Switch

Abstract: A switch includes a fixed contact having a first conductor portion (4a) connected to a terminal (5), a second conductor portion (4e) having a stationary contact (3), and a third conductor portion (4d). The third conductor portion is disposed on the side of the other end of a moving contact (1) to which a traveling contact is not mounted with respect to a position of the stationary contact, and on the side opposed to the terminal. The first conductor portion is disposed above a contact surface of contacts at a contact closing time, and is disposed below a contact surface of the traveling contact at a contact opening time. A part of the first conductor portion facing a surface of the traveling contact at an opening time of the contacts is coated with an insulator (15). Thereby, it is possible to provide an excellent current-limiting performance since an entire current path of the fixed contact generates electromagnetic force to stretch an arc (A) on the side of the terminal.

Description: The present invention relates to a switch such as a circuit breaker, current limiting device or electromagnetic contactor, in which an arc may be formed in a housing at a time of current cutoff. Fig. 1 is a side view showing a circuit breaker in an opening condition as an example of conventional switches, and Fig. 2 is a side view showing a condition immediately after contact opening in the circuit breaker of Fig. 1. Fig. 3 is a side view showing the maximum opening condition of a moving contact in the circuit breaker of Fig. 2. In the drawings, reference numeral 1 means a moving contact of the circuit breaker, and the moving contact 1 is supported so as to rotate about a rotation supporting point (rotating center) 14 (see Figs. 2 and 3) of a base portion. Reference numeral 2 means a traveling contact secured to one end (a lower surface of a free end) of the moving contact 1, and 3 means a stationary contact making and breaking contact with the traveling contact 2 by the rotation of the moving contact 1. Reference numeral 4 means a fixed contact having the stationary contact 3 at one end thereof, and a configuration of the fixed contact 4 will be described later. Reference numeral 5 means a terminal on a side of a power source, which is connected to the other end of the fixed contact 4, and 6 means an arc-extinguishing plate which functions to stretch and cool the arc formed between the traveling contact 2 and the stationary contact 3 at an opening time therebetween. Reference numeral 7 means an arc-extinguishing side plate holding the arc-extinguishing plates 6, and 8 means a mechanism portion which causes the moving contact 1 to rotate. The mechanism portion 8 includes a current detecting element (not shown), and is operated according to detection of short-circuit current by the current detecting element. Reference numeral 9 means a handle for manually operating the mechanism portion 8, 10 means a terminal on a side of a load, and 11 is a conductor for connecting the terminal 10 to the moving contact 1. Further, reference numeral 12 means a housing containing these circuit breaker components, and 13 means an exhaust hole provided in a wall portion of the housing 12. A description will now be given of the configuration of the fixed contact 4. In Figs. 1 to 3, the fixed contact 4 is integrally provided in a from including a conductor portion 4a connected to the terminal 5 on the side of the power source to horizontally extend, a vertical conductor portion 4b downward bent at an end of the conductor portion 4a opposed to the terminal 5, a conductor portion 4c serving as a step-shaped lower portion horizontally extending from a lower end of the conductor portion 4b toward the opposite side of the conductor portion 4a, a conductor portion 4d vertically rising from a distal end of the conductor portion 4c, and a conductor portion 4e horizontally extending from an upper end of the conductor portion 4d toward the conductor portion 4a. Further, the stationary contact 3 is mounted on the conductor portion 4e. In the fixed contact 4 shaped as set forth above, the conductor portion 4d connecting the conductor portion 4c serving as the step-shaped lower portion to the side of the stationary contact 3 is positioned on the side of the other end of the moving contact 1, to which the traveling contact 2 is not secured with respect to the stationary contact 3, and on the side opposed to the terminal 5. The conductor portion 4e having the stationary contact 3 is positioned below a contact surface between the traveling contact 2 and the stationary contact 3-at a time of contact closing therebetween. The fixed contact 4 is used in a skin exposed condition where an entire surface thereof is not insulated. A description will now be given of the operation. In a condition shown in Fig. 1, the terminal 5 of the fixed contact 4 is connected to the power source, and the terminal 10 on the side of the load is connected to the load. In this condition, if the handle 9 is operated in a direction shown by the arrow B, the mechanism portion 8 is actuated so as to downward rotate the moving contact 1 about the rotation supporting point 14 (see Figs. 2 and 3) of the base portion. Thereby, a contact closing condition where the traveling contact 2 contacts the stationary contact 3 is provided to feed power from the power source to the load. In this condition, the traveling contact 2 is pressed toward the stationary contact 3 with a specified contact pressure so as to ensure reliability of power supply. If a short-circuit event or the like occurs in a circuit on the side of the load with respect to the circuit breaker to feed large short-circuit current into the circuit, the current detecting element in the mechanism portion 8 detects the large current so as to actuate the mechanism portion 8. The moving contact 1 is thereby rotated in a contact opening direction to open the traveling contact 2 from the stationary contact 3. At a time of the contact opening, an arc A forms between the traveling contact 2 and the stationary contact 3 as shown in Figs. 2 and 3. However, when the larger current such as the short-circuit current flows, extremely strong electromagnetic repulsion is generally caused on the contact surface between the traveling contact 2 and the stationary contact 3. Accordingly, the moving contact 1 is rotated in the contact opening direction before the action of the mechanism portion 8 in order to overcome the contact pressure applied to the traveling contact 2. Therefore, the rotation causes the opening between the traveling contact 2 and the stationary contact 3 so as to stretch and cool the arc A generated between the contacts 2 and 3 by the arc-extinguishing plate 6. As a result, arc resistance increases, and a current-limiting action is generated to diminish the short-circuit current so that the arc A is extinguished at a zero point of current, resulting in completion of current cutoff. The current-limiting action is very important for improvement of a protection function of the circuit breaker. As set forth above, it is necessary to increase the arc resistance so as to enhance a current-limiting performance. Preferred techniques to stretch the arc so as to increase the arc resistance includes a method using a fixed contact having a shape which is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 60-49533 and 2-68831. The shape of the fixed contact disclosed in these Japanese Patent Application publications is basically identical with that of the fixed contact 4 shown in Figs. 1 to 3. Referring to Figs. 1 to 3, a current path including the fixed contact 4 extends from the terminal 5 on the side of the power source to the stationary contact 3 through the conductor portions 4a, 4b, 4c, 4d and 4e in this order. In such a current path, current in the current path 4e on the side of the stationary contact 3 of the fixed contact 4 causes electromagnetic force applied to the arc A, and the electromagnetic force serves as force to stretch the arc A toward the arc-extinguishing plate 6. As a result, it is possible to increase the arc resistance so as to provide the circuit breaker having an improved current-limiting performance. In order to enhance the current-limiting performance in a normal AC cutoff, it is necessary to increase the arc resistance as set forth above. In this case, it is however necessary to increase the arc resistance before the current reach the maximum value immediately after opening the contacts 2 and 3. Even if the arc resistance is increased after the current becomes large, it is difficult to limit the current due to inertia effect of the current. Rather worse damage is caused to the breaker because arc energy generated in the breaker becomes large due to the large current and the high resistance. Consequently, it is necessary to provide the fixed contact shape which can largely stretch the arc immediately after opening the contacts 2 and 3 by the strong electromagnetic force so as to rapidly increase the arc resistance. However, the switch having the conventional fixed contact shape is provided as set forth above. Thus, as shown in Fig. 2, only the conductor portion 4e on the side of the stationary contact 3 can serve as the current path of the fixed contact 4 which can concurrently generate the electromagnetic force exerting in a direction to open the moving contact 1 immediately after opening the contacts 2 and 3, and the electromagnetic force to stretch the arc A in the direction of the terminal 5 on the side of the power source. Other current paths (conductor portions) 4a, 4b, 4c and 4d prevent an opening action of the moving contact 1 and generate electromagnetic force to stretch the arc A on the side opposed to the terminal 5. The current in the current path 4d has the same direction as that of the current of the arc A to attract each other while the current in the current path 4b has the direction opposed to the current of the arc A to repel each other. Therefore, the arc A should be stretched in the direction opposed to the terminal 5. Further, the current in the current paths 4a and 4c flow in the direction opposed to that of the current in the current path 4e so as to generate electromagnetic force to stretch the arc A in the direction opposed to the terminal 5. In addition, only the current path 4e of the fixed contact 4 can exert the electromagnetic force in a rotating direction on the entire moving contact 1 as set forth above. In other current paths 4a and 4c, current flows in the same direction as that of the moving contact 1 so as to exert the electromagnetic force in a direction to close the moving contact 1. The current in the current path 4d can exert the electromagnetic force in the rotating direction on the side of the rotating center 14 of the moving contact 1, but exert the electromagnetic force in the closing direction on the side of the traveling contact 2. Accordingly, with the shape of the fixed contact 4 used in the conventional switch, there is a problem in that the electromagnetic force generated by the current in the fixed contact 4 can not effectively act in order to stretch the arc A. Further, though only the electromagnetic force by the current path 4e of the fixed contact 4 contributes to high speed opening of the moving contact 1, the electromagnetic force rapidly decreases due to an extended distance between the traveling contact 2 and the stationary contact 3 as the moving contact 1 is rotated. Additionally, there is generated a relatively large effect of the current in other current paths 4a, 4b, 4c and 4d which generate the electromagnetic force in the direction to prevent the opening action. Hence, there is another problem of a reduced speed of the opening action. As a result, there are other problems in that the opening speed is reduced, and a required current-limiting performance can not be provided. Fig. 4 is a side view showing a closing condition of the circuit breaker serving as the conventional switch disclosed in, for example, Japanese Patent Application Laid-Open No. 60-49535. Fig. 5 is a side view showing an opening condition of only a moving element in Fig. 4, and Fig. 6 is a side view showing an opening condition of the moving element and a repelling element in Fig. 4. In the drawings, reference numeral 101 means one electric contact (hereafter referred to as moving element) of the circuit breaker, and the moving element 101 can rotate with a supporting shaft P1 of a main end as the rotating center as shown in Figs. 7 and 8. Reference numeral 102 means a contact secured to a lower surface of a free end of the one moving element 101, and 103 means the other electric contact (repelling element) disposed under the one moving element 101. The electric element 103 can also rotate with a shaft P2 of a main end as the rotating center. Reference numeral 104 means the other contact secured to an upper surface of a free end of the other electric contact 103 so as to make and break contact with the other contact 102. The moving element 101 and the other electric contact 103 form a pair of electric contacts. Reference numeral 105 means a terminal of a power source system, and 106 means a conductor electrically connecting the other electric contact 103 to the terminal 105. Reference numeral 107 means a first conductor portion horizontally extending at a position below the moving element 101, and the terminal 105 is connected to one end of the first conductor portion 107. Reference numeral 108 means a second conductor portion continuously formed with the other end of the first conductor portion 107 so as to rise at a position below the moving element 101, and the conductor 106 includes the first conductor portion 107 and the second conductor portion 108. Here, the second conductor portion 108 has flexibility so as not to prevent rotation of the electric contact 103. Further, the main end of the repelling element 103 is rotatably coupled with an upper end of the second conductor portion 108 through the shaft P2. Reference numeral 109 means a torsion spring which is fitted with a main end coupling shaft P2 of the other electric contact 103, and 110 means a mechanism portion for rotating the moving element 101. The mechanism portion 110 has a function to automatically rotate the moving element 101 in the opening direction when current having a predetermined current value or more (short-circuit current) flows in the circuit breaker. In view of the fact, in general, the other electric element 101 is referred to as the moving element 101, and the contact 102 will be referred to as traveling contact 102. Reference numeral 110a means a spring anchor which is provided at a side surface portion of a casing of the mechanism portion 110. One end of the torsion spring 109 anchors the spring anchor 110a, and the other end of the torsion spring 109 anchors the moving element 101. The torsion spring 109 contacts the contacts 102 and 104 with a predetermined force at a closing time. Further, a stopper (not shown) is provided for the electric contact 103 such that the other electric contact 103 is held at a position shown in Fig. 5 at an opening time of the moving element 101. Therefore, the other electric contact 103 can rotate in the opening direction if force larger than that of the torsion spring 109 is applied to the other electric contact 103. As noted above, since the electric contact 103 can repel with a large force, the electric contact 103 will be hereafter referred to as repelling element, and the contact 104 will be referred to as repelling contact. Reference numeral 111 means a handle for manually operating the mechanism portion 110, and the handle 110 is operated so as to manually switch the moving-element 101. Reference numeral 112 means a stopper to set the maximum opening position of the repelling element 103, 113 means an arc-extinguishing plate, and 114 is an arc-extinguishing side plate holding the arc-extinguishing plate 113. Reference numeral 115 means a terminal on a side of a load, 116 means a housing containing the components of the circuit breaker, and 117 is an exhaust hole provided in a wall portion of the housing 116. A description will now be given of the operation. In Fig. 4, in case the one terminal 105 is connected to the power source and the other terminal 115 is connected to the load, it is possible to feed the power from the power source to the load. At this time, the traveling contact 102 and the repelling contact 104 are in a closing condition where the traveling contact 102 and the repelling contact 104 contact each other with a predetermined contact pressure by a contact pressure spring (not shown) of the moving element 101 and the torsion spring 109 of the repelling element 103. In the closing condition, current as shown in Fig. 7 flows in the moving element 101 and the repelling element 103. That is, as shown by the narrow arrow in Fig. 7, the current enters the terminal 105 to pass through the first conductor portion 107, the second conductor portion 108, the repelling element 103, and the repelling contact 104 in this order. Subsequently, the current reaches the moving element 101 after passing through a contact surface between the repelling contact 104 and the traveling contact 102. The current in the moving element 101 exits from a conductor in a vicinity of the rotating center P1 to the side of the load. As will be clear in Fig. 7, the current in the repelling element 103 and the current in the moving element 101 are substantially parallel to each other, but have opposite directions. Accordingly, electromagnetic repulsion F is applied between the moving element 101 and the repelling element 103. The contact pressure between the traveling contact 102 and the repelling contact 104 is set to a magnitude larger than that of electromagnetic repulsion which is generated by small current such as load current or overload current. With the small current, the traveling contact 102 and the repelling contact 104 are never opened by rotating the moving element 101 or rotating the repelling element 103 without operating the mechanism portion 110. The moving element 101 may be rotated by the handle 111 in order to cut off normal load current, and the mechanism portion 110 is automatically operated to rotate the moving element 101 to an opening position shown in Fig. 5 when the overload current flows. In either case, the repelling element 103 is never operated by the torsion spring 109 in the opening direction. This condition is shown in Fig. 8. In Fig. 8, magnetic field generated by the current in the repelling element 103 exerts force Fm on the arc A in a direction of the arc-extinguishing plate 113. As a result, the arc A is stretched in the direction marked Fm, and is cooled and extinguished by the arc-extinguishing plate 113, resulting in completion of the current cutoff. On the other hand, in the closing condition shown in Fig. 7, if the large current such as short-circuit current flows, the electromagnetic repulsion F applied between the moving element 101 and the repelling element 103 becomes larger than the contact pressure between the contacts 102 and 104, that is, the pressure of the torsion spring 109 or the contact pressure spring of the moving element 101. Consequently, the moving element 101 and the repelling element 103 are started to rotate in the respective opening directions. As shown in Fig. 9, since both the moving element 101 and the repelling element 103 move in the opening directions, that is, move in each opposite direction, an interval between the traveling contact 102 and the repelling contact 104 thereof increases twice as compared with a case where only the moving element 101 is moved. In other words, the opening speed becomes twice as fast. Hence, it is possible to reach a condition where the moving element 101 and the repelling element 103 rotate to the maximum extent as shown in Fig. 10 in a short time after the short-circuit current starts to flow. The magnetic field generated by the current in the repelling element 103 exerts the force Fm in the direction of the arc-extinguishing plate 113 on the arc A so as to stretch the arc A. As a result, it is possible to rapidly increase arc voltage, and provide an excellent current-limiting performance. Though the arc A is still generated by the current diminished by the excellent current-limiting performance, the arc A is extinguished by undergoing the cooling operation by the arc-extinguishing plate 113. Since the conventional switch is provided as set forth above, the electromagnetic repulsion F is reliably generated between the moving element 101 and the repelling element 103 by the current path as shown in Fig. 7. However, another electromagnetic repulsion is also generated between the repelling element 103 and the first conductor portion 107, and the electromagnetic repulsion serves as force in a direction opposed to the opening direction of the repelling element 103. Further, magnetic field generated by the second conductor portion 108 exerts electromagnetic force on the repelling element 103, and the electromagnetic force also serves as force in a direction opposed to the opening direction of the repelling element 103. That is, there is a problem in that the electromagnetic force generated by the current of the moving element 101 to rotate the repelling element 103 in the opening direction may considerably decreased by the electromagnetic force in the opposite direction generated by the current in the first and the second conductor portions 107 and 108. As shown in Figs. 9 and 10, as the moving element 101 and the repelling element 103 rotate in the respective opening directions, the interval therebetween becomes larger. Accordingly, electromagnetic force to rotate the moving element 101 and the repelling element 103 in the respective opening directions also becomes weak. To the contrary, intervals between the repelling element 103 and the first conductor portion 107, and between the repelling element 103 and the second conductor portion 108 are decreased. Therefore, the electromagnetic force to rotate the repelling element in the direction opposed to the opening direction becomes large. As a result, as the interval between the contacts 102 and 104 becomes large because of the rotation of the moving element 101 and repelling element 103, the electromagnetic force to rotate the moving element 101 and repelling element 103 in the opening direction is decreased. In particular, since the electromagnetic force in the direction opposed to the opening direction also increases in the repelling element 103, reduction of the electromagnetic force in the opening direction is remarkable. In a typical arrangement in the housing 116 of the circuit breaker as shown in Fig. 4, the repelling element 103 is shorter than the moving element 101 because of the mechanism portion 110. In general, in case the rotating center is provided at one end of a rod, moment of inertia with respect to the rotating center is proportional to the square of a length of the rod, and moment of force is proportional to the length of the rod. Accordingly, angular acceleration with respect to the rotating center is inversely proportional to the length of the rod. In case this relationship is applied to the moving element 101 and the repelling element 103, the repelling element 103 can rotate faster than the moving element 101 immediately after the short-circuit current starts to flow because the repelling element 103 is shorter than the moving element 101. Hence, it can be considered that the repelling element 103 rather than the moving element 101 greatly contributes to the increased arc length initially generated between the contacts 102 and 104, that is, the current-limiting performance. However, in the circuit breaker having a terminal structure as set forth above, it is impossible to effectively generate electromagnetic force to rotate the repelling element 103 in the opening direction. Consequently, there is a problem in that the rotation of the repelling element 103 is slow, and rapid initial rising of the arc voltage required for the current-limiting can be obtained. Further, the electromagnetic force to rotate the repelling element 103 in the opening direction is considerably reduced in a condition where the repelling element 103 is rotated to the maximum extent as shown in Fig. 10. Hence, the repelling element 103 easily turns back to an original position by the force of the torsion spring 109 if the electromagnetic force is slightly reduced due to reduction of the current. As a result, there are problems in that, even if the repelling element 103 is rotated to the maximum extent so as to provide the maximum arc voltage, the repelling element 103 immediately turns back, and the arc voltage is easily reduced. The repelling element 103 exerts the electromagnetic force in the direction of the arc-extinguishing plate 113 on the arc A between the contacts 102 and 104. The current in the first conductor portion 107 exerts the electromagnetic force in the direction opposed to the arc-extinguishing plate 113 on the arc because the current in the first conductor portion 107 has a direction opposed to that of the current in the repelling element 103. Further, the current in the second conductor portion 108 and the current in the arc attract each other because of the same direction thereof. Therefore, the arc A is stretched in the direction opposed to the arc-extinguishing plate 113. Accordingly, only the current in the repelling element 103 can be used for the electromagnetic force to stretch the arc A, and other current in the first conductor portion 107 and the second conductor portion 108 exert the electromagnetic force in the opposite direction. As a result, there are problems in that the electromagnetic force extending the arc A in the direction of the arc-extinguishing plate 113 is weak, and high arc voltage can not be obtained since the arc can not be stretched. As set forth above, in the conventional circuit breaker, there is a problem in that a sufficient current-limiting performance can not be provided due to the above causes. EP 0 003447 A1 discloses a switch comprising a movable contact which is disposed on a portion of an arm within a breaker block, wherein an arc extinguishing chamber 36 is also disposed within the breaker block. As can be seen from the shape of the portion of the arm within the arc extinguishing chamber being within the breaker block, the movable contact is held within the breaker block even in a contact-opening condition. Therefore, the arc generated between the contacts is treated within the breaker block. An electromagnetic force due to the current flowing in the arm is applied to the arc generated during the contact-opening operation. However, an electromagnetic force due to the current flowing in the fixed conductor is applied to the arc in an opposite direction. Therefore, the driving force acting in the arc is decreased. In view of the foregoing, it is an object of the present invention to provide a switch having an excellent current-limiting performance, in which an entire current path of a fixed contact immediately after contact opening generates electromagnetic force to stretch an arc on the side of a terminal so as to rapidly rise arc voltage, and when an opening distance of a moving contact is increased, it is possible to generate and maintain high arc voltage by cooling the arc. It is another object of the present invention to provide a switch which can increase rise of an opening speed of a moving contact by electromagnetic force. These objects are achieved by switches according to the independent claims. The invention is further developed by the features mentioned in the dependent claims. Fig. 1 is a side view showing an opening condition of a conventional circuit breaker; Fig. 2 is a side view showing a condition immediately after contact opening in the circuit breaker shown in Fig. 1; Fig. 3 is a side view showing the maximum opening condition of a moving contact in the circuit breaker of Fig. 2; Fig. 4 is a side view showing a closing condition of the circuit breaker as an example of conventional switches; Fig. 5 is a side view showing the opening condition of only a moving element in Fig. 4; Fig. 6 is a side view showing the maximum opening condition of the moving element and a repelling element in Fig. 4; Fig. 7 is a side view showing the closing condition of an electrode portion, for purpose of illustration of the operation of the conventional circuit breaker; Fig. 8 is a side view of the electrode portion, showing a condition where the moving element is opened from the closing condition shown in Fig. 7; Fig. 9 is a side view of the electrode portion, showing a condition where the moving element and the repelling element in Fig. 4 respectively move in their opening directions; Fig. 10 is a side view of the electrode portion, showing the maximum opening condition of the moving element and the repelling element in Fig. 9; Fig. 11 is a side view of the arc-extinguishing plate, showing the closing condition of the circuit breaker serving as a switch according to the embodiment 1 with a housing broken away; Fig. 12 is a side view showing the opening condition of the circuit breaker of Fig. 11; Fig. 13 is a plan view of a related configuration of a repelling element, a first conductor portion and a second conductor portion of Fig. 11; Fig. 14 is a front of Fig. 12; Fig. 15 is a perspective view of Fig. 12; Fig. 16 is a side view of an electrode portion, showing the closing condition of the circuit breaker so as to illustrate the operation in the embodiment 1; Fig. 17 is a side view of the electrode portion immediately after contact opening, illustrating the operation at a time of large current cutoff in the embodiment 1; Fig. 18 is a side view showing the maximum opening condition of a moving element and the repelling element; Fig. 19 is a side view showing a closing condition of a circuit breaker according to the embodiment 2; Fig. 20 is a side view of the electrode portion showing a contact opening condition of Fig. 19; Fig. 21 is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 3; Fig. 22 is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 4; Fig. 23 is a side view of an arc-extingulshing portion of a circuit breaker according to an-alternative embodiment of the embodiment 4; Fig. 24 is a side view of an electrode portion, showIng an opening condition of a circuit breaker according to the embodiment 5; Fig. 25 is a side view of an electrode portion, showIng an opening condition of a circuit breaker according to the embodiment 6; Fig. 26 is a side view of an electrode portion, showing an opening condition of a circuit broader according to the embodiment 7; Fig: 27 is a side view of the electrode portion, showing an opening condition of a repelling element; Fig. 28 is a side view showing the electrode portion in a.condition where only a moving element is opened at a time of small current cutoff in the circuit breaker according to an alternative embodiment of the embodiment 7; Fig. 29 is a side view showing a condition where both the moving element and the repelling element are opened at a time of large current cutoff in Fig. 28; Fig. 30 is a side view of an electrode portion, showIng a closing condition of a circuit breaker according to the embodiment 8; Fig. 31 is a side view showing an electrode portion according to an alternative embodiment of the embodiment 8; Fig. 32 is a side view showing an electrode portion according to another alternative embodiment of the embodiment 8 ; Fig. 33(a) is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 9; Fig. 33(b) is a sectional view taken along line A-A of Fig. 33; Fig. 34 is a side view showing an electrode portion of a circuit breaker according to the embodiment 10; Fig. 35 is a sectional view of Fig. 34; Fig. 36(a) is a side view showing an electrode portion of a circuit breaker according to the embodiment 11; Fig. 36(b) is a sectional view of the electrode portion without a moving element and an insulator shown in Fig. 36(a); Fig. 37(a) is a side view of the electrode portion, showing an opening condition of a repelling element of Fig. 36(a); Fig. 37(b) is a sectional view of Fig. 37(a); Fig. 38 is a side view of an electrode portion, showing another alternative embodiment of the circuit breaker according the embodiment of present invention ; Fig. 39 is a side view of an electrode portion, showing still another alternative embodiment of the circuit breaker according to the embodiment of the present invention; Fig. 40 is a plan view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention; Fig. 41 is a side view of Fig. 40; Fig. 42 is a bottom view of Fig. 41; Fig. 43 is a side view of an electrode portion, showing a still further alternative embodiment of the circuit breaker according to the embodiment of the present invention ; Fig. 44 is a side view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention; Fig. 45(a) is a plan view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present Invention; Fig. 45(b) is a sectional view taken along line B-B of Fig. 45(a); Fig. 46 is a side view of an electrode portion, showing an alternative example ; Fig. 47 is a plan view of Fig. 46 without a moving element; Fig. 48 is a side view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention; Fig. 49 is a front view of Fig. 48 without a moving element and an insulator, Fig. 50 is a side view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention; Fig. 51 is a front view of Fig. 50 without insulators; Fig. 52 is a side view showing a closing condition of a repelling element at a circuit breaker according to the embodiment 12 of the resent invention ; Fig. 53 is a side view of an electrode portion, showing the closing condition of the repelling element of Fig. 52; and Fig. 54 is a perspective view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention. Embodiment 1 A description will now be given at the embodiment 1 of the present invention with reference to the drawings. Fig. 11 is a side view of an arc-extinguishing plate, showing a closing condition of a circuit breaker serving as a switch according to the embodiment 1 with a housing broken away. Fig. 12 is a side view showing an opening condition of the circuit breaker of Fig. 11. The component parts common or equivalent to Figs. 4 to 10 are designated by common reference numerals. The descriptions of the common component parts are omitted here to avoid unnecessary repetition. In the drawings, reference numeral 107 means a first conductor portion connected to a terminal 105 on the side of a power source. As shown in Fig. 11, the first conductor portion 107 is disposed on an upper portion of a conductor portion 103a forming a repelling element 103 so as to horizontally extend at a closing time. Reference numeral 108 means a second conductor portion connecting the first conductor portion 107 to the repelling element 103, and the second conductor portion 108 includes a flexible conductor so as not to prevent rotation of the repelling element 103. Accordingly, the first conductor portion 107 and the second conductor portion 108 form a conductor to electrically connect the repelling element 103 to the terminal 105. Fig. 13 is a plan view showing a related configuration between the repelling element, the first conductor portion and the second conductor portion shown in Fig. 11. Fig. 14 is a front view of Fig. 13, and Fig. 15 is a perspective view of Fig. 13. In the drawings, reference numeral 170 means a substantially U-shaped slit provided in the first conductor portion 107, and the slit 170 is provided to allow a switching action of a moving element 101 and the repelling element 103. Reference numerals 170a, 170b mean conductor portions on both sides of the first conductor portion 107, which are formed by the slit 170, and 180a, 180b are two right and left flexible conductors forming the second conductor portion 108. The flexible conductors 108a, 108b connect an open end of the slit 170 of the first conductor portion 107 (i.e., an end on the side opposed to the terminal 105 of the first conductor portion 107) with the repelling element 103. Reference numeral 118 means an insulator covering a position of the first conductor portion 107 which can be surveyed from a surface of the traveling contact 102 at an opening time of the moving element 101. The insulator 118 continuously includes an insulator 118d covering a surface of the first conductor portion 107, an insulator 118b covering both side inner surfaces of the slit 170 of the first conductor portion 107, and an insulator 118c covering an inner end surface of the slit 170 on the side of the terminal 105. The repelling element 103 is rotatable by downward force which is stronger than upward force generated by a torsion spring 109, and the maximum opening position of the repelling element 103 is defined by a stopper 112. Other structures are identical with those in Figs. 4 and 5. A description will now be given of the operation. In the closing condition shown in Fig. 11, the traveling contact 102 is in contact with a repelling contact 104 with a predetermined contact pressure by the torsion spring 109 generating upward rotating force of the repelling element 103 and a contact pressure spring (not shown) of the moving element 101. The contact pressure is set so as not to open the traveling contact 102 from the repelling contact 104 due to small current such as load current or overload current. In a small current cutoff operation, only the moving element 101 is rotated upward while the repelling element 103 is held in a position of the closing condition as in an operation of a conventional circuit breaker. Fig. 16 is a side view of an electrode portion, showing a closing condition of the circuit breaker. In Fig. 16, a current path from the terminal 105 to the moving element 101 is shown by the thin arrows. Current enters the terminal 105, and exits from a vicinity of a rotating center P1 of the moving element 101. When large current such as short-circuit current flows, current in the moving element 101 has a direction opposed to that of current in the repelling element 103 so that electromagnetic repulsion is applied therebetween, resulting in force F in each opening direction as in the conventional circuit breaker. However, in the electrode structure of the circuit breaker according to the invention, current in the conductor portion 103a forming the repelling element 103 has a direction opposed to that of current in the first conductor portion 107, and the conductor portion 103a of the repelling element 103 is positioned below the first conductor portion 107. Hence, electromagnetic repulsion is also applied between the repelling element 103 and the first conductor portion 107, and the electromagnetic repulsion can serve as the force F to rotate the repelling element 103 downward. Further, current in the second conductor portion 108 generates magnetic field at a portion of the conductor portion 103a of the repelling element 103, and the magnetic field exerts from the other side to this side facing Fig. 16. Consequently, the magnetic field can also serve as force to rotate the repelling element 103. That is, the electromagnetic force to rotate the repelling element 103 in the opening direction is generated by the entire current path from the terminal 105 to the repelling element 103, as well as the moving element 101. Therefore, in the electrode structure of the circuit breaker according to the invention, it is possible to considerably increase the electromagnetic force to rotate the repelling element 103 in the opening direction. As set forth above, a rotation speed of the repelling element 103 having small moment of inertia contributes to increasing distance between the contacts 102 and 104 for an opening initial period. Accordingly, in the electrode structure of the circuit breaker according to the invention, it is possible to considerably increase a contact opening speed so as to provide rapid rising of arc voltage. Fig. 17 is a side view of an electrode portion, showing a condition immediately after contact opening of the circuit breaker according to the embodiment 1. An arc A forms below the first conductor portion 107 immediately after the contact opening. At this time, current passes through the first conductor portion 107, the second conductor portion 108, and the repelling element 103 in this orderto generate magnetic field, and the magnetic field exerts from the other side to this side facing Fig. 17. The magnetic field exerts force Fm in a direction of the terminal 105 on the arc A on the repelling contact 104. That is, the entire current between the terminal 105 and the terminal 105 can generate electromagnetic force so as to stretch the arc A. Therefore, an arc length is extended longer than the distance between the contacts, and rapid rising of the arc voltage can be provided. Fig. 18 is a side view of an electrode portion, showing the maximum opening condition of the moving element 101 and the repelling element 103 shown in Fig. 17. The moving element 101 is more largely separated from the repelling element 103 as the moving element 101 and the repelling element 103 are rotated in opening directions. Consequently, the electromagnetic repulsion, of the moving element 101 to the repelling element 103 becomes weak, but there is not large variation in a relationship between the repelling element 103, the first conductor portion 107 and the second conductor portion 108. Hence, the electromagnetic force applied to the repelling element 103 by the first conductor portion 107 and the second conductor portion 108 is not so decreased. Therefore, even if the moving element 101 and the repelling element 103 are in the maximum opening condition, the force to rotate the repelling element 103 in the opening direction is not extremely reduced. Further, even if current becomes small, the repelling element 103 is difficult to turn back so as to maintain the maximum distance between the contacts for a long period. As a result, it is easy to maintain the maximum arc voltage. In large current arc such as short-circuit current, it has been generally known that a metallic vapor flow is ejected from a leg of the arc on a contact surface in a direction perpendicular to the contact surface because of vaporization of the contact, and the vapor flow is an essential constituent component of the arc A. In the embodiment 1, the metallic vapor flow ejected from the surface of the traveling contact 102 collides with the insulator 118 covering the first conductor portion 107 so as to cool the arc A as shown in Fig. 18. As set forth above, the entire current path exerts the electromagnetic force on the arc A below the first conductor portion 107 in the direction of the terminal 105. As a result, the arc A is pressed for a cooling effect onto the insulator 118 of the first conductor portion 107, in particular, onto the inner end surface insulator 118c of the slit 170 of the first conductor portion 107. The cooling effect enables further increase of the arc voltage. As described hereinbefore, according to the embodiment 1, it is possible to rapidly rise the arc voltage immediately after the contact opening, and maintain the high arc voltage. As a result, it is possible to provide a circuit breaker having an excellent current-limiting performance. Embodiment 2 Fig. 19 is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 2. In the embodiment 1, a description and a illustration have been given with reference to a case where a contact surface between a traveling contact 102 and a repelling contact 104 is positioned above a first conductor portion 107 when a moving element 101 and a repelling element 103 are in a closing condition. However, in the embodiment 2, the first conductor portion 107 is positioned above a conductor portion 103a of the repelling element 103 and positioned above the contact surface between the traveling contact 102 and the repelling contact 104 at the closing time shown in Fig. 19. In such a configuration, it is possible to provide the same effects as those in the embodiment 1. According to the embodiment 2, even in case of small current cutoff in which the repelling element 103 is not operated, the repelling element 103 is positioned below the first conductor portion 107 as shown in Fig. 20, and the arc A exists below the first conductor portion 107 as well as above the first conductor portion 107. An entire current path including an area from the first conductor portion 107 to the repelling element 103 exerts electromagnetic force on the arc A in a direction of a terminal 105. Therefore, the arc A is largely stretched in the direction of the terminal 105, and is pressed onto an insulator 118 of the first conductor portion 107 so as to be cooled. As a result, in an electrode structure according to the embodiment 2, it is possible to enhance a cutoff performance at a time of small current cutoff. Embodiment 3 Fig. 21 is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 3. In the embodiment 3, a first conductor portion 107 is positioned above a conductor 103a of a moving element 101 at a closing time. In this configuration, it is possible to provide the same effect. Further, current in the first conductor portion 107 has the same direction as that of current in a conductor 101a of the moving element 101 so as to attract each other at a closing time of contacts. Accordingly, for an initial period at a time of short-circuit current cutoff, force to rotate the moving element 101 in an opening direction may include electromagnetic force generated by current in the first conductor portion 107 as well as electromagnetic repulsion generated by the repelling element 103. Therefore, rotation of the moving element 101 is accelerated for the initial period at the time of the short-circuit current cutoff so as to increase a contact opening speed, resulting in an enhanced current-limiting performance. As described in the above embodiments 1, 2 and 3, in case the terminal 105 is coplanar with the first conductor portion 107, the current in the terminal 105 and the current in the first conductor portion 107 can exert the same electromagnetic effect on the moving element 101, the repelling element 103 and the arc, resulting in a further improved current-limiting performance. Embodiment 4 Fig. 22 is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 4. In the embodiment 4, a terminal 105 and a first conductor portion 107 are continuously connected through a vertical third conductor portion 119 so as to position the terminal 105 above the first conductor portion 107. Further, a position of the third conductor portion 119 which can be surveyed from the side of a traveling contact 102 in an opening condition is coated with an insulator 118e. In the configuration, it is possible to provide the same effects as those in the embodiment 1. According to embodiment 4, current in the third conductor portion 119 has a direction opposed to that of current in an arc A so as to repel each other in an opening condition of the moving element 101 shown in Fig. 22. The arc A above the first conductor portion 107 extends in a direction of the terminal 105, and is turned back by current in the third conductor portion 119 so that the arc A never contacts a power source barrier 120. Consequently, it is advantageously possible to reduce damage to the power source barrier 120, and reduce hot gas of the arc discharged from an exhaust hole 117. Fig. 23 is a side view of an arc-extinguishing portion of a circuit breaker according to an alternative embodiment of the embodiment 4. In the alternative embodiment, the power source barrier 120 also serves as an insulator for the third conductor portion 119 instead of the insulator 118e of the third conductor portion 119 shown in Fig. 22. In this case, it is possible to provide the same effect. Embodiment 5 Fig. 24 is a side view of an electrode portion, showing an opening condition of a circuit breaker according to the embodiment 5. In the embodiment 5, in contrast with the embodiment 4, a terminal 105 and a first conductor portion 107 are continuously connected through a vertical third conductor portion 119 so as to position the terminal 105 below the first conductor portion 107, and a position of the third conductor portion 119 which can be surveyed from the side of a traveling contact 102 in an opening condition is coated with an insulator 118e. In the configuration, it is possible to provide the same effects as those in the embodiment 1. According to the embodiment 5, as shown in Fig. 24, current in the third conductor portion 119 has the same direction as that of current in an arc A so as to attract each other. Accordingly, force to stretch the arc A below the first conductor portion 107 in a direction of the terminal 105 is increased, and the arc A is further strongly pressed onto an insulator 118 so as to be cooled. As a result, it is possible to enhance a cooling effect, and improve a current-limiting performance. Embodiment 6 Fig. 25 is a side view of an electrode portion, showing an opening condition of a circuit breaker according to the embodiment 6. In the embodiment 6, a terminal 105 is continuously connected to a first conductor portion 107 through a third conductor portion 119, and is positioned below the first conductor portion 107, and the terminal 105 is positioned above a surface of a repelling contact 104 of a repelling element 103 positioned at a closing position in the configuration shown in Fig. 24. In such a configuration, it is possible to provide the same effects as those in the embodiment 5. According to the embodiment 6, current in the terminal 105 generates electromagnetic force in a direction of the terminal 105 to an arc A on the repelling contact 104 even if the repelling element 103 is not operated at a time of small current cutoff as shown in Fig. 25. Therefore, in an electrode structure of the embodiment 6, it is advantageously possible to increase the electromagnetic force to stretch the arc A, and enhance a small current cutoff performance. Embodiment 7 Fig. 26 is a side view of an electrode portion, showing an opening condition of a circuit breaker according to the embodiment 7. Fig. 27 is a side view of the electrode portion, showing an opening condition of a repelling element shown in Fig. 26. In the embodiment 7, a terminal 105 is continuously connected to a first conductor portion 107 through a third conductor portion 119, and is positioned below the first conductor portion 107 and below a surface of a repelling contact 104 of a repelling element 103 positioned at a closing position shown in Fig. 26. When the repelling element 103 is in the maximum opening condition, the terminal 105 is positioned above at least one portion 103b of the repelling element 103. In such a configuration, it is possible to provide the same effects as those in the embodiment 5. According to the embodiment 7, since the one portion 103b of the repelling element 103 is positioned below the terminal 105 at the maximum opening time of the repelling element 103, current in the terminal 105 generates electromagnetic force in an opening direction to the one portion 103b of the repelling element 103. Therefore, electromagnetic force generated by a moving element 101 and the first conductor portion 107 to open the repelling element 103 is decreased by rotation of the repelling element 103. However, the decreased electromagnetic force can be compensated to some extent by electromagnetic force generated by current in the terminal 105. As a result, it is possible to provide a circuit breaker having a further improved current-limiting performance. Fig. 28 is a side view showing an electrode portion in a condition where only a moving element is opened at a time of small current cutoff in a circuit breaker according to an alternative embodiment of the embodiment 7. Fig. 29 is a side view of the electrode portion, showing a condition where both the moving element and the repelling element are opened at a time of large current cutoff in Fig. 28. In the alternative embodiment, a conductor portion 106 is provided so as to position a rotating center P2 of the repelling element 103 below the terminal 105. In this case, it is possible to provide the same effects as those in the embodiment 125. Embodiment 8 Fig. 30 is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 8. In the embodiment 8, a first conductor portion 107 is connected to a repelling element 103 through a second conductor portion 108 between a rotating center P2 of the repelling element 103 and a repelling contact 104. In such a configuration, it is possible to provide the same effects as those in the embodiment 1. In the embodiment 8, entire current in the repelling element 103 flows on the side of the repelling contact 104 with respect to the rotating center P2. Magnetic field generated by a moving element 101 or a first conductor portion 107 exerts downward force on current in the repelling element 103. Therefore, if current flows in a conductor of the repelling element 103 with respect to the rotating center P2 on the side opposed to the secured repelling contact 104, the electromagnetic force to the current may serve as moment to rotate the repelling element 103 in a closing direction with respect to the rotating center P2. However, in the embodiment 8, no current flows on the side opposed to the side of the repelling contact 104 with respect to the rotating center P2. Accordingly, the entire electromagnetic force can serve as moment to rotate the repelling element 103 in the opening direction with respect to the rotating center P2. As a result, a rotation speed of the repelling element 103 can be further increased. Figs. 31 and 32 are side views showing an electrode portion according to each different alternative embodiment of the embodiment 8. In the alternative embodiment shown in Fig. 31, the first conductor portion 107 is connected to the repelling element 103 through the second conductor portion 108 at the rotating center P2 of the repelling element 103. In the alternative embodiment shown in Fig. 32, the second conductor portion 108 bypasses the rotating center P2 on the side opposed to a moving contact of the repelling element 103, and the second conductor portion 108 is connected to the repelling element 103 on the side of the repelling contact 104 with respect to the rotating center P2. In either case, it is possible to provide the same effects as those in the embodiment 8. Embodiment 9 Fig. 33(a) is a side view of an electrode portion, showing a closing condition of a circuit breaker according to the embodiment 9. Fig. 33(b) is a sectional view taken along line A-A of Fig. 33(a). In Fig. 33(b), a moving element in Fig. 33(a) is omitted. In the embodiment 9, a rotating center P2 of a repelling element 103 is provided between a second conductor portion 108 and a repelling contact 104 as shown in Fig. 33(a). As shown in Fig. 33(b), conductor portions 107a and 107b on both sides of a slit 170 of a first conductor portion 107 are integrally connected to the repelling element 103 through flexible conductors 108a and 108b of the second conductor portion 108. In such a configuration, in case large current such as short-circuit current flows at a closing time, parallel components of current in the flexible conductors 108a, 108b on both sides of the second conductor portion 108 attract each other as shown in Fig. 33(b). Thus, upward resultant force F is applied to the repelling element 103 because of flexibility of the flexible conductors 108a and 108b. A point of application of the resultant force F on the repelling element 103 is positioned at a position at which the flexible conductors 108a and 108b of the second conductor portion 108 are connected to the repelling element 103, that is, on the left side with respect to the rotating center P2 of the repelling element 103 in Fig. 33(a). Consequently, the resultant force F can serve as the moment to rotate the repelling element 103 in the opening direction. As a result, according to the embodiment 9, it is possible to transform the electromagnetic force applied to the second conductor portion 108 itself into the force to rotate the repelling element 103 in the opening direction, and improve a rotation speed of the repelling element 103. Embodiment 10 Fig. 34 is a side view showing an electrode portion of a circuit breaker according to the embodiment 10, and Fig. 35 is a sectional view of Fig. 34. In Fig. 34, Pa is a plane including a locus of a moving element 101 and a repelling element 103 at a switching time, N is a surface center point of a repelling contact 104, and Pb is a plane perpendiculartoa surface of the repelling contact 104, passing through the center point N, and perpendicular to the plane Pa. In Fig. 35, A is the center of gravity in a section of a conductor portion 103a of the repelling element 103, which is defined by the plane Pb. In Fig. 34, Pc is a plane passing through the center of gravity A and perpendicular to conductors 107a and 107b of a first conductor portion 107 on both sides of the plane Pa. Further, B and C shown in Fig. 35 are the respective centers of gravity in respective sections of the conductors 107a and 107b, which are defined by the plane Pc. In the embodiment 10, a triangle ABC is an isosceles triangle with a base BC, and has angles A and B set to θ (θ = 45° ± 10°) as shown in Fig. 35. In such a configuration, it is possible to provide the following advantages as well as the same effects as those in the embodiment 1. In the embodiment 10, when current I enters the terminal 105, uniform current 1/2 flows in the conductors 107a and 107b on both sides of the first conductor portion 107, and current I flows in the repelling element 103. It is approximately considered that these current pass through the centers of gravity B and C of the conductors 107a, 107b, and the center of gravity A. Assumed that the base BC of the isosceles triangle ABC shown in Fig. 35 has a middle point at the origin 0, and the x-axis be in a direction of OC and the y-axis be in a direction of OA. If current passing through the points B and C flows from the other side to this side facing Fig. 35, resultant magnetic field generated by the current at the point A has a direction of x. Since the current passing through the point A flows with respect to the view face from the other side to this side, the resultant magnetic field exerts electromagnetic force in a direction of y on the current in the point A. Therefore, the force to rotate in the opening direction is applied to the repelling element 103 by the current in the first conductor portion 107 as set forth above. When the resultant magnetic field is defined as Bx, it is possible to express as follows: Bx = K • µ 0 ⁢ lsin ⁢ 2 ⁢ θ / 4 ⁢ πL where K is a proportional constant, µ 0 is a magnetic permeability in vacuum, π is a circle ratio, L is a distance between the centers of gravity B and C. Obviously, Bx can have the maximum value for θ = 40°. When the maximum is defined as Bmax, Bx ≥ 0.94Bmax in a range of θ = 45° ± 10°. Accordingly, for the maximum value of magnetic field to rotate the repelling element 103 in the opening direction, which is generated by the conductors 107a and 107b on both sides of the first conductor portion 107 at the closing time, it is possible to exert at least 0.94 times or more the magnetic field on the repelling element 103 in an electrode structure of the embodiment 10. As a result, it is possible to improve a rotation speed of the repelling element 103 for an initial period at a time of short-circuit current cutoff. Embodiment 11 Fig. 36(a) is a side view showing an electrode portion of a circuit breaker according to the embodiment 129, and Fig. 36(b) is a sectional view of Fig. 36(a). In the drawings, a moving element 101 and an insulator 118 are omitted. In the embodiment 11, the centers of gravity of the conductors 107a and 107b on both sides of the first conductor portion 107, and the center of gravity of a conductor 103a of the repelling element 103 are respectively defined as B, C, and A as in the embodiment 128. Further, as shown in Fig. 36(b), base angles B, C (θ = θ') in a triangle ABC are set so as to have a value less than 45° when the repelling element 103 is in the opening condition. Fig. 37(a) is a side view of an electrode portion, showing an opening condition of the repelling element 103 shown in Fig. 36(a), and Fig. 37(b) is a sectional view of Fig. 37(a). As shown in Fig. 37(a), Pc' is a plane passing through the center of gravity A of the conductor 103a of the repelling element 103 and perpendicular to the conductors 107a and 107b of a first conductor portion 107 on both sides the first conductor portion 107 at the maximum opening time of the repelling element 103. As shown in Fig. 37(b), B', C' are respectively the centers of gravity in respective sections of the conductors 107a, 107b on both sides of the first conductor portion 107, and basic angles (θ = θ°) in a triangle AB'C' are set to a value of 40° or more. In such a configuration, it is possible to provide the following advantages as well as the same effects as those in the embodiment 1. As described in the embodiment 10, when θ = 45°, there is provided the maximum magnetic field applied to the repelling element 103, which is generated the current in the conductors 107a, 107b on both sides of the first conductor portion 107. Therefore, electromagnetic force applied to the repelling element 103 in the opening direction by the first conductor portion 107 is more increased as the repelling element 103 is rotated in an opening direction in an electrode structure according to the embodiment 11. As a result, though electromagnetic force to rotate the repelling element 103 in the opening direction which is generated by the moving element 101 is decreased according to the rotation of the repelling element 103, the decreased electromagnetic force can be compensated. Hence, it is possible to avoid a decreased rotation speed of the repelling element 103. In addition, when the repelling element 103 is rotated so as to have θ which is more than 45°, electromagnetic force to rotate the repelling element 103 in the opening direction which is generated by the first conductor portion 107 is decreased, resulting in reduced rotation of the repelling element 103. In case the repelling element 103 is in the maximum opening condition, a downward rotation of the repelling element 103 is stopped by a stopper 112. At this time, since the rotation speed of the repelling element 103 is decreased, impact of the repelling element 103 on the stopper 112 can be avoided. Consequently, it is possible to prevent damage to the stopper 112, and bounce of the repelling element 103. Figs. 38 and 39 are side views of an electrode portion, showing each different alternative embodiment of a circuit breaker according to the embodiment of the present invention. Although a first conductor portion 107 is substantially horizontally provided in the embodiments 1 to 11, the first conductor portion 107 may be provided in an inclined form as shown in Figs. 38 and 39. Fig. 40 is a plan view of an electrode portion showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention. Fig. 41 is a side view of Fig. 40, and Fig. 42 is a bottom view of Fig. 41. In the alternative embodiment, a surface coated with an insulator 118a includes a lower surface of the first conductor portion 107 as well as an upper surface of the first conductor portion 107 (a moving element 101 facing the surface at an opening time of the moving element 101). Figs. 43 and 44 are side views of an electrode portion, showing still further alternative embodiments of the circuit breaker according to the embodiment of the present invention. In the alternative embodiments, an insulator 118c covering an inner end surface of a slit 170 of a first conductor portion 107 is upward extended such that an arc A can contact a further increased area of the moving element 101 at an opening time of a moving element 101. Fig. 45(a) is a plan view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention. Fig. 45(b) Is a sectional view taken along line B-B of Fig. 45(a). In the alternative embodiment, a more increased thickness is provided for an insulator 118c covering an inner and surface of a slit 170 on the side of a terminal 105 which is most susceptible to damage by an arc than that of an insulator 118b in the insulators 118b, 118c covering an inner surface of the slit 170 of a first conductor portion 107. Fig. 46 is a plan view of an electrode portion, showing an alternative example. Fig. 47 is a plan view of Fig. 46 without a moving element. Though a second conductor portion 108 connecting a first conductor portion 107 to a repelling element 103 includes two flexible conductors 108a, 108b in the embodiments 1 to 9, 11 and 12, the second conductor portion 108 connecting the first conductor portion 107 to the repelling element 103 includes one flexible conductor in the alternative example. That is, a window-like opening 170' is provided in the first conductor portion 107 as shown in Fig. 47 instead of a U-shaped slit 170 in the first conductor portion 107 of the embodiments. Further, an end of the first conductor portion 107 on the side opposed to the side of a terminal 105 is integrally connected to the repelling element 103 through the second conductor portion 10B including one flexible conductor. The alternative example according to Figures 46 and 47 does not belong to the invention. Fig. 48 is a side view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention. Fig. 49 is a from view of Fig. 48 without a moving element and an insulator. In the alternative embodiment, trailing conductor portions 107c are integrally formed with a first conductor portion 107 having a slit 170 at ends of conductor portions 107a, 107b on both sides of the first conductor portion 107 on the side opposed to a terminal 105. Further, lower ends of the trailing conductor portions 107c are integrally connected through a horizontal conductor portion 170d, and the horizontal conductor portion 170d is integrally connected to the repelling element 103 through a second conductor portion 108 including one flexible conductor. Fig. 50 is a side view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the present invention. Fig. 51 is a front view of Fig. 50 without insulators. In the alternative embodiment, trailing second conductor portions 108 are integrally formed with a first conductor portion 107 having a slit 170 at ends of conductor portions 107a, 107b on both sides of the first conductor portion 107 on the side opposed to a terminal 105. Respective lower ends of the trailing second conductor portions 108 are integrally formed with bracket portions 120 between which a main portion of a repelling element 103 Is interposed. A rotating center shaft P2 of the repelling element 103 is supported by the bracket portions 120. Embodiment 12 Fig. 52 is a side view of an electrode portion, showing a closing condition of a repelling element of a circuit breaker according to the embodiment 12 of the invention. Fig. 53 is a side view of an electrode portion, showing an opening condition of a repelling element of Fig. 52. In the drawings, reference numeral 112 means a convex stopper whose upper surface is substantially parallel to a repelling element 103 holding a substantially horizontal position. Reference numeral 121 means a guide rod integrally coupled with a lower surface of the repelling element 103, and 122 means a guide hole provided in the stopper 112. The guide rod 121 is slidably inserted into the guide hole 122. Reference numerals 109a, 109b are press springs which are interposed between the repelling element 103 and the stopper 112, and the press springs 109a and 109b load the repelling element 103 in a closing direction. The embodiment 12 is different from the above embodiments in the following point. That is, while the repelling element 103 is rotated about a rotating center P2 so as to perform a switching action in the embodiments 1 to 8, 11 and 12, the repelling element 103 is vertically moved so as to perform a switching action in the embodiment 12. In such a configuration, it is possible to provide the same effects as those in the above embodiments. Fig. 54 is a perspective view of an electrode portion, showing a further alternative embodiment of the circuit breaker according to the embodiment of the invention. In the alternative embodiment, a first conductor portion 107 is provided with a conductor portion 107a only on the single side. In this case, the same effects can be provided. Although the respective embodiments 1 to 12 have been described with reference to a circuit breaker, the present invention may be applied to another switch in order to provide the same effects as those in the embodiments 1 to 12.

Claims: A switch comprising a moving element (101) having a travelling contact (102) at one end thereof, a repelling element (103) having a repelling contact (104) at a first end thereof and extending substantially parallel to said moving element, and said repelling element pivotally mounted so that said repelling contact is capable of making and breaking contact with said travelling contact, said repelling element comprising a repelling element conductor portion (103a), biasing means (109) for biasing said repelling element so that said repelling contact touches said travelling contact in a closed condition, a terminal (105) connected to a power source system, a conductor (107, 108) connecting said repelling element to the terminal, and said conductor including a first conductor portion (107) being straight and coplanar with said terminal (105), and a second conductor portion (108) connecting said first conductor portion (107) to said repelling element (103) at an end of the side opposed to said repelling contact (104), and wherein said repelling element conductor portion (103a) is positioned below said first conductor portion (107) such that when a large current flows through said switch, current in said repelling element conductor portion (103a) has a direction opposed to that of current in said first conductor portion (107), and an electromagnetic repulsion is applied between said repelling element (103) and said first conductor portion (107) to rotate said repelling element (103) in the opening direction, characterized in that said biasing means (109) is connected to a second end of said repelling element and that said first conductor portion (107) is substantially flat U-shaped or flat L-shaped and is positioned between said travelling contact (102) and said repelling contact (104) when said moving element (101) and said repelling element (103) are opened so as to be connected to said terminal (105). A switch according to claim 1, wherein said first conductor portion (107) is connected at one end thereof to a terminal (105) such that said first conductor portion (107) is positioned above surfaces of said travelling contact (102) and said repelling contact (104) when said moving element (101) and said repelling element (103) are closed. A switch according to claim 1, further comprising an insulator (118) covering at least a portion of said first conductor portion (107) wherein an arc resulting from opening said travelling contact (102) and said repelling contact (104) is pressed onto said insulator so as to generate and maintain a high arc voltage. A switch according to claim 1, further comprising stopper means (112) disposed below said repelling element (103) for defining a maximum opening position of said repelling element (103). A switch according to claim 2, further comprising an insulator (118) covering at least a portion of said first conductor portion (107) wherein an arc resulting from opening said travelling contact (102) and said repelling contact (104) is pressed onto said insulator so as to generate and maintain a high arc voltage. A switch according to claim 1, wherein said moving element (101) comprises a moving element conductor (101a) to which said travelling contact (102) is connected and said first conductor portion (107) is positioned above said moving element conductor when said moving element (101) and said repelling element (103) are closed. A switch according to claim 1, wherein said second conductor portion (108) connects said first conductor portion (107) to said repelling element (103) at a position between a pivot point (P2) of said repelling element (103) and said repelling contact (104). A switch according to claim 1, wherein said first conductor portion (107) comprises means (107a, 107b) forming a slit (170) to allow a switching action of said moving element (101) and said repelling element (103), said means (107a, 107b) forming a slit (170) comprising two arms extending substantially parallel to one another connected at one end by a connecting portion. A switch according to claim 8, further comprising a first insulator (118) covering at least one surface of said connecting portion and a second insulator (118) continuously formed with said first insulator covering at least one surface of said arms. A switch according to claim 9, wherein said second conductor portion (108) connects said first conductor portion (107) to said repelling element (103) at a point-on an opposite side of a pivot point (P2) of said repelling element (103), said second conductor portion (108) comprising two flexible conductors (108a, 108b) connected between a respective one of said arms (107a, 107b) and said repelling element (103). A switch according to claim 10, wherein said moving element (101) and said repelling element (103) are disposed according to the following relationship a plane (Pa) includes a locus described by movement of said moving element (101) and said repelling element (103), a plane (Pb) is a plane perpendicular to a surface of said repelling element (103), passing through a center point of said repelling contact (104), and passing through a center of gravity A in a section of said repelling element conductor portion (103a), a plane (Pc) is a plane passing through said center of gravity A and perpendicular to said arms (107a or 107b) of said first conductor portion (107) on both sides of said plane (Pa), B and C centers of gravity in respective arms (107a, 107b) which are defined by plane (Pc), and wherein a triangle ABC is an isosceles triangle with a base BC and angle AB set to θ where (θ = 45° ± 10°). A switch according to claim 10, wherein said moving element (101) and said repelling element (103) are disposed according to the following relationship a plane (Pa) includes a locus described by movement of said moving element (101) and said repelling element (103), a plane (Pb) is a plane perpendicular to a surface of said repelling element (103), passing through a center point of said repelling contact (104), and passing through a center of gravity A in a section of said repelling element conductor portion (103a), a plane (Pc) is a plane passing through said center of gravity A and perpendicular to said arms (107a, 107b) of said first conductor portion (107) on both sides of said plane (Pa), B and C centers of gravity in respective arms (107a, 107b) which are defined by plane (Pc), and wherein triangle ABC is an isosceles triangle with a base BC and angles AB set to θ' where (θ' < 45°) when said repelling element (103) is in an opening condition. A switch comprising a moving element (101) having a travelling contact (102) at one end thereof, a repelling element (103) having a repelling contact (104) at a first end thereof and extending substantially parallel to said moving element, and said repelling element pivotally mounted so that said repelling contact is capable of making and breaking contact with said travelling contact, said repelling element comprising a repelling element conductor portion (103a), biasing means (109) for biasing said repelling element so that said repelling contact touches said travelling contact in a closed condition, a terminal (105) connected to a power source system, a conductor (107, 108) connecting said repelling element to said terminal, and said conductor including a first conductor portion (107), a second conductor portion (108) connecting said first conductor portion (107) to said repelling element (103) at an end of the side opposed to said repelling contact (104), and wherein said repelling element conductor portion (103a) is positioned below said first conductor portion (107) such that when a large current flows through said switch, current in said repelling element conductor portion (103a) has a direction opposed to that of current in said first conductor portion (107), and an electromagnetic repulsion is applied between said repelling element (103) and said first conductor portion (107) to rotate said repelling element (103) in the opening direction, characterized in that said biasing means (109) is connected to a second end of said repelling element, that said first conductor portion (107) is substantially flat U-shaped or flat L-shaped and is positioned between said travelling contact (102) and said repelling contact (104) when said moving element (101) and said repelling element (103) are opened so as to be connected to said terminal (105), said terminal (105) being positioned below said first conductor portion (107) of said conductor (107, 108), and that a vertical third conductor portion (119) continuously connecting said terminal (105) and said first conductor portion (107) is arranged. A switch according to claim 13, further comprising an insulator (118e) covering a portion of said third conductor portion (119) which can be surveyed from a side of said travelling contact (102) in an opening condition. A switch according to claim 13, wherein said terminal (105) is positioned above a surface of said repelling contact (104) in a closing condition. A switch according to claim 13, wherein said terminal (105) is positioned below a surface of said repelling contact (104) in a closing condition and when said repelling element (103) is in a maximum opening condition, said terminal (105) is positioned above at least a portion of said repelling element (103). A switch comprising a moving element (101) having a travelling contact (102) at one end thereof, a repelling element (103) having a repelling contact (104) at a first end thereof and extending substantially parallel to said moving element, and said repelling element pivotally mounted so that said repelling contact is capable of making and breaking contact with said travelling contact, said repelling element comprising a repelling element conductor portion (103a), biasing means (109) for biasing said repelling element so that said repelling contact touches said travelling contact in a closed condition, a terminal (105) connected to a power source system, a conductor (107, 108) connecting said repelling element (103) to the terminal (105), and said conductor including a first conductor portion (107), and a second conductor portion (108) connecting said first conductor portion (107) to said repelling element (103) at an end of the side opposed to said repelling contact (104), and wherein said repelling element conductor portion (103a) is positioned below said first conductor portion (107) such that when a large current flows through said switch, current in said repelling element conductor portion (103a) has a direction opposed to that of current in said first conductor portion (107), and an electromagnetic repulsion is applied between said repelling element (103) and said first conductor portion (107) to rotate said repelling element (103) in the opening direction, characterized in that said biasing means (109) is connected to a second end of said repelling element, and that said first conductor portion (107) is substantially flat U-shaped or flat L-shaped and is positioned between said travelling contact (102) and said repelling contact (104) when said moving element (101) and said repelling element (103) are opened so as to be connected to said terminal (105), said first conductor portion (107) being inclined with respect to said terminal (105).

Inventors: HUKUYA KAZUNORI, MITSUHASHI TAKAO, NISHINA KENICHI, TAKAHASHI MITSUGU, YAMAGATA SHINJI, HUKUYA, KAZUNORI, MITSUHASHI, TAKAO, NISHINA, KENICHI, TAKAHASHI, MITSUGU, YAMAGATA, SHINJI, Hukuya, Kazunori, c/o Mitsubishi Denki K. K., MITSUHASHI, TAKAO, C/O MITSUBISHI DENKI K. K., NISHINA, KENICHI, C/O MITSUBISHI DENKI K. K., Takahashi, Mitsugu, c/o Mitsubishi Denki K. K., YAMAGATA, SHINJI, C/O MITSUBISHI DENKI K. K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: H01H9
IPC codes: H01H9, H01H77