ES2234156T3 - CURRENT LIMITING SWITCH WITH CURRENT SWITCH. - Google Patents

Abstract

A COMPACT CURRENT LIMITING CIRCUIT THAT INCLUDES TWO PAIRS OF SERIAL CONNECTED CONTACTS AND PROVIDED WITH A PARALLEL CURRENT LIMITER WITH THE SECOND COUPLE OF CONTACTS TO ENSURE BETTER PROTECTION AGAINST EXCESSIVE CURRENT INTENSITIES. WHEN THE CONTACTS ARE SEPARATED, AN ARC IS FORMED AT THE LEVEL OF THE FIRST COUPLE OF CONTACTS, BUT NOTHING HAPPENS AT THE LEVEL OF THE SECOND PAIR. THE PRESENCE OF THE POLYMER CURRENT LIMITER PLACED IN PARALLEL WITH THE SECOND PAIR OF CONTACTS CAUSES THE EXCHANGE VOLTAGE SWITCH IN THE POLYMER CURRENT LIMITER FAIR AT THE TIME THE SECOND CONTACTS SEPARATE. A DEVICE THAT ALLOWS THE IMPROVEMENT OF THE DIELECTRIC RESISTANCE TO THE LEVEL OF THE SECOND OPEN CONTACT PAIR IMPROVES AN ARC HIT TO AVOID THE POLYMER CURRENT LIMITER DURING A STRONG CIRCUIT OF STRONG INTENSITY.

Description

Current limiting switch with switch of current.

Background of the invention

The use of arc arresters in switches Compact electric to extinguish the arc is well known in the engineering field of switches. The role of arc arrester is to attract the induced electric arc between the mobile and fixed contacts when contacts are opened in response to a condition of overcurrent. The magnetic influence of arc unloader attracts the arc, which then breaks into some smaller arcs between the multiple plates existing in the inside the arc arrester. Each small arc has associated a fall between anode and cathode, defined in this document as the voltage that appears between each pair of existing arc plates within the arc arrester, which, considered collectively, produces sufficient electrical potential to overcome the voltage of the system and zero the intensity, thereby extinguishing Effectively overcurrent. Such arc arrester is described in US Patent No. 4,463,849 entitled "Compact Current Limiting Circuit Breaker with intensity limitation) ". During this process of interruption, the intense heat of the ionized plasma arc vaporizes The edge and surface of the arc plates, produces a high internal gas pressure and causes the ionized particles to escape from the switch to the housing of the switch. With the final purpose to avoid an electrical impact on the grounded metal during the interruption process, the performance of the switch they have to be coordinated with the physical conditions of the switch housing

US Patent Application Series No. 08 / 797,151 titled "Current Suppressing Circuit Breaker Unit for Inductive Motor Protection (Switching device with suppression of intensity for inductive motor protection) ", presented on February 10, 1997, describes a current suppression device connected in series with a pair of contacts of a switch. During a short overcurrent condition, the suppressor apparatus of current quickly suppresses the short-circuit current which, It is then extinguished by the opening of the contacts of the switch. The current suppression device uses an element current limiter, which operates in the manner described in the Patent US No. 5,614,881 entitled "Current Limiting Device (Current limiting device) ", and that introduces quickly a high resistance to effectively limit the maximum circulating current. The current limiting element, highly resistive in its switched state, quickly suppresses the circulating current to a small residual value, which at then it is extinguished by the opening of the contacts of the switch connected in series. The resulting arc of the current residual is conducted to an arc arrester where it is extinguished according to the aforementioned US Patent No. 4,963,849.

Italian Patent Application No. MI97A 001564, filed on July 2, 1997, and the Patent Application American Series No. 09 / 108,684, filed on July 1, 1998, both titled "Rotary Contact Assembly for High Ampere-Rated Circuit Breakers contacts for high intensity switches) ", describe a rotary contact arm assembly that includes an arm contacts with two mobile contacts, one at each end, and a center pivot Mobile contacts are connected electrically in series when the contact arm assembly is in the CLOSED position. Each mobile contact supports on a fixed contact The articulation of the contact arm assembly makes both mobile contacts open simultaneously, thus introducing two electric arcs in series. The advantage of two electric arcs in series, with respect to only one, is that it doubles the arc tension growth rate, which Quickly suppresses short circuit overcurrent.

US Patent Application Series No. 08 / 797.152, entitled "Circuit Breaker Current Limiting Arc Runner (Arc slide with current limitation for switch electrical) ", filed on February 10, 1997, describes a arc slide with current limitation that includes a polymeric current limiter that quickly suppresses a short circuit overcurrent. The proximity of the slide arc with current limitation and mobile contact arm promotes arc current to commute to the arc slide during contact separation.

U.S. Patent No. 5,424,503, entitled "Buffer Type Circuit ITU Improved Blast Valve And Switch Permanent Contact (Electric Switch Type with Valve perfected jet and permanent contacts) ", describes a electric blower type switch that uses an insulating gas to pressure to effect arc interruption. The patent American No. 3,632,926, entitled "Current Limiting Circuit Breaker Having Arc Extinguishing Means Which Includes Improved Arc Initiation And Extinguishing Chamber Construction (Switch electric with current limitation with a means to extinguish the arch that includes an improved chamber construction of arc initiation and extinction) ", describes the use of a material ablative in the vicinity of fixed contacts to effect the arc interruption Both systems require the introduction of a specialized material designed specifically to introduce an insulating gas in the arc interruption chamber.

U.S. Patent No. 4,677,266, entitled "Switch Device Having An Insulation Screen Inserted Between The Contacts During Breaking (Switching device that has a insulating screen inserted between the contacts during rupture) ", describes a device that blocks the separation between contacts and acts effectively to fork the separation between contacts by increasing the gas pressure produced by the arc induced between the contacts. The operation of this type of system depends on the existence of an arc induced between the contacts U.S. Patent No. 4,752,660, entitled "Current Limiting Circuit Breaker With An Arc Shearing Plate (Electric current limiting switch with a plate arc rupture) ", describes a shutter device of the separation between contacts that acts effectively to fork the separation between contacts by the same actuator element, sensitive to overcurrent, which starts the separation of contacts The operation of this type of system depends on the actuator element sensitive to overcurrent that works arranged with the opening action of the contacts separable

A purpose of the present invention is provide an effective short circuit interruption system that uses a polymeric current limiter, as described in the aforementioned US Patent 5,614,881, in parallel with a second pair of contacts of a double rotary set contact, as described in Italian Patent Application No. MI97A 001564 and in US Patent Application Series No. 09 / 108,684, cited above, and arranged with a means to increase dielectric strength through the pair of contacts open, connected in parallel with the current limiter polymeric, to prevent the arc from deviating from the limiter of polymeric current

EP 0 212 661 describes a device according to the preamble of claim 1.

Summary of the Invention

A compact electrical switch with limitation of current uses a polymeric current limiter and a set of rotating contacts for protection effective against overcurrents. When the contact separation, the overcurrent is switched from a second pair of contacts to a current limiter polymeric, and an arc is induced between a first pair of contacts that are conducted to an arc arrester. The overcurrent switching in the current limiter polymer effects a rapid suppression of overcurrent. He polymeric current limiter comprises a conductive polymer with flush electrodes and interfaces between electrodes of higher resistance

Brief description of the drawings

Figure 1 is a side view of a compact rotary electric switch with current limitation of the prior art with the cover removed so that the operating components of the switch in the CLOSED condition; Y

Figure 2 is a side view of a compact rotary electric switch with current limitation equipped with a polymeric current limiter according to the invention.

Figure 3 is a side view of a compact rotary electric switch with current limitation equipped with a polymeric current limiter and a blower gas according to the invention.

Figure 4 is a partial side view of the Switch housing of Figure 3 with details removed for more clarity.

Figure 5 is a partial sectional view of the switch housing of Figure 4, cut by Section A-A, except that the two halves of the switch housing

Figure 6 is a partial side view of a compact rotary electric switch with current limitation equipped with a polymeric current limiter and a shutter the separation between contacts according to the invention, with the details removed for clarity.

Description of the preferred embodiment

Figure 1 represents an electrical switch 10 with molded case that works according to the teachings contained in Italian Patent Application No. MI97A 001 564 and the Application for US Patent Series No. 09 / 108,684, mentioned previously. A housing 11 contains an operating mechanism (not represented) that works by articulating the arm 12 of the contacts between an open position and a closed position, in the way described in Italian Patent Application No. MI97A 001 564 and the US Patent Application Series No. 09 / 108,684, mentioned previously, to isolate a protected circuit. Contacts mobiles 13, 14 located on arm 12 of the contacts rest on the fixed contacts 15, 16 located in line bar 17 and in the loading bar 18. Under stable operating conditions, the electric current passes through line bar 17, contact fixed 15, mobile contact 13, arm 12 of contacts, contact mobile 14, fixed contact 16 and load bar 18. 17 line bar provides an electrical connection between the power source external and internal switch components. A terminal of Charge (not shown) provides a means to connect electrically the circuit protected to the load bar 18. The articulation of the arm 12 of the contacts during a condition of Short circuit overcurrent is described in the Request for Italian Patent No. MI97A 001 564 and in the Patent Application American Series No. 09 / 108,684. This action produces an arc electric (not shown) that goes to the arresters of arc 19, 20, with an eventual extinction through the holes of exhaust 21, 22. The opening speed of arm 12 of the contacts are increased by slotted motors 23, 24.

First embodiment with polymeric current limiter

A compact electric switch 40 with current limitation is represented in Figure 2, in the which the same reference numbers in Figure 1 identify corresponding parts. The loading bar 18 is connected to a first electrode 41 that rests on one side of the polymeric conductor 42 and is captured by a fixation 45 that is an integral part of the housing 11. The other side of the polymeric conductor 42 is pressed against a second electrode 43 by a spring 44 captured in the housing 11. A second electrode 43 is connected electrically to the arm 12 of the contacts by means of a braid 46. Opening the arm 12 of the contacts produces an arc electrical between the mobile contact 13 and the fixed contact 15, which it is magnetically driven to arc arrester 19, and it also switches overcurrent from mobile contact 14 and the fixed contact 16 to a current path constituted by the first electrode 41, polymeric conductor 42, the second electrode 43 and braid 46. The switched current is suppressed quickly by the action of the polymeric current limiter that works as described in the aforementioned Patent Application American Series No. 08 / 797,152. The suppressed residual current it is eventually extinguished by arc unloader 19, remaining a reduced effluent that escapes through the exhaust hole 21. The opening speed of arm 12 of the contacts is increased by middle of slotted motors 23, 24.

The dimensions d1 and d2 of Figure 2 can be set according to the requirements of the application. For a given angle of rotation of the arm 12 of the contacts to the OPEN position, a condition in which d1 > d2 provides a greater voltage drop in the polymeric current limiter 47, typically required for a high level short-circuit overcurrent , and a condition in which d1 < d2 provides a greater voltage drop in the arc arrester 19, typically required for a low level short-circuit overcurrent.

Second embodiment with polymeric current limiter and gas arc blower

The compact electric switch 40 with Current limiter of Figure 2 has been reproduced in Figure 3 adding an arc blower 48 by gas, the other parts being similar, although reference numbers have been omitted for more clarity The details of the gas arc blower 48 are they better appreciate seeing together Figures 3, 4 and 5. The conduit 49 of gas, formed by the outer structure of the housing 11 and the barrier 59, connects a first hole 50, also identified by 50a-50h in Figure 4, with a second hole 51 which allows the gas to be transported under pressure from zone 60, which contains the polymeric current limiter 47 composed of a first electrode 41, a polymeric conductor 42, a second electrode 43 and compression means such as a spring 44 and a fastener 45, to an area behind the movable contact 14 and of the fixed contact 16, when the polymeric current limiter 47 undergoes a switching as described in the aforementioned Request for US Patent Series No. 08/797,152. Essentially, the polymeric current limiter switching 47 occurs during a short circuit overcurrent condition in which opening of the arm 12 of the contacts switches overcurrent towards the polymeric current limiter 47 and causes a resistive heating at the interface between the polymeric conductor 42 and the first electrode 41, or the second electrode 43, or both, what which causes rapid thermal expansion and vaporization of polymeric conductor 42. This superficial ablative phenomenon introduces a sharp change in circuit resistance due to the resistive nature of the polymer binder become gas, and is called switching, that is, switching from low to high resistance, and is clearly different from resistance with positive temperature coefficient (PTCR) that use the volumetric resistive heating to effect a change of volumetric material that produces a change in resistance volumetric The vaporization of the polymeric conductor 42 causes the pressurization of zone 60. The gas flow is then directed from a relatively high pressure zone, zone 60 near the first hole 50, towards a relatively low pressure zone close to the second hole 51. The speed of the gas flow that out through the second hole is increased by the reduction of cross-sectional area of the gas flow between the first hole 50 and the second hole 51. During this event, the arm 12 of the contacts has turned at least partially, creating a separation between the mobile contact 14 and the fixed contact 16. The gas under pressure expelled by the second hole 51 expands in the area between the mobile contact 14 and the fixed contact 16, effectively increasing the dielectric strength of the separation between contacts while the rapid suppression of the overcurrent due to the action of the polymeric current limiter previously described. The increase in local pressure in the separation between contacts, or removal of contaminants from internal separation between contacts, or the cooling effect of the gas at high speed inside the separation between contacts, or any combination thereof, serve to increase the dielectric strength of the separation between contacts. He increased dielectric strength of the separation between contacts allows the polymeric current limiter to withstand higher voltages without an arc occurring through the separation between contacts, thus avoiding a sudden appearance of a excess overcurrent that could damage the devices of the protected circuit located downstream. The suppressed current residual is also extinguished, as described above, by the opening action of the space between the contact fixed 15 and mobile contact 13, and by arc arrester 19.

Third embodiment with polymeric current limiter and contact separation shutter

The compact electric switch 40 with current limitation of Figure 2 has been reproduced partially in Figure 6 adding the shutter 53 of the separation between contacts and guide 54, having omitted the Details for clarity. The pieces of Figure 6 that correspond to similar pieces of Figure 2 have the numbers of reference omitted for clarity. Shutter 53 has a first end 53a, or insulating barrier, which cooperates with the guide 54 formed in the housing 11, a second end 53b having a leg 53d adjacent to arm 12 of the contacts, and an anchor 53c pivotally coupled to arm 12 of the contacts. Guide 54 it has a first surface 55 that forms a cavity 57, extended on either side of the paper plane and on both sides of the contact fixed 16, and in which the fixed contact 16 is located, and a second surface 56 forming an opening 58, extended to one and other side of the paper plane and on both sides of the fixed contact 16, through which the mobile contact 14 passes during opening or the closing of the arm 12 of the contacts. Anchor 53c shutter 53 is located on the arm 12 of the contacts for that effectively promotes the translation of the shutter 53 by the inside the guide 54 during the opening or closing of the arm 12 of the contacts During an overcurrent condition in which the arm 12 of the contacts opens as described previously, the clockwise rotation of arm 12 of the contacts on pivot axis 52 produces a displacement angle of the anchor 53c with an appreciable horizontal component. So well, when the arm 12 of the contacts opens to produce a separation between the contacts, the shutter 53 moves to the inside the guide 54 to branch the contact spacing It is developing. The first and second surfaces 55, 56 of the guide 54 cooperate with the first end 53a of the shutter 53 to confine the translation movement of the shutter 53 by the inside the guide 54. The effective fork of the separation between the mobile contact 14 and the fixed contact 16 occurs when the first end 53a of the shutter 53 has moved as enough to completely cover both cavity 57 of the first surface 55 as the opening 58 of the second surface 56. The width and length dimensions of the first end 53a of the shutter 53 are appropriate to ensure coverage complete, both of the cavity 57 and the opening 58, when the arm 12 of the contacts is fully open, thus increasing the dielectric strength of the separation between contacts and promoting the rapid suppression of overcurrent by the action of polymeric current limiter as described above. The placement of the insulation barrier between the mobile contact 14 and the fixed contact 16 serves to increase the travel that would have to perform an arc to short circuit the limiter of polymeric current, thus effectively increasing the resistance Dielectric separation between contacts. The suppressed current residual is also extinguished in the manner described above by the opening action of the separation between the fixed contact 15 and the mobile contact 13, and by the arc arrester 19 (Figure 2).

Claims (25)

1. A compact electric switch (40) with current limitation comprising: a housing (11) of the electrical switch; a first pair of fixed contacts (15, 16), one (15) of such first fixed contacts (15, being connected, 16) to a line bar (17) located at one end of said housing (11) of the electrical switch for connection to a circuit electrical distribution protected and another (16) of said first fixed contacts to a load bar (18) located in an opposite end of said housing (11) of the electrical switch for connection to said protected circuit; a rotor pivotally arranged between said pair of fixed contacts (15, 16) and supporting an arm (12) of the mobile contacts, defining said arm (12) of the contacts mobiles a first and a second dimension d1 and d2 which are the distances between the axis of rotation of said arm (12) of the contacts to a first pair of mobile contacts (13, 14) located respectively at each end of said arm (12) of the contacts, being arranged one of said first mobile contacts at each end of said arm (12) of the contacts to join and separate from said first contacts fixed (15, 16) to make and break the electrical connection with said protected circuit; an operating mechanism located inside said housing (11) of the electrical switch next to said rotor, said operating mechanism being arranged to rotate said rotor and said arm (12) of the mobile contacts and separate said first mobile contacts (13, 14) of said first fixed contacts (15, 16) to cut off the electrical connection with said protected circuit when an overcurrent occurs in said protected circuit; characterized by a polymeric current limiter (47) electrically connected in parallel with said load bar (18) and said arm (12) of the contacts for switching said overcurrent towards said polymeric current limiter when said first fixed contacts and said first are separated mobile contacts (13, 14, 15, 16) to quickly suppress said overcurrent, the first and second being different dimension d1 and d2. 2. The compact electric switch (40) with current limitation of claim 1 including a means (45) to fasten said polymeric current limiter (47) to said housing (11) of the electrical switch. 3. The compact electric switch (40) with current limitation of claim 1 wherein said polymeric current limiter (47) comprises a first and a second electrode (41, 43) located on opposite sides of a polymeric conductor (42). 4. The compact electric switch (40) with current limitation of claim 3 wherein said polymeric conductor (42) comprises a polymeric binder whose vaporization temperature, at which an evolution occurs significant gas, is less than 800 ° C and a conductive filler of the electricity contained in said polymeric binder. 5. The compact electric switch (40) with current limitation of claim 4 which further includes an interface close to said polymeric conductor (42), having said interface a resistivity greater than said polymeric conductor (42), whereby the resistive heating of said interface causes rapid expansion and thermal vaporization of said polymeric conductor (42), causing a separation at least partial of at least one of said first or second electrodes (41, 43) with respect to said polymeric conductor (42) in said Interface. 6. The compact electric switch (40) with current limitation of claim 5 which includes a means (44) to exert a compressive pressure on said conductor polymeric (42) for switching current to said polymeric current limiter (47) under said condition of Overcurrent 7. The compact electric switch (40) with current limitation of claim 3 wherein said Polymeric conductor (42) does not depend on a PTCR effect. 8. The compact electric switch (40) with current limitation of claim 3 wherein said first electrode (43) is electrically connected to said bar (18) loading. 9. The compact electric switch (40) with current limitation of claim 3 wherein said second electrode (43) is electrically connected to said arm (12) of the contacts. 10. The compact electric switch (40) with current limitation of claim 3 wherein said second electrode (43) is electrically connected to said arm (12) of the contacts by means of a flexible conductor (46). 11. The compact electric switch (40) with current limitation of claim 6 wherein said Compression means consists of a spring (44). 12. The compact electric switch (40) with current limitation of claim 2 wherein said fastening means (45) has a tight fit inside said housing (11) of the electrical switch. 13. The compact electric switch (40) with current limitation of claim 1 wherein the first dimension d1 is larger than the second dimension d2 sufficiently so that the voltage drop produced through said polymeric current limiter (47) is greater than that produced between said second fixed contact (16) and said second contact mobile (14) in order to increase the current limitation in said current limiter (47) during said condition of Overcurrent 14. The compact electric switch (40) with current limitation of claim 1 wherein the first dimension d1 is smaller than the second dimension d2 enough such that the voltage drop produced between said second fixed contact (16) and said second mobile contact (14) is greater than that produced through said polymeric current limiter (47) in order to increase the arc voltage generation a through the separation of contacts between said second contact fixed (16) and said second mobile contact (14) during said overcurrent condition. 15. The compact electric switch (40) with current limitation of claim 1 further comprising a gas arc blower (48), located next to said first fixed contact (15) and said first mobile contact (13), to promote the gas flow between said first fixed contact (15) and said first mobile contact (13) during the switching of said limiter of polymeric current (47) in order to increase stiffness Dielectric separation between contacts. 16. The compact electric switch (40) with current limitation of claim 15, wherein said gas arc blower (48) comprises at least one duct (49) of gas with at least a first orifice (50) next to said limiter of polymeric current (47) and at least a second hole (51) close to said first fixed contact (15) to direct the flow of gas from said at least one first hole (50) towards said at minus a second hole (51). 17. The compact electric switch (40) with current limitation of claim 16 wherein said at minus a second hole (50) is located between said first fixed contact (15) and the pivot of said rotor to promote that the gas flow is separated from the pivot of said rotor in order to increase the dielectric strength of the separation between contacts 18. The compact electric switch (40) with current limitation of claim 16 wherein said at less a gas conduit (49) is disposed inside said electrical switch housing (11) with a sectional area transverse gas flow that is reduced between said at least one first hole (50) and said at least a second hole (51) for promote a higher gas velocity at the exit of said at least one second hole (51). 19. The compact electric switch (40) with current limitation of claim 1 further comprising a shutter (53) of the separation between contacts arranged between said first fixed contact (15) and said first mobile contact (13) during separation of said first fixed contact (15) and said first mobile contact (13) to increase the dielectric strength of The separation between contacts. 20. The compact electric switch (40) with current limitation of claim 19 wherein said shutter (53) of the contact spacing comprises a isolation barrier (53a) having a first end close to said first fixed contact (15) and a second end (53b) anchored on said arm (12) of the contacts and directed by a guide (54) located inside said housing (11) of the switch electric. 21. The compact electric switch (40) with current limitation of claim 20 wherein said guide (54) comprises a first surface (55) and a second surface (56), whose first surface forms a cavity (57) in which is placed said first fixed contact (15), and whose second surface (56) forms an opening through which said first passes mobile contact (13). 22. The compact electric switch (40) with current limitation of claim 21 wherein said isolation barrier (53a) is greater than said cavity (57) and said opening in order to effectively close said cavity (57) and said opening when said first fixed contact (15) and said first mobile contact (13). 23. The compact electric switch (40) with current limitation of claim 20 wherein said anchor is effectively located on said arm (12) of the contacts to promote the translation of said barrier from isolation (53a) between said first fixed contact (15) and said first mobile contact (13) when said first contact is separated fixed (15) and said first mobile contact (13). 24. The compact electric switch (40) with current limitation of claim 20 wherein said second end (53b) of said isolation barrier (53a) it comprises at least one leg adjacent to said arm (12) of the contacts and pivotally coupled to said arm (12) of the contacts 25. The compact electric switch (40) with current limitation of claim 20 wherein said Insulation barrier (53a) is composed of a material insulating.