US2396742A - Circuit breaker - Google Patents

Description

March 19, 1946. M|LL|KEN 2,396,742

CIRCUIT BREAKER Filed Dec. 2. 1942 3 Sheets-Sheet l INYENTOR l-LMILLIKEN ATTORNE March 19, 1946. MILLIKEN CIRCUIT BREAKER I 3 Sheets-Sheet 2 Filed Dec. 2. 1942 III/I 7 4 8?) 3 7 lblvElzl'aiiR HMILLI BY Mwfimyflfi ATTORNEY March 19, 1946. H. MILLIKEN 2,396,742

CIRCUIT BREAKER "III/III] nqVENTOR HMILLIKBN ATT RNEY S 'IIIIIIII Patented Mar. 19, 1946 CIRCUIT BREAKER Humphreys Milliken, Mount Royal, Quebec, Canada Application December 2, 1942, Serial No. 267,643

9, Claims.

This invention relates to circuit breakers for interrupting power currents at high voltage and has particular reference to 3-pole circuit breakers of the gas blast type.

The main object is to provide a generally improved circuit breaker in which the number of component parts and the space occupied by said parts is reduced to a minimum without sacrificing anything in the way of interrupting capacity and speed of operation.

Other objects, advantages and characteristic features of the invention will be more readily understood from the following detailed description taken in connection with the accompanying drawings, in which Fig. 1 is a side view of a 3-pole gas blast circuit breaker designed in accordance with my invention.

Fig. 2 is a rear view of the circuit breaker shown in Fig. 1.

Fig. 3 is an enlarged transverse sectional view of one of the interrupter units, the plane of the section being substantially along the line 3-3 of Fig.2.

Fig. 4 is a transverse sectional view taken su-bstantially along the line 4-4 of Fig. 3.

Fig. 5 is a sectional view taken substantially along the line 5-5 of Fig. 3.

Fig. 6 is a sectional View taken substantially along the line 65 of Fig.5.

The three poles of the circuit breaker shown in Figs. 1 to 6 inclusive are respectively indicated at A, B and C. Each pole includes an arc chute :0 open at both ends, an arc chute enclosing housing ll, an interrupter switch comprising a main movable interrupter blade 12 and an extensible interrupter arm 13 and a load current switch comprising movable switch contact 14 and stationary switch contact [5. The casing ll of each pole is carried by a hollow insulator 16 which, in turn, is secured to the upper end of a gas blast conduit H. The conduits I"! of the several poles extend downwardly through the top of a tank l8 and merge together at their lower ends to provide a large diameter valve seat l9 surrounding an orifice 20 common to all of said conduits. A blast valve 23 closes against seat l9 and may be operated in substantially the same manner as the similar blast valv described in my U. S. Patent No. 2,089,286.

In the open position of valve 23 a blast of compressed air is discharged from tank It through the blast conduit 11 and are chute H] of each pole and serves to extinguish the arcs which are drawn in the several chutes it when the interrupter contact blades l2 are separated from the interrupter arms l3 as hereinafter described.

Th interrupter blade l2 of each pole is carried by the upper free end of the associated movable load switch contact i l, the lower end of the latter being connected through hinge 38 to circuit breaker terminal 39 mounted on a supporting insulator it. The several blades 14 are thus mounted for swinging movement relative to the cooperating stationary load-switch contacts [5 which are attached to the housings II' and connected through conducting structure 6'1 to the other terminal Sla of the circuit breaker. Each blade i4 is also connected by bracket 43, insulating rod l i and crank to a common crank shaft 42 to provide simultaneous operation thereof to either a closed-circuit or an open-circuit position. In the present drawings only one blade I4 is shown connected to shaft 52 but it will be understood that identical connections are provided between the remaining blades I4 and said shaft. As indicated in Figure 1, an additional crank 46 on shaft 42 is connected, by rod 4'1 and crank 48, to a standard control switch 35.

A fourth crank 45a is connected by slotted cross-head to a piston rod 54 which extends downwardly through an air cylinder 55 and is secured to a piston 55 working in said cylinder.

The upper end of cylinder 55 is connected to one of the air blast conduits H by an air pipe 58. The lower end of the cylinder is connected to tank 18 by an air pipe 59 controlled by 2. normally closed electrically actuated valve 60. The operating coil (not shown) of valve 80 is connected in circuit with a current sourc BI and a normally open manually-operable control switch 62. When switch 52 is closed valve 60 is opened against the resistance of a spring or other suitable biasing means (not shown), which normally serves to hold the valve in its closed position. An exhaust line '63 is connected between cylinder 5'5 and valve til. This exhaust line is controlled by a pressure operated valve 6 3 spring-biased to closed position and to which opening pressure is supplied from pipe '58 through pipe 65. In the open position of valve'fit the air previously supplied to the lower end of cylinder 55 through valve 60 is exhausted to the atmosphere through exhaust line 63.

The main interrupter blade l2 comprises an extension lea of load-switch contact is to which is secured a horn portion l2 curved in the arc of a circle centered at the hinge of contact M. In the closed-circuit position of the circuit breaker interrupter blade 12 extends across arc chute l0 and engages the movable interrupter arm l3 which is mounted in a housing 61 attached to casing H. An opening 68 in the wall of casing ll fits closely around the horn portion l2 of interrupter blade l2 to minimize leakag of air.

The free end of interrupter blade I2 is provided with a convexly curved surface lZa which is adapted for rolling butt-contact with the complementary concavely curved surface l3a of the movable interrupter arm l3. Arm i3 is mounted for sliding and swinging movement in its housing ti. As here shown arm I3 is provided with a stem ll which slides through the transverse opening it of a hinge member 13, the latter being provided with tubular trunnions 14 mounted in bearing sleeves l5 screwed into threaded open-' ings 'r'ca provided in opposite side walls of housing iii. The stem 'H is encircled by a compression spring 1% which acts against insulating washers i8 and 9 to resist sliding movement of contact is in the direction of hinge member 13, said spring being insulated from stem H by insulating sleeve as. The end of stem H adjacent to hinge i3 is connected, by flexible conductor 8|, to load-circuit terminal Ella. The housing 61 is lined with insulating material 82 so that the only electrical connection between contact l3 and said housing is that afforded by flexible conductor 8|.

Guide rollers 83 are mounted on opposite ends of a pin 34 extending through contacts [3. These rollers travel .along inclined guide ways 85 which are formed by and between separated sections of the insulating material applied to the side walls of housing 67.

When contact i2 is swung to its closed-circuit position extending across the arc chute ID, the convexly curved end l2a of said contact engages the concavely curved end of contact l3 and causes the latter to be swung from the full to the dotted line position shown in Fig. 3. During the downward movement thereof contact I3 is forced to the right against the resistance of spring 16 which serves to maintain the requisite contact pressure between the engaging surfaces of the two contacts.

When contacts l2 and I3 are in the dotted line position shown in Figs. 1 and 3 the free end of contact l2 bears against an insulating block 8'1 carried by a piston 38 working in cylinder 89, which is carried by and opens into housing 61. The lower closed end of cylinder 89 is provided with a port 9i) which is connected by pipe 9| to the blast passage of the adjacent arc chute I0. Piston 38 is normally held at the lower end of cylinder 8%) by a spring 92 acting against the enlarged end 93 of piston rod 94.

The operation of the circuit breaker described herein may be described as follows:

In the closed-circuit position of the circuit breaker the air supply valve 21 of tank 18 is open. Tank i8 and pressure chamber 22 are both filled with air under pressure since the leakage port 3| of valve to provides restricted communication between air supply conduit 26 and pressure chamber 22, The pressure thus established in chamber 22 is eifective to hold the diaphragm or blast valve 23 tightly closed against its seat 24. The interrupter contacts l2 and I3 and the loadswitch contacts M and I5 of each pole are in the closed-circuit position shown in Fig. 1.

When a fault occurs on the circuit relay contact 3t closes automatically thus energizing the solenoid of valve 33 and causing said valve and blast valve 23 to open, sending a blast of compressed air through the air blast conduit ii and are chute is of each pole of the circuit breaker. A small portion of the air thus delivered to are chute iii passes through pipe 9i into the lower closed end of cylinder exerting upward pressure on piston 83, maintaining pressure on the contacting ends of blade l2 and arm l3, preventing their separation until they have moved about 5" at which time arm it strikes the top wall of housing (ill which stops arm i3 instantly, while blade 52 continues its motion, both interrupter contacts having been accelerated to a high velocity before they part, thus minimizing the time required to separate blade i2 from arm it by a distance sufiicient to prevent re-striking of the are (after momentary interruption) at the instant of current-zero and peak voltage. Many interrupting tests on this design have shown this feature reduces the time of this critical separation to less than /8 of a cycle /430 of a second).

After contact 62 leaves the piston-carried block 8'! the opening motion of said contact is continued by its momentum and. by the piston 5E5 operating in cylinder said piston being forced downwardly by the air blast pressure which is supplied to the upper end of cylinder 55 through pipe 53. At this time the building up of opposing pressure in the lower end of cylinder is pre- Vented by the opening of exhaust valve E i which is opened by pressure transmitted through branch line 65.

In the opening operation just described, the combined angular motion and radial motion of contact l3 and stem it maintains contact with i2 until after blade M has moved out of engagement with contact i5, thereby shunting all current to contacts l 2 and it before they part, draw ing an are which is extinguished by the blast of air.

During the downward movement of the piston 56 the rotation of crankshaft 42 serves, through the connections previously described, to open the mechanicall actuated switch 35 thereby deenergizing the solenoid of valve 33 and permit ting said valve and blast valve 23 to close.

In the open-circuit position of the circuit breaker the interrupting contacts l2 of the three poles are swung completely out of the arc chute it as indicated by dotted lines in Fig. l.

The re-closing of the circuit breaker is accomplished by closing the manually operable control switch 62 to energize the operating coil of valve 60 which is thus opened to permit flow of air from tank 38 into the lower end of cylinder 55. Piston 56 is thus moved upwardly in cylinder 55 and operates through the agency of crankshaft 42 to cause the three interrupting contacts I2 to be swung back to their closed-circuit position extending across the arc chutes id as shown. The piston 88 operating in cylinder 89 is returned to its starting position by spring s2 as soon as the pressure in pipe 9! drops following the re-closing of the air blast valve 23.

My improved circuit breaker, when constructed and operated as described hereinfis characterized by a number of important advantageous features. The design and arrangement of the component parts permits the amount of space occupied by the circuit breaker to be substantially reduced by arranging the several poles so that the centers thereof are spaced apart the minimum permissible distance which is approximately 10" center to center. Such close spacin of the poles is made possible by providing a large diameter blast-valve seat 25 and locating said seat a distance below the several poles which is considerably greater than the distance between the centers of said poles. This permits the use of blast conduits I! which have a minimum pneumatic resistance; that is to say, conduits which have a minimum change in direction and in which the necessary bends have maXimum radius of curvature.

In the closed-circuit position of the circuit breaker the interrupter contacts 1' 2 and I3 of each pole are shunted by the associated load contacts I4 and I5 which are capable of carrying the rated load current.

During the circuit-opening operation of the circuit breaker it is important that the load contacts I4 of the three poles be separated from the load contacts I5 before the interrupter contacts I2 are separated from the contacts I3. It is equally important that, during the circuit-closing operation of the circuit breaker, the interrupter contacts I2 be engaged with the cooperating interrupter contacts I3 before the load contacts I4 are engaged with load contacts I5. These requirements are adequately provided for by the present invention. In this connection it will be noted that, in the circuit-opening operation of the interrupter, the interrupter contacts I2 and I3 remain engaged with each other until the contact I3 has swung upwardly a distance of approximately 5" from the dotted line position shown in Fig. 3. During this 5" movement of the interrupter contact I3 while still engaged with the interrupter contact I2, the load-carrying contact I4 is withdrawn a substantial distance from contact I5 so that, at the time the interrupter contact I2 separates from the interrupter contact I3, there is a suflicient air gap between the contacts I I and I5 to ensure that no arc is drawn between these contacts which would cause serious damage in the case of a short-circuit current. During the closing operation of the circuit breaker the interrupter contact I2 engages the interrupter contact I3, as indicated by full lines in Fig. 3, before the shunt contact I4 engages the contacts I5. This prevents any danger of arcing or burning at the shunt contacts I4 and I5 during the closing operation of the circuit breaker. I

It is important to maintain butt contact between the engaging interrupter contacts l2 and I3 during the travel of these contacts from the full to the dotted line position shown in Fig. 3 and vice versa. When the interrupter contact I3 is mounted as shown in the present drawings the desired butt contact pressure is provided by the springs 16 with a change of only approximately 1 /2 in the length of the springs during the swinging motion of contacts I3 to and from the full and dotted line position shown in Fig. 3. This is an important feature since it minimizes the length of the spring required and the resulting maximum spring pressure and the force required to close the contacts. A further advantage is that, in the closed position, the spring I6 is on dead center and therefore its pressure does not tend to open the circuit breaker.

One of the troubles commonly experienced with interrupter contacts is the accidental welding together of the contacts as they slide against one another while carrying short circuit current thereby interfering with the proper full movement of the interrupter contacts in the next subsequent operation of the circuit breaker. Such interference would, of course,- prevent the spring I8 from maintaining proper contact between the interrupter contacts I2 and I3 so that, in the subsequent opening operation of the circuit breaker, the circuit would be opened by the loadcarryi'ng contacts I4 and I5 instead of by the opening movement of the interrupter contacts I2 and I3 and this would result in failure .to interrupt the short circuit current. In the circuit breaker described herein this difficulty is avoided by insulating the interrupter contacts I3 from their casings 5? and from their swivel members 13 so that the only electrical connection between the interrupter contact I3 and casing 67 is through the flexible conductor 8| which must therefore carry all of the short circuit current after the load contact M has separated from contact I5.

A very desirable rolling type of butt contact is provided between the interrupter contacts I2 and I3 by forming the contact I2 with a convexly curved surface I2a for engagement with the complementary concavely curved surface I311 of contact I3.

If the circuit breaker shown in Figs. 1 to 6 inclusive should close on a short circuit its quick re-opening will not be impeded by the residual closing air in the cylinder 55 since the blast pressure resulting from the opening of blast valve 23 will cause exhaust valve B l to open so that the residual closing pressure in the lower end of cylinder 55 will be exhausted therefrom and therefore will not impede the prompt opening of the circuit breaker by the blast pressure transmitted to cylinders 55 and 89.

As shown to advantage in Fig. 3, an arcing contact I3?) is arranged in the arc chute ID of each pole at a point adjacent the extreme upper limit of movement of the interrupter contact I3. As the interrupter contact it leaves the contact t3 the are drawn between these contacts is transferred to the arcing contact I 3?) which is insulated from the interrupter contact I3.

Having thus described what I now conceive to be the preferred embodiment of this invention it will be understood that various modifications may be resorted to within the scope and spirit of the appended claims.

Having thus described my invention, what I claim is:

1. An air blast circuit breaker comprising two terminals, an air blast passage, means for sending a blast of compressed air through said passage, a load current switch, an interrupter switch in shunt with the load current switch when the circuit breaker is fully closed, said interrupter switch comprising a main movable interrupter blade electrically joined to one of said terminals, an extensible interrupter arm electrically joined to the other terminal, means whereby said interrupter blade and arm make and/or break contact when they are in the edge of said air blast passage with the blade positioned across said passage, said blade being hinged at one end adjacent the terminal to which it is electrically joined, said arm being hinged at a point outside of said air passage and having a radial component of motion, said radial component being spring-biased to maintain contact-pressure against said main interrupter blade during a portion of their motion, said radial component of motion being less than the total angular motion of the contact-end of said arm, and pneumatic means co-acting with the biasing spring of said arm to maintain contact between said main interrupter blade and said arm during the first portion of their opening motion.

2. An air blast circuit breaker comprising two terminals, an air blast passage, means for sending a blast of compressed air through said passage, a load current switch, an interrupter switch in shunt with the load current switch when the circuit breaker is fully closed, said interrupter switch comprising a main movable interrupter blade electrically joined to one or" said terminals, an extensible interrupter arm electrically joined to the other terminal, means whereby said interrupter blade and arm make and/or break contact when they are in the edge of said air blast passage with the blade positioned across said passage, said blade being hinged at one end adjacent the terminal to which it is electrically joined, said arm being hinged at a point outside of said air passage having a radial component of motion, said radial component being suing-biased to maintain contact-pressure against said main interrupter blade during a portion of their mot n, said radial component of motion being less than the total angular motion of the contact-end of said arm, and pneumatic m ans co-acting with the biasing spring of said arm to maintain contact between said main interrupter blade and said arm during the first portion of their opening motion until the contact-end of said arm reaches said air blast passage.

3. An air blast circuit breaker comprising two terminals, an air blast passage, means for sending a blast of compressed air through said passage, a load current switch, an interrupter switch in shunt with the lead our ent switch when the circuit breaker is fully closed, said interrupter switch comprising a main movable interrupter blade electrically joined to one of said terminals, an extensible interrupter arm electrically joined to the other terminal, means whereby said interrupter blade and arm make and/or break contact when they are in the edge of said air blast passage with the blade positioned across said passage, said blade being hinged at one end adjacent the terminal to which it is electrically joined, said arm being hinged at a point outside of said passage and having a radial component of motion, sai radial component being spring-biased to maintain contact-pressure against said main interrupter blade during a portion of their motion, said radial component of motion bein less than the total angular motion of the contact-end of said arm, pneumatic means coaoting with the biasing spring of said arm to maintain contact between said main interrupter blade and said arm during the first portion of their opening motion until the contact-end of said arm reaches said air blast passage, and m ans instantly stopping and holding the contact-end of said arm at the edge of said air passage.

4. An air blast circuit breaker comprising two terminals, an air blast passage, means for sending a blast of compressed air through said passage, a load current switch, an interrupter switch in shunt with the load current switch when the circuit breaker is fully closed, said interrupter switch comprising a main movable interrupter blade electrically joined to one of said terminals, an extensible interrupter arm electrically joined to the other terminal, means whereby said interrupter blade and arm make and/or break contact when they are in the edge of said air blast passage with the blade positioned across said passage, said blade being hinged at one end adjacent the terminal to which it is electrically joined, said arm being hinged at a point outside of said air passage and having a radial component of motion, said radial component being spring-biased to maintain contact-pressure against said main interrupter blade during a portion of their motion, said radial component of motion being less than the total angular motion of the contact-end of said arm, pneumatic means co-acting with the biasing spring of said arm to maintain contact between said main interrupter blade and said arm during the first portion of their opening motion until the contact-end of said arm reaches said air blast passage, means instantly stopping and holding the contact-end of said arm at the edge of said air passage and spring means returning said pneumatic means to its normal position upon cessation of said air blast in said air blast passage.

5. An air blast circuit breaker comprising two terminals, an air blast passage, means for sending a blast of compressed air through said passage, a load current switch, an interrupter switch in shunt with the load current switch when the circuit breaker is fully closed, said interrupter switch comprising a main movable interrupter blade electrically joined to one of said terminals, an extensible interrupter arm electrically joined to the other terminal, means whereby said interrupter blade and arm make and/or break contact when they are in the edge of said air blast passage with the blade positioned across said passage, said blade being hinged at one end adjacent the terminal to which it is electrically joined, said arm being hinged at a point outside of said air passage and having a radial component of motion, said radial component of motion being spring-biased to maintain contact-pressure against said main interrupter blade during a portion of their motion, said extensible arm having a contacting-end shaped to maintain rolling contact with the contacting-end of said main movable interrupter blade.

6. An air blast circuit breaker comprising two terminals, an air blast passage, means for sending a blast of compressed air through said passage, an interrupter switch comprising a main movable interrupter blade electrically joined to one of said terminals, an extensible interrupter arm electrically joined to the other terminal, means whereby said interrupter blade and arm make and/or break contact when they are in the edge of said air blast passage with the blade positioned across said passage, said blade being hinged at one end adjacent the terminal to which it is electrically joined, and said extensible arm being hinged at a point outside of said air blast passage and having a contacting-end concave in pro-file, spring-biased, and shaped to maintain rolling contact with the contacting-end of said main interrupter blade.

7. A multi-pole air blast circuit breaker in which each pole comprises two terminals, an air last passage, means for sendin a blast of compressed air through said passage, an interrupter switch comprising a main movable interrupter blade hinged at one end, an extensible springbiased interrupter arm normally in series with said blade, said arm being hinged at one end, means for moving said blade so that its contacting-end moves across said air blast passage, means whereby said blade and arm make and/or break contact when their contacting-ends are at the edge of said air blast passage, means whereby said contacting-ends of said blade and arm move in contact with each other outside of said air blast passage and pneumatic means co-acting with the biasing spring of said extensible arm to maintain contact between said main interrupter blade and said arm during the first portion of their opening motion.

8. An air blast circuit breaker having an air blast passage, means for sending a blast of compressed air through said passage, :3. load-current switch, an interrupter switch in shunt with the load current switch When said circuit breaker is fully closed, said interrupter switch comprising a main interrupter switch-blade having a radial portion hinged at one end and a curved portion joined to the other end of said radial portion, said curved portion being shaped to the arc of a circle concentric with the center of said hinged end and having a contact-end, said air blast passage having openings in its walls permitting movement of said curved portion of said blade through said openings and across said air blast passage, a movable and extensible interrupter arm having a contact end spring-biased to engage the contact-end of said blade, said extensible arm having a hinge rotatable about an axis parallel to the axis of rotation of said main interrupter switch-blade, the perpendicular distance between the two said parallel axes of rotation being greater than the radius of rotation of said curved switch-blade but less than the sum of said radius and the length of said extensible arm when the latter is fully extended by its biasing spring, means whereby said two contact-ends make and/or break contact when they are in the edge of said air blast passage with the curved portion of said switch-blade extending across said air blast passage and pneumatic means co-acting with,the biasing spring of said extensible arm to maintain contact between the two said contact-ends during the first portion of the opening motion of said circuit breaker.

9. An air blast circuit breaker having an air blast passage, means for sending a blast of compressed air through said passage, a load-current switch, an interrupter switch in shunt with the load current switch when said circuit breaker is fully closed, said interrupter switch comprising a main interrupter switch-blade having a radial portion hinged at one end and a curved portion joined to the other end of said radial portion, said curved portion being shaped to the arc of a circle concentric With the center of said hinged end and having a contact-end, said air blast passage having openings in its Walls permitting movement of said curved portion of said blade through said openings and across said air blast passage, a movable and extensible interrupter arm having a contact-end spring-biased to engage the contact-end of said blade in abutting contact, said extensible arm having a hinge rotatable about an axis parallel to the axis of rotation of said main interrupter switch-blade, the perpendicular distance between the two said parallel axes of rotation being greater than the radius of rotation of said curved switch-blade but less than the sum of said radius and the length of said extensible arm when the latter is fully extended by its biasing spring, means Whereby said two contact-ends make and/or break contact when they are in the edge of said air blast passage with the curved portion of said switchblade extending across said air blast passage and pneumatic means co-acting with the biasing spring of said extensible arm to maintain butting contact between the two said contact-ends during the first portion of the opening motion of said circuit breaker.

HUMPHREYS MILLIKEN.

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