US2916579A

US2916579A - Electrodynamic circuit breaker

Info

Publication number: US2916579A
Application number: US558522A
Authority: US
Inventors: Kesselring Fritz; Zurich Zollikon; Diebold Edward John
Original assignee: Siemens AG; ITE Circuit Breaker Co
Current assignee: Siemens Schuckertwerke AG; Siemens AG; ITE Circuit Breaker Co
Priority date: 1954-03-11
Filing date: 1956-01-11
Publication date: 1959-12-08
Anticipated expiration: 1976-12-08
Also published as: CH342624A; US2937344A; CH342614A; GB814307A; DE1067105B; FR1130045A

Description

Dec. 8, 1959 F. KESSELRING ETAL 2,916,579

ELECTRODYNAMIC CIRCUIT BREAKER Filed Jan. 11, 1956 /e m X Q1; 15 /A m VHVTO S FZ/Tz 'ssEL /A G fawn/20 Jaws M51010 United States Patent ELECTRODYNAMIC CIRCUIT BREAKER Fritz Kesselring, Zollikon Zurich, Switzerland, and Edward John Diebold, Ardmore, Pa.; said Kesselring assignor to Siemens-Schuckertwerke A.G., Berlin, Germany, a corporation of Germany, and said Diebold assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application January 11, 1956, Serial No. 558,522

Claims priority, application Germany January 13, 1955 9 Claims. (Cl. 200-87) Our invention relates to an electrodynamic circuit breaker of the type described in copending application Serial No. 558,349, filed January 10, 1956, and assigned to the assignee of the instant invention and more particularly to an electromagnetic circuit breaker wherein the relation:

holds true and is achieved within fractions of a millisecond with the above quantities to be defined hereinafter.

The above noted application Serial No. 558,349 more specifically shows a contacting device in which a unitary member serves as a movable contact for a pair of cooperating contacts as well as a winding which is so disposed as to interact with a second or operating winding, the energization of which will give rise to magnetic fields in both the movable contact winding and the operating winding which are so directed as to cause the movable contact to move with relation to its cooperating contact.

We have, however, found that for optimum operation of devices of the above described type that the relation:

HOIINIJ 21raa'y should be achieved within a fraction of a millisecond, where I is the peak current in the operating Winding in amperes N is the number of turns of the operating winding, I is the current density in the operating wind ing in amperes per square meter, a is the effective coupling distance between the operating winding and the movable contact Winding in meters, 7 is the weight density of the current carrying material in kilograms per cubic meter and a is a correction factor to be used when a mass other than the mass of the movable contact is to be accelerated, and n is the permeability of free space in volt seconds per ampere meter or More specifically, the correction factor a is given by 2 where m, is the mass of an additional body attached to the movable contact and m is the mass of the contact ring or winding, both quantities being expressed in kilogram seconds squared per meter.

The derivation of the above relationship will be given hereinafter and may be applied to any form or structure which operates in accordance with the above noted principle.

Accordingly, the primary object of our invention is to provide a contacting device in which the movable contact of the contacting device is constructed to form 2,916,579 Patented Dec. 8, 1959 teract with a second energizable winding whereby motion of the movable contact is obtained, the functional relationships between the components of the contacting device being determined so that is achieved within fractions of a millisecond.

In the application of a contacting device which is constructed to achieve the above relationship, to a circuit interrupting duty, it is desirable to maintain the movable contact in a disengaged position after it has been moved thereto in order to prevent reclosure of the cooperating contacts.

One novel method of accomplishing this end is to further construct the unitary movable contact and operating winding so that it has a magnetic material at-. tached thereto. A magnetic means is then provided which is so disposed as to engage this magnetic material when the movable contact has reached the full length of its travel. In the event that a biasing means is utilized to obtain contact pressure between the cooperable contact, the seal in force of the magnet must be great enough to overcome this biasing force. However, upon engagement of this magnetic material by the above mentioned magnetic means which could be a permanent magnet, it is well known that the holding force or seal in force is much greater than the normal forces acting at a distance between the magnet and magnetic material, and the contact will therefore be rigidly maintained in the disengaged position.

Accordingly, another object of our invention is to provide a contacting device utilizing a unitary movable contact and winding which may be a single short circuited winding wherein the movable contact device is further constructed to have a magnetic material attached thereto for latching purposes.

Another object of our invention is to provide a means to maintain the movable contact of our novel contacting device in a disengaged position after it has been moved thereto.

A still further object of our invention is to provide the movable contact of the above described contacting device with a magnetic material disposed for engagement with a permanent magnet when the movable contact is moved to a disengaged position.

We have further found that the operating winding and the movable contact winding need not be two individual bodies but may in fact be components of an individual winding.

As is well known, a coil of wire carrying a current will tend to contract. That is to say, there will be an attractive force between each of the adjacent windings. If, however, a portion of the coil is wound in a first direction and the remainder of the coil is wound in an opposite direction, then it is clear that there will be a repulsive force between the oppositely wound portions of the coil. We propose to utilize this principle by making the first portion a relatively stationary portion as by imbedding it in a relatively stationary body, and to utilize the second and oppositely wound portion as a movable contact member. Therefore, when the entire coil is energized, it is seen that the movable portion which is wound oppositely to the stationary portion will move away from the stationary portion with an extremely high acceleration.

In this case, it is to be realized that for best results that the design should be such that once again, the relationship given above should be followed.

Accordingly, a still further object of our invention is to provide a contacting device of the above noted type wherein the operating winding and unitary movable contact winding are portions of the same winding wherein the stationary portion is wound in a first direction and the movable portion is wound in an opposite direction so that energization of the complete winding will impart repulsive forces to the two portions. 7

Another object of our invention is to provide a movable unitary contact and operating winding which are integral parts of a single winding.

These and many other objects of our invention will become apparent when taken in conjunction with the following description in which:

1 Figure 1 shows one form which may be taken by an operating winding and a cooperating unitary movable body and winding whereby magnetic interaction between the two Winding effects relative motion therebetween.

T Figure 2 shows an embodiment of an operating coil and a contacting structure which may be driven to short circuit a pair of stationary contacts.

Figure 3 shows an embodiment of a unitary movable contact and winding, which winding is a continuation of the operating winding, where the operating winding and the contact winding are wound in opposite directions. Figure 4 shows a still further embodiment of a contact device constructed in accordance with our novel invention as specifically applied to a D.-C. circuit wherein magnetic latching means are provided to latch the movable contact in a disengaged position.

' Figure 5 shows a still further embodiment of our novel invention as applied to a vacuum switch.

Referring now to Figure 1, it is seen that an operating winding having a number of turns N is positioned with respect to a movable winding 11 having a number of turns N The winding 11 could, if desired, form the movable contact of a contact device and, in the case of Figure 1, it is shown as having two turns. The windings 10 and 11 of Figure l are then shown as being separated by a separation of dimension a.

Capacitor 12 is then shown as being connectible in series with the winding 10 by means of the switching device 13 which could be of any desired type. Capacitor 12 is further shown as being maintained in a charged condition by means of the DC. source 14 which is connected in series with the capacitor 12 and resistor 15.

In operation, when it is desired to impart motion to the winding 11, it is seen that one need only close the switch 13 to thereby allow capacitor 12 to discharge through winding 10. The flow of current through the winding 10, of course, produces a magnetic field which will then induce a flow of current in the winding 11. This flow of current in the winding 11 will in turn induce a second magnetic field and the interaction between the two magnetic fields is then such as to cause a repulsion between the coils 10 and 11. Therefore coils 10 and 11 will move away from one another at extremely high acceleration if a high discharge current is obtained from capacitor 12.

It can be found with the application of the law of Biot-Savart, that the instantaneous force between current carrying conductors which are disposed as the conductors of Figure 1 is given by F 21rd (newtons) where The acceleration of the movable member may be expressed from the law of motion as where b=acceleration in meters per second squared m =mass of movable member in kilograms where m is any additional mass attached to the movable member in kilograms.

Furthermore, m can be expressed as where: A is the cross-sectional area of the movable conductor in square meters and g is the gravitational constant.

Since where: J is the current density in the movable conductor in amperes per square meter.

Hence, m may be written as m 7l'dI2 It now the relation for force F, and mass m are sub-' stituted into the equation of motion, it is seen that H o h 1) J 9 Upon rationalization of the above equation, and dividing both sides by g, it is seen that:

21raa'y It is to be noted that this relationship may be stated in different form.

One way for example uses the energy stored in the dischargable capactor which energizes the operating winding. If then:

where W==energy in the capacitor E=voltage on the capacitor C=capacitance of capacitor Since this energy is transferred to the operating winding, one may write:

ICE

where: L is the inductance of the operating winding. If the inductance is then expressed as:

where k and A are constants determined by the coil construction, then;

and

CE, (1''k) if the above expressions are then substituted into the equation of motion, the following relation is obtained:

where, in the term on the right, the first bracket contains the invariable constants of the system, the second bracket expresses the available capacitor energy, and the third bracket describes the system constants.

By proper manipulation of a design, these constants must, in accordance with our invention be chosen to give a value of b/ g of at least 10,000.

In the embodiment, of Figure 2, which shows a slightly modified form of embodiment of Figure 1, it is seen that the operating winding 16 is now comprised of a fiat winding and the movable winding 17 is now comprised of a single turn. Figure 2 further shows first and second relatively

stationary contacts

18 and 19 which are so positioned as to be engaged by the movable winding 17 responsive to energization of the winding 16. These contacts may thereby be short circuited to protect faulted electrical apparatus. In the case of Figure 2, it is seen that the above equation derived for the case of Figure 1 may be rewritten in a slightly modified form:

I }lgJ S 9 2104 since a of the previous equation is now equal to:

where S is the radial width of coil 16.

For illustrative purposes only, it may be assumed that the distance x through which the movable contact of Figure 2 is to move is of a millimeter. An application of the above relationships would therefore result in a force of 600 kilograms and an acceleration of 40,000 times the acceleration due to gravity if, by way of example, the peak discharge current in the coil 16 is 2,000 a'tnperes, the number of turns of coil 16is 20, the dimension d or the mean diameter of the coil 17 is three centimeters, the thickness S is cm., the dimension a is .26 centimeter, the weight of the movable conductor kilogram, and the current density is 300,000 amperes per square centimeter. In view of this result, it is seen that switching times of the order of 10 seconds may be obtained, which time is sufiiciently short for operation of low voltage switch S.

If it is desired to apply or novel contacting device to a high voltage switching device, then one need only utilize a medium of high dielectric strength, such as a compressed gas or insulating liquid to assure that the instantaneous flash over voltage will always be greater than the instantaneous recovery voltage across the separating contacts.

Figure 3 illustrates a still further embodiment of our novel invention when the movable portion, which could be a movable contact, is comprised of the portion 20 of the winding seen generally at 21, and the operating winding, which could be relatively stationary, is seen as winding portion 22. In operation of the device in Figure 3, the terminals 23 and 24 of the winding 21 could be energizable by a charged capacitor in the same manner as was the embodiment of Figure 1.

The embodiment of Figure 3 more specifically utilized the phenomenon of a mutual attraction between adjacent turns of a coil when these turns are wound in the same direction. If, by way of example, a stationary contact were positioned on top of the movable portion Of the coil 20, then upon energization of the terminals 23 and 24 the complete coil will contract and the mova ble portion 20 would move downward at high acceleration if high instantaneous currents are used.

In contradistinction, the movable portion of the coil 20 can have its winding direction reversed as is shown in the figure, whereby energization of the coil 21 at the terminals 23 and 24 will then cause a repulsion between the winding portion 20 and the winding portion 22. Here again, this movement can be operative to bring the movable portion 20 of the winding 21 into or out of engagement with a relatively stationary contact.

Insofar as the currents in the stationary and movable portions of the contacting devices seen in Figures 1 through 3 have a phase opposition of zero or degrees, either an attractive or repelling force occurs which varies in accordance with the instantaneous value of the mag* nitude of the currents in the coil. However, if the phase displacement can be made to vary between the value of zero or 180 degrees, then it is seen that forces with varying directional elfect may be produced.

By way of example, the force may start out as a repelling force and end up as an attractive force if the phase shift between the two currents may be sutficiently varied during motion of the movable conductor.

One can, therefore, take advantage of the electrodynamic forces for a deceleration as well as an acceleration. For example, in the case of Figures 1 and 2, the production of phase shift offers no difliculties. That is to say, by inserting a suitable impedance in the movable conductors 11 or 17 of Figures 1 or 2 respectively, then a desired phase displacement may be obtained at a. desired time. This could therefore result in an extremely rapid acceleration of the movable member until a predetermined distance has been reached at which the forces due to the mutual magnetic fields would be in a direction for deceleration of the moving member. By this means, the damping or stopping of the motion of the movable member may be considerably simplified and braking means may not be needed.

Figure 4 shows the application of a contact device of the type shown in Figures 1 through 3 wherein specific application is made of a device of the type described herein to a D.-C. circuit, and the utilization of a magnetic latch means for maintaining movable contact in a disengaged position is shown. Reference to Figure 4 shows a pair of

stationary contacts

25 and 26 which are bridged by a movable contact ring 27.

The movable contact ring 27 is more specifically constructed so as to have a strip of ferro-magnetic material 28 attached thereto. Hence, in the above described equation, the. quantity M would be the mass of ferromagnetic strip 28.

A relatively stationary operating winding 29 is shown as being positioned in close coupling relationship with respect to the movable contact ring 27, the operating winding 29 being chargeable by the capacitor 30 which is maintained charged by means not shown in the drawing. Capacitor 30, however, cannot discharge until ionization takes place in the gap shown generally at 31 in order to connect the

electrodes

32 and 33 together.

In order to effect ionization at the gap 31, it is seen that a transductor device 34 is provided, having an air gap 35 therein. The transductor 34 more specifically has a winding 36 which is connected to the DC. circuit being protected by the contact device. If then a reverse current occurs, it is seen that the transductor 34 which is normally saturated in the direction given by the flow of load current I in the winding 36 will have its flux reversed as D.-C. current decreases towards zero and a voltage pulse will be induced in the winding 37.

This voltage pulse is impressed across the

electrodes

32 and 38 to thereby initiate ionization in the gap 31 to thereby efiectively connect

electrodes

32 and 33 to connect the condenser 30 in series with the operating winding 29 and the small inductor 39.

The energization of the coil 29, will, as has been previously described, induce a current in the movable contact ring 27 to thereby cause it to move away from the relatively stationary operating winding 29 and hence, move the contact ring 27 to a disengaged position with respect to the

stationary contacts

25 and 26.

If desired, the

electrodes

32 and 33 may be connected manually or automatically by the movable contact bridge 32a to thereby achieve interruption of the contact device in the absence of reverse current in the protected D.-C. circuit.

Figure 4 further shows a magnetic structure 40 which is so constructed as to have a plunger 41 extending therethrough and provides a support means for a biasing spring 42 which may be adapted to maintain high pressure contact engagement between the movable contact ring 27 and its cooperating

stationary contacts

25 and 26. Clearly, however, upon engagement of the ferro-magnetic strip 28 and the magnetic structure 40, seal in forces of relatively high magnitude will occur between the movable contact member 27 and the magnetic structure 40 to thereby maintain the movable contact structure 27 in the disengaged position in opposition to the biasing forces of spring 42.

When it is desired to return the movable contact 27 to its contact engaged position with respect to the

stationary contacts

25 and 26, plunger handle 43 may be forced down to force the movable contact structure away from the engaged position with the magnetic structure 40, when the biasing force of spring 42 will be sufiicient to move the contact to the engaged position.

It is to be noted that the saturable reactor 34 is provided with an air gap 36 in order that the flux reversal may start at a time prior to the zero passage of current. In a tripping system of this type, it is then seen that the instantaneous current interrupted by the movable contact 27 and its cooperating

stationary contacts

25 and 26 may be extremely small, and if, in the event an arc is drawn between the separating contacts, the arc will be extinguished when the current subsequently passes through the zero value.

Clearly, a similar arrangement to that of Figure 4 could have been utilized for an alternating current circuit wherein the tripping system is slightly modified to produce ionization in the air gap 31 responsive only to predetermined faults in the defective line as is shown in the above mentioned application, Serial No. 558,349, filed January 10, 1956.

Figure shows a novel vacuum switch utilizing the same principles of operation as have been described with reference to each of the above noted Figures 1 through 4. In the case of vacuum switches, a high initial force for contact separation is of great importance. Moreover, experience has shown that vacuum circuit breakers operate safely only when the amount of material as operated from the contacts through the arc is as small as possible. Hence, an arcless operation for a vacuum circuit breaker is greatly desirable and may be obtained in our novel high speed device in view of the extremely high accelerations imparted to the movable contact structure.

Figure 5 more specifically shows a semi-circular metallic housing 50 into which relatively stationary conductors 5'1 and 52 are introduced through the vacuum tight insulating ducts 53 and 54. The ends of the conductors S1 and 52 act as

stationary contacts

55 and 56 which cooperate with the current bridge 57. The membrane 58 is connected in a vacuum type manner to the flange 59 and has a cylindrical drum 60 attached thereto. At the lower end of the cylindrical drum 60, the current bridge 57 is attached, while the movable ring 62 is fastened to the upper front surface through a connecting piece 61.

The stationary impulse winding or operating winding 63 is fused into the ring shaped insulating piece 64 which in turn is attached to the flange 59. A pin 65 is then led through the

bearings

66 and 67 and is pressed against the ring 62 by the spring member 68. Hence, pin 68 is biased to move into a position between the winding 63 and the ring 62 upon movement of the ring 62 responsive to energization of the operating winding 63. Therefore, a reclosure of the contact bridge member 57 and its c0- operating

stationary contacts

55 and 56 is prevented until, by a displacement of the spring 68, the pin 65 is moved to the left of the ring 62 and the membrane 58, under atmospheric pressure moves downward to thereby reclose the circuit breaker.

In the foregoing we have described our invention solely in connection with specific illustrative embodiments thereof. Since many variations and modifications of the invention will now be obvious to those skilled in the art, we prefer to be bound not by the specific disclosure herein contained but only by the appended claims.

We claim:

1. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said stationary contact; said relatively movable contact being constructed to form a first winding; an operating winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current flow therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect to said stationary contact; said contacting device being further constructed to impart an acceleration of at least 10,000 times the acceleration due to gravity Within a fraction of a millisecond after energization of said operating winding.

2. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said stationary contact; said relatively movable contact being constructed to form a first winding; an operating winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current induced therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect to said stationary contact; the quantity being at least 10,000.

3. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said stationary contact; said relatively movable contact being constructed to form a first winding; an operating winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current induced therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect to said stationary contact; said contacting device being further constructed to impart an acceleration of at least 10,000 times the acceleration due to gravity within a fraction of a millisecond after energization of said operating winding; a latching means; said latching means being constructed to latch said movable contact in the disengaged position after said movable contact is moved to said disengaged position.

4. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said stationary contact; said relatively movable contact being constructed to form a first winding; an operating winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current induced therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect to said stationary contact; said contacting device being further constructed to impart an acceleration of at least 10,000 times the acceleration due to gravity within a fraction of a millisecond after energization of said operating winding; said movable contact being further constructed to have magnetic material attached thereto; a magnetic structure; said magnetic structure being constructed to engage said magnetic material of said movable contact when said movable contact is moved to said disengaged position; said movable contact thereby being latched in the disengaged position by the seal-in force between said magnetic structure and said magnetic material attached to said magnetic material.

5. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said stationary contact; said relatively movable contact being constructed to form a first winding; an operating winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current induced therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect to said stationary contacts; the quantity being at least 10,000; said movable contact being further constructed to have magnetic material attached thereto; a magnetic structure; said magnetic structure being constructed to engage said magnetic material of said movable contact when said movable contact is moved to said disengaged position; said movable contact thereby being latched in the disengaged position by the seal-in force between said magnetic structure and said magnetic material attached to said magnetic material.

6. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said stationary contact; said relatively movable contact being constructed to form a first winding; an operating Winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current induced therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect tosaid stationary contact; said contacting device being further constructed to impart an acceleration of at least 10,000 times the acceleration due to gravity within a fraction of a millisecond after energization of said operating winding;

said first winding being further constructed to have an impedance connected in series therewith whereby phase shift between the current in said operating winding and the current in said first winding is effected, the instantaneous force between said first winding and said operating winding being varied by variation in said phase shift.

'7. A contacting device; said contacting device comprising a continuous Winding of current carrying material; said continuous winding having a first relatively stationary portion and a second relatively movable portion; said relatively movable portion being further constructed to form a relatively movable contact member; a relatively stationary contact disposed for contact cooperation with said relatively movable portion; an energizing means; said energizing means being connectable across said continuous winding, the passage of current through said continuous winding causing relative motion between said first and second portions of said winding; said relatively movable contact thereby moving in a predetermined direction with respect to said stationary contact.

8. A contacting device; said contacting device comprising a continuous winding of current carrying material; said continuous winding having a first relatively stationary portion wound in a first direction and a second relatively movable portion wound in a direction opposite to said first direction; said relatively movable portion being further constructed to form a relatively movable contact member; a relatively stationary contact disposed for contact cooperation with said relatively movable portion; an energizing means; said energizing means being connectable across said continuous winding; the passage of current through said continuous winding causing repulsive forces between said first and second winding portions; said relatively movable contact thereby moving in a predetermined direction with respect to said stationary contact.

9. A contacting device; said contacting device comprising a stationary contact and a relatively movable contact disposed for contact cooperation with said cooperating contact; said relatively movable contact being constructed to form a first winding; an operating winding and an energizing means for passing current through said operating winding; said first winding being positioned with respect to said operating winding to have a current flow therein responsive to the passage of current in said operating winding; the currents in said first winding and said operating winding being in a direction to move said movable contact to a disengaged position with respect to said stationary contact; said contacting device being further constructed to impart an acceleration of at least 10,000 times the acceleration due to gravity within a fraction of a millisecond after energization of said operating winding, said operating winding and said first winding being continuous with one another.

References Cited in the file of this patent UNITED STATES PATENTS 363,186 Thomson May 17, 1887 953,584 Bishop et al Mar. 29, 1910 1,066,081 Coleman July 1, 1913 1,996,599 Thompson Apr. 2, 1935 2,180,661 Baruch Nov. 21, 1939 2,389,999 Rypinski Nov. 27, 1945 2,499,394 Kesselring Mar. 7, 1950 FOREIGN PATENTS 170,580 Switzerland Oct. 1, 1934