blasting. The contact is designed primarily in relation to the magnetic blasting component and hence more compressed air than is necessary for successful interruption of the arc must be consumed. Moreover, the boundary zone, where the compressed air blasting should be in effect and Where the magnetic blasting effect should preponderate, is not clearly determined.

' The present invention seeks to overcome these past difficulties and is characterized in that the switch is provided with both compressed air and magnetic arc blast producing means and each such means is associated with a different set of movable and stationary contacts of the switch. Moreover, the improved arrangement is such that the magnetic blasting effect preponderates when switching off currents above a predetermined amplitude and the air blasting'effect preponderates when switching off currents below that predeteirnined amplitude. Also the improved arrangement includes means responsiveto the current and effective when a predetermined current amplitude exists toshift the position of the movable 2. switch contact member associated with the air blasting effect relative to the position of the movable switch contact member associated with the magnetic blasting effect such that when the movable switch contacts are actuated in an opening stroke of the switch, the movable switch contact member associated with the magnetic blasting effect will be the last to separate from its associatedstationary contact member. Similarly, the movable switch contact associated with the compressed air blasting effect will be the last to separate from its associated stationary contactmember when the switch current is below said predeterminedlevel. Or, to state the matter in another way, whenever the magnetic blasting effect prepo'nderates in an opening operation of the switch, the switch contacts associated with the magnetic blasting effect will be the last to open and, whenever the air blasting effect preponderates in an opening operation of the switch, the switch contacts associated with the air blasting effect will be the last to open. Thus when the current is equal to or greater than the predetermined magnitude the magnetic blasting effect is applied to the contacts last to open, and when the current is below the predetermined level the-compressed air blasting effect is applied to the contacts last to open. By such an arrangement a most satis-' factory arc blasting effect is thus produced for both high and low current intensities. According to a further feature of the invention, a single current responsive solenoid is utilized both to adjust the position of the movable switch contact member associated with the air blasting effect relative to its stationary contact member and also to control the flow of compressed air to such contact members.

These and other features of the invention will become more apparent from the following detailed description of a preferred embodiment thereof and from the accompanying drawings wherein Figs. 1 and'2 show side views of the improved switch construction and with the switch contacts in closed position. Fig. 1 shows the positions of the sets of contacts associated respectively with the magnetic and air blasting effects when the current to be interrupted by the switch is above the predetermined amplitude and hence the magnetic blasting effect is dom inant during the opening operation of the switch. Fig. 2 shows the positions of the sets of contacts when the current to be interrupted is below the predetermined level and when the air blasting effect is dominant during an opening operation of the switch.

With reference now to Fig. 1, only a portion of the circuit breaker structure essential to an understanding of the present invention has been shown. Pursuant to the invention, two sets of contacts are incorporated in the switch or circuit breaker. One of these sets, associated with the magnetic blasting, consists ofa stationary contact member 1a and a movable contact member 1b located at the outer end of an arm 17 which is pivoted for movement about a pivot pin 5 located at the lower end of the arm. The magnetic blasting chamber for the set of contacts 1a, 1b is indicated at'2. The coil ener-' gized by the current to be interrupted and'which produces a magnetic field proportional to the current for causing the are drawn between contacts 1a, 1b as'they separate to be forced into the chamber 2, is indicated at '20. The other set of contacts associated with the compressed air blasting consists of a stationary contact member 3a in the form of a nozzle and a movable contact m'ember'3'b" in the form of a pin which moves into and out of the nozzle contact member 3a. The movable contact mem ber 3b is located at the outer end of an arm 4 which is likewise pivoted for movement about the pivot pin 5 and arm 4 is made angularly displaceable relative to arm 17 about the pivot pin 5 within limits established by two 3 spaced stop flanges 16 carried by the arm 17, the arm 4 being located intermediate those flanges.

Compressed air is delivered to the nozzle contact member 3a through a tube 6 and a valve 7 from a source of supply, not shown. Operation of the valve 7 is controlled by a magnetic device comprising a coil 8 energized by the current in the line and which is to be interrupted by the two sets of

switch contacts

1a, 1b and 3a, 3b, and an armature element 9 which is articulated in the manner shown in the drawings to a lever '18 such that when the current in coil 8 is equal to or exceeds a predetermined amplitude, the armature 9 and lever 18 will be drawn towards coil 8 against the biasing action of a counter spring 19 to the position shown in Fig. 1. In such position, the armature 9. and its lever 18 are horizontal and the valve 7 is closed by virtue of the fact that the valve stem and head 7a are connected to lever 18 and have been moved with the latter to a closed position on the valve seat thus cutting off the supply of compressed air to the nozzle contact 3a.

Mounted on armature 9 at the outer end thereof is a cam 10 adapted to cooperate with a cam follower dog member 11 mounted pivotally intermediate its ends upon a pivot pin 12 carried by contact arm 17. The dog 11 is biased clockwise by a spring 13 at one side of the pivot 12 and the cam 10 engages the dog 11 along a sloped upper surface at the opposite side of pivot 12 so as to rock the dog 11. Adapted to engage the dog 11 on the same side of the pivot as spring 13 is a roller 14 carried by contact arm 4.

When armature 9 and cam 10 occupy the positions indicated in Fig. 2, which means that the current in coil 8 is below the predetermined amplitude above referred to, dog 11 is moved clockwise by its biasing spring 13 into a position such that roller 14 engages a sloping upper surface of the dog inwardly from the dog end. In such position, the movable contact 35) carried by contact arm 4 occupies its innermost position within the nozzle contact 3a and the side edge of contact arm 4 rests against the left-hand flange 16. The effect of this is that when the contacts of the switch are moved to an open position by downward movement of a lever arm 15 which is secured to and moves contact arm 17 clockwise, the movable contact member 1b will be caused to separate from its associated stationary contact member 1a prior to separation of the movable contact member 3b from its associated stationary nozzle contact member 3a. Under such conditions it will also be noted that valve 7 is open and that hence compressed air is blown through the nozzle contact member 3a so as to effectively extinguish the arc which is drawn upon separation of the contact members 3a, 3b. Consequently, under these conditions the arc blasting effect which predominates is that due to the compressed air action on the contact members 3a, 312.

When armature 9 and cam 1i occupy the positions indicated in Fig. 1, which means that the current in coil 8 is equal to or above the predetermined amplitude, dog 11 has been moved in a counterclockwise direction by cam 11) causing the roller 1 to roll down the sloped surface of the dog to and behind the end of the latter thus causing contact arm 4 to be shifted clockwise and stop against the right hand flange 16 and causing the contact member 3b to be partially withdrawn from its associated nozzle contact member 3a. The eiiect of this is that when the contacts of the switch are moved to open position by downward movement of arm 15, the movable contact member 3b will be caused to separate from its associated nozzle contact member 3a prior to separation of the movable contact member 1b from its associated stationary contact member 1a. Under such conditions, valve 7 is closed denying flow of compressed air to the set of contact members 3a, 3b and the are drawn upon subsequent separation of the set of contact members 1a, 1b is efiectively extinguished by the magnetic blasting effect established at the latter. Consequently, under these 4 conditions the arc blasting efiect which predominates is that due to the magnetic blasting on the contact members 1a, 1b.

Relative positions between the contact arms 4 and 17' can be established such that with the attraction of the magnetic coil 8, both arms are immediately connected in a positive manner while with currents of an amplitude below the predetermined value, first the arm 17 is moved and then, only after a certain delay, the contact arm 4 is taken along through the projection 16. The arrangement is similar to that shown in Figs. 1 and 2, except that the contact member 3b should be imagined as being entirely closed while the contact member 1b in Fig. 2 has already completed a part of the disconnection movement. Such an arrangement has the advantage that no motion of the arm 4 is required prior to disconnection and thus the magnetic forces may be maintained smaller. In such case, the cam 10 moves only the dog 11 while in the first mentioned case a preliminary movement of the contact arm 4 had'to be performed.

I claim:

1. In a heavy duty switch, the combination comprising a first set of stationary and movable switching contacts, magnetic blasting means cooperative with said first set of contacts for breaking up the arc formed upon contact separation, a second set of stationary and movable contacts, compressed air blasting means cooperative with said second set of contacts for breaking up the are formed upon contact separation, and means controlled by the amplitude of the current to be cut off by said switch for adjusting the sets of contacts such that the contacts of said first set are the last to open when said current is equal to or exceeds a predetermined amplitude while the contacts of said second set are the last to open when said current is below said predetermined amplitude.

2. In a heavy duty switch, the combination comprising a first set of stationary and movable switching contacts, said movable switching contact being mounted upon a first movable arm, magnetic blasting means cooperative with said first set of contacts, a second set of stationary and movable switching contacts and wherein the movable one of said contacts is mounted upon a second movable arm, compressed air blasting means cooperative with said second set of switching contacts, and means controlled by the current to be interrupted by said switch and efiective when said current is equal to or exceeds a predetermined amplitude for initially adjusting said second arm and the movable contact of the second set carried thereby such that the contacts of said first set are the last to be opened upon an opening operation of the switch, the contacts of said second set being the last to open when the amplitude of said current is less than said predetermined value.

3. A heavy duty switch as defined in claim 2 wherein said current controlled means also functions to cut 011 the air supply to said compressed air blasting means when said current is equal to or exceeds said predetermined amplitude.

4. A heavy duty switch as defined in claim 3 wherein said current controlled means comprises a coil adapted to be energized by the current to be switched oif, an armature moved by said coil, a cam mounted on said armature, a dog actuated by said cam, said dog being pivotally mounted on said first arm and including an inclined surface cooperative with a projection on said second arm for positioning the latter.

5. A heavy duty switch as defined in claim 2 wherein said first and second arms are pivo-tally mounted and said second arm is actuated by said dog between a pair of spaced stops on said first arm.

6. A heavy duty switch as defined in claim 2 wherein at the beginning of the opening operation of said switch said first and second arms are coupled together by said current controlled means and said second arm and movable contact thereon is carried along by said first arm after a predetermined initial movement of said first arm and the movable contact thereon.

7. A heavy duty switch as defined in claim 2 wherein said second set of contacts is comprised of a nozzle contact and a pin contact adapted to slide in and out of the nozzle contact and said compressed air is delivered to said nozzle contact for flow therethrough.

References Cited in the file of this patent UNITED STATES PATENTS