US3575676A

US3575676A - High-speed, high-current solenoid

Info

Publication number: US3575676A
Application number: US873968A
Authority: US
Inventors: Norman R Beaudoin; Robert W Lauben
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1969-11-04
Filing date: 1969-11-04
Publication date: 1971-04-20
Anticipated expiration: 1988-04-20

Abstract

A current-limiting circuit breaker incorporates an improved ultra high-speed solenoid operator for carrying continuous current loads substantially in excess of 100 amperes without exceeding 80* C. The solenoid operator is comprised of a generally C-shaped nonhelical winding of substantially one full turn having a cross-sectional area controlled to provide a minimum space factor and flux path, a magnetic cup-shaped stator including an efficient flux path return shell confining the winding and a generally cylindrical armature axially projecting into the winding and having a radial flange spaced from the shell by a small radial gap to reduce the length of the flux path through air while completing a flux path of minimum reluctance.

Description

United States Patent 2,715,669 8/ 1955 Dicke Norman R. Beaudoin Bristol; Robert W.

Lauben, Farmington, Conn. "873,968

Nov. 4, 1969 Apr. 20, 197 1 General Electric Company lnventors Appl. No. Filed Patented Assignee HIGH-SPEED, HIGH-CURRENT SOLENOID 282, 299, 229, 224, l4, l7, 18, 21, 22, 24, 172, 174, 176, 195; 337/(Cursory); 219/235 References Cited UNITED STATES PATENTS 3,384,845 5/1968 Johnson etal.

Forman ABSTRACT: A current-limiting circuit breaker incorporates an improved ultra high-speed solenoid operator for carrying continuous current loads substantially in excess of 100 amperes without exceeding 80 C. The solenoid operator is comprised of a generally C-shaped nonhelical winding of substantially one full turn having a cross-sectional area controlled to provide a minimum space factor and flux path, a magnetic cup-shaped stator including an efficient flux path return shell confining the winding and a generally cylindrical armature axially projecting into the winding and having a radial flange spaced from the shell by a small radial gap to reduce the length of the flux path through air while completing a flux path of minimum reluctance.

BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates generally to circuit breakers and is particularly concerned with a new and improved current-limiting circuit breaker having a high-speed contact operator.

Recently a new type of electric circuit breaker has been developed which perfomis a current-limiting function as well as the functions of conventional prior art circuit breakers in acting as a switch and in automatically interrupting low level short circuit current overloads. These new current-limiting circuit breakers incorporate a high-speed contact-operating mechanism, such as a solenoid, to provide the desired current interruption in substantially less than one-half cycle of a 60 cycle per second time wave. Although conventional solenoid construction has provided effective and reliable operation at continuous current loads of about I amperes and less, it has been found that an increase in the current-carrying load capacity of the circuit breaker causes undesirably excessive heating, i.e., temperatures in excess of 80 C., and a substantial loss in efficiency.

Accordingly, it is an object of the present invention to provide a new and improved high capacity current-limiting circuit breaker capable of handling continuous currentloads substantially in excess of I00 amperes without overheating and yet still provide current interruption at the ultra high speeds characteristic of current-limiting circuit breakers of lower current-carrying capacity for current levels substantially in excess of its rating.

Another object of the present invention is to provide a current-limiting circuit breaker of the type described having an inline high-speed contact operator designed for carrying continuous current loads of up to about 400 amperes without exceeding a temperature of 80 C. Included in the object is the provision for an operator having a minimum mean flux path providing a faster response time and a more efficient operation. a

A further object of the present invention is to provide a circuit breaker of the type described capable of trip indicating at all short circuit levels and incorporating a new and improved solenoid operator having a stator construction capable of controlling the efficiency of the solenoid and hence the solenoid trip point at dI/dts within a range up to 20,000 I amperes per millisecond.

A still further object of the present invention is to provide a current-limiting circuit breaker of the type described incorporating a new and improved contact operator of the solenoid type having a substantially reduced flux path length through air coupled with an ultra high-speed response time and a greater efficiency of operation.

Still another object of the present invention is to provide a new and improved current-limiting circuit breaker of the type described incorporating the features set forth hereinbefore in a compact and economical unit exhibiting ease of assembly and durability of construction.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

These and related objects are accomplished in accordance with the present invention by providing a current-limiting circuit breaker with an ultra high-speed solenoid operator comprised of a generally C-shaped solenoid winding of less than one full turn and a minimum flux path, a stator including a flux path return shell and a generally cylindrical armature having a radial flange reducing the length of the flux path through air.

A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth an illustrative embodiment and are indicative of the way in which the principle of the invention is employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a top plan view of a three-pole-circuit breaker incorporating the features of the present invention;

FIG. 2 is an enlarged elevational view, partially broken away and partially in section, illustrating the operating mechanism associated with one pole of thecircuit breaker of FIG. 1;

FIG. 3 is an enlarged sectional view of. the high-speed solenoid operator taken along the line 3-3 of FIG. 2;

FIG. 4 is a further enlarged side elevational view of the movable contact arm assembly of the circuit breaker of FIG. 2 including the contact operating mechanism associated therewith, the view being taken along the line 44 of FIG. 3 and showing the positioning of the assembly when the contacts are in both their closed and open circuit positions; and

FIG. 5 is an exploded perspective view of the high-speed solenoid operator shown in FIG. 3.

DESCRIPTION OF-A PREFERRED EMBODIMENT Referring now to the drawings in greater detail wherein like referenced numerals indicate like parts throughout the several FIGS, a three-pole electric circuit breaker of the currentlimiting type is shown in FIG. I as having a generally rectangular housing 10 including an insulating cover 12 through which extends a manually operated handle 14 movable between its ON, OFF and TRIP positions. The handle 14 is ,operatively connected to a conventional contactoperating mechanism, generally designated 16, of the overcenter toggle linkage type for manually opening and closing all circuits controlled by the breaker.

A single contact operating mechanism 16 actuates all three of the breakers three poles. The contact operating mechanism 16 is located on the center pole. Additionally, as is conventional, manual operation of the handle 14 will effect simultaneous opening and closing of all circuits controlled by the breaker while automatic opening of any one circuit will result in a corresponding open circuit condition throughout the entire circuit breaker.

As shown in FIG. 2, each pole of the circuit breaker is provided with a pair of spaced

stationary contacts

18, 20 fixedly positioned within an arc-initiation chamber 22 of the current-limiting circuit breaker. The stationary contacts are mounted on a field strap assembly, partially shown at 24, with stationary contact 18 being electrically connected to its line terminal 28 through a conductive line strap 30 while the other stationary contact 20 is electrically connected through a highspeed solenoid operator 32 mounted on trip unit strap 34 to a load terminal 36 at the opposite end of the housing. A pair of movable contacts 38, 40 are secured to a movable contact arm assembly 42 passing through the solenoid operator 32, the assembly 42 being adapted for linear movement toward and away from the stationary contacts. In this manner the movable contacts 38, 40 are moved into and out of surface-abutting contact with

stationary contacts

18 and 20, respectively, causing the desired open and closed circuit conditions.

The embodiment of the movable contact arm assembly chosen for illustrative purposes is best shown in FIG. 4 as including an elongated contact rod 46 fixedly mounting the movable contacts 38, 40 at one end thereof. The rod 46 is axially secured to a tubular operating shaft 48 by means of the axially extending connector 50 which provides a lost motion connection between the rod and the shaft. The tubular shaft 48 extends rearwardly from the contact rod 46 and passes axially through the high-speed solenoid operator 32 for linkage with the conventional overcenter mechanism 16, the linkage being completed through a high-speed connecting plate 52 operatively associated with the overcenter mechanism 16.

Thus, manual operation of the handle 14 between its ON and OFF positions causes linear movement of the movable contact arm assembly 42 relative to the stationary contacts to effect the desired open and closed circuit conditions illustrated by full and phantom lines, respectively, in FIG. 4.

With the manual operating handle 14 in its ON position so that the full-line closed circuit condition exists, the occurrence of an excessive current load or low level short circuit current condition will cause activation of a trip unit 56 electrically connecting trip unit strap 34 and load terminal 36. The trip unit 56 will effect release of the releasable lever 58 coupled to mechanism 16 resulting in a shift of its pivot point. This shift is sufficient to cause activation of the mechanism 16 together with retraction of the movable contact arm assembly 42 and opening of the circuit across the breaker. The handle 14 is also thereby moved to its TRIP position to visually indicate the tripped condition of the breaker.

As best shown in FIG. 4 the elongated contact rod 46 fixedly mounts a magnetic armature 60 of the solenoid operator 32 so that upon activation of the solenoid the armature will be attracted rearwardly causing movement of not only the armature but also the contact rod 46 and movable contacts 38, 40 fixedly secured thereto. The solenoid armature 60 is a generally cylindrical tubular member telescopically received over the operating shaft 48 to facilitate the relative movement therebetween permitted by the lost motion connection, the connector 50 being fixedly secured to both the contact rod 46 and armature 60. A thin, planar flange 62 integrally extends radially inwardly and outwardly of the cylindrical armature 60 from one end thereof at substantially a right angle thereto. The inwardly extending portion of the flange mounts the armature 60 on contact rod 46 for fixed retention thereon by the connector 50. The outwardly projecting portion of the magnetic flange is disclike in configuration with a diameter approximately equal to the outside diameter of the winding 66.

The stator 68 of the solenoid operator is a cup-shaped steel member having a generally arcuate tubular shell portion 70 and a smaller cylindrical pole piece 72 disposed within the shell and integrally connected thereto through a mounting base portion 74 of relatively greater thickness. The stationary pole piece 72 is substantially identical to the cylindrical armature 60 in configuration and diameter and is fixedly positioned in coaxial alignment with both the armature and the shell portion 70. Thus, as best'seen in FIGS. 3 and 4, a cross-sectional view of the circuit breakers high-speed solenoid operator 32 reveals a plurality of coaxially aligned concentric members from the central contact spring 78 mounted within the tubular operating shaft 48 to the arcuate outer shell 70 of the stator. Both the pole piece 72 and the armature 60 are positioned within the winding 66 of the solenoid operator and during normal closed circuit position are in spaced confronting relationship thereby defining a solenoid operating gap 80 which in the preferred embodiment has a length of about nine thirty-seconds inch. The outer shell 70 of the stator circumscribes the winding 66 and forms a substantial portion of the magnetic flux return path. Advantageously, the shell is of sufficient length so that its free end 84 is positioned in spaced juxtaposed relationship with the peripheral edge 86 of the disclike flange 62 when the armature is in its fully withdrawn or on" position. In this manner there is provided a minimum air gap between the stator and the armature which the flux path must traverse thereby substantially improving the efficiency of the solenoids operation. Additionally, the construction of the present invention reduces the solenoid trip point to a level which permits coordination with the conventional automatic trip mechanism of the breaker while at the same time permitting greater control over the trip point at dl/dts within a range up to about 20,000 amps/millisecond.

As mentioned hereinbefore, stationary contact is fixedly and electrically connected to the load terminal 36 through the solenoid operator 32 and particularly through the nonhelical solenoid winding 66. Thus, during normal operation current continuously flows through the winding which, in accordance with the present invention, readily handles continuous current flow of up to about 400 amperes without overheating, that is, without developing temperatures in excess of'80 C. As shown, the winding 66 is a solid conductivev member of generally cylindrical configuration having only slightly less than one full turn. In the preferred embodiment it is an axially cored copper member having a smoothly arcuate interior surface interrupted only by a narrow slot 88 extending through the entire thickness of the member along its full length. The end surfaces 90 defining the slot 88 are in substantially parallel fully confronting relationship.

The outer surface of the solenoid winding 66 is arcuate except for a pair of flat terminal faces 92 adjacent the slot 88 and at right angles to surfaces 90. The flat faces 92 provide large areas assuring good surface contact between the winding 66 and the current-carrying

connecting plates

96, 98 secured thereto.

The cylindrical solenoid 66 provides a winding of only slightly less than one full turn with an effective electrical path of about 0.9 turn and exhibits a generally rectangular crosssectional configuration which in the embodiment illustrated possesses a length approximately equal to twice that of its thickness. It will be appreciated that the length of the solenoid also is advantageously about twice the length of and centrally located with respect to the solenoid gap 80 so that it not only provides the necessary working length but also exhibits a cross-sectional area which results in a minimum space factor and minimum flux path length for the required armature movement. As shown, the solenoid winding is covered by a thin coating of insulating plastic 102 such as nylon or epoxy which covers all exposed surfaces of the winding with the exception of the flat terminal faces 92 and thus is electrically insulated from the circumscribing stator shell-70 and pole piece 72 as well as armature 60 and flange 62.

The entire solenoid operator 32 is supportably mounted on the trip unit strap 34 by means of the current-carrying connector plate 98. As best shown in H6. 5, a pair of flat insulating

strips

104, 106 are threadably secured to opposite sides of

plates

96, 98 by the connectors 108 and in turn mount the cup-shaped stator 68 in assembled relationship with the winding 66 and armature 60. The stator 68 is, of course, of segmented configuration to accommodate both the concentricity of the assembly 32 and its own mounting on strips 104, M6 by the threaded connectors 110 extending through the strips for secure attachment to its mounting base portion 74. As shown in FIG. 4, the stator is mounted in such a way that the stationary pole piece 72 extends into the cored winding for a distance equal to approximately one-fourth of thesolenoids length. Additionally, a thin. sheet 114 of insulating material is preferably mounted within the assembly so as to cover both ends of the solenoid winding 66 and further isolate them from both the stator and armature. The pole face areas of the armature and the stator advantageously are designed so that in conjunction with the configuration of the solenoid winding a one-half cycle trip point of about 8,000 A r.m.s. is provided. Additionally, as mentioned hereinbefore, the outwardly extending radial flange of the armature is in close spaced relationship to the shell of the stator so that the flux path through the shell and armature has a minimum length of travel through air.

In operation, a low level short circuit current condition will effect an open circuit condition through activation of the trip unit 56 and overcenter operating mechanism 16. On the other hand, a high level short circuit current flow through the winding 66 will immediately create a magnetic field of sufficient strength to cause movement of armature 60 along a distance of inch within about 2 milliseconds. Thus, the contacts are immediately fully opened, followed by trip indicating movement of handle 14. As mentioned hereinbefore, this high efficiency, high-speed operation is associated with the minimum space factor, minimum flux path and low reluctance design of the solenoid operator of the present invention which substantially reduces the length of the flux pathin air. At the same time, the C-shaped, 0.9 turn winding is capable of continuous normal operation at current loads of up to 400 ampere's without exceeding 80 C.

As will be apparent to persons skilled in the art, various modifications, adaptations, and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

What we claim is new and desire to secure by Letters Patent of the United States is:

We claim:

1. A current-limiting circuit breaker comprising:

a. a pair of relatively movable contacts;

b. a contact rod assembly operatively connected to the contacts for effecting movement thereof between open and closed circuit positions;

' c. a high-speed operator in driving engagement with the contact rod assembly for moving the contacts out of a closed circuit position in response to the occurrence of a predetermined high level current condition across the contacts; r

d. said high-speed operator comprising a generally C- shaped solenoid winding electrically connected to the contacts for continuously carrying currents well below said predetermined high level current condition without overheating;

e. a generally cylindrical stator fixedly mounted in proximity to said winding and including a flux path return shell; and

. an armature operatively connected to the contact rod assembly for driving the contacts out of the closed circuit position in response to activation of the winding by said predetermined high level current condition, said armature including means cooperating with the-stator for reducing the length of the flux path in air.

2. The circuit breaker of claim 1 wherein the C-shaped solenoid winding is a cored cylindrical conductor of nonhelical configuration forming an effective winding of substantially one full turn.

3. The circuit breaker of claim 2 wherein the conductor has a generally rectangular cross-sectional area configured to provide a minimum space factor and flux path length.

4. The circuit breaker of claim 2 wherein the conductor has a pair of fully confronting end surfaces defining a longitudinally extending turn-limiting slot.

5. The circuit breaker of claim 1 wherein the C-shaped conductor is a cored cylindrical member forming an effective winding of less than one full turn and having a generally rectangular cross-sectional configuration providing a minimum flux path, the conductor having a pair of planar terminal faces at each end of the winding facilitating continuous current flow through the winding with minimum heating.

6. The circuit breaker of claim 1 wherein the stator is a cupshaped member positioned coaxially of the winding and having a tubular stationary pole member through which extends the contact rod assembly, the return shell coaxially confining the stationary pole member.

7. The circuit breaker of claim 1 wherein the stator is a generally tubular member positioned coaxially of the solenoid in underlying relationship therewith, the contact rod assembly extending through said tubular member for axial movement relative thereto, the return shell confining said tubular member and being integrally connected thereto at one end thereof, said armature being mounted for movement with said contacts-coaxially of said tubular member.

8. The circuit breaker of claim 1 wherein the armature is a tubular member mounted with the contact rod assembly for telescopical movement into the winding.

9. The circuit breaker of claim 1 wherein the armature is a generally cylindrical member provided with a radially extending flange movable along the flux path return shell in close spaced relationship therewith during the magnetically responsive movement of the armature, said flangfi forming a portion of the flux path and effectively reducing e length of the flux path in air.

10. The circuit breaker of claim 1 wherein the stator includes a cylindrical stationary pole piece and the armature is a generally cylindrical member, said pole piece and said member being positioned within the winding in spaced coaxial confronting relationship.

11. The circuit breaker of claim 1 wherein the stator includes a cylindrical tubular member positioned coaxially within the winding and integrally connected to the flux path return shell, coaxially enclosing the stator and integrally connected thereto at one end thereof, the armature being a generally cylindrical member mounted in spaced confronting relationship to said tubular member for movement longitudinally of the shell, the armature including a radially extending flange in close spaced relationship with the shell forming a portion of the flux path and effectively reducing the length of the flux path in air.

12. The circuit breaker of claim 1 wherein the C-shaped winding is a cored cylindrical conductor of less than one full turn having a generally rectangular cross-sectional configuration providing a minimum flux path, the stator includes a tubular stationary pole piece positioned within the winding and a mounting base portion integrally connecting the pole piece to the flux path return shell, the armature is a generally cylindrical member fixedly mounted relative to at least one of the movable contacts in coaxial alignment with the pole piece, the armature including a radially extending flange in adjacent spaced relationship to the return shell for movement longitudinally thereof toward and away from the pole piece, said flange effectively reducing the flux path length in arr.

Claims

1. A current-limiting circuit breaker comprising: a. a pair of relatively movable contacts; b. a contact rod assembly operatively connected to the contacts for effecting movement thereof between open and closed circuit positions; c. a high-speed operator in driving engagement with the contact rod assembly for moving the contacts out of a closed circuit position in response to the occurrence of a predetermined high level current condition across the contacts; d. said high-speed operator comprising a generally C-shaped solenoid winding electrically connected to the contacts for continuously carrying currents well below said predetermined high level current condition without overheating; e. a generally cylindrical stator fixedly mounted in proximity to said winding and including a flux path return shell; and f. an armature operatively connected to the contact rod assembly for driving the contacts out of the closed circuit position in response to activation of the winding by said predetermined high level current condition, said armature including means cooperating with the stator for reducing the length of the flux path in air.

6. The circuit breaker of claim 1 wherein the stator is a cup-shaped member positioned coaxially of the winding and having a tubular stationary pole member through which extends the contact rod assembly, the return shell coaxially confining the stationary pole member.

7. The circuit breaker of claim 1 wherein the stator is a generally tubular member positioned coaxially of the solenoid in underlying relationship therewith, the contact rod assembly extending through said tubular member for axial movement relative thereto, the return shell confining said tubular member and being integrally connected thereto at one end thereof, said armature being mounted for movement with said contacts coaxially of said tubular member.

9. The circuit breaker of claim 1 wherein the armature is a generally cylindrical member provided with a radially extending flange movable along the flux path return shell in close spaced relationship therewith during the magnetically responsive movement of the armature, said flange forming a portion of the flux path and effectively reducing the length of the flux path in air.

12. The circuit breaker of claim 1 wherein the C-shaped winding is a cored cylindrical conductor of less than one full turn having a generally rectangular cross-sectional configuration providing a minimum flux path, the stator includes a tubular stationary pole piece positioned within the winding and a mounting base portion integrally connecting the pole piece to the flux path return shell, the armature is a generally cylindrical member fixedly mounted relative to at least one of the movable contacts in coaxial alignment with the pole piece, the armature including a radially extending flange in adjacent spaced relationship to the return shell for movement longitudinally thereof toward and away from the pole piece, said flange effectively reducing the flux path length in air.