CA1119219A - Electromagnetic circuit breaker arc extinguishing device comprising a helically-shaped arcing chamber - Google Patents
Electromagnetic circuit breaker arc extinguishing device comprising a helically-shaped arcing chamberInfo
- Publication number
- CA1119219A CA1119219A CA000319841A CA319841A CA1119219A CA 1119219 A CA1119219 A CA 1119219A CA 000319841 A CA000319841 A CA 000319841A CA 319841 A CA319841 A CA 319841A CA 1119219 A CA1119219 A CA 1119219A
- Authority
- CA
- Canada
- Prior art keywords
- arc
- arc chamber
- electrodes
- chamber
- axial channel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
- H01H85/02—Details
- H01H85/38—Means for extinguishing or suppressing arc
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/30—Means for extinguishing or preventing arc between current-carrying parts
- H01H9/34—Stationary parts for restricting or subdividing the arc, e.g. barrier plate
Landscapes
- Arc-Extinguishing Devices That Are Switches (AREA)
- Fuses (AREA)
- Discharge Heating (AREA)
- Circuit Breakers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electromagnetic arc extinction apparatus for switchgear comprises an arc chamber made of an electrically insulating material and having an axial channel. There are two electrodes arranged in axial relationship to the axis of the arc chamber and adapted to form an arc having a helical shape. To provide for movement of the arc in a radial direction, the arc chamber defines a helical cavity whose pitch is at least 10 times smaller than the diameter of the arc chamber measured over its cross-section. In the apparatus of the invention, the helical arc has a small pitch with the result that the associated switchgear offers small overall dimensions and can handle high voltages.
An electromagnetic arc extinction apparatus for switchgear comprises an arc chamber made of an electrically insulating material and having an axial channel. There are two electrodes arranged in axial relationship to the axis of the arc chamber and adapted to form an arc having a helical shape. To provide for movement of the arc in a radial direction, the arc chamber defines a helical cavity whose pitch is at least 10 times smaller than the diameter of the arc chamber measured over its cross-section. In the apparatus of the invention, the helical arc has a small pitch with the result that the associated switchgear offers small overall dimensions and can handle high voltages.
Description
~119219 Th~ invention relates to switchgear in which an arc is formed between electrodes, namely, to electromagnetic switch-gear using a magnetic blast which provides for the lengthening of the arc when the arc column is acted upon by the force resulting from electromagnetic interaction between the arc current and a magnetic field. In particular, the invention relates to eleetromagnetic arc extinction apparatus used in switchgear.
The apparatus of t~e invention is suitable for use on any desirable alternating or direct current circuits and can find use in high-voltag~ heavy-current switchgear including circuit breakers, fuses and electroexplosion trips.
A quenching arc occurring in switchgear can be extinguished by recovering the arc voltage up to that existing across the eontacts of the circuit being switched.
It is known that the breaking arc voltage is given by U = E 11 ~ ~ UN, where E is the intensity of the electric field in the arc column, la is the length of the arc, and ~ UN is the sum of the voltage drops at the electrodes. There are therefore three ~ethods by which the arc voltage can be increased:
increasing the number of voltage drops at the
The apparatus of t~e invention is suitable for use on any desirable alternating or direct current circuits and can find use in high-voltag~ heavy-current switchgear including circuit breakers, fuses and electroexplosion trips.
A quenching arc occurring in switchgear can be extinguished by recovering the arc voltage up to that existing across the eontacts of the circuit being switched.
It is known that the breaking arc voltage is given by U = E 11 ~ ~ UN, where E is the intensity of the electric field in the arc column, la is the length of the arc, and ~ UN is the sum of the voltage drops at the electrodes. There are therefore three ~ethods by which the arc voltage can be increased:
increasing the number of voltage drops at the
-2 B 7~
lll9Z~9 electrodes; increasing the intensity of the electric field in B the arc column; and lengthening the quenching arc.
During the switching of alternating-current circuits, the arc can be extiguished (the electric strength of the in-terelectrode gap can be restored) at current zero in an al-ternatin~-current circuit. This feature can be used effecti-vely in the case of vacuum-type circuit breakers which are bein~ develop~d on a wide ba~is at the present time.
Increasing the number of voltage drops at the electrodes is basically applicable to low-voltage switchgear. In this case t the quenching arc is split into a number o~ series-con-nected smaller arcs each of which ha~ its own voltage drop at the anode and cathode. Since the sum of these voltage drops does not usually exceed several tens o~ voltsthis method is used as an auxiliary one in the case of high-voltage switch-gear.
At present, the method o~ increasing the intensity of the electric field in the arc column is basically ~uitable ~or high-voltage applications where U exceeds 10 to 20 kV.
The method can find use in a.c. oil, small oil volume, air--blast and S~6-filled circuit breakers. For the~e voltages, a.c. circuit breakers rated for higher parameters act as d.c.
circuit breakers.
In these apparatus, the intensity of the electric field in the arc column is increased in a manner that the arc column is subjected to longitudinal, lateral or radial/longitudinal blast using the working gas (compressed air or sulphur hexa-.
: :
.
.
~119Zl9 fluoride gas) or the products obtained during the decomposi-tion of the working liquid (oil). In this case, the inten~ity E is e~ual to hundreds or thousands of V/cm, the spacing bet-~een the electrodes amounts to several ten~ of centimeter, the arc le~gth 11 reaches one to two meters, and a maximum turn--off voltage for one pair of electrodes reaches a ~alue of 100 to 300 kV. However, the disadvantage of the apparatus is that they have a low switching time, ~ , which is usually equal to 0.2 to 0.06 s. In the latest embodiments, attempts are made to attai~ 0.02 s swi~ching time by using sulphur he,~afluoride gas.
Another disad~antages of the described apparatus are con-cerned with large dimensions and weight and with sophisticated design and laborious maintenance. Indeed, oil is fire-hazar-dous, air must be compressed, and S~6 gas requires that the construction be hermeticalb sealed.
B The lengtheniDg of the 4DeD~bi*~ arc basically applies to electromagnetic switchgear in which case an arc is caused to move under the action of the force ~ resulted from electromag-netic interaction between the arc current and a magnetic field, ; that movement being performed over di~erging (horn-shaped) electrodes and accompanied b~ a lengthening of the arc. The ma~netic field is formed by external sources suoh a~ arc--quenching coils or the magnetic field of the arc current it-self is employed.
Electromagnetic switchgear offers simple d~sign feature~
and good reliability, allows for multip~e switching of circuits, does not require special work~ng medium and pro~ides for a r ~ 4 ~
2i9 higher operational speed that is increased with an increase of the current being interrupted, which makes this switchgear current-limiting during the interruption of short-circuit currents.
Finally, with electromagnetic switchgear a.c. and d.c. uses are possible.
The switching time T of electromagnetic switchgear is determined by the distance _ covered by the arc column when it is moved in a direction of t~e driving force F, and is also determined by the velocity Va which is dependent upon the force F and upon the conditions under which the arc column is moved.
Therefore, T = a/Va. In the case of a straight arc, its length may exceed the value of a several times at most. For example, 1 = ~a if the arc is semicircular. ~ith la~U/E, a relationship between the switching time T and the turn-off voltage U in the case of electromagnetic switchgear is given by ~=U/kEVa where k = la/a is the proportionality coefficient to relate the arc length and the path covered by the arc column, this coefficient being dependent upon the arc shape. In the case of a freely moving arc, the intensity E is dependent upon the arc velocity and current and is usually equal to 10 to 100 V/cm. ~ith U = 10 kV at Va%50 m/s, E~30 V/cm and k = ~, the switching time T be-comes equal to 0.02 s, which gives the overall size of the arc extinction apparatus equal to 2a x 2 m.
To reduce the overall size of the arc extinction apparatus and provide for better operating conditions and good arrangement of its components, electromagnetic switchgear is us-ually provided with an arc cham~er which is a slit-shaped struc-ture.
~ - 5 -~' ~119219 formed from plates made of electrically insulating material.
The arc chamber operates to form the arc and to determine the direction of its movement, provides for an increase the inten-sity ofthe electric field in the arc column by compressing and cooling the latter, and makes it possible to utilize magnetic circuits that help enhance magnetic blast. When a labyrinth (zig-zaglike) slit is used the ~uenching arc can be lengthened additionally. However, the length of the arc can be increased using a labyrinth arc chamber only several times since the force F responsible for the movement of the arc column is decreased in this case with the result that switchgear is given a lower response.
To interrupt currents that are smaller in comparison to rated current magnitude and that therefore result in a decrease in the effectiveness of magnetic blast, electromagnetic circuit breakers are usually provided wi~h a self-blast air system.
Labyrinth arc chambers made it possible to develop electromagnetic circuitbreaker-s rated, for example, for 10 to 20 kV and having the overall size of 1 m approximate-y and the switching time not exceeding 0.06 s. However, electromagnetic circuit breakers cannot find use at the present for switching higher voltages since their dimensions would become too large in this case along ~ith a decreased switching time which is an im-portant parameter of a circuit breaker.
The range of working voltages handled by electro-magnetic circuit breakers can be increased by employing a spiral or helix-shaped breaking arc, the helix having a small value of the pitch ~.
r~ 6 ~,~
Known in the art is a circuit breaker utili~ing a helix-B shaped ~le~ch~*~ arc (cf. J. Miyachi, H.Naganawa, Spiral Arc in SF6 Facilitating DC Interruption, III International Confe-rence on Gas Dischsrges, Lo,ndon, 1974, p. 521). In this circuit breaker, a free straight arc is ~ormed between electrodes closed by a wire a~ter the latter is exploded electrically or after the parting of the electrodes in an axial direction. The arc surrounded by a ma~netic field applied in a longitudinal direc-tion relati~e to the electrodes axi-~ takes the for~ of a helix that expa~d~ in a radial direction and the voltage across the electrodes tends to rise in this case. ~owever, the helix featu-res a nonregular form due to the presence of a large number of random distortions o~ very diversified shapes and dimensions.
~his results in a condition where certain portions or turns of the arc column are caused to converge and a brealEdo~n there-fors ta'~es place with the result that a sudden decrease in thè
voltage across the electrodes occurs, while the portions of the arc column brought together are shunted and disintn-grated. This phenomenon basically applies to small-scale dis-tortions of the arc column which tend to de~elop at a greater rate.
This arc is therefore difficult to ubilize; a ratio bet-ween the arc length and the electrode spacing amounts to 10 to 12 with the arc diameter of 4 to 6 cm and the helix pitch o~ 3 cm approximately.
There is an arc extinction apparatus for switchgear (cf. German Patent ~o. 330,268, cl. 23c 355, 1919), which apparatus comprises two electrodes adspted to produce a lll9Z:l9 quenching arc in the the from o~ a helix that expands in a raclial direction.
In the described apparatus, the electrodes are mounted on a cylinder member made of an electrically insulating material and are bent to take the form o~ a heli~. ~o protect the elec-trode turns from breakdown, the cylinder member has a heli~--shaped partition made of an electrically insulating material and having the value of the pitch of its helix equal to the electrode helix pitch.
The e~pansion of the arc in a radial direction is attained due to the force of electromagnetic interaction between the tanOential component o~ the arc current and the longitudinally oriented ma~netic field formed by an arc-que~ching coil disposed within the cylinder member.
When the electrodes are caused to move in opposite direc-tlons the parting of the electrodes takes place and~a qusn^hi~
arc is struck. The electromagnetic interaction between the ra-dial component of the arc current at the areas adjacent the electrodes and a longitudinally oriented magnetic field causes the "winding" of the arc on to the helix-shaped electrodes ~ith the result that the arc assumes the form of a helix.
The ~u~ching arc expands in a radial direction and moves away from the surface of the cylinder member at a location where the helix partition does not give in~luence on the from of the arc column and on the direction in which the latter is moved and does not resist the occurrence of a breakdown bet-ween the adjacent turns of the helix arc. As a result, the arc can be lengthened within specific limits only and the working ~, lll9Z19 voltage at which the switchgear operates reliably amounts to a value of several kV, the proper overall size of the apparatus not exceeding 1 m in thïs case.
The described apparatus is therefore disadvantageous in that the working voltage is low due to a small length of the helix-shaped arc so produced, which is equal to one or more turns. In addition, the electrodes must follow a helix path and must have a helix shape, which results in complex design features of the associated switchgear.
~n object of the invention is to provide an electro-magnetic arc extinction apparatus for switchgear, which apparatus can provide for an increase in the working voltage at the given overall dimensions of the switchgear so that its switching time is maintained at a preset level or increased.
Another object of the invention is to provide a relatively simple electromagnetic arc extinction apparatus for switchgear operating at the working voltage exceeding 10 kV.
Still another o~ject of the invention is to provide an electromagnetic arc extinction apparatus for switchgear, which apparatus can be used in different switching devices s-uch as circuit ~reakers, fuses and electroexplosion trips.
Accordingly, the present invention provides an electromagnetic arc extïnction apparatus for switch~ear, comprising: an arc chamber formed of electrically insulating material and defining a helical cavity having a pitch which is at least 10 times smaller than the diameter of the arc chamber measured over the cross-section t~ereof, an axial channel in sa;d arc chamber communicating throughout its extent with the helical cavity, and two electrodes disposed in alignment in said axial channel such that, in the presence of a magnetic field, an arc struck between said two electrodes will be expanded out-wardly into said helical cavity thereby to extend the length of B
lll~Zl9 the arc.
Advantageously, the electromagnetic arc extinction apparatus has an arc chamber whose cavity narrows in a radial direction.
Preferably, the electromagnetic arc extinction apparatus has an arc chamber that comprises strengthening members disposed in its cavity and rigidly attached to its walls, with the result that the apparatus is robust and has good mechanical strength and vibration stability.
Advantageously, the electromagnetic arc extinction apparatus has an arc cham~er that includes elements made of an electrically conducting material and adapted to shift the ends of the arc in a radial direction, said elements being disposed on respective end faces of the arc chamber and electrically connected to respective electrodes which are located on corresponding end faces of the arc chamber, said elements being used to provide for greater service life of the electrodes.
Preferably, the electromagnetic arc extinction apparatus has a first electrode allowed to be moved in the axial channel of an arc chamber, the first electrode having a rod made of an electrically inqulating material, adapted to resist the oacur-~.
B
Z~g rence of a breakdown in the axial channel, and affixed to that end of the firstelectrodewhich faces a second electrode having an axial hole that accomodates the rod, the length of the latter being selected to be equal at least to the spacing between the two electrodes with the first electrode held in its extreme position.
Advantageously, the electromagnetic arc extinction apparatus has an arc chamber that narrows towards that its end face on which said first electrode is located and is allowed to be moved in the axial channel of said arc chamber.
Preferably, the electromagnetic arc extinction appa-ratus comprises a fusible element in the form of a wire that con-nects two electrodes, andalso comprises an arc chamber, said fusible element being disposed in the axial channel of the arc chamber, the diameter of the wire being selected to be equal to that of the axial channel.
Advantageously, the electromagnetic arc extinction apparatus for switchgear comprises a fusible element in the form of a wire that connects two electrodes, and also comprises an arc chamber having an insert made of an electrically insulating material, the insert being disposed in the axial channel of the arc chamber and having its diameter equal to that of the axial channel, and the fusible element being arranged in the form of a helix and disposed on the insert in the cavity of the arc chamber.
The apparatus of the invention provides for a helix-shaped arc whose helix has a small pitch. This ensures a higher compactness of spatial arrangement of the arc and small ",, ~:
~g219 overall dimensions of the apparatus of the invention ~hich is capable of switching high voltages reaching hundreds of kYs and more and is suitable ~or a.c. and d.c. applications. ~he path covered by the arc column during its movement in a radial di-rection, caused by electromagnetic interaction between the arc current and a magnetic field, is maintained during the switch-ing process at a low magnitude reachin~ 1 m approximately, with the result that the switching time is high and the apparatus can be operated as a currentlimiting one during the interruption of shoxt-circuit currents.
A small pitch of the helix of the arc provides for effect-iYe use of the magnetic field of the arc current itself, which ensures higher switching time of the apparatus of the inven-tion and simpler design of the associated switchgear since the-re is no need in some cases for arc-quenching coils and magne-tic circuits.
~ he apparatus of the invention provides for high-voltage heavy-curre~t electromagnetic circuit breakers uhich are compa-rsble with the present-day competitors l~noY~ in the art such as oil, small oil volume, air-blast and SF6-filled circuit breakers rated ~or the voltages of tens and hundreds of ~ and more and for currents of hundreds and thousands of A and more. The elec-tromag~etio circuit breakers provide for multiple switching o~
the controlled circuits and for higher switching time (for example, halfwave current interruption is attained in the case of a.c. circuits). ~hese circuit breakex~ also offer good re-liability and convenient maintenance.
, .
.
In the case of fuse gear, the apparatus of the in-vention makes it possible to construct simple, inexpensive and high-speed protective devices of the overall dimensions whieh can handle working voltages of hundreds of kV and can be operated on a.c:. and d.e. circuits; such devices are not known in the prior art.
In addition, the apparatus of the invention can pro-vide for the construction of high-voltage heavy-current trips which fund use in some special eases sueh as the switching of in-10 - duetion-type aeeumulators.
The invention will now be described in more detail, by way of example only, with reference to the accompanying draw-ings, in whieh:-Figure 1 is a cut-away perspective view of an electro-magnetie are extinetion apparatus for switehgear, aecording to the invention;
Figure 2 is a longitudinal seetion view of an embodi-ment of the are ehamber of the eleetromagnetie are extinetion apparatus, the cavity of the are ehamber having its seetion nar-rowing in a radial direetion, according to the invention;
~ Figure 3 i5 a longitudinal seetion view of another ; embodiment of the are ehamber of the eleetromagnetic are extine-tion appatatus, the cavity of the are ehamber having a zig-zag like seetion, aeeording to the invention;
Figure 4 is a longitudinal seetion view of the are chamber of the ~leetromagnetie are extinetion apparatus, having fixation members;
~7~?"' ~19Z19 Figure 5 is a section taken along the line V-V of Fig.
4, according to the invention;
Figure ~ is a longitudinal section view of the electromagnetic arc extinction apparatus having end face discs, according to the invention;
Figure 7 is- a longitudinal section view of an embod-iment of the electromagnetic arc extinction apparatus, including a rod made of an electrically insulating material ana disposed in the axial channel of the arc chamber, according to the invention;
- Figure 8 shows an electromagnetic arc extinction apparatus for fuse gear, according to the invention;
Figure g shows an electromagnetic arc extinction apparatus for fuse gear and electroexplosion trip, according to the invention.
The electromagnetic arc extinction apparatus for switchgear, according to the invention, is described as an arc extinction apparatus intended for a circuit breaker. The apparatus is intended for connection to the power contacts of a 2~ circuit breaker which serve to carry the current during a time interval ~etween two successive switchings.
The apparatus of the invention comprises an arc chamber 1 (Fig. 1~ including a helical cavity and an axial channel 2.
The latter accommodates two electrodes 3,4. The diameter of the electrodes 3,4
lll9Z~9 electrodes; increasing the intensity of the electric field in B the arc column; and lengthening the quenching arc.
During the switching of alternating-current circuits, the arc can be extiguished (the electric strength of the in-terelectrode gap can be restored) at current zero in an al-ternatin~-current circuit. This feature can be used effecti-vely in the case of vacuum-type circuit breakers which are bein~ develop~d on a wide ba~is at the present time.
Increasing the number of voltage drops at the electrodes is basically applicable to low-voltage switchgear. In this case t the quenching arc is split into a number o~ series-con-nected smaller arcs each of which ha~ its own voltage drop at the anode and cathode. Since the sum of these voltage drops does not usually exceed several tens o~ voltsthis method is used as an auxiliary one in the case of high-voltage switch-gear.
At present, the method o~ increasing the intensity of the electric field in the arc column is basically ~uitable ~or high-voltage applications where U exceeds 10 to 20 kV.
The method can find use in a.c. oil, small oil volume, air--blast and S~6-filled circuit breakers. For the~e voltages, a.c. circuit breakers rated for higher parameters act as d.c.
circuit breakers.
In these apparatus, the intensity of the electric field in the arc column is increased in a manner that the arc column is subjected to longitudinal, lateral or radial/longitudinal blast using the working gas (compressed air or sulphur hexa-.
: :
.
.
~119Zl9 fluoride gas) or the products obtained during the decomposi-tion of the working liquid (oil). In this case, the inten~ity E is e~ual to hundreds or thousands of V/cm, the spacing bet-~een the electrodes amounts to several ten~ of centimeter, the arc le~gth 11 reaches one to two meters, and a maximum turn--off voltage for one pair of electrodes reaches a ~alue of 100 to 300 kV. However, the disadvantage of the apparatus is that they have a low switching time, ~ , which is usually equal to 0.2 to 0.06 s. In the latest embodiments, attempts are made to attai~ 0.02 s swi~ching time by using sulphur he,~afluoride gas.
Another disad~antages of the described apparatus are con-cerned with large dimensions and weight and with sophisticated design and laborious maintenance. Indeed, oil is fire-hazar-dous, air must be compressed, and S~6 gas requires that the construction be hermeticalb sealed.
B The lengtheniDg of the 4DeD~bi*~ arc basically applies to electromagnetic switchgear in which case an arc is caused to move under the action of the force ~ resulted from electromag-netic interaction between the arc current and a magnetic field, ; that movement being performed over di~erging (horn-shaped) electrodes and accompanied b~ a lengthening of the arc. The ma~netic field is formed by external sources suoh a~ arc--quenching coils or the magnetic field of the arc current it-self is employed.
Electromagnetic switchgear offers simple d~sign feature~
and good reliability, allows for multip~e switching of circuits, does not require special work~ng medium and pro~ides for a r ~ 4 ~
2i9 higher operational speed that is increased with an increase of the current being interrupted, which makes this switchgear current-limiting during the interruption of short-circuit currents.
Finally, with electromagnetic switchgear a.c. and d.c. uses are possible.
The switching time T of electromagnetic switchgear is determined by the distance _ covered by the arc column when it is moved in a direction of t~e driving force F, and is also determined by the velocity Va which is dependent upon the force F and upon the conditions under which the arc column is moved.
Therefore, T = a/Va. In the case of a straight arc, its length may exceed the value of a several times at most. For example, 1 = ~a if the arc is semicircular. ~ith la~U/E, a relationship between the switching time T and the turn-off voltage U in the case of electromagnetic switchgear is given by ~=U/kEVa where k = la/a is the proportionality coefficient to relate the arc length and the path covered by the arc column, this coefficient being dependent upon the arc shape. In the case of a freely moving arc, the intensity E is dependent upon the arc velocity and current and is usually equal to 10 to 100 V/cm. ~ith U = 10 kV at Va%50 m/s, E~30 V/cm and k = ~, the switching time T be-comes equal to 0.02 s, which gives the overall size of the arc extinction apparatus equal to 2a x 2 m.
To reduce the overall size of the arc extinction apparatus and provide for better operating conditions and good arrangement of its components, electromagnetic switchgear is us-ually provided with an arc cham~er which is a slit-shaped struc-ture.
~ - 5 -~' ~119219 formed from plates made of electrically insulating material.
The arc chamber operates to form the arc and to determine the direction of its movement, provides for an increase the inten-sity ofthe electric field in the arc column by compressing and cooling the latter, and makes it possible to utilize magnetic circuits that help enhance magnetic blast. When a labyrinth (zig-zaglike) slit is used the ~uenching arc can be lengthened additionally. However, the length of the arc can be increased using a labyrinth arc chamber only several times since the force F responsible for the movement of the arc column is decreased in this case with the result that switchgear is given a lower response.
To interrupt currents that are smaller in comparison to rated current magnitude and that therefore result in a decrease in the effectiveness of magnetic blast, electromagnetic circuit breakers are usually provided wi~h a self-blast air system.
Labyrinth arc chambers made it possible to develop electromagnetic circuitbreaker-s rated, for example, for 10 to 20 kV and having the overall size of 1 m approximate-y and the switching time not exceeding 0.06 s. However, electromagnetic circuit breakers cannot find use at the present for switching higher voltages since their dimensions would become too large in this case along ~ith a decreased switching time which is an im-portant parameter of a circuit breaker.
The range of working voltages handled by electro-magnetic circuit breakers can be increased by employing a spiral or helix-shaped breaking arc, the helix having a small value of the pitch ~.
r~ 6 ~,~
Known in the art is a circuit breaker utili~ing a helix-B shaped ~le~ch~*~ arc (cf. J. Miyachi, H.Naganawa, Spiral Arc in SF6 Facilitating DC Interruption, III International Confe-rence on Gas Dischsrges, Lo,ndon, 1974, p. 521). In this circuit breaker, a free straight arc is ~ormed between electrodes closed by a wire a~ter the latter is exploded electrically or after the parting of the electrodes in an axial direction. The arc surrounded by a ma~netic field applied in a longitudinal direc-tion relati~e to the electrodes axi-~ takes the for~ of a helix that expa~d~ in a radial direction and the voltage across the electrodes tends to rise in this case. ~owever, the helix featu-res a nonregular form due to the presence of a large number of random distortions o~ very diversified shapes and dimensions.
~his results in a condition where certain portions or turns of the arc column are caused to converge and a brealEdo~n there-fors ta'~es place with the result that a sudden decrease in thè
voltage across the electrodes occurs, while the portions of the arc column brought together are shunted and disintn-grated. This phenomenon basically applies to small-scale dis-tortions of the arc column which tend to de~elop at a greater rate.
This arc is therefore difficult to ubilize; a ratio bet-ween the arc length and the electrode spacing amounts to 10 to 12 with the arc diameter of 4 to 6 cm and the helix pitch o~ 3 cm approximately.
There is an arc extinction apparatus for switchgear (cf. German Patent ~o. 330,268, cl. 23c 355, 1919), which apparatus comprises two electrodes adspted to produce a lll9Z:l9 quenching arc in the the from o~ a helix that expands in a raclial direction.
In the described apparatus, the electrodes are mounted on a cylinder member made of an electrically insulating material and are bent to take the form o~ a heli~. ~o protect the elec-trode turns from breakdown, the cylinder member has a heli~--shaped partition made of an electrically insulating material and having the value of the pitch of its helix equal to the electrode helix pitch.
The e~pansion of the arc in a radial direction is attained due to the force of electromagnetic interaction between the tanOential component o~ the arc current and the longitudinally oriented ma~netic field formed by an arc-que~ching coil disposed within the cylinder member.
When the electrodes are caused to move in opposite direc-tlons the parting of the electrodes takes place and~a qusn^hi~
arc is struck. The electromagnetic interaction between the ra-dial component of the arc current at the areas adjacent the electrodes and a longitudinally oriented magnetic field causes the "winding" of the arc on to the helix-shaped electrodes ~ith the result that the arc assumes the form of a helix.
The ~u~ching arc expands in a radial direction and moves away from the surface of the cylinder member at a location where the helix partition does not give in~luence on the from of the arc column and on the direction in which the latter is moved and does not resist the occurrence of a breakdown bet-ween the adjacent turns of the helix arc. As a result, the arc can be lengthened within specific limits only and the working ~, lll9Z19 voltage at which the switchgear operates reliably amounts to a value of several kV, the proper overall size of the apparatus not exceeding 1 m in thïs case.
The described apparatus is therefore disadvantageous in that the working voltage is low due to a small length of the helix-shaped arc so produced, which is equal to one or more turns. In addition, the electrodes must follow a helix path and must have a helix shape, which results in complex design features of the associated switchgear.
~n object of the invention is to provide an electro-magnetic arc extinction apparatus for switchgear, which apparatus can provide for an increase in the working voltage at the given overall dimensions of the switchgear so that its switching time is maintained at a preset level or increased.
Another object of the invention is to provide a relatively simple electromagnetic arc extinction apparatus for switchgear operating at the working voltage exceeding 10 kV.
Still another o~ject of the invention is to provide an electromagnetic arc extinction apparatus for switchgear, which apparatus can be used in different switching devices s-uch as circuit ~reakers, fuses and electroexplosion trips.
Accordingly, the present invention provides an electromagnetic arc extïnction apparatus for switch~ear, comprising: an arc chamber formed of electrically insulating material and defining a helical cavity having a pitch which is at least 10 times smaller than the diameter of the arc chamber measured over the cross-section t~ereof, an axial channel in sa;d arc chamber communicating throughout its extent with the helical cavity, and two electrodes disposed in alignment in said axial channel such that, in the presence of a magnetic field, an arc struck between said two electrodes will be expanded out-wardly into said helical cavity thereby to extend the length of B
lll~Zl9 the arc.
Advantageously, the electromagnetic arc extinction apparatus has an arc chamber whose cavity narrows in a radial direction.
Preferably, the electromagnetic arc extinction apparatus has an arc chamber that comprises strengthening members disposed in its cavity and rigidly attached to its walls, with the result that the apparatus is robust and has good mechanical strength and vibration stability.
Advantageously, the electromagnetic arc extinction apparatus has an arc cham~er that includes elements made of an electrically conducting material and adapted to shift the ends of the arc in a radial direction, said elements being disposed on respective end faces of the arc chamber and electrically connected to respective electrodes which are located on corresponding end faces of the arc chamber, said elements being used to provide for greater service life of the electrodes.
Preferably, the electromagnetic arc extinction apparatus has a first electrode allowed to be moved in the axial channel of an arc chamber, the first electrode having a rod made of an electrically inqulating material, adapted to resist the oacur-~.
B
Z~g rence of a breakdown in the axial channel, and affixed to that end of the firstelectrodewhich faces a second electrode having an axial hole that accomodates the rod, the length of the latter being selected to be equal at least to the spacing between the two electrodes with the first electrode held in its extreme position.
Advantageously, the electromagnetic arc extinction apparatus has an arc chamber that narrows towards that its end face on which said first electrode is located and is allowed to be moved in the axial channel of said arc chamber.
Preferably, the electromagnetic arc extinction appa-ratus comprises a fusible element in the form of a wire that con-nects two electrodes, andalso comprises an arc chamber, said fusible element being disposed in the axial channel of the arc chamber, the diameter of the wire being selected to be equal to that of the axial channel.
Advantageously, the electromagnetic arc extinction apparatus for switchgear comprises a fusible element in the form of a wire that connects two electrodes, and also comprises an arc chamber having an insert made of an electrically insulating material, the insert being disposed in the axial channel of the arc chamber and having its diameter equal to that of the axial channel, and the fusible element being arranged in the form of a helix and disposed on the insert in the cavity of the arc chamber.
The apparatus of the invention provides for a helix-shaped arc whose helix has a small pitch. This ensures a higher compactness of spatial arrangement of the arc and small ",, ~:
~g219 overall dimensions of the apparatus of the invention ~hich is capable of switching high voltages reaching hundreds of kYs and more and is suitable ~or a.c. and d.c. applications. ~he path covered by the arc column during its movement in a radial di-rection, caused by electromagnetic interaction between the arc current and a magnetic field, is maintained during the switch-ing process at a low magnitude reachin~ 1 m approximately, with the result that the switching time is high and the apparatus can be operated as a currentlimiting one during the interruption of shoxt-circuit currents.
A small pitch of the helix of the arc provides for effect-iYe use of the magnetic field of the arc current itself, which ensures higher switching time of the apparatus of the inven-tion and simpler design of the associated switchgear since the-re is no need in some cases for arc-quenching coils and magne-tic circuits.
~ he apparatus of the invention provides for high-voltage heavy-curre~t electromagnetic circuit breakers uhich are compa-rsble with the present-day competitors l~noY~ in the art such as oil, small oil volume, air-blast and SF6-filled circuit breakers rated ~or the voltages of tens and hundreds of ~ and more and for currents of hundreds and thousands of A and more. The elec-tromag~etio circuit breakers provide for multiple switching o~
the controlled circuits and for higher switching time (for example, halfwave current interruption is attained in the case of a.c. circuits). ~hese circuit breakex~ also offer good re-liability and convenient maintenance.
, .
.
In the case of fuse gear, the apparatus of the in-vention makes it possible to construct simple, inexpensive and high-speed protective devices of the overall dimensions whieh can handle working voltages of hundreds of kV and can be operated on a.c:. and d.e. circuits; such devices are not known in the prior art.
In addition, the apparatus of the invention can pro-vide for the construction of high-voltage heavy-current trips which fund use in some special eases sueh as the switching of in-10 - duetion-type aeeumulators.
The invention will now be described in more detail, by way of example only, with reference to the accompanying draw-ings, in whieh:-Figure 1 is a cut-away perspective view of an electro-magnetie are extinetion apparatus for switehgear, aecording to the invention;
Figure 2 is a longitudinal seetion view of an embodi-ment of the are ehamber of the eleetromagnetie are extinetion apparatus, the cavity of the are ehamber having its seetion nar-rowing in a radial direetion, according to the invention;
~ Figure 3 i5 a longitudinal seetion view of another ; embodiment of the are ehamber of the eleetromagnetic are extine-tion appatatus, the cavity of the are ehamber having a zig-zag like seetion, aeeording to the invention;
Figure 4 is a longitudinal seetion view of the are chamber of the ~leetromagnetie are extinetion apparatus, having fixation members;
~7~?"' ~19Z19 Figure 5 is a section taken along the line V-V of Fig.
4, according to the invention;
Figure ~ is a longitudinal section view of the electromagnetic arc extinction apparatus having end face discs, according to the invention;
Figure 7 is- a longitudinal section view of an embod-iment of the electromagnetic arc extinction apparatus, including a rod made of an electrically insulating material ana disposed in the axial channel of the arc chamber, according to the invention;
- Figure 8 shows an electromagnetic arc extinction apparatus for fuse gear, according to the invention;
Figure g shows an electromagnetic arc extinction apparatus for fuse gear and electroexplosion trip, according to the invention.
The electromagnetic arc extinction apparatus for switchgear, according to the invention, is described as an arc extinction apparatus intended for a circuit breaker. The apparatus is intended for connection to the power contacts of a 2~ circuit breaker which serve to carry the current during a time interval ~etween two successive switchings.
The apparatus of the invention comprises an arc chamber 1 (Fig. 1~ including a helical cavity and an axial channel 2.
The latter accommodates two electrodes 3,4. The diameter of the electrodes 3,4
3~
B
....
ill9;~19 ls determined by the magnitude of the working current and is equal to the diameter of the axial channel 2. The electrodes 3,4 are usually made of copper, copper/tungsten alloys and the like. The apparatus of the invention also comprises conventional arc-quenching coils (not shown) which are connected, for example, in series with the apparatus. These arc-quenching coils produce the magnetic field B (shown by a respective arrow in the figure) within the arc chamber 1 during the switching process. In the given embodiment, the magnetic field B is oriented in a direc-tion coincident with the axis of the arc chamber 1 and the elec-trodes 4,3 and is, therefore, a longitudinal one.
The arc chamber 1 causes a breaking arc 5 having a helical shape to move in a radial direction. In Fig. ~, r is the instantaneous radius of the arc 5 and F is the radial com-ponent of the force of electromagnetic interaction between the arc 5 and the magnetic field B, respective arrows being used to show the directions in which the column of the arc 5 is acted upon by that force. The arc chamber 1 is formed by a screwlike body which is a helical blade 6 having a pitch ~ and defining between adjacent turns thereof, the helical cavity having width . The helical cavity serves as an arc-quenching slit structure of the apparatus. The width of the slit structure and the magni-tudes of the current of the arc 5 and of the magnetic field B
determine the parameters of the arc 5 as follows: The current density; the size and shape of the arc column and the intensity of the electric field thereof; and the velocity of the arc column.
The :1119Z19 width of the helical cavity of the arc chamber 1 is usually selected to be equal to 2 to lOmm.
It is common practice to select the value of the pitch of the helical cavity of the arc cham~er 1 as small as possible.
It is dependent upon the material, fabrication techniques, operating conditions and service life of the arc chamber 1 and, more speci-fically, upon a maximum permissible thickness of the helical blade 6 which equals to ~ ). The helical blade 6 or the arc chamber 1 can be manufactured from different electrically insula-ting materials such as arc-resistant and gas-generating ones.
For example, cast plastics including polysulfone, polycarbonate and lavsan can be used for the purpose.
In the given embodiment, the heat load applied to the walls of the arc chamber 1 is less than the thermal load that affects the walls of the known electromagnetic labyrinth-type arc chambers due to the fact that in the former case the arc column moves with a greater velocity ( this phenomenon will be explained hereinafter). In addition, the helical blade 6 of the arc chamber 1 is subjected tb a relatively small mechanical load since the arc 5 acts upon it from two sides. As a result, the material of the helical blade 6 may possess properties that are inferior to those of the material from which the known electromagnetic labyrinth-type arc chambers are made.
The arc chamber 1 can be manufactured by casting or stamping. It is possible to construct a cheap sectional variant of the chamber comprised of the elements of the helical blade which connect one another.
~119Z19 The absolute values of the diameter D and length L
of the arc chamber 1 are determined by the working voltage and switching time of the associated switchgear (see calculation examples given below). The ratio between the diameter D of che chamber 1 and the pitch of the helical cavity must be not less than 10 in order to obtain a sufficient lengthening of the arc 5 which is 102 to 103 times the ~ength L of the chamber l, which determine the maximum separation between the electrodes 3,4.
The helical cavity of the arc chamber 1 (Fig. 1) is rectangular in cross-section in the radial direction. It is good practice, however, to make the cavity narrow in a radial direction in order to obtain a variation of the intensity of the electrical field of the arc column as the current decreases during the switching process. Figure 2 shows an arc chamber 7 whose helical cavity has a trapezoidal section.
Figure 3 shows an arc chamber 8 whose helical cavity has a zig-zag like section extending in a radial direction.
According to this embodiment, the arc chamber 8 may also have its helical cavity with a variable pitch ~, which makes it possible to vary the velocity of the arc column. This embodiment is advantageous in that the axial channel 2 (Fig. l) can be protected from light radiation emitted by the arc 5, that tends to expand in a radial direction, with the result that the electrical strength of the medium contained in the axial channel 2 is restored at a higher rate. In addition, the zig-zag like section of the - helix cavity of the arc chamber 8 ` 30 - ~ L
lll9Z19 (Fig. 3) allows the sound effect occurring during the switching proces,s to be reduced.
To provide for mechanical strength, robustness and vibration stability of the apparatus of the invention, it com-prises strengthening members 9, io (Figs. 4,5) which are disposed within the helical cavity of an arc chamber 11 (Fig. 4) and are rigidly coupled with the walls of the chamber, said walls being formed by a helix blade 12. The arc chamber 11 has an axial channel 13 which accomodates electrodes 14, 15.
The strengthening members 9,10 (Fig. 5) are arranged in two rows in circumferential relation to the arc chamber 11.
One of the two rows includes the strengthening members 9 made as cylindrical inserts, while the other row includes the strengh-ening members 10 made as ribs.
The position and dimensions of the strengthening members 9,10 are dependent upon the materials and fabrication processes used for the manufacture of the members and the arc chamber 11 and must be s~ch that an arc 16 (Fig. 5) is allowed to pass freely around the members. The position of the column of the arc 16 is shown for two- successive points in time occupied by the arc in the course of its movement in a radial direction:
a is the point in time when the arc passes around the members 9 and b is the point in time when the arc approaches the members 10.
~19219 The strengthening members 9,10 can be fabricated from metal. In this case, they additionally act as an arc-quen-ching grid with the result that the parameters of the arc chamb~r 11 are improved. In this embodiment, the strengthening member 9,10 must be electrically insulated one from another.
In addition, the strengthening members can provide a means for coupling separate parts of a sectional arc chamber with an appreciable assembly accuracy.
To allow the ends of the arc to be moved in a radial direction, additional horn-shaped electrodes are introduced in the arc chamber. These electrodes, made of an electrically conducting material, are oriented in a radial direction at the beginning and end of the helical cavity; the electrodes must be electrically connected to respective main electrodes.
Figure 6 shows an embodiment of the apparatus of the invention which comprises elements17,18 made of an electrically conducting material and allowing for the movement of the support spots of the arc in a radial direction. The elements 17,18 are implemented as metallic discs having axial holes and disposed on the end faces of the arc chamber 19. The elements 17,18 are electrically connected to respective electrodes 20,21 which are located at corresponding end faces in an axial channel 22.
The elements 17,18 can be fabricated, for example, from copper.
Figure 6 shows how the arc 23 expands in a radial direction as its ends move o~er the elements 17,18.
~. -- 19 --~., 1~92~g ~igure 7 shows an electromagnetic arc extinction appara-tus for a high-~oltage heavy-current circuit breaker. In the given embodiment, an immovable electrode 24 is implemented, for example, as a tubing that has its inner diameter equal to the diameter of a movable electrode 25. There is a rod 26 ma-de of an electrically insulating material and coupled, for example, by thread connection with the movable electrode 25.
~he diameter of the rod 26 is equal to the diameter of the movable electrode 25 and has its length equal at least to the spacing between the electrodes ~4, 25 with the electrode 25 held in it~ extreme position.
~he rod 26 provides ~or a condition where no breakdown occurs between the electrodes 24, 25 which are bein~ dra~n apart during the switching process, a feature ensuring reliab-le operation of an arc chamber 27.
A preferred material for the rod 26 is an arc-resistant and gas-~enerating one. Since the shape of the rod 26 is simple, ~arious materials such as ceramics, boron nitride and asbestos--cement can be used for the purpose. It ic~ feasible to make the electrode 24, for example, from one or more current-collecting ja~s.
B Note that the position of a quenchin6 arc 28 in the figu-re corresponds to a certain point in time during which the ap-paratus oY the invention is operated.
It is pre~erable to select that outline of the arc chamber 27 which corresponds to the form of the quenching arc 28, caused to expand in a radial direction, which form being attained at the moment when the switching process is terminated. According -- _ , ~, -.
, , 1~9Z19 to one of the embodiments, the arc chamber 27 narrows to-wards the end face at which the movable electrode 25 is lo-cated.
Let us calculate the overall and working dimensions of a circuit breaker which can handle a voltage U of 100 kV and which is operated in conjunction with the apparatus of the invention. Assume that the circuit breaker o~fers a s~itch-ing time of 10 ms, which provides for a half-wave interrupt-ion in the case of an a.c. circuit being switched. With an average velocity Va of the arc column equal to 50 to 100 m/s approximately, the permissible height of the slit and, therefo-re, the diameter D of the apparatus of the invention is given by D ~ 2V2Z = 1 to 2 m With an avérage intensity E of the electric field in the column of the breaking arc being moved equal to 20 to 30 VtcmJ
the desired arc length la is given by la = EU~?O to 100 m, a twofold margin for the turned-off voltage U being selected to take into account an overvoltage condition.
To provide for proper design of the apparatus of the in-vention, let the pitch ~ of the helix blade be equal to 1 cm approximately and the length L of the arc chamber be equal to its diameter D. This gives le --~
; D - L = ~ a ~ ~ 0.48 to 0.55 m ~ . .
' ll~9Z19 Therefore, the arc chamber h~;ing the dimensions D c o.55 m and L ~ 0.55 m is capable o~ switching a.c. and d.c. circuits at a voltage U of 100 kV (with a two~old voltage margin) and a switching time ~ c 0.01 s. With the apparatus of the i~ven-tion, there is no need for the following components of modern 100-kV circuit breakers: a reservoir accommodating 6 to 12 tons of oil in an oil circuit breaker, that weighs itself 8 to 15 tons; a reservoir accommodating 0.5 to 1.5 tons o~ oil in a small volume oil circuit breaker, that ~eighs itself 4 to 8 tons; a receiver with a compressor rated for 2 to 6 ~a in a compressed-air circuit brea~er, that weighs itsel~ 5 to 8 tons; and a hermetically sealed casing rated for 0.3 to 0.6 ~æa and filled with an expensive SF6 gas, in a self-blast S~6 cir-cuit breaker, that weighs itself 5 to 8 tons. Note that these modern circuit breakers can provide for a switching time of 0.06 to 0.1 s i~ the case of a.c. applications only.
~ igure 8 sho~s an electromagnetic arc extinction apparat-us for a high-voltage fuse. The apparatus comprises an arc ; chamber 29 made of an electrically insulating material. Immo-vable electrodes 30, 31 are located in axial relationship to the arc chamber 29 at it~ end faces and are connected by a fu-sible element 32 implemented as a wire made, for example, of copper. ~he fusible element 32 is disposed in the axial channel o~ the arc chamber 29, ths diameter of the ~usible element 32 being equal to the diameter o~ the axial channel.
It is known that ~uses are basically intended to protect the associated circuits ~rom short circuit and must there~ore ; o~fer a shorter switching time. In addition, fuses must be ~ - 22 -lll~Z19 appreciably simple and cheap. ~odern high-voltage fuses offer normal operation at voltage levels not exceeding 30 to 50 kV.
The basic component of a fuse is a fusible element that connect-q immovable electrodes serving in this case as po~er leads. The ratio between the arc length at the e~d o~ the switching pxocess and the length of the ~usible element is one of the most critical parameters that influence the design and operation of a fuse.
The high-voltage fuse of ~ig. 8 has a maximum permissible value of the above-mentioned ratio due to the fact that a straight fusible element 32 is used which has its length equal to the length of the arc chamber 29.
For example, an arc chamber of a 100-kv fuse (with a twofold voltage margin) has a quenching time of 3 ms at ~= 1 cm, E = 25 V~cm and Va = 50 m/s. In this case, the para-meters ~.L and ratio la/L are determined as follows:
D = 2Va ~= 0.3 m, L =~ = 0.9 m, and la/L = 90.
These dimensions ensure proper technical implementation of an arc ch~mber for a 100-kV fuse.
~ igure 9 shows another embodiment of the apparatus of the invention intended for a fuse and an electroexplosion trip, which embodiment comprises an arc chamber 33 whose axial channel accommodates a cylindrical insert 34. The diameter of the latter is equal to the diameter of the axial channel of the arc chamber 33. Wound on the insert 34 is a fusible ele-~ ment 35 having a pitch equal to the pitch of the ~ cavity ;~ of the arc chamber 33. The insert 34 is made o~ an electrically insulating material identical, for example, with that of the ' ~ :
',:
., , 1~19219 arc chamber 33. T'he end faces o~ the insert 34 ha~e respective metallic discs 36,37 which provide for electric contact bet-ween the fusible element 35 and immovable electrodes 38,39 o~ a ~use or electroexplosion trip.
In the given embodiment, the insert 34 can be replaced after the fusible element 35 has been blown. It is feasible, i~ the case of fuse application, to allow the insert 34 to be moved alon~ the axis of the arc cha~ber 33 after the fuse blowing so as to indicate that the circuit is turned off. A
new insert 34 with a new fusible element 35 is inserted in the arc chamber 33 and is ~ixed in a manner that a due space B alignment between the fusible element 35 and the ~ ca~ity of the arc chamber 33 is attained.
~ he arc chamber intended for fuse application can be made a multiturn one and the insert can be provided with se-veral fusible elements equal in number to the number o~ the turns of the helix cavity of the arc chamber. If a ~usible ele-me~t is blown, the next one can be connected in the curcuit by rotating the insert or the arc chamber together with the insert by a certain angle.
~ he embodiments of the present invention can be used in conjunction with the kno~n method~ dealing with arc extinction and employed in electromagnetic switching devices so as to impro~e the parameters o~ the latter.
The working medium in the circuit breaker housing can be changed; for examplet the latter is filled with the SF6 ~as.
The pressure within the housing can be ~aried; ~or example, the pressure is increased or decreased, or the housing is lll~Zl9 evacuated, the two latter cases being concerned with an increasein the switching time of the circuit breaker.
The arc voltage can be increased by virtue of arc-quenching and deionizing grids implemented as the sets of insula-ted plates arranged at the outlet of the arc-quenching slit in a direction of movement of the arc column.
Like conventional electromagnetic arc chambers, the arc chamber of the invention may have its helical cavity arranged in a zig-zag like (labyrinth) fashion along the quenching arc, namely, in a tangential direction, which provides f~r an additional increase of 1.5 to 3 times in the arc length without considerable increase in the overall dimensions of the arc chambers.
It is known that electromagnetic arc extinction de-vices cannot work effectively in the case of circuit breaker appli-cations when small currents are interrupted (which means that gas switching must be effected at a small load). To eliminate this drawback, the arc chamber of the present invention can be provided, like conventional electromagnetic arc chambers, with a gas `~: blast which is directed into the helical cavity with the result that a small-current quenching arc is lengthened.
Such a gas blast, for example, an air blast, can be delivered through the axial holes made in the movable and immo-vable e`lectrodes as well as~;n the rod of an electrically insula-ting material, connected with the movable electrode, and can be led into the helical cavity of the arc chamber through evenly distributed radial holes. The blast can also be delivered through the body of the helical blade and led into the cavity ~ - 25 -, lll9Zi9 through respective holes in the base of the blade in the vicini-ty of the axial channel of tne arc chamber~
The circuit breaker provided with the apparatus of the invention operates in the following manner. After an interrupt control signal is generated, the power contacts of the circuit breaker are separated with the result that the circuit current passes through the electrodes 3,4(Fig. 1) of the apparatus of the invention.
The arc 5 formed in the axial channel 2 of the arc 10 - chamber after the parting of the electrodes 3,4 is surrounded by the longitudinal magnetic field B produced by magnetic-blast coils (not shown). Under these conditions and at specific values of the associated parameters, the arc column changes to a helix-like shape (cf. an article by E.I. Asinovsky, A.A. Afanasyev, E.P.Pakhomov, entitled "Helix Instability of Arc in Longitudinal Magnetic Field" Proceedings of the Academy of Sciences of the USSR, 231, No. 2, 1976). Thus, there results a radial component of the force F of electromagnetic interaction between the arc current and the magnetic field due to the occurrence of the tan-gential component of the current of the quenching arc 5. Thatradial component of the force F causes the helical quenching arc to be drawn into the helical cavity of the arc chamber 1 and expand in a raaial direction.
In the presence of the longitudinal magnetic field, the radial components of the current of the quenching arc 5, existing at the areas adjacent the electrodes, cause a rotation of respective portions of the arc 5 in opposite directions under the action of the tangential compo-~ - 26 -"~
~119Zi9 nents of the force F. The arc 5 is therefore wound on the elec-trodes 3,4 in the form of a helix determined by the helical cavity of the arc chamber 1. As a result the rate of rise of the longi-tudinal s~ze of the quenching arc 5, which expands in a radial direction, is always greater than the rate of parting of the electrodes 3,4.
After the arc S reaches the length which allows for the recovery of a voltage across the contacts of the circuit breaker e~ual to the voltage across the contacts of the circuit being switch-ed, the current drops to zero. At this point in time, the break-ing process is terminated.
The making process is effected in a reverse order as follows: first, the electrodes 3,4, of the apparatus of the in-vention are closed, and then, the power contacts (not shown) of the circuit breaker.
The apparatus of the invention provides for a condition where the arc 5 expands in a radial direction on a stable basis so that no considerable leading or lagging of separate turns of the arc takes place. This is due to the fact that the currents through the adjacent turns act upon one another, i.e., the attrac-tion of parallel currents takes place. In this case, the helix blade 6 of the arc chamber 1 is not subjected practically to mechanical stress since the arc column 5 acts upon it from two sides, ~ote that an unbalanced condition of the longitudinal component of the force ~ of interaction of the turns of the arc 5 produce a force that is always directed to the centre of the arc chamber 1.
A first approximation of the characteristics of the appa-ratus of the invention is given by the following equations. One ~ - 27 -of them describes the arc volta~e U(t) - ~r ~t)l(t)E/~, and the other describes the rate of recovery o~ the arc voltage aU/~t = ~(t)EVa/~, where r(t) and l(t) are the current radius and the longitudinal size of the arc 5, respectively.
According to the invention, the inductance of the arc 5 itself must be taken into conslderation.
Referring to Figs. 4,5, there is shown an arc 16 which expands in a radial direction and approaches the fixation members 9 (the position a in Fig. 5) where it is distorted and passes around the members. At this point in time there results a break-down betweenthe approaching portions of the arc column 16a behind the obstacles passed àround, namely, the fixation members 9, with the result that a new helix arc 16b is formed which is practically an undisturbed one.
Figure 6 shows the arc chamber 19 provided with respec-tive metallic discs 17,18 on its end faces. In this case, the arc 23 tends to expand in a radial direction as well as in a longi-tudinal direction (as it is "wound" on the electrodes 20,21).
When the arc 23 approaches the chamber end faces it then appears at the discs 17, 18 and changes to a barrelshaped form which may further become practically cylindrical. Like the case with horn-shaped electrodes, thls allows for a reduction of the erosion of the electrodes 20,21.
The apparatus of the invention shown in Fig. 7 is operated in a distinct manner during the first operational step. Here, the rod 26, adjacent the movable electrode 25 and caused to be moved therewith, is ~ntroduced into the axial channel of the ~ - 28 -1119 Zl~ ~ r arc chamber 27 during the parting o~ the electrodes 24,25. The resulting arc 28 is drawn i~mediately into the he~ix cavity of the arc chamber 27 which connects the separated electrodes 24,25.
As a result, the arc 28 is caused t~ assume a helical form corres-ponding to that of the cavity of the arc chamber 27. The rod 26 therefore allows for im~nediate production of a helical shaped arc 28 with the result that the intermediate steps of forming and introducing the arc into the helical cavity of the arc chamber are not included in the switching process.
As previously described, the arc 28 so produced tends to expand in a radial direction under the action of the force F and is wound on the electrodes 24,25, following the path of the helix cavity of the arc chamber 27. Thus, the arc 28 acts upon the rod 26 for a short time interval, which provides for favour-able operating conditions of the rod.
Since the arc 28 has a small pitch ~, it is practically a heavy-current plasma solenoid which produces an additional longitudinal magnetic field B, thereby providing for due operation of the arc chamber 29. This means that the magnetic field of the current of the arc 28 is utilized on a very effective basis. In the example described above, the interruption of a current of 2 and 20 kA with the help of a lOOkV apparatus is accompanied by the occurrence of a longitudinal magnetic field obtainable from 55 current turns of the quenching arc, said field amounting to 0.2 and 2 T, respectively, as measured at the axis of the arc chamber.
The apparatus of the invention therefore makes it possible to sim-plify the design !
~ ,_ lllgZi9 of the associated switchgear due to the fact that magnetic--blast coils and magnetic circuits are not necessary in many ca,ses.
There are specific cases concerned with the use of the apparatus of the invention in conjunction with fuses and electroexplosion trips. The embodiment of the invention shown in ~ig. 8 is operated in conjunction with a fuse as follows.
After th~ ~usible element 32 has been blown, a breaking arc is so formed and the resulting arc column tends to expand at a higher rate during the initial period of the arc formatio~
since plasma conductivity is considerably less than metal con-ductivity. ~he arc column can e~pand only towards the ~*}~
cavity of the arc chamber with the result that a helix-shaped quonching arc is produced already during that period.
The helix-shaped ~e~R~ arc then expands in a radial direction and is given a considerable lengthening. Under these conditions, the longitudinal size of the arc is held equal to the length of the arc chamber. This provides for an additional increase in the rate of the arc lengthening so that the rate of recovery of the ~oltage across-the contacts of the swit-chgear is increased too.
After the fusible element 35 (~ig. 9) has been blown, the breaking arc immediately assumes a helix-like shape ha~ing a preset radius and pitch. In addition, the current being in-terrupted creates its o~n longitudinal magnetic field during the blowing of the fusible element 35. As a result, a greater switch'ing time is attained~
:
'~
B
....
ill9;~19 ls determined by the magnitude of the working current and is equal to the diameter of the axial channel 2. The electrodes 3,4 are usually made of copper, copper/tungsten alloys and the like. The apparatus of the invention also comprises conventional arc-quenching coils (not shown) which are connected, for example, in series with the apparatus. These arc-quenching coils produce the magnetic field B (shown by a respective arrow in the figure) within the arc chamber 1 during the switching process. In the given embodiment, the magnetic field B is oriented in a direc-tion coincident with the axis of the arc chamber 1 and the elec-trodes 4,3 and is, therefore, a longitudinal one.
The arc chamber 1 causes a breaking arc 5 having a helical shape to move in a radial direction. In Fig. ~, r is the instantaneous radius of the arc 5 and F is the radial com-ponent of the force of electromagnetic interaction between the arc 5 and the magnetic field B, respective arrows being used to show the directions in which the column of the arc 5 is acted upon by that force. The arc chamber 1 is formed by a screwlike body which is a helical blade 6 having a pitch ~ and defining between adjacent turns thereof, the helical cavity having width . The helical cavity serves as an arc-quenching slit structure of the apparatus. The width of the slit structure and the magni-tudes of the current of the arc 5 and of the magnetic field B
determine the parameters of the arc 5 as follows: The current density; the size and shape of the arc column and the intensity of the electric field thereof; and the velocity of the arc column.
The :1119Z19 width of the helical cavity of the arc chamber 1 is usually selected to be equal to 2 to lOmm.
It is common practice to select the value of the pitch of the helical cavity of the arc cham~er 1 as small as possible.
It is dependent upon the material, fabrication techniques, operating conditions and service life of the arc chamber 1 and, more speci-fically, upon a maximum permissible thickness of the helical blade 6 which equals to ~ ). The helical blade 6 or the arc chamber 1 can be manufactured from different electrically insula-ting materials such as arc-resistant and gas-generating ones.
For example, cast plastics including polysulfone, polycarbonate and lavsan can be used for the purpose.
In the given embodiment, the heat load applied to the walls of the arc chamber 1 is less than the thermal load that affects the walls of the known electromagnetic labyrinth-type arc chambers due to the fact that in the former case the arc column moves with a greater velocity ( this phenomenon will be explained hereinafter). In addition, the helical blade 6 of the arc chamber 1 is subjected tb a relatively small mechanical load since the arc 5 acts upon it from two sides. As a result, the material of the helical blade 6 may possess properties that are inferior to those of the material from which the known electromagnetic labyrinth-type arc chambers are made.
The arc chamber 1 can be manufactured by casting or stamping. It is possible to construct a cheap sectional variant of the chamber comprised of the elements of the helical blade which connect one another.
~119Z19 The absolute values of the diameter D and length L
of the arc chamber 1 are determined by the working voltage and switching time of the associated switchgear (see calculation examples given below). The ratio between the diameter D of che chamber 1 and the pitch of the helical cavity must be not less than 10 in order to obtain a sufficient lengthening of the arc 5 which is 102 to 103 times the ~ength L of the chamber l, which determine the maximum separation between the electrodes 3,4.
The helical cavity of the arc chamber 1 (Fig. 1) is rectangular in cross-section in the radial direction. It is good practice, however, to make the cavity narrow in a radial direction in order to obtain a variation of the intensity of the electrical field of the arc column as the current decreases during the switching process. Figure 2 shows an arc chamber 7 whose helical cavity has a trapezoidal section.
Figure 3 shows an arc chamber 8 whose helical cavity has a zig-zag like section extending in a radial direction.
According to this embodiment, the arc chamber 8 may also have its helical cavity with a variable pitch ~, which makes it possible to vary the velocity of the arc column. This embodiment is advantageous in that the axial channel 2 (Fig. l) can be protected from light radiation emitted by the arc 5, that tends to expand in a radial direction, with the result that the electrical strength of the medium contained in the axial channel 2 is restored at a higher rate. In addition, the zig-zag like section of the - helix cavity of the arc chamber 8 ` 30 - ~ L
lll9Z19 (Fig. 3) allows the sound effect occurring during the switching proces,s to be reduced.
To provide for mechanical strength, robustness and vibration stability of the apparatus of the invention, it com-prises strengthening members 9, io (Figs. 4,5) which are disposed within the helical cavity of an arc chamber 11 (Fig. 4) and are rigidly coupled with the walls of the chamber, said walls being formed by a helix blade 12. The arc chamber 11 has an axial channel 13 which accomodates electrodes 14, 15.
The strengthening members 9,10 (Fig. 5) are arranged in two rows in circumferential relation to the arc chamber 11.
One of the two rows includes the strengthening members 9 made as cylindrical inserts, while the other row includes the strengh-ening members 10 made as ribs.
The position and dimensions of the strengthening members 9,10 are dependent upon the materials and fabrication processes used for the manufacture of the members and the arc chamber 11 and must be s~ch that an arc 16 (Fig. 5) is allowed to pass freely around the members. The position of the column of the arc 16 is shown for two- successive points in time occupied by the arc in the course of its movement in a radial direction:
a is the point in time when the arc passes around the members 9 and b is the point in time when the arc approaches the members 10.
~19219 The strengthening members 9,10 can be fabricated from metal. In this case, they additionally act as an arc-quen-ching grid with the result that the parameters of the arc chamb~r 11 are improved. In this embodiment, the strengthening member 9,10 must be electrically insulated one from another.
In addition, the strengthening members can provide a means for coupling separate parts of a sectional arc chamber with an appreciable assembly accuracy.
To allow the ends of the arc to be moved in a radial direction, additional horn-shaped electrodes are introduced in the arc chamber. These electrodes, made of an electrically conducting material, are oriented in a radial direction at the beginning and end of the helical cavity; the electrodes must be electrically connected to respective main electrodes.
Figure 6 shows an embodiment of the apparatus of the invention which comprises elements17,18 made of an electrically conducting material and allowing for the movement of the support spots of the arc in a radial direction. The elements 17,18 are implemented as metallic discs having axial holes and disposed on the end faces of the arc chamber 19. The elements 17,18 are electrically connected to respective electrodes 20,21 which are located at corresponding end faces in an axial channel 22.
The elements 17,18 can be fabricated, for example, from copper.
Figure 6 shows how the arc 23 expands in a radial direction as its ends move o~er the elements 17,18.
~. -- 19 --~., 1~92~g ~igure 7 shows an electromagnetic arc extinction appara-tus for a high-~oltage heavy-current circuit breaker. In the given embodiment, an immovable electrode 24 is implemented, for example, as a tubing that has its inner diameter equal to the diameter of a movable electrode 25. There is a rod 26 ma-de of an electrically insulating material and coupled, for example, by thread connection with the movable electrode 25.
~he diameter of the rod 26 is equal to the diameter of the movable electrode 25 and has its length equal at least to the spacing between the electrodes ~4, 25 with the electrode 25 held in it~ extreme position.
~he rod 26 provides ~or a condition where no breakdown occurs between the electrodes 24, 25 which are bein~ dra~n apart during the switching process, a feature ensuring reliab-le operation of an arc chamber 27.
A preferred material for the rod 26 is an arc-resistant and gas-~enerating one. Since the shape of the rod 26 is simple, ~arious materials such as ceramics, boron nitride and asbestos--cement can be used for the purpose. It ic~ feasible to make the electrode 24, for example, from one or more current-collecting ja~s.
B Note that the position of a quenchin6 arc 28 in the figu-re corresponds to a certain point in time during which the ap-paratus oY the invention is operated.
It is pre~erable to select that outline of the arc chamber 27 which corresponds to the form of the quenching arc 28, caused to expand in a radial direction, which form being attained at the moment when the switching process is terminated. According -- _ , ~, -.
, , 1~9Z19 to one of the embodiments, the arc chamber 27 narrows to-wards the end face at which the movable electrode 25 is lo-cated.
Let us calculate the overall and working dimensions of a circuit breaker which can handle a voltage U of 100 kV and which is operated in conjunction with the apparatus of the invention. Assume that the circuit breaker o~fers a s~itch-ing time of 10 ms, which provides for a half-wave interrupt-ion in the case of an a.c. circuit being switched. With an average velocity Va of the arc column equal to 50 to 100 m/s approximately, the permissible height of the slit and, therefo-re, the diameter D of the apparatus of the invention is given by D ~ 2V2Z = 1 to 2 m With an avérage intensity E of the electric field in the column of the breaking arc being moved equal to 20 to 30 VtcmJ
the desired arc length la is given by la = EU~?O to 100 m, a twofold margin for the turned-off voltage U being selected to take into account an overvoltage condition.
To provide for proper design of the apparatus of the in-vention, let the pitch ~ of the helix blade be equal to 1 cm approximately and the length L of the arc chamber be equal to its diameter D. This gives le --~
; D - L = ~ a ~ ~ 0.48 to 0.55 m ~ . .
' ll~9Z19 Therefore, the arc chamber h~;ing the dimensions D c o.55 m and L ~ 0.55 m is capable o~ switching a.c. and d.c. circuits at a voltage U of 100 kV (with a two~old voltage margin) and a switching time ~ c 0.01 s. With the apparatus of the i~ven-tion, there is no need for the following components of modern 100-kV circuit breakers: a reservoir accommodating 6 to 12 tons of oil in an oil circuit breaker, that weighs itself 8 to 15 tons; a reservoir accommodating 0.5 to 1.5 tons o~ oil in a small volume oil circuit breaker, that ~eighs itself 4 to 8 tons; a receiver with a compressor rated for 2 to 6 ~a in a compressed-air circuit brea~er, that weighs itsel~ 5 to 8 tons; and a hermetically sealed casing rated for 0.3 to 0.6 ~æa and filled with an expensive SF6 gas, in a self-blast S~6 cir-cuit breaker, that weighs itself 5 to 8 tons. Note that these modern circuit breakers can provide for a switching time of 0.06 to 0.1 s i~ the case of a.c. applications only.
~ igure 8 sho~s an electromagnetic arc extinction apparat-us for a high-voltage fuse. The apparatus comprises an arc ; chamber 29 made of an electrically insulating material. Immo-vable electrodes 30, 31 are located in axial relationship to the arc chamber 29 at it~ end faces and are connected by a fu-sible element 32 implemented as a wire made, for example, of copper. ~he fusible element 32 is disposed in the axial channel o~ the arc chamber 29, ths diameter of the ~usible element 32 being equal to the diameter o~ the axial channel.
It is known that ~uses are basically intended to protect the associated circuits ~rom short circuit and must there~ore ; o~fer a shorter switching time. In addition, fuses must be ~ - 22 -lll~Z19 appreciably simple and cheap. ~odern high-voltage fuses offer normal operation at voltage levels not exceeding 30 to 50 kV.
The basic component of a fuse is a fusible element that connect-q immovable electrodes serving in this case as po~er leads. The ratio between the arc length at the e~d o~ the switching pxocess and the length of the ~usible element is one of the most critical parameters that influence the design and operation of a fuse.
The high-voltage fuse of ~ig. 8 has a maximum permissible value of the above-mentioned ratio due to the fact that a straight fusible element 32 is used which has its length equal to the length of the arc chamber 29.
For example, an arc chamber of a 100-kv fuse (with a twofold voltage margin) has a quenching time of 3 ms at ~= 1 cm, E = 25 V~cm and Va = 50 m/s. In this case, the para-meters ~.L and ratio la/L are determined as follows:
D = 2Va ~= 0.3 m, L =~ = 0.9 m, and la/L = 90.
These dimensions ensure proper technical implementation of an arc ch~mber for a 100-kV fuse.
~ igure 9 shows another embodiment of the apparatus of the invention intended for a fuse and an electroexplosion trip, which embodiment comprises an arc chamber 33 whose axial channel accommodates a cylindrical insert 34. The diameter of the latter is equal to the diameter of the axial channel of the arc chamber 33. Wound on the insert 34 is a fusible ele-~ ment 35 having a pitch equal to the pitch of the ~ cavity ;~ of the arc chamber 33. The insert 34 is made o~ an electrically insulating material identical, for example, with that of the ' ~ :
',:
., , 1~19219 arc chamber 33. T'he end faces o~ the insert 34 ha~e respective metallic discs 36,37 which provide for electric contact bet-ween the fusible element 35 and immovable electrodes 38,39 o~ a ~use or electroexplosion trip.
In the given embodiment, the insert 34 can be replaced after the fusible element 35 has been blown. It is feasible, i~ the case of fuse application, to allow the insert 34 to be moved alon~ the axis of the arc cha~ber 33 after the fuse blowing so as to indicate that the circuit is turned off. A
new insert 34 with a new fusible element 35 is inserted in the arc chamber 33 and is ~ixed in a manner that a due space B alignment between the fusible element 35 and the ~ ca~ity of the arc chamber 33 is attained.
~ he arc chamber intended for fuse application can be made a multiturn one and the insert can be provided with se-veral fusible elements equal in number to the number o~ the turns of the helix cavity of the arc chamber. If a ~usible ele-me~t is blown, the next one can be connected in the curcuit by rotating the insert or the arc chamber together with the insert by a certain angle.
~ he embodiments of the present invention can be used in conjunction with the kno~n method~ dealing with arc extinction and employed in electromagnetic switching devices so as to impro~e the parameters o~ the latter.
The working medium in the circuit breaker housing can be changed; for examplet the latter is filled with the SF6 ~as.
The pressure within the housing can be ~aried; ~or example, the pressure is increased or decreased, or the housing is lll~Zl9 evacuated, the two latter cases being concerned with an increasein the switching time of the circuit breaker.
The arc voltage can be increased by virtue of arc-quenching and deionizing grids implemented as the sets of insula-ted plates arranged at the outlet of the arc-quenching slit in a direction of movement of the arc column.
Like conventional electromagnetic arc chambers, the arc chamber of the invention may have its helical cavity arranged in a zig-zag like (labyrinth) fashion along the quenching arc, namely, in a tangential direction, which provides f~r an additional increase of 1.5 to 3 times in the arc length without considerable increase in the overall dimensions of the arc chambers.
It is known that electromagnetic arc extinction de-vices cannot work effectively in the case of circuit breaker appli-cations when small currents are interrupted (which means that gas switching must be effected at a small load). To eliminate this drawback, the arc chamber of the present invention can be provided, like conventional electromagnetic arc chambers, with a gas `~: blast which is directed into the helical cavity with the result that a small-current quenching arc is lengthened.
Such a gas blast, for example, an air blast, can be delivered through the axial holes made in the movable and immo-vable e`lectrodes as well as~;n the rod of an electrically insula-ting material, connected with the movable electrode, and can be led into the helical cavity of the arc chamber through evenly distributed radial holes. The blast can also be delivered through the body of the helical blade and led into the cavity ~ - 25 -, lll9Zi9 through respective holes in the base of the blade in the vicini-ty of the axial channel of tne arc chamber~
The circuit breaker provided with the apparatus of the invention operates in the following manner. After an interrupt control signal is generated, the power contacts of the circuit breaker are separated with the result that the circuit current passes through the electrodes 3,4(Fig. 1) of the apparatus of the invention.
The arc 5 formed in the axial channel 2 of the arc 10 - chamber after the parting of the electrodes 3,4 is surrounded by the longitudinal magnetic field B produced by magnetic-blast coils (not shown). Under these conditions and at specific values of the associated parameters, the arc column changes to a helix-like shape (cf. an article by E.I. Asinovsky, A.A. Afanasyev, E.P.Pakhomov, entitled "Helix Instability of Arc in Longitudinal Magnetic Field" Proceedings of the Academy of Sciences of the USSR, 231, No. 2, 1976). Thus, there results a radial component of the force F of electromagnetic interaction between the arc current and the magnetic field due to the occurrence of the tan-gential component of the current of the quenching arc 5. Thatradial component of the force F causes the helical quenching arc to be drawn into the helical cavity of the arc chamber 1 and expand in a raaial direction.
In the presence of the longitudinal magnetic field, the radial components of the current of the quenching arc 5, existing at the areas adjacent the electrodes, cause a rotation of respective portions of the arc 5 in opposite directions under the action of the tangential compo-~ - 26 -"~
~119Zi9 nents of the force F. The arc 5 is therefore wound on the elec-trodes 3,4 in the form of a helix determined by the helical cavity of the arc chamber 1. As a result the rate of rise of the longi-tudinal s~ze of the quenching arc 5, which expands in a radial direction, is always greater than the rate of parting of the electrodes 3,4.
After the arc S reaches the length which allows for the recovery of a voltage across the contacts of the circuit breaker e~ual to the voltage across the contacts of the circuit being switch-ed, the current drops to zero. At this point in time, the break-ing process is terminated.
The making process is effected in a reverse order as follows: first, the electrodes 3,4, of the apparatus of the in-vention are closed, and then, the power contacts (not shown) of the circuit breaker.
The apparatus of the invention provides for a condition where the arc 5 expands in a radial direction on a stable basis so that no considerable leading or lagging of separate turns of the arc takes place. This is due to the fact that the currents through the adjacent turns act upon one another, i.e., the attrac-tion of parallel currents takes place. In this case, the helix blade 6 of the arc chamber 1 is not subjected practically to mechanical stress since the arc column 5 acts upon it from two sides, ~ote that an unbalanced condition of the longitudinal component of the force ~ of interaction of the turns of the arc 5 produce a force that is always directed to the centre of the arc chamber 1.
A first approximation of the characteristics of the appa-ratus of the invention is given by the following equations. One ~ - 27 -of them describes the arc volta~e U(t) - ~r ~t)l(t)E/~, and the other describes the rate of recovery o~ the arc voltage aU/~t = ~(t)EVa/~, where r(t) and l(t) are the current radius and the longitudinal size of the arc 5, respectively.
According to the invention, the inductance of the arc 5 itself must be taken into conslderation.
Referring to Figs. 4,5, there is shown an arc 16 which expands in a radial direction and approaches the fixation members 9 (the position a in Fig. 5) where it is distorted and passes around the members. At this point in time there results a break-down betweenthe approaching portions of the arc column 16a behind the obstacles passed àround, namely, the fixation members 9, with the result that a new helix arc 16b is formed which is practically an undisturbed one.
Figure 6 shows the arc chamber 19 provided with respec-tive metallic discs 17,18 on its end faces. In this case, the arc 23 tends to expand in a radial direction as well as in a longi-tudinal direction (as it is "wound" on the electrodes 20,21).
When the arc 23 approaches the chamber end faces it then appears at the discs 17, 18 and changes to a barrelshaped form which may further become practically cylindrical. Like the case with horn-shaped electrodes, thls allows for a reduction of the erosion of the electrodes 20,21.
The apparatus of the invention shown in Fig. 7 is operated in a distinct manner during the first operational step. Here, the rod 26, adjacent the movable electrode 25 and caused to be moved therewith, is ~ntroduced into the axial channel of the ~ - 28 -1119 Zl~ ~ r arc chamber 27 during the parting o~ the electrodes 24,25. The resulting arc 28 is drawn i~mediately into the he~ix cavity of the arc chamber 27 which connects the separated electrodes 24,25.
As a result, the arc 28 is caused t~ assume a helical form corres-ponding to that of the cavity of the arc chamber 27. The rod 26 therefore allows for im~nediate production of a helical shaped arc 28 with the result that the intermediate steps of forming and introducing the arc into the helical cavity of the arc chamber are not included in the switching process.
As previously described, the arc 28 so produced tends to expand in a radial direction under the action of the force F and is wound on the electrodes 24,25, following the path of the helix cavity of the arc chamber 27. Thus, the arc 28 acts upon the rod 26 for a short time interval, which provides for favour-able operating conditions of the rod.
Since the arc 28 has a small pitch ~, it is practically a heavy-current plasma solenoid which produces an additional longitudinal magnetic field B, thereby providing for due operation of the arc chamber 29. This means that the magnetic field of the current of the arc 28 is utilized on a very effective basis. In the example described above, the interruption of a current of 2 and 20 kA with the help of a lOOkV apparatus is accompanied by the occurrence of a longitudinal magnetic field obtainable from 55 current turns of the quenching arc, said field amounting to 0.2 and 2 T, respectively, as measured at the axis of the arc chamber.
The apparatus of the invention therefore makes it possible to sim-plify the design !
~ ,_ lllgZi9 of the associated switchgear due to the fact that magnetic--blast coils and magnetic circuits are not necessary in many ca,ses.
There are specific cases concerned with the use of the apparatus of the invention in conjunction with fuses and electroexplosion trips. The embodiment of the invention shown in ~ig. 8 is operated in conjunction with a fuse as follows.
After th~ ~usible element 32 has been blown, a breaking arc is so formed and the resulting arc column tends to expand at a higher rate during the initial period of the arc formatio~
since plasma conductivity is considerably less than metal con-ductivity. ~he arc column can e~pand only towards the ~*}~
cavity of the arc chamber with the result that a helix-shaped quonching arc is produced already during that period.
The helix-shaped ~e~R~ arc then expands in a radial direction and is given a considerable lengthening. Under these conditions, the longitudinal size of the arc is held equal to the length of the arc chamber. This provides for an additional increase in the rate of the arc lengthening so that the rate of recovery of the ~oltage across-the contacts of the swit-chgear is increased too.
After the fusible element 35 (~ig. 9) has been blown, the breaking arc immediately assumes a helix-like shape ha~ing a preset radius and pitch. In addition, the current being in-terrupted creates its o~n longitudinal magnetic field during the blowing of the fusible element 35. As a result, a greater switch'ing time is attained~
:
'~
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electromagnetic arc extinction apparatus for switchgear, comprising an arc chamber formed of electrically insulating material and defining a helical cavity having a pitch which is at least 10 times smaller than the diameter of the arc chamber measured over the cross-section thereof, an axial channel in said arc chamber communicating throughout its extent with the helical cavity, and two electrodes disposed in alignment in said axial channel such that, in the presence of a magnetic field, an arc struck between said two electrodes will be expanded outwardly into said helical cavity thereby to extend the length of the arc.
2. An apparatus as claimed in claim 1, wherein the width of each turn of the helical cavity decreases in a radially outward direction.
3. An apparatus as claimed in claim 1, wherein the arc chamber is provided with strengthening members disposed in said cavity and rigidly attached to the walls thereof.
4. An apparatus as claimed in claim 1, further comprising electrically conductive elements adapted to permit the ends of the arc to move outwardly as the arc expands, said elements being disposed on respective end faces of said arc chamber and being electrically connected to the respective electrodes which are located at corresponding end faces of said arc chamber.
5. An apparatus as claimed in claim 1, wherein said two electrodes comprise a first electrode displaceable in said axial channel of said arc chamber and a second electrode provided with an axial bore, and wherein an electrically insulating rod is fixed to one end of said first electrode which faces said second electrode and said rod extends into the axial bore of said second electrode and has a length at least equal to the spacing between said first and second electrodes when said first electrode in its extreme position, said rod being effective in operation to resist the occurrence of a breakdown in said axial channel.
6. An apparatus as claimed in claim 5, wherein said arc chamber narrows towards the end face at which said first electrode is located.
7. An apparatus as claimed in claim 1, further comprising a wire adapted to connect said electrodes, disposed in said axial channel of said arc chamber and used as a fusible element, said wire having its diameter equal to the diameter of said axial channel.
8. An apparatus as claimed in claim 1, further comprising an insert made of electrically insulating material, disposed in said axial channel of said arc chamber and having its diameter equal to the diameter of said axial channel and a wire interconnecting said electrodes, said wire being arranged on said insert in the form of a helix, disposed in said cavity of said arc chamber, and acting as a fusible element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SU782609044A SU773788A1 (en) | 1978-04-28 | 1978-04-28 | Fuse |
| SU2609044 | 1978-04-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119219A true CA1119219A (en) | 1982-03-02 |
Family
ID=20761749
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000319841A Expired CA1119219A (en) | 1978-04-28 | 1979-01-18 | Electromagnetic circuit breaker arc extinguishing device comprising a helically-shaped arcing chamber |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS54143880A (en) |
| CA (1) | CA1119219A (en) |
| CH (1) | CH648151A5 (en) |
| DE (1) | DE2903426C2 (en) |
| FR (1) | FR2424620A1 (en) |
| GB (1) | GB2020113B (en) |
| IT (1) | IT1166635B (en) |
| SE (1) | SE442563B (en) |
| SU (1) | SU773788A1 (en) |
| YU (1) | YU39862B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102007033180B4 (en) * | 2007-07-13 | 2010-11-18 | Auto-Kabel Management Gmbh | Circuit breaker for supply lines in motor vehicles |
| GB2461024B (en) | 2008-06-16 | 2012-06-13 | Converteam Technology Ltd | Fuses |
| CN107578864B (en) * | 2017-08-24 | 2024-01-30 | 王巨丰 | Zigzag synchronous compression arc extinguishing lightning protection device with four-side injection channels |
| EP3979292A4 (en) * | 2019-05-28 | 2022-10-19 | Mitsubishi Electric Corporation | Direct-current circuit breaker |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE602544C (en) * | 1934-09-11 | Voigt & Haeffner Akt Ges | Electric switch or fuse with spark chamber and arc extinguishing by magnetic blowing | |
| DE926146C (en) * | 1944-06-29 | 1955-04-07 | Siemens Ag | Arrangement to increase the arc gradient |
| FR1100959A (en) * | 1954-03-10 | 1955-09-27 | Gardy Particip App | Electric arc breaking method and device and their applications |
-
1978
- 1978-04-28 SU SU782609044A patent/SU773788A1/en active
-
1979
- 1979-01-18 CA CA000319841A patent/CA1119219A/en not_active Expired
- 1979-01-30 DE DE2903426A patent/DE2903426C2/en not_active Expired
- 1979-02-14 SE SE7901320A patent/SE442563B/en not_active IP Right Cessation
- 1979-02-14 IT IT20196/79A patent/IT1166635B/en active
- 1979-03-02 GB GB7907511A patent/GB2020113B/en not_active Expired
- 1979-03-06 JP JP2516779A patent/JPS54143880A/en active Pending
- 1979-04-02 YU YU766/79A patent/YU39862B/en unknown
- 1979-04-24 FR FR7910363A patent/FR2424620A1/en active Granted
- 1979-04-27 CH CH3989/79A patent/CH648151A5/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE2903426C2 (en) | 1986-06-19 |
| IT1166635B (en) | 1987-05-05 |
| IT7920196A0 (en) | 1979-02-14 |
| GB2020113A (en) | 1979-11-07 |
| SE7901320L (en) | 1979-10-29 |
| SU773788A1 (en) | 1980-10-23 |
| DE2903426A1 (en) | 1979-11-15 |
| JPS54143880A (en) | 1979-11-09 |
| SE442563B (en) | 1986-01-13 |
| YU76679A (en) | 1982-06-30 |
| FR2424620B1 (en) | 1982-10-15 |
| GB2020113B (en) | 1982-09-02 |
| YU39862B (en) | 1985-04-30 |
| FR2424620A1 (en) | 1979-11-23 |
| CH648151A5 (en) | 1985-02-28 |
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