US1918151A - Electric circuit breaker - Google Patents

Description

July 11, 1933 w. TURNPENNY ET A1.

EECTRIC CIRCUIT BREAKER Filed April 23, 1930 www@ gw Inventors; Wil liomn Tur'n'p enhg,

Wiffreci F'. Skeos bg www Their Atto-#neg Patented July 11, 1933 UNITED STATES 1,918,151 PATENT OFFICEI WILLIAM TURN PENNY, OF ALBANY, AND WILFRED F. SKEATS, OF SCOTIA, NEW YORK, ASSIGNORS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC CIRCUIT BREAKER Application filed April 23,

Our invention relates to electric circuit breakers, and more particularly, to large capacity circuit breakers of the so-called eX- plosion chamberltype wherein a power arc is drawn in an insulating fluid, as oil, between separating contacts within a partially confinedY` space or chamber.

en a power arc is drawn between separatling contacts in an alternating current circuit, there is a tendency for the arc to persist if deionization of the arc space during the current reversal, or period when the arc current is substantially zero, does not take place at a suiiiciently -high rate to prevent the recovery v-oltage across the contacts from reestablishing the arc. In other words, in order that the arc shall bev eXtinguished, the dielectric strength of the arc space must increase at such a rate during the current reversal that the rise of recovery voltage across the contacts is unable to break down the dielectric strength of the gap to reignite or reestablish the arc. One method of building up the dielectric strength of the arc space is by forcibly injecting fresh dielectric into and through it, so that the arc products are not only swept away, but fresh dielectric is interposed between the terminals of the arc.

It is an object of our invention to provide an improved circuit breaker of the explosioncharnber type which shall have means for74N creating a pressure within the chamber in,

response to initial opening movement ofthe breaker and for utilizing this pressure to 1nject or force fresh fluid dielectric radially into and across the are space formed during the switch-opening operation.

It is a further object of our invention to provide an improved circuit breaker of the above described type which shall be simple and rugged in construction and which s hall interrupt the circuit equally well within a comparatively wide range of current values.

Our invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize our invention will "'be pointed out with particularity in the claims annexed to and forming a part of this specification.

1930. Serial No. 446,744.

Referring to the drawing, the single figure thereof is an elevational view, partly 1n section, of a portion of a circuit, breaker embodying our invention.

In the ligure above referred to there is illustrated arc-extinguishing means of the eX- plosion chamber type comprising a partially closed chamber l formed by the steel cylinder la, secured, as by screw threaded engagement at its upper end to the usual adapter structure 2 which is connected to the lead-in conductor stud 3. Since the two poles of the circuit breaker are similar in construction, it will be suiiicient to illustrate and describe but a single pole. rlhe explosion chamber, as is well known, is normally immersed in a body of insulating liquid, as oil. The circuit through the switch comprises a butt contact 4 suitably electrically connected as will be hereinafter described to the adapter 2, a floating butt contact 5 adapted to beengaged by the butt contact 4 within predetermined limits of movement of the floating contact 5, and a movable tubular contact, as the hollow rod 6 carried by the bridging member 7 and adapted to extend within the chamber 1 in the closed circuit position of the switch, and abut the floating contact 5. The butt contact 4 which is cylindrical in form is guided for reciprocal movement within a retaining structure 8 of conducting material, and is provided with an annular shoulder 9 adapted to engage the lower wall of the retainer 8 for the purpose of limiting its downward movement. Suitable means, as the spring l0 positioned by the stop member l0', is provided for normally resiliently biasing the butt contact 4 into following engagement with the floating contact 5. The butt contact 4 may be electrically connected to the adapter 2 by a ilexible lead l1 connected to the retainer cap 12 which is in turn in metallic contact with the retainer 8 and adapter 2. Openings 8a in the retainer lower wall are provided for equalizing thefluid pressure on opposite sides of the butt contact 4. The metallic cylinder 1 forming the main part of the explosion chamber is insulated in any suitable manner to prevent flash-over during opening. of thi'e switch or at other times, and is provided with an inner insulating cylinder or liner 13 and an outer insulating cylindrical shield 14 which is supported by an insulating flange 15 secured to' the lower part of the cylinder 1 by al clamping ring 16. The open or exhaust end of the cylinder 1 is fitted with an insulating bushing 17. clamped inposition by the insulating rings 18 and is provided with a nozzle-shaped exhaust opening 19 through which the hollow contact rod 6 may extend. The inner portion of the exhaust passage 19 may comprise a cu -shaped or other suitably shaped recess 20 fo med in a separate insulating disc 2l within the chamber. c

The'floating contact 5 is adapted to move vertically' within the chamber 1 and to this end it is provided with a supporting member as the spider 22 having openings 23 disposed Hcircumferentially thereof and norm-ally biased as by the compression spring 24 into seating engagement with the insulating disc 21. The spring 24 may be protected from the injurious effects of arcing by a cylindrical insulating shield 25. It will be apparent that the floating Contact and the spring 24 y may be insulated with respect to the explosion chamber in any suitable manner.

The hollow rod contact 6 which is adapted to abut the lower contact surface 26 of the floating contact is provided with a removable arcing tip 27 of suitable material and is likewise provided at a region spaced from the abutting end of the contact with relief passages 28 formed in the sides of the rod contact. It shall be understood, of course, that the relief passages may be omitted if the contact rod is limited in length so that the open end thereof carried by the bridging member is approximately in the position where the relief passages would normally be.

I The operation of the arc-extinguishing apparatus is as follows:

Assuming, of course, that the explosion chamber and bridging member are immersed in an insulating liquid, as oil, as is the case in the usual fluid-break switch, the insulating liquid will have filled the interior of the chamber 1, the contact retainer 8 .and the hollow contact rod 6. For the purpose of preventing air pockets within the chamber the retainer cap 12 is provided with a vent 12a so that theoil may fill all parts of the structure. In the closed circuit position of the switch as illustrated wherein the bridging member 7 has been moved upwardly by suitable means to cause the rod 6 to bias the floating contact 5 against its spring into following engagement with the butt contact 4, the

circuit includes in series the two abutting surfaces of the floating contact with the butt contact and rod contact respectively. Accordingly, separation of these contacting surfaces forms two breaks in series` resulting in arcing in the case of usual current values handled by this type of switch.

For the purpose of formingone break a very'brief interval before forming the second break in order that the fluid pressure developed by arcing at the first brealg shall materially aid in interruption of the arc formed at the second break, the travel of the butt contact 4 is so limited bythe flange 9 that the floating contact 5" may still move away from the butt contact 4 when said butt contact is stopped by the retainer 8. vThe downward or switch opening movement of the bridging member 7 accordingly permits the abutting contact surfaces to remain in engagemcnt during the initial switch opening movement until the flange 9 seats on the lower wall of the retainer 8, at which time an arc is formed between the separating contacts 4 and 5. As is well known, the drawing of an arc in oil rapidly forms large quantities of gas resulting in high pressure when the gases are partially confined. The fluid pressure on opposite sides of the butt contact 4 is more or less equalized at moderate current values by the vents 8a so that lthe contact in normal operation is not forced upwardly against its spring by the arc pressure.

However, in the event that the pressure of the initial arc generated by large currents is such that the butt contact 4 is projected upwardly, or pops back, notwithstanding the relief passages 8a, the arc is simply transferred across the arcing structure formed by the short annular gap to the flared lower side of the retainer wall so that the upper terminal of the arc remains substantially fixed.

As the opening movement of rod 6 continues, the spider 22 seats on the insulating disc 21 within a very limited movement, as of the order of approximately 1/.1 inch, after separation of the floating contact from the butt contact 4. Accordingly, lthe floating contact is no longer in following engagement with the rod contact 6, further downward movement of which results in the second break. Upon separation of the hollow contact 6 from the abutting surface 26 of the floating contact, a second arc is formed substantially within the cup-shaped recess 20 at the exhaust passage of the explosion chamber. The pressure, however, now existing in the explosion chamber is effective to force the oil through the openings 23 in the spider into the recess 20 and radially into the hollow contact 6 and through the same for a short distance to exhaust by way of they relief passages 28. It will therefore be noted that the arc between the hollow contact 6 and the floating contact 5 is practically'washed into the hollow contact due to the velocity of the oil flowing radially into the rod. This high velocity of the insulating fluid is permitted by the relief passages 28 which are so positioned that the oil in flowing through the rod may exhaust at the earliest opportunity into the main body of oil within the switch tank which is under -atmospheric pressure only.

The formation of the initial arc is regulated by its short length so that the pressure in the explosion chamber will not be excessive while at the same time being sufficient for the purpose of injecting oil at high velocity radially across the second arc and into the hollow contact rod. It will be noted that the separation of contacts 4 and 5 takes place substantially at the lower annular edge of the lower retainer wall against which the arc may strike, so that the initial arc is not in-4 creased in length causing excessive pressure in case the butt contact 4 pops back.

The second or main arc which is theoretically annularin shape is not only washed into the interior of the hollow contact rod at all points, but a fresh dielectric is interposed between the end of the hollow contact and floating contact so that reignition of the arc is substantially precluded. When the contact rod 6 is moved out of and'away from the explosion chamber to the open circuit position, the oil in the main switch tank flows into the explosion chamber again and fills up the same to replace the oil which was gasied or ejected from the chamber during the circuit opening operation. c

It has been found by actual tests that circuit breaker apparatus embodying our invention not only consistently clears the circuit effectively and within a very short period on comparatively heavy overloads and/ short circuits, but also operates with the same effectiveness and consistency over the entire range of current values which the breaker may be called upon to handle. This is a `highly important consideration in operating systems wherein a switch failure may cause great damage, since, in the case of the usual oil circuit breaker, a large factor of safety must be taken into consideration, thereby increasing the size and cost of the breaker, in order that the same shall not fail on interruptions that it would normally handle without distress.

Although the arc-extinguishing apparatus embodying our invention as illustrated and described comprises` a type of circuit breaker having the movable bridging contact and explosion chambers -immersed in a main body of insulating fluid, it shall be understood that our invention lis not specifically limited to this type of breaker, and that it may readily be embodied in other types, as for example,

the Well-known type wherein the movable contact rods carried by the bridging memberl move into the explosion chambers from the top and the insulating fluid is contained entirely within the explosion chambers.

W'hat we claim as new and desire to se-y rial, a resiliently mounted butt -contact guid- Y ed for reciprocal movement in said retainer, a floating butt contact resiliently biased away from the first contact, said floating contact and retainer being separated by a short annular gap, and a movable hollow butt contact adapted to extend through the 'exhaust passage of the explosion chamber to abut the floating contact and to force it into abutting engagement with the rst contact in the closed. circuit position of the switch, said abutting contactingsurfaces being so arranged that upon switch opening movement of the hollow butt contact a substantially fixed short initial break of the order of approximately 1/4 in. is formed by the floating contact, and thereupon a second break is formed between the hollow butt contact and the floating contact, the resulting arc at the fixed initial break generating pressure which is effective to direct a blast of insulating fluid from all sides radially across the second break and into the hollow butt contact to extinguish the main arc.

2. In a fluid-break switch ofthe explosion chamber type, circuit interrupting means comprising a butt contact mounted within the explosion chamber, arcing structure in conducting relation and fixed with respect to said contact, and a floating butt contact spaced by a short annular gap from said structure having limited movement within the explosion chamber adapted to engage the first-named Contactin the closed circuit positionof the switch and to effect a break of lfixed length with the same during opening movement of the switch for creating pressure within said chamber, said arcing structure being so related 1 J the first-named butt contact and said floating contact that an arc formed between said contacts is transferred to said structure in response to reverse or arc lengthening movement of the first-named contact.

3. A fluid-break switch comprising means forming an explosion chamber including an adapt-er of conduc-ting material, a contact retainer mounted within said adapter and in conducting relation therewith and a steel cylinder secured to said adapter, arc extinguishing means disposed within said chamber including a butt contact guided for limited reciprocal movement within a lower wall of said retainer, a coacting floating butt contact having a supporting spider mounted for limited reciprocal 'movement within said chamber, the lower wall of said retainer having a flared arcing portion spaced by a short annular gap with respect to the aforesaid contacts at the point of Yengagement thereof, in-

lsulating structure to form a second are at said exhaust opening.

4. A fluid-break switch comprising means forming an explosion chamber including an adapter of conducting material, a steel cylinder mounted on and secured to said adapter, are extinguishing means disposed within said chamber including a butt contact guided for limited reciprocal movement, a coacting floating butt Contact mounted for limited re ciprocal movement within said chamber, an

arcing portion in conducting relation to said adapter having a flared arcing surface spaced by'a short annular gap with respect to the aforesaid contacts at the point of engagement thereof, insulating structure forming a chamber exhaust opening at the lower part of said cylinder through which a movable rod contact is arranged to extend and engage said floating contact, said fioating contact being resiliently biased r into following engagement with said rod contact so that upon lowering of said rod contact an initial pressure generating arc is formed between said first-named butt contacts for extinguishing arcing between said floating contact and rod Contact.

In witness whereof, we have hereunto set our hands this 22nd day of April, 1930.

WILLIAM TURNPENNY. WILFRED F. SKEATS.

lll.

Images