US 3728505 A
An opening resistor for a circuit interrupter consists of first and second concentric helically wound resistor sections normally spaced from one another, and are respectively connected to the cooperating contacts of a circuit interrupter. When the contacts open, an initial arc is transferred by a blast of gas to extend across the ends of the resistor sections. This gas blast and the magnetic field of the arc current exert a force on the arc causing the arc roots to rotate on the helical resistor sections so that the arc moves toward the other end of the helical resistor windings, thereby to insert increasing resistance in parallel with the contacts, and arc, in a non-step fashion.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 McConnell RESISTOR AND MEANS FOR GRADUALLY INSERTING RESISTOR IN PARALLEL WITH INTERRUPTER CONTACTS 51 Apr. 17, 1973 Primary Examir'zerRobert S. Macon Attorney--Sidney G. Faber et a1.
[5 7 ABSTRACT An opening resistor for a circuit interrupter consists of first and second concentric helically wound resistor sections normally spaced from one another, and are respectively connected to the cooperating contacts of a circuit interrupter. When the contacts open, an initial arc is transferred by a blast of gas to extend across the ends of the resistor sections. This gas blast and the magnetic field of the arc current exert a force on the are causing the arc roots to rotate on the helical resistor sections so that the arc moves toward the other end of the helical resistor windings, thereby to insert increasing resistance in parallel with the contacts, and arc, in a non-step fashion.
6 Claims, 6 Drawing Figures My F? 5510?:
PATENTED APR 1 71973 SHEET 1 OF 3 m M M WM 2 m V PATENTED APR 1 71973 SHEU 3 [IF 3 INVENTOR.
Aflfl/l/i 0. M ran #171 ATTORNEYS RESISTOR AND MEANS FOR GRADUALLY INSERTING RESISTOR IN PARALLEL WITH INTERRUPTER CONTACTS SUMMARY OF THE INVENTION This invention relates to circuit interrupters and more specifically relates to a novel opening resistor for a circuit breaker and a novel arrangement for inserting the resistor in parallel with the contacts when the contacts are moved to an open position.
The use of resistors for interrupting devices is well known, and the benefits derived from their use is well understood. Generally, such resistors are connected in parallel with the main interrupter contacts, through a separate resistor switch device. When the main contacts are opened, the resistor switch becomes conductive, thereby to place the resistor in parallel with the arc. The are current is then interrupted. A current limited by the resistor continues to flow and is ultimately interrupted by the resistor switch.
A major problem in such devices is to insert the resistance device into the power circuit when the main contacts open. This is commonly accomplished by developing a considerable arc' voltage between the separating main contacts to cause current to commutate into the resistance circuit, where the resistor may be switched from small discrete values to larger discrete values. Thus, the resistor is commonly changed in value instantaneously, thereby to apply undesired voltage surges in the system, and considerable time is needed to effect full resistor insertion.
' In accordance with the present invention, a novel resistor is provided for an interrupter wherein the resistor consists of two elongated, coextensive members directly connected to respective contacts of the main interrupter contacts. The interrupter is further provided with gas blast means, which may be of a conventional type, and which causes initial transfer of an initial arc from the separating contacts to the adjacent ends of the elongated resistor elements.
The total resistance is then gradually inserted, in a non-step fashion, by causing the arc to travel along the two, coextensive resistor members and toward its opposite end, under magnetic forces caused by the arc current and the continued gas blast force. The magnetic forces include the motor effect and magnetic loop effect caused by the configuration of the resistor elements and are current path.
Thus, in accordance with the invention, the resistor is inserted in parallel with the contacts, and is then gradually increased from zero resistance to its maxsystem which is operated either synchronously or randomly with respect to the through current.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of an interrupter incorporating the present invention with the interrupter contacts closed.
FIG. 2 is a view similar to that of FIG. 1 with the contacts open.
FIG. 3 is a top plan view of FIGS. 1 and 2.
FIGS. 4 to 6 are schematic diagrams of the interrupter of FIGS. 1, 2 and 3, and schematically illustrate the operation of the interrupter.
DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIGS. 1 to 3, there is shown an interrupter which comprises a pair of stationary main contact rings 10 and 11 which are, in turn, connected to suitable terminals 12 and 13, which are connected in series with a power circuit to be protected. Main contact rings 10 and 11 hold suitable ring-shaped sliding contacts 14 and 15 respectively, which may be of any desired type, and which slidably engage main movable contact cylinder 16. Thus, in the position of FIG. 1, which shows the interrupter closed, the movable contact cylinder 16 bridges contacts 14 and 15 and thus connects terminals 12 and 13 together.
Movable contact cylinder 16 is axially movable, under the guiding influence of rings 14 and 15 to the upper and closed position of FIG. 1 to the lower, and open position of FIG. 2. Suitable stop means (not shown) may be added to control the open position of contact 16. Any suitable operating means may be used .to move contact 16. For purposes of illustration, FIGS.
l and 2 show a pneumatic operating mechanism whereby cylinder 16 is fitted over a piston 17, carried on a stationary mounting rod 18. Rod l8 has a central channel 19 which leads to a radial slot 20 disposed just above the bottom wall 21 of contact cylinder 16 when the contact 16 is closed as in FIG. 1. With the above structure, it is clear that contact 16 can be moved between its engaged and disengaged positions by appropriately controlling the pressure in channel 19. Note that the pressure on top of piston 17 may be atmospheric pressure, or a relatively low pressure of the order of about 40 psia, in the case of a two-pressure breaker of the type shown in copending application, Ser. No. 823,115 (Cl354[ER]), filed May 8, 1969, in the name of Otto Jensen, entitled Gas Blast Circuit Interrupter Using Main Movable Contact As Blast Valve, and assigned to the assignee of the present invention.
The interior of cylinder 16 then receives an interior ring 30 which carries a sliding contact ring 31 which slidably engages a transfer contact rod 32 of conduc tive material. Rod 32 is fixed to rodl8 and thus is mounted stationary relative to contact 16.
An insulation support tube 34, which may be of ceramic, is then suitably mounted above rod 32 as shown in FIGS. 1 and 2. A-winding 35 of resistive material, for example, nichrome wire, is helically wound on rod 34, with the lower end of wire 35 being electrically connected to transfer rod 32. Note that any desired material may be used for the resistor wire and may be of material having non-linear temperature characteristics, such as pure iron or tungsten, or the like and may have any desired cross-section, such as a circular crosssection, or flat ribbon section, or the like.
The upper end of the resistor wire 35 is connected to ring-shaped spark gap electrode 36.
Ring-shaped electrode 36 is spaced from and parallel to cooperating ring-shaped spark gap electrode 37. RIng-shaped electrodes 36 and 37 may be of any suitable conductive material. Note that electrode 36 has openings, such as openings 38, 39, 40 and 41 therethrough (FIG. 3) which will later be seen to permit easy flow of gas through electrode 36.
Ring-shaped electrode 37 is fitted over the top of insulation tube 40, which is of any suitable insulation, such as polytetrafluoroethylene or ceramic, and is atop insulation tube 41 which concentrically surrounds tube 40. Tube 41 may be a glass-epoxy reinforced tube or can be any other desired type. I
The interior of tube 40 supports therein a helical winding 42 of resistance wire which may be of the same type as resistance wire 35. The top of wire 42 is connected to ring-shaped electrode 37, and its bottom is connected to contact ring and terminal 12. It should be noted that resistors 35 and 42 are wound in the same direction, and that they are spaced by an annular volume which extends from transfer rod 32 to electrode 36.
FIGS. 1 and 2 further show an arcing contact 50 being provided for movable contact 16 and extending from ring 30. Arcing contact 50 makes connection between enlarged section 51 of transfer rod 32 and contact 10 to encourage the formation of an initial arc between these points when the interrupter contacts being to open.
The interrupter of FIGS. 1 and 2 is further provided with a source of gas 60 (FIG. 1) under high pressure, where the gas may be sulfur hexafluoride. The highpressure gas is connected to chamber 61 (FIG. 1) surrounding the exterior of contact 16 and is normally prevented from flowing by blast valve seal 62 carried on contact disk 10 and engaged by the end of contact 16 when contact 16 is closed. When contact 16 is opened, as shown in FIG. 2, gas flows, as shown by the arrows, under pressure, through the are drawn by opening contact 16,v through the annular region between windings 35 and 42, and through the space between ring-shaped electrodes 36 and 37, and through openings 39 to 42. A suitable cutoff valve (not shown) may cut off the flow of gas after arc interruption is completed. Note that the entire interrupter may be contained in the two-pressure system of above-noted copending application, Ser. No. 823,115 (C-l354 [ER]) with high pressure source 60 being disposed in the high-pressure region and with the annular region above seal 62 being disposed in the low-pressure region.
The operation of the interrupter of the invention is described hereinafter with reference to FIGS. 4 to 6 as well as FIGS. 1, 2 and 3. FIGS. 4 to 6 mechanically show the arrangement of FIGS. 1 to 3 and similar numerals identify similar components.
In the closed position of FIGS. 1 and 4, there is a direct current carrying path from terminal 12, contact 14, movable contact 16, contact and terminal 13. Resistor windings 35 and 42 are shorted by the closed contacts and gas flow is prevented by the movable contact seating against seal 62. In order to open the interrupter, movable contact 16 is moved downward (by application of pressure to channel 19 in FIG. 1). An initial arc is then struck from contact 10 to arcing contact 50, shown in FIG. 5 as arc A. The cross-blast action of the blast gas moves this are into the resistor section, as shown in FIGS. 2 and 6, by arc B which terminates on the bottom of inner and outer resistor elements 35 and 42, respectively.
The gas blast action then moves the arc upward between resistors 35 and 42, with the upward movement further forced by the tendency of the arc to bow outwardly. At the same time, a magnetic field is set up in the annular arc zone in such a direction as to rotate the are about the axis of support 34, thereby causing the arc roots to move helically upward on the resistors 35 and 42 (shown schematically as moving through positions C, D and E in FIG. 6). This then causes a stepless increase of resistance (and inductive reactance) in series with the arc current.
The are will rapidly reach the top of resistors 35 and 42 and ultimately will terminate between ring electrodes 36 and 37, shown as position Fin FIGS. 2 and 6. The are current of the arc between electrodes 36 and 37 will have a relatively low current value, and is nearly in phase with the source voltage. Thus, this are can be easily interrupted by minor gas flow through the space between the electrodes.
During the time that the arc moves up the resistance coils 35 and 42, there is gas flow which serves to cool resistors 35 and 42. This gas continues to flow until complete interruption and provides thenecessary insulation across the open contacts and between the resistor sections.
Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art and, therefore, it is preferred that the invention be limited not by the specific disclosure herein but only by the appended claims.
The embodiments of the invention in which an'exclusive privilege or property is claimed are defined as follows:
1. An opening resistor structure for a circuit interrupter; said circuit interrupter including: first and second separable contact means, first and second terminals connected to said first and second separable contact means, respectively, operating means for operating said first and second contact means between an engaged and a disengaged position; said opening resistor structure including first and second elongated resistor members extending substantially co-extensively with one another; said first and second elongated resistor members having generally adjacent first ends connected to said first and second separable contact means, respectively; and means for transferring an are drawn between said first and second separable contact means to said first ends of said first and second elongated resistor members, and for forcing said arc to thereafter move along the length of said first and second elongated resistor members, thereby gradually to increase the resistance in series with said first and second terminals; said first and second elongated resistor members comprising concentric helical windings separated from one another by an annular space.
2. The opening resistor structure of claim 1 which includes blast valve means connectedto said first and second separable contact means for directing a gas blast between said first and second separable contact means during the opening thereof; said means for transferring an are including the gas blast released by said blast valve means during the operation thereof to direct said gas blast.
3. The opening resistor structure of claim 1 which further includes first and second spaced electrodes; said first and second elongated resistor members having second ends connected to said first and second spaced electrodes, respectively.
4. The opening resistor structure of claim 2 which further includes means for directing said gas blast axially through said annular space.
5. The opening resistor structure of claim 4 which further includes first and second spaced electrodes; said first and second elongated resistor members having second ends connected to said first and second spaced electrodes, respectively.
6. The opening resistor structure of claim 5 which further includes means for directing said gas blast between said first and second spaced electrodes.