GB2128408A

GB2128408A - Operating apparatus for circuit breaker

Info

Publication number: GB2128408A
Application number: GB08325204A
Authority: GB
Inventors: Tsutomu Ouhara; Youji Yamada; Minoru Barada
Original assignee: Meidensha Corp; Meidensha Electric Manufacturing Co Ltd
Current assignee: Meidensha Corp; Meidensha Electric Manufacturing Co Ltd
Priority date: 1982-09-21
Filing date: 1983-09-21
Publication date: 1984-04-26
Also published as: MY8600657A; IN159435B; JPS6240509Y2; GB8325204D0; GB2128408B; JPS5947920U

Abstract

The operating apparatus of a circuit breaker enhances the reliability of protection of a main power supply circuit by the provision of two trip coils (7 and 10) and includes a toggle mechanism (44) for connecting or separating a pair of contacts in the circuit, throw-in means (60) for extending the toggle mechanism (44) to connect the contacts, an interruption accelerating spring (37) for retracting the toggle mechanism (44) to separate the contacts and a trip hook (59) for the toggle mechanism (44). One of the trip control electromagnets (10) is operated by a control power supply (14) independent of a load-side circuit of the main power supply circuit the other trip-control electromagnet (7) being operated by current derived from over-current through the main circuit. An over-current relay (11a, 11b or 11c) is activated in response to over-current to provide both electromagnets (7 and 10) with trip- instruction signals. The operating apparatus securely interrupts the main circuit even if the electromagnetic trip coil (10) malfunctions. <IMAGE>

Description

SPECIFICATION Operating apparatus for circuit breaker The present invention relates to an operating apparatus for a circuit breaker, particularly to a spring-operated-type operating apparatus.

Generally, spring-operated-type operating apparatuses of oil or vacuum circuit breakers or the like include a toggle mechanism opening or closing a pair of contacts of the circuit breaker, a throw-in spring supplying energy for drawing the toggle mechanism, a charger for the throw-in spring, an interruption accelerating spring for retracting the toggle mechanism, a throw-in control electromagnet for starting discharge of the throw-in spring, a trip-control electromagnet for starting discharge of the interruption accelerating spring and a trip hook for holding the toggle mechanism in either the latched or free position.

In countries where supply of commercial alternating current is unreliable and voltage variation may be more than 20%, power cut-outs or other failures often occur, so generating stations and substations often employ a single direct-current power supply of rechargeable batteries as an operation and control power supply for ali of their electrical equipment.

In cases where a DC power supply is employed as a control power supply, the rechargeable batteries are normally continuously recharged by commercial alternating current. Therefore, even if commercial alternating current, for example, experiences a power cut-out, the DC power supply will function normally as a control power supply for all of the electrical equipment for a set period of time.

However, a network of control circuits which supplies electric power from the single DC power supply not only to an electric motor for charging the throw-in spring, the throw-in control electromagnet and the trip control electromagnet in the operating apparatus of the circuit breaker, but also to the rest of control devices in the other electrical equipment will be complicated and accordingly subject to such failures as short circuiting or disconnection.

According to the operating apparatuses of the circuit breaker of the prior art as mentioned above, if some malfunction of the network of control circuits prevents the trip control electromagnet from being excited, the pair of contacts of the circuit breaker can not be immediately disengaged if a short circuit in a load-side circuit to the circuit breaker should occur. Consequently, the circuit breaker will not be able to interrupt the short-circuit current flowing through the main power supply circuit, which could lead to gross failures.

The object of the present invention is to provide an operating apparatus of a circuit breaker which will enhance the reliability and thus the safety, of a main power supply circuit. The operating apparatus of the circuit breaker includes a toggle mechanism for disengaging a pair of contacts by retraction and for engaging the pair of contacts by extension, throw-in means for extending the toggle mechanism, an interruption accelerating return spring for retracting the toggle mechanism, a trip hook for holding the toggle mechanism in a trip latch or trip latch or trip free position, a trip control electromagnet for actuating the interruption accelerating spring, operated with electric power supplied by a control power supply independent of the load-side circuit of a main power supply circuit, other trip control electromagnet for actuating the interruption accelerating spring, operated by over-current flowing through the main power supply, and an over-current relay connected via a current transformer to the main power supply and providing both of the trip control electromagnets with trip-instruction signals.

According to the operating apparatus of the present invention, even if the circuit between the control power supply independent of the loadside circuit of the main power supply circuit and the one trip-control electromagnet should malfunction, preventing this electromagnet from operating, the other trip-control electromagnet will still interrupt short-circuit current or other over-current.

Fig. 1 is a schematic diagram of a trip-control circuit for an operating apparatus of a circuit breaker according to an embodiment of the present invention; Fig. 2 is a side elevation of a track-type vacuum circuit breaker equipped with an operating apparatus according to the embodiment of the present invention; Fig. 3 is a plan view of the vacuum circuit breaker of Fig. 2; Fig. 4 is a detailed cross-sectional view of the output terminal mechanism of the operating apparatus of the circuit breaker of Fig. 3, taken along the line IV--IV; Fig. 5 is a front elevation of the operating apparatus of the circuit breaker according to the embodiment of the present invention; Fig. 6 is an exploded view of a throw-in operating mechanism; Fig. 7 is a side elevation of an alternating current trip operating mechanism;; Figs. 8 to 10 are diagrams illustrating the operations of a dual-toggle mechanism, Fig. 8 illustrating a closing position of vacuum interrupters, a releasing step of the throw-in spring and a loading step of interruption accelerating springs, Fig. 9 illustrating a trip free position, Fig. 10 illustrating an opening position of vaccum interrupters, a loading step of the throwin spring and a releasing step of interruption accelerating springs; Fig. 11 is a side elevation of an auto-return mechanism of an alternating current tripoperating mechanism.

Trip control circuit As shown in Fig. 1 , the first, second and third trip control circuits 1, 2 and 3 are provided in the operating apparatus of the circuit breaker of the present invention, respectively corresponding to the first, second and third load-side circuits of transmission lines for three-phase alternating current. The first, second and third trip control circuits 1, 2 and 3 are respectively provided with first, second and third alternating current tripcontrol electromagnets 7, 8 and 9.

The first trip control circuit 1 is different from the second and third trip control circuits 2 and 3 by additionally including a DC current trip control circuit therein. Therefore, the first trip control circuit 1 will be explained in detail below while the second and third trip control circuits 2 and 3 will only be described when necessary.

The first trip control circuit 1 includes not only a direct current trip-control electromagnet 10 but also the first alternating current trip-control electromagnet 7. The excitation time of the first alternating current trip-control electromagnet 7 is controlled by a trip-instruction signal from an over-current relay 1 a of the first trip-control circuit 1. The excitation time of the direct current trip-control electromagnet 10 is controlled by a trip-instruction signal from at least one of overcurrent relays 1 a, 1 b and 1 c of the first, second and third trip control circuits 1, 2 and 3.

The first alternating trip control electromagnet 7, which is connected in parallel to a selfreturn-type normally-closed contact 1 2a of the over-current relay 1 a, is excited by a secondary current of a current transformer 13 of the first load-side circuit 4 in response to alternating overcurrent flowing through the first load-side circuit 4. Thereupon, the first alternating current tripcontrol electromagnet 7 performs a trip operation: in a well-known manner.

The direct current trip-control electromagnet 10 is connected in series to a direct current control power supply 14 of rechargeable batteries. The direct current control power supply 14 is connected not only to a charge circuit, not shown, so as to be normally charged by a commercial alternating current which is independent of all of the first, second and third load-side circuits 4, 5 and 6, but also to the integrated network of control circuits in the generating stations or substations.

The direct current trip control electromagnet 10 and direct current control power supply 14 which are connected in series are each connected in parallel to a normally-opened contacts 1 spa, 1 5b and 1 Sc of the over-current relays 1 a, 11 b and 11 c.The normally-opened contacts 1 spa, 1 sub and 1 sic and normally-closed contacts 1 2a, 1 2b and 1 2c of the over-current relays 1 a, 1 b and 1 c are mechanically associated with each other such that the closing operations of the respective normally-opened contacts 1 spa, 1 sub and 1 sic can be expected to occur within minimum time lapses of the opening operations of the normally-closed contacts 1 2a, 1 2b and 1 2c A self-return-type button switch 1 6 is connected in parallel to the normally-opened contacts 1 spa, 1 sub and 1 sic which are connected in parallel. Normally, manual operation of the button switch 1 6 controls the direct current tripcontrol electromagnet 10.

Consequently, a load current flowing through the load-side circuit 4 can be manually interrupted at any time by way of the direct current trip control electromagnet 10. On the other hand, over-current flowing through the load-side circuit 4, especially a short-circuit current, will be automatically interrupted by way of the first alternating current trip-control electromagnet 7 and direct current control electromagnet 10.

Output terminal mechanism of the operating apparatus As shown in Figs. 2 through 4, the vacuum circuit breaker equipped with the operating apparatus, which is portable by means of a carriage 16, is bf the so-called track type. At the front end of the carriage 1 6 is provided a rectangular box 1 7 which extends across the base of the carriage 1 6 and stands erect from the base of the carriage 1 6. The box 1 7 accommodates a major portion of a throw-in and interruption operating apparatus.

The first, second and third poles 18, 19 and 20 are secured in parallel laterally across the back surface of the box 17. The poles 18, and 20 respectively include the first, second and third vacuum interrupters 21,22 and 23 (see Fig. 1).

Since the structures of the first, second and third poles 18, 19 and 20 are of the same, the first pole 1 8 will be explained in detail below, and the second and third poles 19 and 20, will be described only when necessary.

Insulating cases 24 of molded insulating resin cover both of the upper and lower portions of the first vacuum interrupter 21 of the first pole 1 8.

Within the insuiating cases 24, upper and lower rod-shaped electrical connections 25 and 26 are electrically and mechanically connected to a stationary lead rod (not shown) and a movable lead rod 27 (best seen in Fig. 4) of the first vacuum interrupter 21, respectively.

The upper and lower electrical connections 25 and 26 which extend outwards from the first pole 18 are provided with upper and lower piugs 25a and 26a at their free ends. The plugs 25a and 26a are mechanically and electrically engageable with and disengageable from a pair of terminals, not shown, of the main power supply circuit, provided, for example, in a vertical partition in a switchboard.

The movable lead rod 27 (see Fig. 4) is fixed to an operating rod 28, but electrically insulated therefrom. The operating rod 28 is mechanically associated with an operating plate 29 by way of a flange 28a provided at the bottom of the rod 28 (see Fig. 4).

The operating plate 29 which extends laterally with respect to the carriage 1 6 is in turn mechanically associated with the corresponding operating rods, not shown, of the second and third poles 19 and 20 in the same manner as that of the operating rod 28. Thus, the throw-in or interruption operation of the first, second and third vacuum interrupters 21,22 and 23 are always performed concurrently.

The center of operating plate 29 has a boss 30 to which one end of a main lever 31, provided with a central fulcrum 41, is pivotably attached by means of a pin 32. A contact spring 34 of compression coil-spring type is seated between the operating rod 28 and operating plate 29 by means of a pair of retainers 33. The contact spring 34 serves to hold a pair of movable and stationary contacts 35 and 36 (see Fig. 1) of the first vacuum interrupter 21 in a closed position while the circuit breaker is thrown-in.

The operating plate 29 is always urged downwards by an interruption accelerating spring 37 of tension spring type which is suspended between the boss 30 and a rod 39 supported by a pair of brackets 38 provided on opposite sides of the carriage 1 6.

The main lever 31 pivots about the central fulcrum 41 which is supported by bearings 40 secured to the main back surface 17a of the box 17. The other end of the main lever 31 is pivotably attached by means of a pin 42 to the bottom of an operation output rod 43.

Body of the operating apparatus As shown in Fig. 5, the body of the operating apparatus is divided into three portions. The first portion, which is located between a pair of parallel base plates 47a and 47b, includes a dual toggle mechanism 44 which directly actuates the operation output rod 43. The second portion, which is located to the right of the dual toggle mechanism 44, is a throw-in operating mechanism 45. The third portion, which is located to the left of the dual toggle mechanism 44, is a trip-operating mechanism 46.

Dual toggle mechanism The toggle mechanism 44 includes first, second and third toggle links 48, 49, and 50. The first toggle link 48 is associated with the second toggle link 49 by way of a first toggle pin 51. The second toggle link 49 is in turn associated with the third toggle link 50 by way of a second toggle pin 52. The end of the first toggle link 48 which is not connected to the second toggle link 49 is pivotably attached to the pair of the base plates 47a and 47b by way of fixed pin 53. The first toggle pin 51 is equipped with a first roller 54.

The second toggle pin 52 is equipped with a second roller 55. The end of the third toggle link 50 which is not connected to the second toggle link 49 is pivotably connected by means of a movable pin 56 with the upper end of the operation output rod 43 and one end of a limit lever 57. The other end of the limit lever 57 is fixed to a pin 58 which is rotatably supported at one point of the base plate 47b.

The first toggle pin 51, equipped with the first roller 54, is mechanically actuated by a trip hook 59 which serves as an output terminal of the tripoperating mechanism 46. The second toggle pin 52, equipped with the second roller 55, is mechanically actuated by a throw-in cam 60 (best seen in Fig. 6) which serves as the operation output terminal of the throw-in operating mechanism 45. The second roller 55 contacts a fixed stopper 61, which is opposite the second toggle pin 52 from the throw-in cam 60, beyond the deadpoint of the juncture of the second and third toggle links 49 and 50.

The first toggle link 48 is urged counterclockwise in Fig, 5 by a toggle return spring 44a which returns the toggle mechanism 44 from a trip-free position to an interrupting position.

Throw-in operating mechanism As illustrated in Fig. 6, the throw-in operating mechanism 45 consists of an electrical springloading mechanism 62 occupying the right side of Fig. 6 and a throw-in mechanism 63 occupying the left side of Fig. 6.

An electrical motor 64 for loading the throw-in spring 79 of the electrical spring-loading mechanism 62 is supplied with direct current power by a direct current operating power supply which is independent of the load-side circuits 4, 5 and 6 of the main power supply circuits, to rotate only in the direction of arrow A. The direct current operating power supply may be the same as the direct current control power supply. Alternatively, the motor 64 may be supplied with alternating current power independent of the load-side circuits 4, 5 and 6 of the main power supply circuits.

A first eccentric cam 66 is secured to the drive shaft 65 of the motor 64. The periphery of the first eccentric cam 66 slidably engages a pair of branches 67a of a swinging first-stage reduction yoke 67. The base of the first-stage reduction yoke 67 is connected to a loading shaft 69 by way of the first one-way clutch 68 transmitting torque in the direction of arrow A. Thus, the loading shaft 69 is intermittently driven in the direction of arrow A only when the first-stage reduction yoke 67 swings in the same direction.

The loading shaft 69 is supported on the base plates 47a and 47b not only by way of a ball bearing, not shown, but also by way of a second one-way clutch 70 to prevent the loading shaft 69 from rotating in the direction of arrow B.

The second eccentric cam 71 is secured to the loading shaft 69. The periphery of the second eccentric cam 71 slidably engages a pair of branches 72a of a swinging second-stage reduction yoke 72. The base of the second-stage reduction yoke 72 is connected to a rotary throwin shaft 74 by way of a ball bearing 73. A laterally projecting portion of the second-stage reduction yoke 72 is provided with a pin 75 about which a feed pawl 76 is free to pivot. The feed pawl 76 is biassed by an auxiliary spring 76a of compression spring type.

The end of the rotary throw-in shaft 74 near the base plate 47b is fixed to one end of a crank arm 77. The other end of the crank arm 77 is attached to one end of a throw-in spring 79 of coiled tension spring type by way of a pin 78. The other end of the throw-in spring 79 is fixed to a shaft 80 installed in the lower portion of the box 17 (see Fig. 1).

The rotary throw-in shaft 74 is supported by the base plates 47a and 47b not only by way of a ball bearing, not shown, but also by way of a third one-way clutch 81 which prevents the rotary from rotating in the direction of arrow B.

There are secured to the rotary throw-in shaft 74 a loading ratchet wheel 82, the throw-in cam 60, a throw-in stopper 83 in the shape of a notched disc and a revolution detecting cam 84.

The loading ratchet wheel 82 will intermittently advance tooth by tooth in the direction of arrow B by way of the feed pawl 76 which is driven by the second-stage reduction yoke 72 to reciprocally turn in the orbit about the loading ratchet wheel 82, thus alternatingly loading and holding the load on the throw-in spring 79.

As shown in Figs. 8 to 10, the profile of the throw-in cam 60 consists of a base circle through 3/4 of its circumference and an involute curve through the remainder. The maximum lift portion 60a of the throw-in cam 60, pushes the second roller 55 of the dual toggle mechanism 44 into contact with the stopper 61, so that the throw-in operation will be performed.

The notch 83a of the throw-in stopper 83 in Fig. 6 will engage or disengage a roller 85a mounted at one end of a throw-in hook 85. When the throw-in spring 79 is loaded, the notch 83a of the throw-in stopper 83 takes the position shown in Fig. 6 in which the roller 85a is free to engage or disengage the notch 83a. The dual toggle mechanism 44 takes the position shown in Fig. 9.

The throw-in hook 85 is a lever which pivots about a pin 86 fixed to the base plate 47a. When the other end 85b of the throw-in hook 85 is driven by a plunger 88 of a throw-in control electromagnet 87, the roller 85a disengages from the notch 83a of the throw-in stopper 83 to release the throw-in spring 79.

The rotary throw-in shaft 74 rotates more than a 1/2 turn in the direction of arrow B to load the throw-in spring 79 to the maximum at a point slightly beyond the highest point of travel of the crank arm 77 since the throw-in spring 79 is inclined slightly from the vertical and further rotates no more than a 1/2 turn in the direction of arrow B to release the load on the throw-in spring 79.

The throw-in control electromagnet 87 is energized with direct current power from a direct current control power supply which is independent of the load-side circuits 4, 5 and 6 of the main power supply circuits.

The revolution detecting cam 84 which is similar to the throw-in cam 60 and smaller than the throw-in cam 60 actuates a limit switch 88 fixed to the base plate 47a to control the starting and stopping of the motor 64.

Trip operating mechanism The trip operating mechanism 46 trips the trip hook 59 to separate the respective pairs of contacts of the first, second and third vacuum interrupters 21,22 and 23 by way of the dual toggle mechanism 44.

As shown in Fig. 5, the trip operating mechanism 46 includes the trip hook 59 which serves as its output terminal and which is urged to pivot counterclockwise about a central shaft 89 bridging the base plates 47a and 47b. The trip hook 59 includes a trip operating arm 59a near the first roller 54 and a driven arm 59b distal from the first roller 54. The end of the trip operating arm 59a which contacts the first roller 54 of the dual toggle mechanism 44 will disengage the first roller 54 when the trip hook 59 is in its clockwise position as shown in Fig. 5. A plunger 1 0a of the direct current trip control electromagnet 10 fixed to the base plates 47a and 47b pushes the driven arm 59b upwardly when activated, thus pivotting the trip hook 59 clockwise in Fig. 5.

As shown in Fig. 7, an alternating current tripoperating rod 90 marginally extends through a hole 90a defined in the driven arm 59b of the trip hook 59. An operating piece 91 provided at the bottom of the alternating current trip-operating rod 90 engages or disengages the undersurface of the driven arm 59b.

The trip hook 59 is actuated clockwise in Fig. 5 not only by the plunger 1 Oa of the direct current trip-control electromagnet 10 but also by the alternating current trip-operating rod 90.

Moreover, even if the plunger 1 Oa of the direct current trip-control electromagnet 10 pushes the driven arm 59b upwardly, upward force will not be applied to the alternating current tripoperating rod 90.

As shown in Fig. 5, the first, second and third alternating current trip control electromagnets 7, 8 and 9 are fixed in parallel across the front surface of the base plate 47a so that plungers 7a, 8a and 9a of the electromagnets 7, 8 and 9 project upwardly from the top of the base plate 47a. A rotary trip-operating shaft 92 of square cross-section, rotatably supported by a pair of bearing brackets 96, extends between the base plates 47a and 47b at substantially the same vertical position as the plungers 7a, 8a and 9a.

Three operating arms 93, 94 and 95 are secured by bolts 97 to the rotary trip-operating shaft 92 at fixed positions opposite the plungers 7a, 8a and 9a. The operating arms 93, 94 and 95 extend from the space between the base plates 47a and 47b so that the ends of each of the operating arms 93, 94 and 95 opposes the end of the corresponding plunger 7a, 8a or 9a.

An L-shaped hook 98 is secured by bolts 99 to one end (the left end in Fig. 5) of the rotary tripoperating shaft 92.

As shown in Fig. 7, the rotary trip-operating shaft 92 is urged by a torsion spring 100 clockwise in Fig. 7. The limit of clockwise angular travel of the rotary trip-operating shaft 92 is determined by a pin stopper 101 which is positioned on one of the bearing brackets 96 so as to limit the clockwise travel of the L-shaped hook 98.

The bottom of the L-shaped hook 98 engages or disengages a roller 102 mounted at the top of the alternating current trip-operating rod 90.

The alternating current trip-operating rod 90 is supported by way of a support 103 with a Cshaped cross-section fixed to one of the bearing brackets 96, and extends movably vertically through upper and lower pieces 1 03a and 1 03b of the support 103. The portion of the alternating current trip-operating rod 90 within the support 103 is equipped with a spring retainer 105 retained in turn by a pin 104 and upwardly urged by a trip spring 106 of compression spring type which is seated between the spring retainer 105 and the lower piece 1 03b of the support 103.

As illustrated in Fig. 7, the alternating current trip-operating rod 90, when the bottom of the Lshaped hook 98 engages the roller 103 at the top of the alternating current trip-operating rod 90, is held in its lower position so that the pin 104 remains separated by a certain distance from the upper piece 1 03a of the support.

The L-shaped hook 98 has been rotated counter-clockwise in Fig. 7 so that the bottom thereof is disengaged from the roller 102 and the alternating current trip-operating rod 90 is elevated by the trip spring 106, thus elevating the end of the driven arm 59b of the trip hook 59 to rotate the trip hook 59 clockwise in Fig. 5.

A rod-shaped manual-return handle 107 is mounted on the downwardly projecting portion of the alternating current trip operating rod 90. The manual-return handle 107 serves to depress the alternating current trip-operating rod 90 so that the L-shaped hook 98 will engage the roller 102 against after the L-shaped hook 98 has once disengaged from the roller 102, preparing the system for the next over-current trip operation.

Operation of the operating apparatus The operation of the operating apparatus of the vacuum circuit breaker will be described below with reference to Figs. 8 to 10 and Fig. 6.

The loading operation of the throw-in spring 79 is automatically performed in such a way that signals from the limit switch 88 actuated by the revolution detecting cam 84 control the motor 64 to start and to stop after a set time.

When the throw-in spring 79 is loaded, the throw-in cam 60 takes the position shown in Fig.

10.

The throw-in operation from the interruption position shown in Fig. 10 to the throw-in position is performed in the following sequence: The throw-in control electromagnet 87, upon receiving a throw-in instruction signal, is immediately excited. Thus, the throw-in stopper 83 disengages the throw-in hook 85 to lead to a discharge of the throw-in spring 79. The throw-in cam 60 rotates in the direction of arrow B to its maximum-lift portion 60a to thrust the second roller 55 of the dual-toggle mechanism 44 into contact with the stopper 61. Thus, the second and third toggle links 49 and 50 substantially align with each other, which depresses the operation output rod 43. Consequently, the main lever 31, associated with the operation output rod 43, elevates the operating plate 30 so that the respective pairs of contacts of the first, second and third vacuum interrupters 21,22 and 23 engage.The elevation of the operating plate 30 loads the interruption accelerating spring 37 for the next interruption operation.

The termination of the throw-in operation causes the revolution detecting cam 84 to immediately actuate the limit switch 88, thus starting the motor 64 in order to load the throw-in spring 79. The loading of the throw-in spring 79 will move the throw-in cam 60 to its initial position shown in Fig. 8.

In case of interruption of normal load current, the direct current trip-control electromagnet 10 is sent an interruption instruction signal by way of the button switch 1 6 to be excited, thus elevating the driven arm 59b of the trip hook 59. The trip hook 59 trips so that the end of the trip-operating arm 59a disengages from the first roller 54 of the dual toggle mechanism 44. The first toggle link 48, urged by the interruption accelerating spring 37, turns clockwise in as seen Fig. 8 to move to the position shown in Fig. 6. Consequently, the operation output rod 43 is elevated, thus disengaging the respective pairs of contacts of the first, second and third vacuum interrupters 21, 22 and 23 with the aid of the interruption accelerating spring 37.

In the throw-in position shown in Fig. 9, even if then maximum lift portion 60a of the throw-in cam 60 causes the second roller 55 to come into contact with-the stopper 61 the operation output rod 43 will not be elevated but rather remains in the interruption position. That is, the dual-toggle mechanism 44 is held in its trip-free position.

When the direct current trip-control electromagnet 10 is not supplied with direct current from the direct current control power supply and an over-current such as a short-circuit current flows through any of the first, second and third load-side circuits 4, 5 and 6 due to some malfunction, any of the normally-closed contacts 12a, 12b and 1 2c and the corresponding one of normally-opened contacts 1 Sa, 1 Sb and 1 sic of the over-current relays 11 a,11 b and 11 c are respectively opened and closed. The direct current trip-control electromagnet 10 will not be excited, while at least one of the first, second and third alternating current trip control electromagnets 7, 8 and 9 will be excited so that the corresponding one of the plungers 7a, 8a and 9a will actuate the L-shaped hook 98 by way of any one of the operating arms 93, 94 and 95 and the rotary trip operating shaft 92 to disengage from the roller 1 02. Thus, the alternating current trip-operating rod 90 is elevated, causing the trip hook 59 to trip. Finally, the respective pairs of contacts of the first, second and third vacuum interrupters 21,22 and 23 will disengage from each other.

Auto-return mechanism for alternating current trip operating rod According to the above embodiment, the alternating current trip operating rod 90 is provided with the manual-return handle 107.

However, in unmanned generating stations or substations, it is necessary for the alternating current trip-operating rod 90 to include an autoreturn mechanism.

The auto-return mechanism will be described in detail with reference to Fig. 11. A drive lever 110 is fixed to the pin 58 of the limit lever 57 so as to project in the direction opposite that of the limit lever 57. The bottom of a connecting rod 112 is pivotally connected to the end of the drive lever 110 by way of a pin 111. The top of the connecting rod 112 is pivotally connected by way of a pin 115 to a central portion of a passive lever 114 which is pivotally supported by the pair of base plates 47a and 47b by way of a square shaft 11 3. A return operating lever 11 6, parallel to the passive lever 114, is fixed to the square shaft 113, so that the passive lever 114 and return operating lever 116 turn integrally.

The free end of the return operating lever 11 6 is provided at its lower edge with a substantially circular projection 11 6a which engages or disengages the upper surface of a block 11 7 secured to a lower portion of the alternating current trip-operating rod 90. The block 117 may comprise nuts screwed into the alternating current trip operating rod 90. When at least one of the first, second and third alternating current trip-control electromagnets 7, 8 and 9 is activated, the trip hook 59 is tripped. Thus, the third toggle link 50 is elevated to turn the limit lever 57 and drive lever 110 counterclockwise in Fig. 11. Consequently, according to the autoreturn mechanism of this embodiment, the circular projection 11 6a of the return operating lever 11 6 depresses the block 117, thus depressing the alternating current trip operating rod 90 to the position in which the L-shaped hook 98 will engage the roller 102.

Claims

1. An operating apparatus for a circuit breaker, which comprises a toggle mechanism for disengaging a pair of contacts by retraction and for engaging the pair of the contacts by extension, throw-in means for extending the toggle mechanism, an interruption accelerating spring for retracting the toggle mechanism, and a trip hook for holding the toggle mechanism in its retracted and extended positions, including one trip-control electromagnet for releasing the interruption accelerating spring, operable with electric power that is supplied by a control power supply independent of a load-side circuit of a main power supply circuit, another trip-control electromagnet for releasing the interruption accelerating spring, operable by over-current flowing through the main power supply circuit, and an over-current relay connected via a current transformer to the main power supply and providing both the trip-control electromagnets with trip instruction signals.

2. An operating apparatus for a circuit breaker as set forth in claim 1, applicable to respective circuit breakers for three main power supply circuits through which three-phase alternating current flows, wherein the other trip-control electromagnet comprises three independent tripcontrol electromagnets, each of which is operable with electric power that is supplied by overcurrent flowing through a corresponding one of the main power supply circuits.

3. An operating apparatus for a circuit breaker as set forth in claim 2, including as a trip hook actuating means a single rotary trip-operating shaft to which three members, actuated by respective plungers of the other trip control electromagnets, are fixed and by which the operating apparatus controls the release of the interruption accelerating spring.

4. An operating apparatus for a circuit breaker substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

5. A circuit breaker associated with apparatus according to any preceding claim.

6. A circuit breaker constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.