CURRENT LIMITING DEVICE

Abstract

 The present invention relates to a current limiting device, which is for limiting an overcurrent generated during a short-circuit fault etc. occurred in a power system, and includes: a current limiting resistor (20) connected between fixed electrodes (4, 5); a plurality of separable contact members (11) which are provided adjacent to each other and form a parallel circuit with the current limiting resistor (20) during a steady-state current; a contact driving portion which separates (open-contact) the contact members (11) by the overcurrent generated in the power system; separation members (12, 13) engaged with the contact members (11) to make separation intervals of the plurality of contact members (11) substantially equal; and a plurality of springs (14 - 19) which bias the separation members (12, 13). The spring force of each spring (14 - 19) is configured to be larger as the spring is located farther from the contact driving portion.

Description

TECHNICAL FIELD

[0001] The present invention relates to a current limiting device which is for limiting (suppressing) an overcurrent (short-circuit current) generated, for example, during the occurrence of a short-circuit fault or the like in a power system.

BACKGROUND ART

[0002] A conventional current limiting device includes: a high-resistance current limiting resistor which is electrically connected between, for example, a power supply side electrical path and a load side electrical path in a power system and is for suppressing an overcurrent when the overcurrent flows in the power system; a plurality of separable contact members which are electrically connected in parallel with the current limiting resistor and are provided adjacent to each other as a low-resistance steady-state electrical path portion that carries a current during a steady state; a contact driving portion which is driven by the overcurrent generated in the power system and separates contacts of the plurality of contact members; separation members which are engaged with engaging portions provided on the side surfaces of the contact members when the contacts are separated and make separation intervals of the plurality of contacts substantially equal; single pushing springs which make the separation members engage with engaging portions of the contact members; and the like. (For example, Patent Document 1.)

RELATED ART DOCUMENT

PATENT DOCUMENT

[0003] Patent Document 1: JP-A-2010-252620

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In the current limiting device described above, when the overcurrent flows in the power system, the overcurrent flows in an electromagnetic coil of the contact driving portion and a contact of the contact members, which is near the contact driving portion, is first forcibly separated (open-contacted) by electromagnetic force generated by the electromagnetic coil. The remained contact members sequentially move from one nearer the contact driving portion toward a space generated by the forcible separation and a contact is separated (open-contacted). In order to accelerate this separation operation, the separation members are engaged with the engaging portions provided on the side surfaces of the contact members; and in a state of completely engaged, separation intervals of the plurality of contacts are made substantially equal. The engagement with the contact members of the separation member is made by the biasing force of the single pushing springs; and thus, the force that separates the contact members equally acts on the plurality of contact members provided adjacent to each other. Accordingly, problems exist in that separation of a contact at a far position from the contact driving portion is delayed, it takes a time to perform commutation of the overcurrent to the current limiting resistor, and current limiting performance is deteriorated.

[0005] The present invention has been made to solve the above described problem, and an object of the present invention is to provide a current limiting device which can improve current limiting performance by smoothly performing contact separation operation when an overcurrent flows in a power system.

MEANS FOR SOLVING THE PROBLEMS

[0006] According to the present invention, there is provided a current limiting device including: a current limiting resistor electrically connected between a power supply side electrical path and a load side electrical path of a power system; a plurality of separable contact members which form a parallel circuit with the current limiting resistor during a steady-state current and are provided adjacent to each other; a contact driving portion which is driven by an overcurrent generated in the power system and separates contacts of the plurality of contact members; and separation members which are engaged with engaging portions provided on the side surfaces of the contact members when the contacts are separated and make separation intervals of the plurality of contacts substantially equal. The current limiting device further includes a plurality of springs by which the separation members are made to engage with the engaging portions of the contact members and in which the spring force of the plurality of springs is set to be larger as the spring is arranged at a farther position from the contact driving portion.

ADVANTAGEOUS EFFECT OF THE INVENTION

[0007] According to the current limiting device of the present invention, there are provided the plurality of springs by which the separation members, which make separation intervals of the plurality of contacts substantially equal when the contacts are separated, are made to engage with the engaging portions of the contact members; and the spring force of the plurality of springs is set to be larger as the spring is arranged at a farther position from the contact driving portion, whereby separation of the contact at the farther position from the contact driving portion is accelerated. As a result, there can be obtained the current limiting device in which commutation of an overcurrent to the current limiting resistor is accelerated and current limiting performance can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] 

FIG. 1 is a sectional view showing the configuration of a current limiting device in Embodiment 1 of the present invention;

FIG. 2 is a sectional view showing an operation state of the current limiting device in Embodiment 1 of the present invention;

FIG. 3 is a general outline view showing the relevant part configuration of a current limiting device in Embodiment 2 of the present invention; and

FIG. 4 is a general outline view showing the relevant part configuration of a current limiting device in Embodiment 3 of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, the present invention will be described based on drawings of embodiments. Incidentally, identical or equivalent members will be described with the same reference numerals assigned thereto.

Embodiment 1.

[0010] FIG. 1 is a sectional view showing the configuration of a current limiting device in Embodiment 1 of the present invention; and FIG. 2 is a sectional view showing a current limiting operation state of the current limiting device in Embodiment 1 of the present invention.

[0011] In FIG. 1, an upper side frame 1 and a lower side frame 2 are provided so as to face to each other at an interval and are coupled to each other by a plurality of coupling frames 3. A first fixed electrode 4 and a second fixed electrode 5 are provided at an interval from each other in a longitudinal direction on the lower surface of the upper side frame 1. The first fixed electrode 4 is connected to either one side of a load side electrical path and a power supply side electrical path of a power system (alternating current).

[0012] A fixed core 6 is fixed to the upper surface of the lower side frame 2; and an electromagnetic coil 7 and a plurality of pressing springs 8 are provided on a central portion of the upper surface of the fixed core 6. The electromagnetic coil 7 is formed by a conductor passing through the upper surface of the fixed core 6; one end portion of the conductor of the electromagnetic coil 7 is connected to the other side of the load side electrical path and the power supply side electrical path of the power system; and other end portion of the conductor of the electromagnetic coil 7 is connected to the second fixed electrode 5. Thus, the electromagnetic coil 7 generates electromagnetic force according to the size of a current flowing in the power system. Furthermore, there is arranged the pressing spring 8 having spring force larger than the electromagnetic force of the electromagnetic coil 7 when a steady-state current flows in the electromagnetic coil 7.

[0013] A plate-like movable core 9 mounted on an upper end portion of the pressing springs 8 and a movable electrode 10 fixed to the upper surface of the movable core 9 are provided between the fixed electrode 4, 5 and the fixed core 6. The movable core 9 and the movable electrode 10 are biased from the fixed core 6 toward the fixed electrode 4, 5 by the pressing springs 8 and are suctioned from the fixed electrode 4, 5 side to the fixed core 6 side by electromagnetic force generated when an overcurrent flows in the electromagnetic coil 7. More specifically, the movable core 9 and the movable electrode 10 are configured so as to be integrally displaceable between a short-circuit position, at which an electrical short-circuit is made between the first fixed electrode 4 and the second fixed electrode 5, and a current limiting position, which is at a position on the fixed core 6 side (on the side opposite to the fixed electrode 4, 5) from the short-circuit position and is for limiting an overcurrent flowing to the power system. As described above, there is configured a contact driving portion which drives contact members (to be described later) by the fixed core 6, the electromagnetic coil 7, the pressing springs 8, and the movable core 9.

[0014] Between the fixed electrode 4, 5 and the movable electrode 10, there are provided: a pair of a plurality of contact members 11 adjacent to each other so as to be continued; a pair of inner separation members 12 which are arranged on the middle in the longitudinal direction of the movable electrode 10 (in the left/right direction of FIG. 1) so as to be along the plurality of contact members 11 and are pointed in the opposite directions to each other; and a pair of outer separation members 13 which are arranged on both end portions in the longitudinal direction of the movable electrode 10 and are faced to the respective inner separation members 12. Incidentally, the contact member 11 is made of, for example, metal containing at least any one of copper, silver, or aluminum.

[0015] Each electrode 4, 5, 10 and each contact member 11 adjacent thereto are joined to each other to be electrically connected when the current limiting device is in a steady state. Furthermore, the contact members 11 adjacent to each other in a vertical direction are separable from each other between one side lower surface and the other side upper surface. Further, the contact member 11 has: a pair of parallel surfaces 11b which are for joining to other contact member 11 or each electrode 4, 5, 10; and concave engaging portions 11a provided on each surface facing the separation members 12, 13. The concave engaging portion 11a is configured by, for example, a V-shaped concave engaging portion recessed in a V-shape to the longitudinal inner side from each end portion of the pair of parallel surfaces 11b. More specifically, a cross-sectional shape of the contact member 11 is configured in a hand drum shape. Further, the contact members 11 receive the spring force of the pressing springs 8 via the movable core 9 and the movable electrode 10; and the contact members 11 adjacent to each other are press-contacted by the spring force of the pressing springs 8.

[0016] The inner separation member 12 and the outer separation member 13 are each configured by an insulator and are each formed with a plurality of engaging projections 12a, 13a. The engaging projections 12a, 13a are each tapered off to a point (tapered shape) toward the V-shaped concave engaging portion 11a of the contact member 11 facing each other and are each formed fittably to the V-shaped concave engaging portion 11a of the contact member 11.

[0017] Furthermore, the inner separation members 12 and the outer separation members 13 are displaceable between an insertion position, which serves as a position where the engaging projections 12a, 13a are inserted in the V-shaped concave engaging portions 11a of the contact members 11 adjacent to each other to separate the contact members 11 from each other, and an extraction position, which serves as a position where the engaging projections 12a, 13a are pulled back from the insertion position to the sides opposite to the contact members 11 and are extracted from the concave engaging portions 11a of the contact members 11 adjacent to each other. A plurality of inner springs 14, 15, 16 are arranged on the back surface (surface on the opposite side of the continuous inclined surface) of each inner separation member 12 in the vertical direction; and each inner separation member 12 is biased toward the contact members 11 by the spring force of the inner springs 14, 15, 16.

[0018] Furthermore, one end portions of a plurality of outer springs 17, 18, 19 are fixed to the back surface (surface on the opposite side of the continuous inclined surface) of each outer separation member 13; and other end portions of the outer springs 17, 18, 19 are fixed to the coupling frame 3. The outer separation member 13 is biased toward the contact members 11 by the spring force of the outer springs 17, 18, 19. In this case, a spring constant of each spring 14, 15, 16, 17, 18, 19 is configured to be larger as the spring is arranged at a farther position (more upper side) from the contact driving portion.

[0019] When the movable core 9 and the movable electrode 10 are displaced from the short-circuit position to the current limiting position, each separation member 12 is made to displace from the extraction position to the insertion position by the spring force of the springs 14, 15, 16 and each separation member 13 is made to displace from the extraction position to the insertion position by the spring force of the springs 17, 18, 19. Then, each separation member 12, 13 is displaced to the insertion position and thus the contact members 11 adjacent to each other are separated from each other. Together with this, the engaging projections 12a, 13a of the respective separation members 12, 13 and the concave engaging portions 11a of the contact members 11 are fitted into each other.

[0020] Furthermore, each uppermost engaging projection 12a, 13a of the engaging projections 12a, 13a of the respective separation members 12, 13 faces each concave engaging portion 11a of the contact member 11 arranged so as to come in contact with each fixed electrode 4, 5.

[0021] Further, in the engaging projections 12a, 13a of the respective separation members 12, 13 and the concave engaging portions 11a of the contact member 11, the positional relationship of upper inclined surfaces between an outer wall of the engaging projection 12a and an inner wall of the concave engaging portion 11a and between an outer wall of the engaging projection 13a and an inner wall of the concave engaging portion 11a is the same with each other when the movable electrode 10 is at the short-circuit position.

[0022] Then, when the engaging projections 12a, 13a of the respective separation members 12, 13 and the concave engaging portions 11a are fitted into each other, separation intervals of the contact members 11 adjacent to each other are substantially equally spaced at any position. An interval between the inclined surfaces of the outer wall of the engaging projection 12a and the inner wall of the concave engaging portion 11a at the extraction position of the separation member 12 and an interval between the inclined surfaces of the outer wall of the engaging projection 13a and the inner wall of the concave engaging portion 11a at the extraction position of the separation member 13 are set to an interval so that the outer walls of the engaging projections 12a, 13a are capable of coming in contact with the inner walls of the V-shaped concave engaging portions 11a when each separation member 12, 13 is at the insertion position. Furthermore, even when the engaging projections 12a, 13a of the respective separation members 12, 13 and the concave engaging portions 11a of the contact members 11 are fitted into each other, a joined state of each electrode 4, 5, 10 and the contact member 11 adjacent thereto is maintained.

[0023] A current limiting resistor 20 which is for limiting (suppressing) a current flowing in the inside is connected between the first fixed electrode 4 and the second fixed electrode 5. In this case, a pair (two lines) of electrical path formation portions which are for forming an electrical path between the power supply side electrical path and the load side electrical path are constituted by: the first fixed electrode 4, the movable electrode 10, and the plurality of contact members 11 arranged between the first fixed electrode 4 and the movable electrode 10; and the second fixed electrode 5, the movable electrode 10, and the plurality of contact members 11 arranged between the second fixed electrode 5 and the movable electrode 10. The pair of electrical path formation portions share the same movable electrode 10 and form a series of electrical paths via the movable electrode 10. Furthermore, the electrical path formation portions form a steady-state electrical path which is for flowing a steady-state current between the power supply side electrical path and the load side electrical path by the respective contact members 11 when the movable electrode 10 is at the short-circuit position. Further, the steady-state electrical path forms an electrical path in parallel with the current limiting resistor 20 connected between the first fixed electrode 4 and the second fixed electrode 5.

[0024] In the electrical path formation portions, the contact members 11 adjacent to each other are separated when the movable electrode 10 is at the current limiting position; and the current limiting resistor 20 electrically connects between the power supply side electrical path and the load side electrical path and thereby forming a current limiting electrical path which is for limiting an overcurrent flowing between the power supply side electrical path and the load side electrical path.

[0025] Therefore, when the steady-state current flows in the power system, the contact driving portion makes the contact members 11 adjacent to each other press-contact to form the steady-state electrical path in the electrical path formation portions. At this time, the respective separation members 12, 13 are maintained at the pulled back extraction position.

[0026] Furthermore, when the contact driving portion receives the overcurrent from the power system, the contact driving portion suctions the movable core 9 to draw down the movable electrode 10; and associated with this, the contact members 11 adjacent to each other are made to separate, respectively, to form the current limiting electrical path in the electrical path formation portions. At this time, the separation members 12 are pushed forward by the springs 14, 15, 16; the separation members 13 are pushed forward by the springs 17, 18, 19; and thus, the separation members 12, 13 are displaced from the extraction position to the insertion position to maintain a separation state of the contact members 11.

[0027] Next, the operation of such a current limiting device will be described.

[0028] First, when the steady-state current flows in the power system, the spring force of the pressing springs 8 is set larger than the electromagnetic force generated from the electromagnetic coil 7; and thus, the movable electrode 10 is maintained at the short-circuit position; the respective separation members 12, 13 are maintained at the extraction position; and the steady-state electrical path is formed between each of the fixed electrodes 4, 5 and the movable electrode 10 by the contact members 11 adjacent to each other. At this time, the current flows in the order from the first fixed electrode 4 to the contact members 11 continued into the first fixed electrode 4 side, the movable electrode 10, the contact members 11 continued into the second fixed electrode 5 side, the second fixed electrode 5, and the electromagnetic coil 7; and then, the current reversely flows by inversion of phases of alternating current.

[0029] On the other hand, when an overcurrent is generated in the power system, the overcurrent flows in the electromagnetic coil 7; and thus, the electromagnetic force generated from the electromagnetic coil 7 becomes larger than the spring force of the pressing springs 8; and the movable core 9 and the movable electrode 10 are suctioned by the electromagnetic force and are displaced from the short-circuit position to the current limiting position. Then, when the movable electrode 10 is displaced from the short-circuit position to the current limiting position, a press-contacted state of the respective contact members 11 is released; and the separation members 12 are displaced from the extraction position to the insertion position by the spring force of the springs 14, 15, 16 and the separation members 13 are displaced from the extraction position to the insertion position by the spring force of the springs 17, 18, 19. Therefore, the engaging projections 12a of the separation member 12 and the engaging projections 13a of the separation member 13 are pushed into the V-shaped concave engaging portions 11a of the contact members 11 adjacent to each other, respectively; and thus, the engaging projections 12a of the separation member 12 and the concave engaging portions 11a of the contact members 11 are fitted to each other and the engaging projections 13a of the separation member 13 and the concave engaging portions 11a of the contact members 11 are fitted to each other. This separates between the respective contact members 11 to make the separation intervals substantially equal as shown in FIG. 2; and thus, the steady-state electrical path between each of the fixed electrodes 4, 5 and the movable electrode 10 is eliminated and only the current limiting electrical path permitting a path of the current limiting resistor 20 served as the parallel circuit is remained. As a result, the overcurrent is limited by the current limiting resistor 20.

[0030] The contact separation operation will be further described in detail. Incidentally, in the following description, the description will be made such that a position near to the contact driving portion is referred to as the lower side and a position far therefrom is referred to as the upper side. The movable core 9 and the movable electrode 10 are displaced from the short-circuit position to the current limiting position by the electromagnetic force generated by the electromagnetic coil 7 due to the overcurrent generated in the a power system; and thus, separation (open-contact) is first forcibly performed between the lowermost contact member 11 joined to the movable electrode 10 and the second contact member 11 from the lower side. A plurality of remained contact members 11 are separated toward a space (in the lower side direction) generated by the displacement. More specifically, the separation operation of the plurality of remained contact members 11 is made by free fall of the contact members 11 and by biasing the separation members 12 toward the contact members 11 by the springs 14, 15, 16 and by biasing the separation members 13 toward the contact members 11 by the springs 17, 18, 19, the springs being for assisting the free fall; and the separation is sequentially made from the lower side contact member 11. The separation members 12 are biased toward the adjacent contact members 11 by the spring force of the springs 14, 15, 16 and the separation members 13 are biased toward the adjacent contact members 11 by the spring force of the springs 17, 18, 19, the spring constant of each of the plurality of springs 14, 15, 16, 17, 18, 19 being set to be larger as the spring is located at more upper side.

[0031] In the case of the separation operation, as described above, the lowermost contact member 11 of the contact members 11 adjacent to each other is first forcibly separated; and therefore, a potential difference larger than a minimum arc generation voltage at which an arc is generated (an arc is generated) between the lowermost contact member 11 and the second contact member 11 from the lower side. By providing the plurality of contact members 11, the arc generation voltage generated between the contact members 11 which are separated first is divided between other contact members 11 to be set smaller than the minimum arc generation voltage to eliminate the arc; and commutation is performed to the current limiting resistor 20. Therefore, as compared to the conventional current limiting device in which the biasing force applied to the plurality of contact members 11 is equal by using the single spring, in the current limiting device of the present invention, the plurality of springs (respective springs 14, 15, 16, 17, 18, 19) which bias the separation members 12, 13 are provided; and the spring constant is set to be larger as the spring is arranged at more upper side. Therefore, separation of the upper side contact member 11 can be accelerated and faster separation speed of the contact members 11 adjacent to each other makes the voltage division between the plurality of contact members more smoothly. Thus, deterioration of the contact members 11 due to the arc can be suppressed and current limiting operation is also accelerated; and therefore, current limiting performance can be improved.

[0032] Incidentally, the spring constant of each spring 14, 15, 16, 17, 18, 19 can be set by changing the winding diameter of the spring, the number of turns of the spring, the diameter of the spring, and material of the spring.

Embodiment 2.

[0033] FIG. 3 is a general outline view showing a relevant part of a current limiting device in Embodiment 2 of the present invention.

[0034] In the above described Embodiment 1, the description has been made on the case where the separation members 12 are pressed by the plurality of springs 14 to 16 and the separation members 13 are pressed by the plurality of springs 17 to 19, toward the side surfaces of the adjacent contact members 11, respectively; however, as shown in FIG. 3, it may be configured such that separation members 12, 13 are drawn by a plurality of springs 21, 22, 23 toward the side surfaces of adjacent contact members 11, respectively. Incidentally, a spring constant of each 21, 22, 23 is set to be larger as the spring is arranged at a farther position from the contact driving portion, as in Embodiment 1. As described above, the separation members 12, 13 are configured so as to be pulled by the springs 21, 22, 23 whose spring constant is sequentially changed; and thus, separation of the contact member 11 placed far from the contact driving portion can be accelerated as in Embodiment 1, and the same effect as Embodiment 1 can be obtained. Further, as compared to Embodiment 1, the inner springs 14, 15, 16 are not required and the number of springs can be reduced.

Embodiment 3.

[0035] FIG. 4 is a general outline view showing a relevant part of a current limiting device in Embodiment 3 of the present invention.

[0036] In the above described Embodiment 2, the description has been made on the case where the spring constant of each spring 21, 22, 23 is set to be larger as the spring is arranged at the farther position from the contact driving portion. However, as shown in FIG. 4, it may be such that the ratio of expansion and contraction of the same spring 22 is changed by setting a mounting interval of the same spring 22 to be larger as the spring is arranged at a farther position from the contact driving portion and larger drawing force is obtained as the spring 22 is arranged at the farther position from the contact driving portion; and types of springs can be reduced in addition to the effect of Embodiment 2.

[0037] Incidentally, there can also be obtained larger drawing force as the spring is arranged at a farther position from the contact driving portion by setting a mounting interval of the spring to be constant and by setting the free length of the spring to be shorter as the spring is arranged at the farther position from the contact driving portion.

[0038] Incidentally, the present invention can freely combine and appropriately change and/or omit the respective embodiments, within the scope of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

[0039] 

1: Upper side frame, 2: Lower side frame,

3; Coupling frame, 4: First fixed electrode,

5: Second fixed electrode, 6: Fixed core,

7: Electromagnetic coil, 8: Pressing spring,

9: Movable core, 10: Movable electrode,

11: Contact member, 12, 13: Separation member,

14 to 19: Pressing spring,

20: Current limiting resistor,

21 to 23: Tension spring

Claims

1. A current limiting device comprising:

a current limiting resistor electrically connected between a power supply side electrical path and a load side electrical path of a power system;

a plurality of separable contact members which form a parallel circuit with said current limiting resistor during a steady-state current and are provided adjacent to each other;

a contact driving portion which is driven by an overcurrent generated in the power system and separates contacts of the plurality of contact members; and

separation members which are engaged with engaging portions provided on the side surfaces of said contact members when the contacts are separated and make separation intervals of the plurality of contacts substantially equal,

said current limiting device further comprising:

a plurality of springs by which said separation members are made to engage with the engaging portions of said contact members and in which the spring force of the plurality of springs is set to be larger as said spring is arranged at a farther position from said contact driving portion.

2. The current limiting device according to claim 1,
wherein the engaging portions of said contact members and said separation members are formed by a V shaped concave portion and a V shaped convex portion to be engaged with each other.

3. The current limiting device according to claim 1 or 2,
wherein said springs are configured such that said separation members are pressed to the side surfaces of said contact members.

4. The current limiting device according to claim 1 or 2,
wherein said springs are configured such that said separation members are drawn to the side surfaces of said contact members.

5. The current limiting device according to any one of claims 1 to 4,
wherein said springs are configured such that the size of the spring force is changed depending on a difference in spring constant.

6. The current limiting device according to any one of claims 1 to 4,
wherein said springs are configured such that the size of the spring force is changed depending on a difference in the ratio of expansion and contraction of said spring.

Drawing