US3128361A

US3128361A - High current switch arrangement for quick break

Info

Publication number: US3128361A
Application number: US5066A
Authority: US
Inventors: Kesselring Fritz
Original assignee: Siemens AG
Current assignee: Siemens Schuckertwerke AG; Siemens AG
Priority date: 1959-02-17
Filing date: 1960-01-27
Publication date: 1964-04-07
Anticipated expiration: 1981-04-07
Also published as: CH379599A

Description

A ril 7, 1964 F. KESSELRING 3,

HIGH CURRENT SWITCH ARRANGEMENT FOR QUICK BREAK Filed Jan. 27, 1960 IN VEN TOR. F B/ 7' Z KEJJA-Z E/N 0; 7190A 8M6, 51 3278, 623215 3 fa /em 14 770,49! 7f Patented Apr. 7, 1964 3,128,361 HIGH CURRENT SWITCH ARRANGEMENT FOR QUICK BREAK Fritz Kesselring, Kusnacht, Zurich, Switzerland, assignor to Siemens-Schuckertwerke A.G., Berlin, Germany, a

corporation of Germany Filed Jan. 27, 1960, Ser. No. 5,066 Claims priority, application Germany Feb. 17, 1959 2 Claims. (Cl. 2.00-151) This invention relates to a high speed circuit breaker having a high voltage rating and is more specifically directed to a high speed, high voltage circuit breaker of the electrodynamic type.

Electrodynamic circuit breakers are well known in the art and are described, for example, in copending application Serial No. 558,349, filed January 10, 1956, now Patent No. 2,951,188 entitled High Speed Contacting Device, and in US. Patent No. 2,916,579 to Kesselring et al.

The electrodynamic concept for the operating means of a circuit breaker results in extremely high speed circuit interruption whereby the recovery voltage during interruption at any instant is insufliicent to cause a breakdown over the distance between the movable and stationary elements.

In the past, the electrodynamic circuit breaker has had application mainly in connection with low voltage circuits. In using this concept for high voltage circuits several problems arise. The most important of these problems is that the stationary contacts must be sufficiently spaced from one another to prevent breakdown or restriking of the arc when the circuit breaker or interrupter is in its open position. Because of this and where the movable contact is of the bridging type, the mass of the movable contact is substantially increased since it must span this relatively large distance between the stationary contacts. Furthermore, the movable contact must retain the same current carrying cross-sectional area to prevent too high a temperature rise during normal operating conditions.

This increase in mass results in a smaller acceleration for a given applied operating energy and could, therefore, prevent the application of such a switching device to high voltage application.

The principle of the present invention is to provide a high speed high voltage circuit breaker which operates on the electrodynamic principle wherein the movable contact is carried in an elongated insulating member which is interposed between the stationary contacts which are bridged by the movable contact. This insulating barrier will, therefore, be interposed between the stationary contacts when the movable contact is moved to its open position and accordingly the stationary contacts may be more closely spaced than if the only dielectric between the stationary contacts were air. By way of example, typical commercially available solid insulat ing materials can be used for the insulating sheet which have a dielectric strength ten or more times greater than the dielectric strength of air at atmospheric pressure.

Since the stationary contacts may be more closely spaced to one another by practicing the present invention, the distance which the movable contact must now span is substantially decreased. Furthermore, since the movable contact will generally have a small current carrying area in order to decrease its mass, its resistance is relatively high, but since the span of the contact is shorter, the net resistance introduced into the circuit by the movable contact is relatively lower so that the temperature increase of the circuit breaker may be decreased.

It is to be noted that the net decrease in the mass of the movable contact is greater than the required increase in mass for the insulating follower construction. However, even in applications where there is no net saving in mass it will be apparent that the overall size of the interrupter is considerably decreased and the highly advantageous insulating barrier which is interposed between the stationary contacts still applies.

In operation the insulating barrier may have a portion thereof connected to a short circuited winding which in turn is coupled to an operating winding. When the operating winding is energized, an extremely high current will be induced in the short circuited winding whereby the short circuited winding and the insulating barrier which carries the movable contact will be accelerated toward the circuit breaker open position in the usual manner.

Accordingly, the primary object of this invention is to provide a novel high speed, high voltage circuit break- Another object of this invention is to provide a novel high voltage circuit breaker using the electrodynamic operating principle.

A further object of this invention is to provide a novel high voltage circuit breaker which operates on the electrodynamic principle and utilizes an insulating follower for carrying the movable contact, whereby the insulating follower is interposed between a pair of stationary contacts.

A further object of this invention is to provide a novel high voltage circuit breaker wherein the movable contact is carried by an insulating sheet which is moved to a position interposed between a stationary contact and other points of different potential.

Yet a further object of this invention is to provide a novel insulating member for carrying the movable contact of an electrodynamic circuit breaker whereby the mass of the movable contact is substantially decreased.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings in which:

FIGURE 1 shows a side cross-sectional view of a preferred embodiment of the present invention.

FIGURE 2 shows a top plan view of FIGURE 1. 7

FIGURE 3 shows a side view of a second embodiment of a contact which can be used for the movable contact in the switch of FIGURE 1.

Referring now to FIGURES 1 and 2, the circuit breaker of the invention is comprised of a first and second stationary contact 1 and 2, respectively, which are connected in a circuit to be protected (not shown) in any desired manner. A bridging movable contact 3 has a prismatic cross-section and is elongated along the tapered contacting surface of the stationary contacts 1 and 2 bridges stationary contacts 1 and 2 as shown. The movable contact 3 is carried by U-shaped insulating sheets 4 and 5 wherein the bottom legs of the U of the sheets are fastened by cementing and a slot is placed in this common bottom leg to accept movable contact 3. More specifically, a flexible strip of material 6, which could be of rubber, is cemented to the top of contact 3 as is shown in FIGURE 1, and this assembly of contact 3 and flexible strip 6 is thereafter inserted in the slot in U-shaped insulating strips 4 and 5 to be held therein by friction or cementing or any other desired 'manner. If desired, strips 4 and 5 could be an integral member which could be extruded to proper shape.

The U-shaped strips -4 and 5, which comprise the insulating follower of the invention, are preferably formed to envelop either end of stationary contacts 1 and 2 as is best seen in FIGURE 2 and have their lower end rigidly connected in any desired manner to a short circuited winding 7 which may be a flat disc of conductive material such as copper or aluminum. The disc 7 is normally supported by an insulating block 8 which is secured to some relatively fixed member and has an operating winding 9 embedded therein.

The circuit for energizing operating winding 9 may be derived from fault sensing elements associated with the circuit being protected as in the manner shown in above noted cope-nding application Serial No. 558,349 or by any method in accordance with the well-known principles of electrodynamic circuit breakers. When winding 9 is energized, an extremely high circulating current will be induced in short circuited winding 7. Since

windings

7 and 9 are very closely coupled to one another, the magnetic fields generated by these windings will be extremely high and will repel one another with very great force. This will impart an extremely high acceleration to the disc 7 and the insulating strips 4 and and low mass movable contact 3 associated therewith in a vertical direction so that the movable contact 3 is moved to an upper, and contatc disengaged position, in an exceedingly short time.

In order to provide a contact engaging force and at the same time provide means for retaining the movable structure in its disengaged position when it is moved from the engaged position of FIGURE 1 to an upper and disengaged position, a pair of spring operated mechanisms 10 and 11 is carried on stationary contacts 1 and 2, respectively. Spring mechanisms 10 and 11 are identical and are shown in FIGURE 1 for the case of mechanism 10. Thus, mechanism 10 is comprised of an insulating housing 12 which has a central bore therein for carrying a com p-ression spring 13. The compression spring 13 operates a plunger .14 which bears on an output link 15 which is pivoted at a relatively fixed pivot 16. A similar output link 17 is provided for spring mechanism 11 as shown in FIGURES 1 and 2. Each of the

output links

15 and 17 bears directly upon the top of insulating members 4 and 5 to bias them downwardly to thereby drive movable contact 3 into high pressure contact engagement with stationary contacts 1 and 2.

At the

same time members

15 and 17 will operate to hold insulating members 4 and 5 in an upward position when the movable switch structure is moved upwardly to a disengaged position.

Thus, when the movable contact structure is accelerated upwardly, the

spring arms

15 and 17 are first cammed apart during the initial extremely high force created by disc 7 and operating winding 9 which are closely coupled. As the movable structure moves upwardly and the coupling between

windings

7 and 9 decreases and the force on the movable structure decreases until, when the movable contact assumes an upwardly displaced disengaged position, the force decreases to zero. At this point the arms 15 and '17 which are driven into relatively frictional force engagement with insulating members 4 and 5 by their respective biasing springs will retain the movable contact structure in this upwardly displaced disengaged position.

In order to reclose the switch, it is only necessary to push the top of insulating members 4 and 5 downwardly to overcome the frictional force exerted by

spring bias arms

15 and 17 until the movable structure resumes the position of FIGURE 1 and the circuit breaker is closed.

In operation it will be apparent that as the movable contact moves to its disengaged position it is followed by a solid sheet of insulating material which is interposed between stationary contacts 1 and 2. This solid dielectric barrier which can completely fill the gap between contacts 1 and 2 and slide between either adjacent stationary contact surface permits a very close spacing of contacts 1 and 2. This reduces the span of movable contact 3 to a minimum, and accordingly, its mass is reduced to a minimum. Furthermore, by forming insulating members 4 and 5 with a U-shaped cross-section the creepage distance, as best seen in FIGURE 2, between contacts 1 and 2 is substantially increased.

In a typical application of the device of FIGURES 1 and 2, the circuit being protected was rated at 10,000

volts at 1,000 amperes. The weight of the movable contact 3 was 1.8 grams, and the total Weight of the movable system not including disc 7 was approximately 40 grams. The closing contact pressure from

links

15 and 17 was 20 kilograms to give a contact resistance of 20 microohms. With this construction, the temperature rise in the movable contact was found to be 2 C. higher than the temperature of the stationary contacts 1 and 2. The operating time for this type of circuit breaker was found to be a fraction of a millisecond.

The shape of the movable contact 3 may, of course, assume many forms. For example, in FIGURE 3 the movable contact is illustrated as being formed of a plurality of segments 18 cemented to a common plate 19 which may be of rubber which serves the purpose of plate 6 of FIGURE 1 as well as to provide a common support for segments 18. With this type of arrangement, the contact resistance was found to be decreased from 20 microohms for the solid movable contact of FIGURE 1 to approximately 10 micro-ohms.

It is to be noted that, because of the small length of the movable cont-act, made possible by the close spacing of stationary contacts 1 and 2, the resistance of the movable contact may be reduced to values comparable to the contact resistance whereby the net resistance of the contact arrangement is reduced and the temperature rise is corre spondin'gly reduced.

If desired, parallel circuit means could be provided for stationary contacts 1 and 2 such as a resistor 20, shown in dotted lines in FIGURE 1, which will reduce the rate of rise of recovery voltage during interrupting conditions. A switching means may be connected in series with resistor 15 to achieve final circuit interruption of the current flow therethrough. If desired, the resistor 15 could be replaced by a fuse which would operate first as a low resistor to control the recovery voltage across contacts 1 and 2 and thereafter serve as a final interrupting means for the circuit.

In the foregoing the invention has been described only in connection with preferred embodiments thereof. Many variations and modifications of the principles of the invention within the scope of the description herein are obvious. Accordingly, it is preferred to be bound not by the specific disclosure herein but only by the appended claims.

What is claimed is:

1. A high voltage circuit breaker; said high voltage circuit breaker comprising a pair of stationary contacts positioned in spaced relation with respect to one another and a movable bridging contact; an operating means for said movable bridging contact; said operating means being operable to move said movable contact between an engaged and disengaged position; said operating means being a high speed operating means operable to move said bridging contact to said contact disengaged position at a speed whereby recovery voltage at any instant is insufficient to cause breakdown from said movable contacts to said stationary contacts; and an insulating barrier means; said insulating barrier means being interposed between said pair of stationary contacts when said movable bridging contact is moved to said disengaged position; said pair of stationary contacts being relatively closely spaced with respect to one another relative to their required spacing in the absence of said insulating barrier whereby the mass of said movable contact is decreased; said movable bridging contact being carried by said insulating barrier; a spring biasing means; said spring biasing means being operatively connected to said insulating barrier for biasing said movable contact toward said engaged position and for providing contact pressure; said spring biasing means being characterized in having its biasing force sharply decreased to zero immediately after movement of said movable bridging contact toward its said disengaged position.

2. A high voltage circuit breaker; said high voltage circuit breaker comprising a pair of stationary contacts positioned in spaced relation with respect to one another and a movable bridging contact; an operating means for said movable bridging contact; said operating means being operable to move said movable contact between an engaged and disengaged position; said operating means being a high speed operating means operable to move said bridging contact to said contact disengaged position at a speed whereby recovery voltage at any instant is insuificient to cause breakdown from said movable contacts to said stationary contacts; and an insulating barrier means; said insulating barrier means being interposed between said pair of stationary contacts when said movable bridging contact is moved to said disengaged position; said pair of stationary contacts being relatively closely spaced with respect to one another relative to their required spacing in the absence of said insulating barrier whereby the mass of said movable contact is decreased; said movable bridging contact being carried by said insulating barrier;

a biasing means; said biasing means being operatively connected to said insulating barrier for biasing said movable contact toward said engaged position and for providing contact pressure; said biasing means being characterized in having its biasing force sharply decreased to Zero immediately after movement of said movable bridging contact toward its said disengaged position.

References Cited in the file of this patent UNITED STATES PATENTS