US3217115A

US3217115A - High velocity arc interrupter

Info

Publication number: US3217115A
Application number: US332008A
Authority: US
Inventors: Harvey C Kaplan
Original assignee: Joslyn Manufacturing and Supply Co
Current assignee: Joslyn Manufacturing and Supply Co
Priority date: 1963-12-20
Filing date: 1963-12-20
Publication date: 1965-11-09
Anticipated expiration: 1982-11-09

Description

Nov. 9, 1965 H. c. KAPLAN HIGH VELOCITY ARC INTERRUPTER Filed Dec. 20, 1965 INVENTOR.

HARVEY C. KAPLAN ATTORNEY TIME Mazda-m5 United States Patent 3,217,115 I-HGH VELOCHTY ARC IWTERRUPTER Harvey C. Kaplan, Cleveland Heights, Ohio, assignor to Joslyn Mfg. and Supply Co., Chicago, llL, a corporation of Illinois Filed Dec. 20, 1963, Ser. No. 332,0ti8 4 Claims. (Cl. 200-48) This invention relates to high voltage arc break disconnect switches and more particularly to switch auxiliary means for minimizing arcs drawn in air when interrupting high voltage circuits.

The switching of high voltage circuits in air presents serious problems, one of which is the tendency to draw long electric arcs which could cause line to ground or line to line faults, thereby causing customer outages. The problem of minimizing arcs drawn in air is one of providing a build up of dielectric strength faster than the rise of recovery voltage across the interrupter, and of being certain that after interruption this dielectric strength is maintained in order to prevent restriking.

In the past, various types of devices have been proposed to minimize arcs drawn in air. One such device is described in Patent No. 2,849,578 issued on an application filed by L. C. Hart and assigned to the assignee of the present invention. The Hart device incorporates a flexible resilient rod which is engageable by a latching device to hold it with respect to stationary contact structure. The resilient rod is mounted parallel to a high voltage disconnect switch and is afiixed and connected to the movable switch arm on one end. When the switch is opened, the resilient rod maintains a temporary by-pass of the main switch contacts. After the switch has opened a predetermined amount the resilient rod, which had been flexed to store energy, is released. It then moves with high velocity away from the stationary structure to interrupt the circuit. While the Hart device has operated very satisfactor-ily for many applications it has required a strong, shock absorbing, non-oscillatory (non-restriking), hence costly, construction, and sometimes its interrupting capability has not been ideal.

A major factor contributing to the successful interruption of a circuit using this type of arc break device is the speed at which the tip of the interrupter moves away from the previously drawn are after a current zero. If the buildup of dielectric strength due to the combination of air dielectric between the interrupter tip and the previous drawn arc plus the deionization of the previous drawn arc is greater than the rise in recovery voltage across the switch, the circuit will be successfully opened. If not, the arc will reignite until the next change for interruption at the next current zero.

It is an object of the present invention to provide inexpensive means for overcoming the above mentioned difficulties.

Another object of the invention is to provide an improved, low cost, light Weight arc break switch useful for interrupting line charging current, transformer magnetizing current, or small load currents.

Other objects and advantages will become apparent and the invention may be better understood from consideration of the following description taken in connection with the accompanying drawing in which:

FIG. 1 is an elevation view of a high voltage air break switch embodying the present invention and showing several difierent positions of the switch during operation;

FIG. 2 is an enlarged sectional view of a portion of the switch of FIG. 1, and

,FIG. 3 is a graph in which separation distance is plotted against time both for the prior art and for the present invention.

Referring first to FIG. 1, a switch indicated generally at 10 might be any form of high voltage air break switch. As illustrated, the switch ltl comprises a base member 11 formed as of channel iron to provide a rigid support for the switching contacts and operating means. A pair of insulators 12 and 13 are fixedly mounted in spaced relation ship on the base 11. There is also provided a movable insulator 14 positioned between the fixed insulators 12 and 13. The insulator 14 includes a downwardly extending shaft 15 which is adapted for rotation in a suitable bearing mounted on the base 11. As illustrated, the end of the shaft 15 disposed on the opposite side of the base 11 from the insulator 14 is provided with a hexagonal end 15:: which may be engaged by a suitable manual operating lever or the like to cause rotation of the insulator 14.

For the purpose of operating the switch 10 as a multipole switch, one or more crank arms 18 may be provided to rotate with the insulator and shaft 15. As illustrated, the crank arm 18 is provided with an operating eye 19 which may be connected to suitable rods interrelating the plurality of poles of the multipole switch to insure simultaneous operation of all poles thereof.

In order to support electrical conductors which together with the switch 10 comprise the circuit to be controlled, there is mounted on the insulator 12 a hinged base and terminal support 21. On the other hand, there is mounted on the insulator 13 a contact support and stationary contact structure 22. It will be understood that the

supports

21 and 22 are suitably fastened to their associated insulators 12 and 13 in a conventional manner. Many details of the lower or main switch structure as shown in FIG. 1 and which includes a movable switch arm or blade 26 form no part of the present invention and, if need be, can be fully understood by reference to the above mentioned Patent 2,849,578.

In accordance with the illustrated embodiment of the present invention a mechanism housing 38 with a weather shielding cover 39 is associated with a resilient, whiplike member 49 as hereafter more fully explained.

As seen in FIG. 2, within housing 38 and cover 39 is a crank 52, a tension spring 53, a pivot bearing 54, a spring adjuster 55, and two

adjustable stops

56a and 56b. Attached to one arm of the crank 52 is the whiplike resilient rod 46 preferably tapered similar to the rod described in the Patent 2,849,578. The housing 38 and its associate parts are mechanically aflixed and electrically connected to the movable switch arm 26.

During opening operation, the interrupter maintains a temporary by-pass of the main switch contacts 26-22 through a hook or latch 58 on the stationary contact structure 26. At a predetermined point the spring loaded interrupter rod 40 releases. It then moves away from the stationary contact with a high velocity to open the circuit.

Referring to FIG. 3, in which the abscissas represent time after release of rod 40 from latch 58 and in which the ordinates represent distance between most relevant parts of rod 40 and latch 58, a curve 61 represents the relationship according to the prior art as exemplified in the previously mentioned Hart patent while curve 62 shows the improved relationship of distance with respect to time when the improvement of the present invention is included with all non sequitur conditions exactly the same as before. One important aspect of the improved relationship has to do with speed (of contact separation) which, of course, may be expressed as dD/dT, and other very important aspects include length of time over which maximal, or near maximal, speed occurs, as well as when maximal speed (and the length of time it prevails) occurs during the opening cycle. For example, if maximum speed lasts but a short time or occurs only at the very beginning or at the very end of the opening cycle (as according to some prior art other than Hart) it is of little help in preventing damage due to arcing. Several types of arc break devices which suffer such defects each use an arc blade member which is non-flexible in the direction of principal movement. The disadvantages caused by the use of a nonfiexible member as the auxiliary interrupter are such that they impose serious limitations on the practicality of the device for more difiicult tasks. Because such a nonflexible member rotates about a pivot axis with constant (e.g., separate spring-caused) acceleration the maximum velocity of the interrupter is not reached until the end of its travel thereby causing longer arcs to be drawn. Further, the non-flexible device requires a strong shock absorber to limit the impact of the non-resilient member, and requires extra parts to position such member in a neutral position before the interrupter can be used, both requirements making the interrupter more costly.

Also known in the past is a construction using a nonflexible auxiliary interrupter rod having a flexible tip added for increasing beginning separation speed, but I have found that such an arrangement is actually a hindrance to the eflicacy of the auxiliary interrupter, since it subtracts from the energy previously stored in the auxiliary interrupter and thus it decreases maximum velocity attained, while it also shifts any new maximum velocity towards the very beginning of opening cycle (where it does little good) With the present invention, however, the auxiliary blade is itself flexible, resilient, and whiplike, and the flexibility enhances (rather than subtracting from) its speed of movement at the most critical time.

During operation, with the present invention, when the disconnect switch starts to open, the resilient rod 40 is caught in the latch 58 on the stationary contact structure 22. The first motion that takes place is a rotation of the resilient rod 40 and crank 52 about the pivot bearing 54 inside the mechanism housing 38, storing energy in the spring 53, attached to the crank 52, as the resilient rod 40 and crank 52 continue to rotate until the crank 52 hits the preset stop 5612. At that time further rotation of the crank 52 is prohibited, and the spring 53 is fully charged. As the main switch continues to open the resilient rod 40 is bent in a cantilever fashion storing energy in the rod 40. Continued motion of the disconnect switch causes the resilient rod 40 to release from the latch 58 at a predetermined point (when the spring 53 and the resilient rod 40 are both fully charged), and then the rod 40 will move away from the latch 58 with a very high velocity due both to the tendency of the rod to unflex and to the force of spring 53 acting in such direction as to move 40 away from 58.

Thus, the storage of energy into the interrupter as caused by the main operating mechanism is broken into two sections: 1) storage of energy into the spring loaded crank 52, and (2) storage of energy into the resilient rod 40. By breaking the work performed in opening the switch into two intervals, each extending over a relatively great distance of operation, the maximum operating force is reduced, thereby not requiring as strong or costly switch operating mechanism as did mechanisms heretofore.

Additionally, as seen from comparing the curves of FIG. 3, the maximum dD/dT velocity of the tip of the whip rod has been greatly improver, providing a greater air dielectric to aid interruption, the total motion of the tip has been more than doubled, allowing, if need be, a greater amount of arc deionization, while the time length of maximum dD/dT, and its orientation with respect to total opening cycle, are both optimum.

It should be noted that a part of the advantage of the present invention is due to the fact that the pivot point (of crank 52 and hence of rod 4%) is moving (e.g., with respect to 58) with movement of main blade 26.

There is thus provided a device of the character described capable of meeting the objects above referred to. The higher velocity obtained through the combination of crank 52. and resilient rod 40 motions insures better interrupting capabilities, while the greater distance of motion of the rod due to the combination of crank 52 and rod 4t motions insures better interrupting capabilities. Furthermore, the greater distance of motion of the interrupter due to the combination of crank 52 and rod 40 motions insures that the device may be used without a costly shock absorber to stop the moving arm, and the damping of the device of the invention need only be the naturally inherent friction and Windage losses thereby lowering the cost of the interrupter unit. All prior devices for similar purposes have used some form of shock absorber to lessen impact or oscillation of the auxiliary interrupter arm to prevent a restrike or failure of the interrupter and damage to other parts. However, because of the greater distance the interrupter rod travels according to the present invention and because of its having maximum velocity for a longer distance, the oscillation of the rod 40 causes no problem, the air dielectric between the interrupter and the stationary contact being great enough to prevent a restrike.

While I have illustrated and described a particular embodiment, various modifications may obviously be made without departing from the true spirit and scope of the invention which I intend to have defined only by the appended claims taken with all reasonable equivalents.

I claim:

1. In a high voltage switch:

a flexible rod contact and a catch member engaging said rod for a substantial time during switch opening initiation sequence whereby to delay separation of a pair of contacts formed by the flexible rod and the catch,

first means including a spring for storing contact opening energy without substantially flexing said rod for one period during switch opening initiation sequence, and

second means for storing contact opening energy by flexing said rod for another period during the switch opening initiation sequence, said second means including a stop (56b) limiting the action of said first means during said last mentioned period.

2. In a high voltage switch of the type having a stationary main contact means and a cooperating relatively movable main contact means and electrically connected in parallel therewith a pair of arc interrupting contact members,

the combination wherein one of said last mentioned members is a resilient whiplike rod contact, having a near end associated with the movable one of the main contact means, and the other of said members is a catch which is fixed with respect to the stationary one of the main contact means and wherein said catch holds the other end of said whiplike rod contact in electrical engagement during a substantial portion of the switch opening operation,

a pivotal crank means for moving said whiplike rod by (a) movement about said pivot and (b) movement of said pivot, and

a stop means for the crank means.

3. A high voltage switch as in claim 2 further character- 3,2 1 7, 1 1 5 5 6 tional to said rod, for causing the additional spring to op- References Cited by the Examiner erate first (during opening) and the rod due to its re- UNITED STATES PATENTS silience to bow substantially its entire length thereafter (during opening) whereby to obtain a large useful output 1,912,615 6 Alsaker et 20048 (as regards distance and speed of separation) with mini- 5 2,779,830 1/57 Turner et a1 200 48 mal peak input effort (for opening and for closing), and 2,886,663 5/59 Powell 200 48 whereby to reduce length of any arc, and obviate the possibility of restrike, and eliminate the need for any shock BERNARD GILHEANY Primary Examiner absorber (for opening). ROBERT K. SCHAEFER, Examiner.

Claims

1. IN A HIGH VOLTAGE SWITCH; A FLEXIBLE ROD CONTACT AND A CATCH MEMBER ENGAGING SAID ROD FOR A SUBSTANTIALLY TIME DURING SWITCH OPENING INITIATION SEQUENCE WHEREBY TO DELAY SEPARATION OF A PAIR OF CONTACTS FORMED BY THE FLEXIBLE ROD AND THE CATCH, FIRST MEANS INCLUDING A SPRING FOR STORING CONTACT OPENING ENERGY WITHOUT SUBSTANTIALLY FLEXING SAID ROD FOR ONE PERIOD DURING SWITCH OPENING INITIATION SEQUENCE, AND SECOND MEANS FOR STORING CONTACT OPENING ENERGY BY FLEXING SAID ROD FOR ANOTHER PERIOD DURING THE SWITCH OPENING INITIATION SEQUENCE, SAID SECOND MEANS INCLUDING A STOP (56B) LIMITING THE ACTION OF SAID FIRST MEANS DURING SAID LAST MENTIONED PERIOD.