US2601417A - Circuit breaker - Google Patents

Description

June 24 52 W. M. SC JR Filed Jan. '7, 7

CIRCUIT BREAKER 3 Sheet et 2 q\ 5 5 7 41 so 11 53 H\ J: 62 7 59 34 77v a 6 c ((pA 64 29 12 *5; 5; 3 28 1 76 65 4 P 94. 93 10 95 97 98 84 L r L r 4g :9 IN OK abin? By I WAKFM June 24, 1952 w. M. SCOTT, JR 2,601,417

' CIRCUIT BREAKER Filed Jan. '7, 1947 s Sheets-Sheet s 4 5o P\ V 53 39 v 77 I: 53 76A 66 v /W W 71 4O 1F 79 8o 81 85 j INVENTOR.

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Patented June 24, 1952 UNITED STATES PATENT OFFICE CIRCUIT BREAKER William M. Scott; Jr., Bryn Mawr, Pa., asslgn'or to 1. T. E. Circuit Breaker Company, Philadelphia, Pa., a corporation ofPenns'ylvania Application January 7, 1947, Serial'No. 720,561

6 Claims. 1v

My inventionfrelatesto circuit'breakers, and more particularly to circuit breakers'which utilize the electromagnetic action of current in the controlled circuit forclosing the breaker as well as for opening the breaker.

Heretofore circuit breakers have been designed so that a loop is formed in the circuit path through thebreakersuch that short circuit current flowing sets up a'magnetic'field which aids the opening spring in operating 'the movable arm to its trip position. This is known as the blowoff effect.

In many instances it isxa'lso desirable during the closing operation of'the circuit breaker to secure first the reverse eiiect, namely a blowon? eiiect, i. e;, to have the'magnetic' field induced by current in the controlled'circuit drive the contacts closed. This ensures good contact on clos ing in cases where the breaker may be closed against excessive current or'short circuit conditions, avoids chattering and freezing at the contacts due to poor contact engagement, and per' mits prompt tripping in response" to short circuit conditions.

A specific object ofmy, invention is the provision of means which permits the utilization solely of the blow-off effect to open'the circuit breaker and which permits the utilization of the low-on effect to drive the contacts into firm engagement when the circuit breakerisclosed.

In accordance with my invention, I provide one pivot'for the movable arm during closing and a diiferent pivot foropening. Thepivotduring closing is such that at the instant the circuit contacts engage (but before closing movement is completed), the electromagneticforces 'set up by the current in the circuit aresuch as 'to drive the movable arm through its remaining small movement to eifect'complete closureor contact engagement."

Thereafter during tripping in response to abnormal currentconditionsin the controlled circuit; the pivotis shift'ed'so that the magnetic force due to the'current'aids-in driving' the movable arm to Reopen position;

Dueto the approximately U-shaped configuration of the studs and contacts of most circuit breakers, high electromagnetic forces are imposed upon the breaker parts when fault cur-- rents of approximately 20,000 amperes or more flow through the circuit. These forces become extremely high'when the current'value' reaches 100,000 amperes. Under such conditions the forces may reach several thousandpounds.

To-withstand these forces; the stationary parts 2. must be made extremely strong and rigid. This can usuallybe done without too much diiiiculty; The movable parts of the'breake'r give'the most difficulty. Many contact arrangements have been devised to construct flexible contacts so that the electromagnetic forces'increase contact pressure, as for instanceshown in application Serial No. 540,803 filed June l7, l944"now PatentfNo. 2,514,839, dated July 11, 1950. Thesecon'structions are necessary so thatthe' breaker may remain closed and so that the contact will open in the proper sequence during the opening stroke, even in the presence of high short circuit current.

The general concept of the blow-open, blow U-shapeol configuration of'the circuit breakeri and opens outwardly away from the" two legs of the U-shape; In this arrangement the'eifect'sof the electromagnetic forces is to force the moving contact towards the open position.

This aids high speed opening'under fault conditions and aidscircuitinterruption' butit presents a real and difficult problem" when the breaker is required to be closed against a short circuit. In fact, many of the present commercial circuit breakers admittedly will not close against a short circuit equal to their interrupting capacity much less against a current value equal-to their momentary rating or the asymmetrical inrush current thatoccursin the first half cycle on an A. 06- short circuit.

In an electrically operated circuit breaker, the electrical operating mechanism is required to function properly over a specified-range of control voltage mechanism is required to close the breaker from volts to volts, at the closing mechanism. This represents a wide rangeandis 'about'as much as can be expected. Breakers that just close on the low voltage'will slam closed on the high voltage with so"'mucli force' th'atth'ereis danger of breaking parts eve'n at no load" and without consideration'of" the forces imposed by short circuit current. lem does not lie in making bigger and stronger closing mechanism which will have power enough to force the breakertothe closed position in the presence of a short circuit. Such a strong mechanism would surely damage the breaker For instance, a'-l25 D. C. closing The solution-to the prob'-' when closing at no load over this wide range of control voltages.

I have solved the problem by providing a novel circuit breaker in which the electromagnetic forces imposed are balanced out during closing stroke or by properly proportioning the parts so that these forces actually assist in closing the breaker and give faster and more positive closing in the presence of a high short circuit current.

The operation of my novel circuit breaker when closing over the control voltage range is practically the same whether it carries large or small amounts of current. That is to say, the breaker operates effectively for all values of current over the entire range up to its momentary rating, because my novel invention employs the natural electromagnetic forces to assist in the operation of closing.

However, when the breaker is opening, my invention contemplates using the electromagnetic forces in such a way as to assist this opening operation and cause the breaker to open faster in direct proportion to the magnitude of the cur rent in the system. It should also be noted that when closing against a short circuit, no electromagnetic blow-off force is imposed on the moving arm (since no current is flowing) until the contacts touch, and thereupon the full electromagnetic blow-off force is then instantly prescut.

The relatively balanced arrangement of the magnetic forces involved in my novel circuit breaker avoids the necessity of trying to match the closing force of the breaker mechanism against the magnetic forces present in the closing arm when carrying high currents.

In general, my invention contemplates a movable contact arm provided with two pivot points and a latching mechanism. When the latching mechanism is engaged, the contact arm moves about one of the pivots to effect closing of the contact. This pivot is so arranged that a blow-on action results about this pivot to effect closing engagement. When the latch is disengaged, the second pivot becomes effective. This second pivot is arranged to produce a blow-off action and is so positioned as to increase the moments of rotation efiected by the blow-off action.

It is thus an object of my invention to utilize the short circuit or fault current itself to aid in the closing of the contacts of the circuit breaker.

It is another object of my invention to so arrange the contacts of a circuit breaker that the blow-on efiect of the electrical and magnetic forces around the contacts will be such as to drive the contacts together when the circuit breaker is closed.

It is another object of my invention to so arrange the contacts that even though a blow-on effect is achieved when the circuit breaker is closed, a blow-01f effect is nevertheless secured during the opening operation of the circuit breaker.

It is another and important object of my invention to so utilize the blow-open effect to secure rapid opening of the circuit breaker that no opening spring will be needed to produce this result. Therefore on closing the circuit breaker, there will be no opening spring or other open ing means to overcome and the circuit breaker will close more readily being forced into fully closed position by the blow-closed effect above mentioned.

The foregoing and many other objects of my invention will become apparent in the following description and drawings in which Figure 1 is a schematic side view of my novel circuit breaker contact arrangement showing the circuit breaker contacts closed.

Figure 1A is a cross-sectional view taken on line lA--IA of Figure 1 looking in the direction of the arrows.

Figure 2 is a view corresponding to that of Figure 1 showing the contacts tripped open but before the latches are re-set.

Figure 3 is a view corresponding to those of Figures 1 and 2, showing the circuit breaker fully open with the latches re-set and prepared to close.

Referring now to the figures, I have here shown my novel circuit breaker l 0 which is so arranged that during the closing movement and just as the contacts engaged, but before they have fully engaged, the current loop through the elements provides a blow-closed efiect. When the circuit breaker is tripped, the elements are so arranged that the current loop provides a blow-open effect.

The circuit breaker I0 is supported in any suitable manner on a panel ll, carrying addi" tional supporting brackets, not shown, to support the variou pivot pins hereinafter described.

The back panel ll carries an upper back connection stud l 5 and a lower back connection stud I 6, mounted in anysuitable insulators l I 5 and I 16. The upper back connection stud I5 carries at the end thereof a stationary contact structure ll. Movalble contact arm 25 carrying movable contact 26 and arc horn 21 is pivotally mounted on the pin 28 which passes through the arcuate horizontally extending slot 29 in extension 3! of the lower back connection stud l6.

As shown in Figure 1A, contact arm 25 is a composite member consisting of two conductive members 25A and 25B mounted on opposite sides of extension 3| of the lower stud l6, and pressed into close engagement with opposite surfaces of the lower stud by the spring washers 32 which in turn are pressed against the outer surfaces of arm 25 by the nuts 33 screwed on to the ends of pin 28. Highly conductive inserts 34 on either side of the extension 3| ensure good current conducting engagement between contact arm 25 and the extension 3 I.

The current path established when the contacts are closed is thus from the upper back connection stud 15 to the stationary contact structure l1, then through movable contact 25 and movable contact arm 25 to the extension 3| of the lower back connection stud I6 and then to the lower back connection stud it.

It will thus be seen that when the contacts are closed, a U-shaped current loop is established with the contact elements ll-26 at one end of the bends or corners of the loop.

The movable contact 25 is held closed during the operation of the circuit breaker by the toggle 52, one link 53 of which is connected to the pin on contact arm 25, the opposite end of the link 53 being connected to the knee pin of the toggle 52.

The other link 54 of the toggle 52 is connected at one end to the knee pin 55 and is pivoted at the other end on the stationary pin 51. Link 54 has a downward extension 62 which with link 54 forms a bell crank lever 54-52. Roller 63 secured at the end of link 62 is engaged in detent 64 of latch 65.

When the overload trip coil H is energized, the armature I2 is raised against extension Bl of latch 65 causing the latch 65 to pivot counter-- clockwise about the-stationarypin '66- so that thedetent fi l thereof :disengages roller 63 and the toggle 52 may break downwardly as shown in Figure 2.

During the closing operation-the possible movement of the toggle upwardly through centeris prevented by th'e cross-bar or stop above the When the toggle 52'has broken Linkis providedat its outer left-hand end with a slot 15 in which rides the pin .1111 Pin 11 is connected. to the upper end of thebell crank lever latch 18 which is pivoted on: the :pin 19.

Latch 18 has.a detent 80 which engagesrollerx 8|. on the closing arm .82., Arm 182 is ,pivotally mounted on the pin 83 and is .biasedtoward the,

right into clockwise movement by the compressicn spring 84.

Whennow the roller 63 rises up toward the left, as shown in Figure 2, on openingof the contacts-the link is drivento the left rapidly and when the end liia of the slot 18 strikes pin ll, latchlfi is given a hammer blow in a counterclockwise direction to disengage the detenttil from roller 8|.

The compression spring- 84 is now in a position to drive the arm 82 clockwise around the pivot '83. This results in the movement of the parts to the condition shown in Figure 3 wherein the closing toggle 95 has collapsed, and in which the adjustable stop member 9| at the upper end of the arm. BZstrikes the extension 62 of the,

link 54 rotating link 54-62 in a counterclockwise direction to re-extend the toggle 52 once more and to re-engage the roller 63 in detent 64 of latch 65.

The re-settingor extending ofthe toggle 52 does not at this time, however, result in closing of the circuit breaker, since'pin 85 on arm 82 which. is connected to arm 6| moves the arm 6! to the right thus moving the pin 60 at the lowerend of contact arm to the'right. This moves thepin 28 of the contact arm 25to the right-hand side-of the slot 29 but at the same timepushes the pin Gil over sufficiently so that the contact arm continues to rotate outwardly toward the left around pin 28 which is held by the right-hand end of slot 29. Thus, even though the latch 65 is re-set, thecircuit breaker remains open.

The closing toggle 90 is prevented from breaking upwardly by the stop; 95.. Toggle 90 comprises ,a'link 93 connected by pin 94 to the closing arm 82-,and connected at the other endto the knee pin 96 Links! is connected at one end to knee pin. 95 and at the other end to thestationary pin 98. Closing solenoid ,99 is provided with the armature I00.

Now when the circuit breaker is in the open position of Figure 3 with latch 63, 64 re-set, the contactsmay be closed by energization of the solenoid coil 99. On such energization the armature I00 is, raised to extend the toggle 9!]. When the toggle-50 is thus extended, closingarm 82 is rotated counterclockwise to the left about pin 83.. This compresses the spring 84 andmoves the arm 82 over to theleit until latch '18 engages roller 8! on the arm 82. At the same time the movement-of arm '82 tothe left pulls the arm 5| to the leftthuspulling on pin 60 and causingthe contact arm,25 to rotate ma 6?; counterclockwise direction around 1 the pivot pin:

Spring 84 isv-provideduonly to re-set the toggle 52 and consequentlyis a relatively light springso thatuit does not interfere with the-closing of contacts as would beuthecase'where opening springs are used; Thus, thexmechanical force needed to .closev the ,contact is'only necessary to overcome the inertia of; the parts and the relatively slight force of the ire-setting .spring 84.

The a contacts areildriven home once they .are initially engaged by the blow-on effect above described. a In fact; the closingcoil'and armature, as hereinafter pointed out, are aided by the arrangement of theparts whichv produce a net bloweclo'sed 'efiect during closing;

Al'so,rthe. travel which is givenvto the closing coil. and. armature VI 00 need merely; be sufficient to complete the ;closing operation and no over.-

travelneed be provided to provide any hammer.

blow or kinetic ,efi'ect toslam the contacts home; The parts may'thus be made lighter and at the same time, owing tothe utilizationof the electromagnetic forces toclose the contacts rather than sheer mechanical. force or. kinetic'energy, the

parts are more durable.

The operations whereby a blow-on, effect is secured during closing and closed conditions, and a blow-open .eifect issecured :during. tripping, willinow be described;

In the position shown in Figure 1 with the circuit'; breaker closed,"when a short circuitv current flowsthrough conductor I5 and the fixed and movable contacts is and 26 through movable contact arm 25 and back through. conductor 16, a force islapplied-to. the movable arm" '25 :which is transferred throughpin SQ torlink .53 and pin 55, to set :up.a*force OD'ithQfbSll crank '54- and 52 which is in a clockwise direction about pin 51.

At this. instantthe force is resisted by the latch 54 engaging pin 63 from :driving the arm 15to the. left. The overload. relay H connected in series in the circuit through conductors l5 and is described above is energized by this same overload current and operates its armature 12 to engage the projection ,5! rocking the latching lever about pin inacounterclockwise direction'a-nd disengaging latch 64 from pin.,li3.,

The above described'forces thereupon are free to act and the contact arm 25is rocked in a counterclockwise direction about the pin 55. It should be noted at this point that the blow-01f effect on the arm 25 described above has a lever arm-extending to the pin 68 so that although the resultant force of this blow-offeffect is applied at the pin 55, it is this force at pin 55 times the lever armformed to the pin 65 which produces the counterclockwise movement of the arm 25.

Upon disengagement of the latch 64 from pin 63, the toggle 52'collapses downwardly as illustrated in Figure 2, rocking the bell crank arm 54 and 52 in a clockwise direction about the pin 51'. The movement of the pin 63 to the left as a result of this operation operates the link 15 to the left until the pin ll engages the righthand end 15a of the slot'lfi. Further movement of the pin 15 thereupon rocks the bell crank 18 about its pivot 19 in a-counterclockwise direction until the latch SEldisengages the pin 8!.

It willbe noted that up to this point the movement ofthe contact-arm '25 has been entirely caused by the action of the magnetic forces set up by the short circuit currents and the movable contact farm 25 islinl full disengaged position, as

. shown in *Figureuzn,

When now the latch 80 disengages pin 8|, the arm 82 is operated clockwise about pin 83 under the action of the compression spring 84, collapsing the toggle 98 so that the links 93 and 91 rock downwardly and the knee pin 96 is moved down to engage the armature I of the closing magnet 99, as shown in Figure 3.

A further result of the movement of arm 82 is to move the link 6| to the right. As the pin 60 of link BI is moved to the right, the contact arm 25 is also carried to the right with the pin 28 moving in the slot 29 until the pin 28 engages the right-hand end of the slot. During this movement the toggle mechanism 55, including links 53 and 54, have been straightened out to the position shown in Figure 3. Movement of the link 54 operates this bell crank about pin 51 in a counterclockwise direction, thus operating the pin 63 and through it the link 15 to the right until the pin 1! is in the intermediate position of the slot '16 as shown in Figure 3.

At this position the latch 65 which has in the meanwhile been restored to its original position as a result of the de-energization of the magnet 'H re-engages the pin 63 to re-set the toggle mechanism 55 and hold it in the position shown in Figure 3 preparatory for the re-closing operation.

On re-closing the holding magnet 99 is operated, operating its plunger armature I00 upwardly against the knee pin 96 and the latter is raised toward the stub 95 thus straightening out the knee toggle 99 to the position shown in Figure 1.

During this operation the link 93 is moved to the left operating the arm 82 in a counterclockwise direction about pin 83 until the pin 8| moves over the latch 80 and re-sets itself in engagement with the latch. The movement of the arm 82 in a counterclockwise direction operates through pin 85 to move link iii to the left. As a result the pin 65 now rotates the arm 25 about pin so which is now fixed by the re-engaged toggle 52 until the contacts re-engage as shown in Figure 1.

If now the contacts close on ashort circuit during the instant of engagement, the magnetic forces set up by the short circuit currents will produce a magnetic action about the pin 50. The portion of the magnetic forces in the sector 4| between pin 58 and the engaging contacts would tend to drive the movable arm in a counterclockwise direction about the pin 58. At the same time the magnetic forces below the pin 55 will operate on the link extending from 60 to 50, including the section 48 between pin 66 and pin 28 and the section 39 between the pin 28 and pivot pin 5!] to drive the movable arm 25 in a clockwise direction about pin 53.

Inasmuch as the length of the link from 60 to 5i] which is driving the contacts closed is greater than the link from 53 to the movable contact, a net blow-on action will result to effect good engagement between the movable and fixed contacts.

As soon, however, as the toggle 52 is broken by the disengagement of the latch 64 from pin 63 in response to the fault currents as described above, the pin 5-3 ceases to be fixed as on pivot point for the movable arm 25 and the pivot point for the movable arm now is transferred to the pin 60 as described above.

Accordingly a blow-01f action on the movable arm 25 is produced extending over the entire len th of the arm 25 from the engaging contacts to the pin 60, thus ensuring high speed disengagement of the contacts. Attention is directed to related application Serial No. 720,555, filed January 7, 1947.

In the foregoing I have described my invention in connection only with a specific illustrative embodiment thereof. Since many variations and modifications of my invention should now be obvious to those skilled in the art, I prefer to be bound not by the specific disclosures herein contained, but only by the appended claims.

I claim:

1. In a circuit breaker for protecting an electrical circuit, a first and second stud, said circuit breaker having a movable contact arm, said movable contact arm and studs forming a loop with the circuit protected by said circuit breaker, said arm being pivotally mounted and having a length greater than the portion of loop formed thereby a latch for maintaining said pivot fixed and means connected to said arm intermediate said studs and responsive to fault currents for operating said arm about said pivot while said latch maintains said pivot fixed.

2. In a circuit breaker, a movable arm having a contact; a cooperating contact; a first pivot for said movable arm, a second pivot for said movable arm, a first latch for maintaining said first pivot fixed; a second latch for maintaining said second pivot fixed; means responsive to fault currents in the circuit protected by said circuit breaker for operating said second latch to release said second pivot for movement; said arm being free thereupon to move about said first pivot to effect disengagement of said movable and cooperating contacts, and means for releasing said first latch for permitting movement of said first pivot and said movable arm about said second pivot to effect engagement of said movable contact and said cooperating contact.

3. In a circuit breaker, a movable arm having a contact; a cooperating contact; a first pivot for said movable arm; a second pivot for said movable arm; a first latch for maintaining said first pivot fixed; a second latch for maintaining said second pivot fixed; means responsive to fault currents in the circuit protected by said circuit breaker for operating said second latch to release said second pivot for movement; said arm being free thereupon to move about said first pivot to efiect disengagement of said movable and cooperating contacts, means for releasing said first latch for permitting movement of said first pivot and said movable arm about said second pivot to effect engagement of said movable contact and said cooperating contact, means for effecting the operation of said second latch to maintain said second pivot fixed during the movement of said movable arm about said second pivot for reengagement of said contacts; the distance from said second pivot to said contacts bein less than the distance from said second to said first pivot.

4. In a circuit breaker, a movable arm having a contact; a cooperating contact; a first pivot for said movable arm, a second pivot for said movable arm, a first latch for maintaining said first pivot fixed; a second latch for maintaining said second pivot fixed; means responsive to fault currents in the circuit protected by said circuit breaker for operating said second latch to release said second pivot for movement; said arm being free thereupon to move about said first pivot to effect disengagement of said movable and cooperating contacts, means for releasing said first latch for permitting movement of said first pivot and said movable arm about said second pivot to effect engagement of said movable contact and said cooperating contact, the distance from said second pivot to said contacts being less than the distance from said second to said first pivot.

5. In a circuit breaker; a movable arm having a contact; a cooperating contact; a first pivot for said movable arm, a second pivot for said movable arm; a first latch for maintaining said first pivot fixed; a second latch for maintaining said second pivot fixed; an electromagnet responsive to fault currents in the circuit protected by said circuit breaker for operating said second latch to free said second pivot for movement with said movable arm about said first pivot to effect disengagement of said contacts; said arm forming a loop with the circuit protected by said circuit breaker; the magnetic forces set up by fault currents in said loop driving said movable arm about said first pivot into contact disengaging position; circuit closing means for operating said first latch to free said first pivot for movement with said arm about said second pivot; means responsive to the movement of said movable arm for effecting re-engagement of said second latch to maintain said second pivot fixed while said first pivot is operable with said arm about said second pivot by said circuit closing means to effect closing of said contacts; said second pivot means being intermediate to said first pivot and said contacts.

6. In a circuit breaker; a movable arm having a contact; a cooperating contact; a first pivot for said movable arm; a second pivot for said movable arm; a first latch for maintaining said first pivot fixed; a second latch for maintaining said second pivot fixed; an electromagnet responsive to fault currents in the circuit protected by said circuit breaker for operating said second latch to free said second pivot for movement with said movable arm about said first pivot to effect disengagement of said contacts; said arm forming a loop with the circuit protected by said circuit breaker; the magnetic forces set up by fault currents in said loop driving said movable arm about said first pivot into contact disengaging position; circuit closing means for operating said first latch to free said first pivot for movement with said arm about said second pivot; means responsive to the movement of said movable arm for effecting re-engagement of said second latch to maintain said second pivot fixed while said first pivot is operable with said arm about said second pivot by said circuit closing means to effect closing of said contacts; said second pivot means being intermediate to said first pivot and said contacts; the distance from said second pivot to said contacts being less than the distance from said second pivot to said first pivot.

WILLIAML M. SCOTT, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number I Name Date 1,123,282 Harris Jan. 5, 1915 2,025,697 Baker Dec. 24, 1935 2,127,813 Graves Aug. 23, 1938 2,227,160 Seaman Dec. 31, 1940 2,275,891 Cox et al Mar. 10, 1942 2,295,307 Thumim Sept. 8, 1942 2,301,462 Schultz Nov. 10, 1942 2,329,003 Seaman Sept. 4, 1943

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