POWER SCHWITCHGEAR DEVICE

Abstract: A power switchgear device comprising: a fixed contact-­ maker (13) having a stationary contact (13a); a movable contact (11a) arranged opposite to the stationary contact (13a) carried by a movable contact-maker (11), an arc runner (13b) electrically connected to the fixed contact-maker (13); a commutation electrode (22) arranged for taking current during disconnection, and a deionisation grid (21), wherein said movable contact (11a), said arc runner (13b) and said commutation electrode (22) are arranged such that the shortest distance (X₀) between said arc runner (13b) and the side of said movable contact-maker (11) remote from a side carrying said movable contact (11a) becomes greater than the shortest distance (Y) between said commutation elec­ trode (22) and said arc runner (13b) when said contacts are moved apart, characterised in that said deionisation grid (21) is arranged between said commutation electrode (22) and a part of said arc runner (13b).

Description: The present invention relates to a power switchgear device comprising: a stationary contact-maker having a stationary contact; a movable contact arranged opposite to said stationary contact carried by a movable contact maker; an arc runner electrically connected to the fixed contact-maker; a commutation electrode arranged for taking current during disconnection; and a deionisation grid comprising a plurality of plates extending parallel to the direction of movement of the movable contact maker. Such a device is known from DE-B-1 051 935. In this device however the distance between the contacts, when fully open, is less than the distance between the commutation electrode and the arc runner. The document makes no suggestion of driving the arc rapidly from the contacts to avoid contact wear. Furthermore, the deionisation grid is arranged between the commutation electrode and a wall of a housing of the device, and the arc runner terminates below the grid. During disconnection, the arc must therefore jump from the arc runner to the grid. Another electrical switching device is known from DE-A-2 826 243. Again, the distance between the contacts, when fully open, is less than the distance between the commutation electrode and the arc runner. Figs. 1 to 4 of the accompanying drawings represent another example of conventional power switchgear. In the drawings, 1 denotes a mounting formed of a metallic steel plate, which is provided with a plurality of fitting holes 1a (see Fig. 3) used to arrange a power switchgear body therethrough; 2 denotes a base formed of an insulating material, which is fixed on the mounting plate 1 with a screw 3; 4 denotes a fixed core having a silicon steel plate laminated thereon. An operating coil 5 is installed on the fixed core 4, and further a leaf spring 6 is arranged in a gap with the mounting plate 1 as a shock absorber. Numeral 7 denotes a moving core arranged opposite to the fixed core 4, which is pulled toward the fixed core 4 when the operating coil 5 is conducting; 8 denotes a cross bar formed of an insulating material, which is coupled to the moving core 7 through a pin 9; 10 denotes a trip spring arranged between the cross bar 8 and the mounting plate 1, which normally lifts the cross bar 8 so that a main circuit of the power switchgear is maintained open; 11 denotes a moving contact-maker provided with moving contacts (11a) which is inserted in a holding hole 8a provided on the cross bar 8 and urged by a pressure spring 12; 13 denotes fixed contact-makers provided with stationary contacts 13a opposite the moving contacts 11a. The fixed contact-makers 13 are fixed on a terminal 15 with a screw 14, and the terminal 15 is fixed to the base 2 with screws 16,17. Numeral 13b denotes an arc runner connected electrically to the fixed contact-makers 13 and which can be unified with the fixed contact-makers 13; 18 denotes a terminal screw connected to main circuit wire, which is fitted to the terminal 15; 19 denotes an arc box formed of an insulating material, which is fixed on the base 2 with a screw 20. The arc box 19 includes a hole 19a through which gas is discharged, a ceiling part 19b and a side plate 19c. Numeral 21 denotes a deionizing grid arranged in a shape as in Fig. 4 and made of a magnetic material; 22 denotes a commutating electrode, which is fixed on the ceiling part 19b of the arc box 19. The stationary contact 13a and the moving contact 11a are formed in the internal space of an arc extinguishing chamber. The operation of the power switchgear as thus arranged will now be described. When a voltage is impressed on the operating coil 5 with the main circuit shown in Fig. 1 open, a magnetic flux is generated between the fixed core 4 and the moving core 7, and the moving core 7 is moved toward the fixed core 4 against the force of the trip spring 10. In this case, the cross bar 8 coupled to the moving core 7 moves downwardly, the moving contacts 11a of the moving contact-maker 11 come in contact with the stationary contacts 13a of the fixed contact-makers 13, and a predetermined pressure is applied by the pressure spring 12 to open the main circuit. Next, when the operating coil 5 is deenergized, the moving core 7 moves away from the fixed core 4 by the force of the trip spring 10, and the cross bar 8 also moves with the moving core 7. Therefore, the cross bar 8 returns to the state shown in Fig. 1, and the moving contacts 11a of the moving contact-makers 11 and the stationary contacts 13a of the fixed contact-maker 13 are separated. In the process, an arc is generated between the moving contact 11a and the stationary contact 13a at a portion indicated in Fig. 1 at A. The movement of the arc until the current is interrupted after it is generated is illustrated for only one side in Fig. 5, as the arc extinguishing chamber B in Fig. 1 is symmetrical. Fig. 5a represents the state wherein the stationary contact 13a and the moving contact 11a are closed. When the stationary contact 13a and the moving contact 11a are opened when the operating coil 5 is conducting, an arc 23 is generated, as shown in Fig. 5b, between the stationary contact 13a and the moving contact 11a. The contact opening distance gets larger as time passes, up to the maximum distance. The arc 23 is driven and expanded, as shown in Fig. 5c, by the current flowing in the moving contact-maker 11 and the fixed contact-maker 13 and the deionising grid 21, and one end of the arc 23 is transferred, as shown in Fig. 5d, from the surface of the stationary contact 13a to the arc runner 13b. Then, there occurs a dielectric breakdown between a tip of the arc 23 shown in Fig. 5d and a portion of the arc runner 13b indicated at B, and an end of the arc 23 is transferred to the portion of the arc runner 13b indicated at B in Fig. 5e. The other end of the arc 23 is transferred, as shown in Fig. 5f, from the stationary contact 11a to the commutating electrode 22 and the arc 23 is extinguished between the deionizing grids 21. Thus, the current is cut off completely. As noted, the power switchgear has a commutating electrode 22 positioned on the rear side of the moving contact 11, and therefore a long time is required for one end of the arc 23 to transfer from the moving contact 11a to the commutating electrode 22. The shortcoming that the expensive moving contact 11a is subject to wear is consequently unavoidable. An object of the present invention is therefore to provide a power switchgear device in which wear of the moving contact is reduced. According to the invention the power switchgear device is characterized in that the the arc runner includes first and second portions arranged at right angles to each other and connected electrically to each other; the second portion of the arc runner extends adjacent to and parallel to the plates of said grid; said deionisation grid is arranged between said commutation electrode and said second portion of said arc runner and said movable contact; and said first portion of said arc runner with the stationary contact and said commutation electrode are arranged such that the shortest distance between said contacts is greater than the shortest distance between said commutation electrode and said first portion of said arc runner when said contacts are moved apart, such that during disconnection the arc moves smoothly from the stationary contact onto the arc runner. In one embodiment, the distance from a plane at which said stationary contact meets said stationary contact-maker to a surface of said arc runner opposite said movable contact is larger than a distance from said plane to a contacting surface of said stationary contact. In another embodiment, at least a portion of said commutation electrode is positioned between a surface of the stationary contact and said opposite side of the moving contact-maker when the distance between said stationary contact and said moving contact is maximized, and has a hollow portion and a planar portion connected to said hollow portion, and said deionization grid faces said planar portion. Preferably, the shortest distance between said arc runner and a contacting surface of said moving contact becomes greater than the shortest distance between said commutating electrode and said arc runner when said contacts are moved apart by a predetermined distance. Preferably, said arc runner has a portion engaged with said stationary contact-maker. Expediently, one portion of the arc runner is attached to said stationary contact-maker, and a second portion is separately electrically connected to said stationary contact-maker, and said deionisation grid is provided adjacent said second portion. For a better understanding of the inventions and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Fig. 1 is a sectional view representing a conventional type power switchgear; Fig. 2 is a side view of the equipment of Fig. 1; Fig. 3 is a plan view of the equipment of Fig. 1; Fig. 4 is a perspective view of the deionizing grid of Fig. 1; Figs. 5a-5f are explanatory drawings showing the arc extinguishing chamber of a conventional type power switchgear, and the movement of the arc; Figs. 6a-6f are structural drawings representing one embodiment of the invention; Fig. 7 shows application of the invention to a wiring breaker; Fig. 8 illustrates a variation of the construction of the arc runner of Figs. 6 and 7; Figs. 9a and 9b are closed and opened views of a pivoting type movable contact; Figs. 10 and 11a-11f illustrate a further modified form of the invention using a partially hollow commutating electrode; and Figs. 12a and 12b, 13a and 13b, 14a and 14b and 15a and 15b are plan and side sectional views, respectively, of different arrangements of the contact, the contact maker and the arc runner according to the invention. The movement of the arc in the power switchgear according to the invention will be described with reference to Fig. 6. Fig. 6a represents the state wherein the stationary contact 13a and the moving contact 11a are closed. When the stationary contact 13a and the moving contact 11a are opened with the operating coil 5 conducting, the arc 23 is generated, as shown in Fig. 6b, between the stationary contact 13a and the moving contact 11a. The contact opening distance increases with time to a predetermined distance. The arc 23 is driven and expanded, as shown in Fig. 6c, by currents flowing through the moving contact-maker 11 and the fixed contact-maker 13, and by the magnetism of the deionizing grid 21. When X, (the distance between the contacts 11a, 13a) becomes larger than Y, (the shortest distance between tip 22a of electrode 22 and runner 13b) as the moving contact 11a moves, one end of the arc 23 is transferred, as shown in Fig. 6d, from the moving contact 11a to the tip 22a of the commutating electrode 22. The arc 23 is driven and expanded by the current flowing to the fixed contact-maker 13, the arc runner 13b and the commutating electrode 22 and approaches the deionizing grid 21, as shown in Fig. 6e. Then the arc 23 is drawn into the deionizing grid 21 as shown in Fig. 6f, thus cutting off the current. As described, since the position of tip 22a is set so that Y in Fig. 6f becomes smaller than X during opening of the moving contact, the time for which one end of the arc is on the moving contact 11a is shortened, and thus the wear of this expensive contact can be decreased. The moving contact-maker 11 is surrounded by a poor conductor, and therefor it is heated to a high temperature by the arc when switching is repeated at short time intervals. Consequently, thermal damage of the cross bar 8 to cause breakage thereof can occur in the conventional system. However, the application of the invention helps to prevent such thermal damage to the cross bar, as the time in which the arc is on one end of the moving contact 11a is shortened. The above description refers to the case wherein the distance Y is made smaller than X in Fig. 6f. However, a similar effect is obtainable when the relation between X O in Fig. 6f, (X₀ being the distance between the arc runner 13b and the rear face of the moving contact-maker) and Y satisfy Y < X O . In this case, however, one foot of the arc 23 on the moving contact is transferred to the commutating electrode 22 by way of the tip 11b of the moving contact-maker 11 (see Fig. 6f). The above embodiment may be used with a power switchgear for an electromagnetic contactor, however, the invention may also be applied to a circuit breaker, as illustrated in Fig. 7 which shows the state wherein the stationary contact 13a and the moving contact 11a are opened. The moving contact-maker 11 and the commutating electrode 22 are connected electrically through the wire 26, and the moving contact-maker 11 is connected to a terminal through the wire 25. The arc is first generated between the moving contact 11a and the stationary contact 13a, one end of the arc 23 is transferred from the stationary contact 13a to the arc runner 13b, and the arc 23 is finally moved between the commutating electrode and the deionizing grid and the arc runner, thus interrupting current. In the illustrated power switchgear according to the invention, the time during which the arc is on the surface of the stationary contact 13a and the moving contact 11a can be shortened resulting in the several advantages noted above. In the preferred embodiments shown in Figs. 6 and 7, the L-shaped arc runner 13b is jointed at the tip of the fixed contact-maker 13, however, a similar effect is obtainable with an arc runner 13b divided into two parts as shown in Fig. 8, and having one part connected to the fixed contact-maker 13 at a spot other than the end thereof. The above embodiment may be applied to power switchgear operating to energise an electro-magnet, i.e. an electromagnetic contactor, however, it also applies to a power switchgear for use as a mold case circuit breaker. The configuration of the arc extinguishing chamber B in such a case is shown in Figs. 9a and 9b. Fig. 9a represents the state wherein the stationary contact 13a and the moving contact 11a are in contact with each other. The moving contact-maker 11 rotates around a rotary shaft 24 through an operating mechanism which is not illustrated. The stationary contact 13a and the moving contact 11a open as illustrated in Fig. 9b. The moving contact-maker 11 and the commutating electrode 22 are connected electrically through wires 25, 26. Since the time during which the arc 23 is kept on the surface of the moving contact 11a is short, the wear of the moving contact 11a is minimized effectively. The arc 23 is driven by a current flowing to the fixed contact-maker 13 and the commutating electrode 22 and is drawn into the gap between the members of the deionizing grid 21 quickly. Therefore, the arcing time is shortened and the arc energy is decreased, and thus a large current can be effectively cut off. In another embodiment of the invention shown in Fig. 10, M denotes a hollow part of the commutating electrode 22, N denotes a plane part of the commutating electrode 22, which is arranged so as to be opposite to the deionizing grid. The shape of the commutating electrode is as shown in Fig. 10. Fig. 10 shows a commutating electrode half. However, since the electrode is symmetrical, the remaining half is identical. The construction is such that the moving contact-maker 11 is capable of moving into a notch of the commutating electrode 22. Thus, when the opening distance of the contacts is maximized, the commutating electrode will be positioned between the contacts. The movement of the arc in the power switchgear according to this embodiment will be described with reference Fig. 11. Fig. 11a represents the state wherein the stationary contact 13a and the moving contact 11a are closed. When the stationary contact 13a and the moving contact 11a are opened with the operating coil 5 conducting, the arc 23 is generated, as shown in Fig. 11b, between the stationary contact 13a and the moving contact 11a. The arc 23 is driven by a magnetic field produced by a current flowing to the moving contact-maker 11 and the fixed contact-maker 13. The contact opening distance increases up to a predetermined size as time passes. When the contact opening distance becomes larger than the shortest distance between the stationary contact 13a or the arc runner 13b and the commutating electrode 22, one end of the arc 23 is transferred, as shown in Fig. 11c, from the moving contact 11a to the commutating electrode 22. Where a magnetic material is used for the commutating electrode, a strong magnetic field indicated by B in Fig. 10 works upon the arc by the current flowing to the moving contact-maker 11 and the commutating electrode 22. A driving force F (Fig. 10) is generated in this case to drive the arc strongly, and thus the arc is quickly transferred from the moving contact 11a to the commutating electrode 22 as shown in Fig. 11c. The quickness of the transfer of the arc will vary according to the driving force F and the shape of the commutating electrode. Then, the arc is driven and expanded, as shown in Fig. 11d, by the current flowing to the commutating electrode 22 and the fixed contact-maker 13 and is then extinguished between the deionizing grids, as shown in Fig. 11f, by way of the state illustrated in Fig. 11e. The current is thereby cut off completely. As described, in the illustrated power switchgear, one end of the arc is transferred very quickly from the moving contact to the commutating electrode, therefore the wear of the moving contact is minimized, the arcing time is shortened, and the arc energy is decreased, thereby improving interrupt performance. The fixed contact-maker 13 and the arc runner 13b will normally be junctioned as in Fig. 11 but can be joined as in Fig. 12, and further, the arc runner 13b can be placed on the fixed contact-maker 13 as shown in Fig. 13. The fixed contact-maker 13 and the arc runner 13b can also be unified as in Fig. 14, or the arc runner 13b can be divided into two as in Fig. 15. In Figs. 7 and 12-15, the distance Y₁ from the junction of the stationary contact 13a and the fixed contact-maker 13 to the face of the arc runner 13b which is opposite to the moving contact 11a is set to be larger-than the distance X₁ from the junction of the stationary contact 13a and the fixed contact-maker 13 to the surface of the stationary contact 13a. Thus the arc remains on the stationary contact 13a for only a short time, and thus the wear thereof can be decreased accordingly. The structures of Figs. 7 and 12-15 may be used, for example, with the devices of Figs. 10 and 11. The above embodiment is used with a power switchgear for a electromagnetic contactor, however, the invention can also apply to a mold case circuit breaker. In the illustrated power switchgear according to the invention, the time during which one end of the arc 23 is on the stationary contact 13a is kept short, and therefore the wear of the moving contact 11a is effectively decreased, the arcing time is shortened and the arc energy is decreased, to obtain superior interrupt performance. Except for the arrangement of the commutating electrode, the power switchgear according to the invention may be substantially identical to that of Figs. 1 - 4. The position of a tip 22a of the commutating electrode 22 is set so that Y (the shortest distance between the tip 22a of the commutating electrode 22 and the arc runner 13b) will be smaller than X (the shortest distance between the moving contact 11a and the stationary contact 13a when the contact opening distance exceeds a given value.

Claims: A power switchgear device comprising: a stationary contact-maker (13) having a stationary contact (13a); a movable contact (11a) arranged opposite to the stationary contact (13a) carried by a movable contact-maker (11); an arc runner (13b) electrically connected to the fixed contact-maker (13); a commutation electrode (22) arranged for taking current during disconnection; and a deionisation grid (21) comprising a plurality of plates extending parallel to the direction of movement of the movable contact-maker, characterized in that: the arc runner (13b) includes first and second portions arranged at right angles to each other and connected electrically to each other; the second portion of the arc runner extends adjacent to and parallel to the plates of said grid (21); said deionisation grid (21) is arranged between said commutation electrode (22) and said second portion of said arc runner (13b) and said movable contact (11a); and said first portion of said arc runner (13b) with the stationary contact (13a) and said commutation electrode (22) are arranged such that the shortest distance (X) between said contacts (11a,13a) is greater than the shortest distance (Y) between said commutation electrode (22) and said first portion of said arc runner (13b) when said contacts are moved apart, such that during disconnection the arc moves quickly from the stationary contact onto the arc runner. A device as claimed in claim 1, wherein the distance (Y₁) from a plane at which said stationary contact (13a) meets said fixed contact-maker (13) to a surface of said arc runner (13b) opposite said movable contact (11a) is larger than the distance (X₁) from said plane to a contacting surface of said stationary contact (13a). A device according to claim 1 or 2 wherein at least a portion of said commutation electrode (22) is positioned between a surface of the stationary contact (13a) and said opposite side of the moving contact-maker (11) when the distance between said stationary contact (13a) and said movable contact (11a) is maximized, said portion of said commutation electrode (22) having a hollow portion (M) and a planar portion (N) connected to said hollow portion (M), and said deionisation grid (21) facing said planar portion (N). A device as claimed in claim 3, wherein said movable contact-maker (11) is movable into the hollow portion (M) when said contacts (11a,13a) are separated. A device as claimed in any one of claims 1 to 4, characterized in that the shortest distance between said stationary contact (13a) and said deionisation grid (21) is larger than the shortest distance between said stationary contact (13a) and said commutating electrode (22). A device as claimed in any one of claims 1 to 5, wherein the shortest distance between said arc runner (13b) and a contacting surface of said movable contact (11a) becomes greater than the shortest distance between said commutating electrode (22) and said arc runner (13b) when said contacts (11a,13a) are moved apart by a predetermined distance. A device as claimed in any one of claims 1 to 6 wherein said arc runner (13b) has a portion engaged with said stationary contact-maker (13). A device as claimed in any one of claims 1 to 6 wherein one portion of said arc runner (13b) is attached to said stationary contact-maker (13), and a second portion is separately electrically connected to said stationary contact-maker, and wherein said deionisation grid is provided adjacent said second portion. A device as claimed in any one of claims 1 to 8 wherein said contact-maker (13) and said arc runner (13b) are integral with each other. A device as claimed in any one of claims 1 to 9 wherein said stationary contact (13a) has respective opposite sides adjacent which respective portions of said arc runner (13b) are arranged.

Inventors: KAKIZOE, MASAHIRO MITSUBISHI DENKI KABUSHIKI KAISH, MASUDA, SHIGERU MITSUBISHI DENKI KABUSHIKI KAISHA, MORI, TEIJIRO MITSUBISHI DENKI KABUSHIKI KAISHA, OKADO, HIROYUKI MITSUBISHI DENKI KABUSHIKI KAISHA, SAKO, YUJI MITSUBISHI DENKI KABUSHIKI KAISH
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1982
Main classification: H01H9
IPC codes: H01H9