US2678412A

US2678412A - Electromagnetic relay with adjustable magnetic shunt

Info

Publication number: US2678412A
Application number: US264886A
Authority: US
Inventors: Floyd O Smeltz
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1952-01-04
Filing date: 1952-01-04
Publication date: 1954-05-11
Anticipated expiration: 1971-05-11

Description

F. 0.-' SMELTZ Filed Jan. 4, 1952 ELECTROMAGNETIC RELAY WITH ADJUSTABLE MAGNETIC SHUNT faIuIIFIIII May 11, 1954 im Il AMW Patented May 11, 1954 ELECTROMAGNETIC RELAY WITH ADJUST- ABLE MAGNETIC SHUNT Floyd O. Smeltz, Milwaukee, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application J anuary-4, 1952, Serial No. 264,886

6 Claims.

This invention relates in general to electromagnetic relays and in particular to electromagnetic relays utilizing magnetic shunts.

It is well known inA electromagnetic relays to utilize an adjustable magnetic member in shunt with the magnetic Working gap for the purpose of causing' the relay to operate or trip at any prescribed value of magnetomotive force within the adjusting range of the relay. However, magnetic shunts differ in physical construction and method of reluctance adjustment. Ordinarily reluctance adjustment of the shunt is accomplished by changing the length of an included shunt magnetic air gap. In simple form such shunts comprise a magnetic member having a plane surface movable in av direction which is essentially parallel to the direction of shunted flux. That is, the shunting member is movable toward or away from a pole piece of the relay. Such construction has the disadvantage that the neness of adjustment obtainable is very limited,

since if the shunting member is quite distant from the pole piece with respect tothe shunted member, the position of the shunting member is without appericable effect on the division of uX between the shunting member and shunted'member. Conversely, if the shunting member is quite close to the pole piece with respect to the position of the shunted member, a small change in the position of the shunting member produces a very large change in the division of flux between the shunting member and shunted member. This results generally in insensitive control and an undesirable, nonlinear relationship between the travel of the shunting member and the total actuating magnetomotive force, thereby rendering calibration of the relay difcult.

lThis disadvantage may be overcome by utilizing a relay in which the magnetic shunt comprises a member of adjustable magnetic cross section normal to the direction of shunted flux. Such a magnetic shunt depends upon the saturation of the member of adjustablel cross section to control the division of flux between the shunting and shunted members. Such a magnetic shunt in addition, may utilize an included, adjustable magnetic air gap to aid in controlling the division of ux between the shunting and shunted members. Thus, a relay may be utilized which-comprises a magnetic shunt providing a very. wide range of reluctance adjustment relative to the reluctance of the shunted member, providing a very precise control of shunt'reluctance and thus a. precise control over total relay actuating magnetomotive force, and having an adjustment characteristic which is substantiallylinear.

to provide an electromagnetic relay having an adjustable magnetic shunt which provides for a high sensitivity of adjustment over a very wide range of total adjustment.

It is an additional object of this invention to l provide an improved electromagnetic relay having an adjustable magnetic shunt provided with indicating means for indicating an operating characteristic of the relay.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation, partly in section, of one embodiment of the invention utilizing an electromagnetic biasing coil in -the main magnetic path;

Fig. 2 is a front view of the relay shown in Fig. l with a portion of the contact cover broken away;

Fig. 3 is a plan view of a portion of the relay illustrating the indicating device;

Fig. 4 is an enlarged side view of a the adjustable magnetic shunt;

Fig. 5 is a vertical section taken along the line V-V of Fig. 4

Fig. 6 is a side elevation of an alternate embodiment of the invention utilizing an electromagnetic biasing coil in a shunted magnetic path; and

Fig. 7 is a view of a portion of an additional alternate embodimentV of the invention utilizing an included shunt air gap.

Referring more particularly to the drawing by character of reference, the preferred embodiment of the invention illustrated in Figs. l to 5", comprises a U-shaped'magnetic yoke 'i having two spaced legs ii, 9 and a base member H. The yoke i is held't'ogether by suitable screws l2. Extending acrossthe'upper ends of legs 8,' 9 is a magnetic bridlng member i3 comprising a pair of magnetic'members I4', lsecured to legs t?, respectively, and separated lby 'an air gap I6 (Fig. 3). v Suitable' adjustable. magnetic means are proportion of Y vided to vary the reluctance ofhthe magnetic path including member I4 and a portion of member I5 to vary operating characteristics of the relay, and such means may comprise a magnetic screw I1. If screw I1 is utilized, the end of members I4, I5 adjacent air gap I6 are tapped to provide a tapped opening in which screw I1 moves to vary the reluctance between magnetic members I4 and I5. Screw I1 may be provided with a lock nut IS to prevent undesired movement of the screw. If additional rigidity of members I4, I5 is desired, pieces or blocks I9 of suitable nonmagnetic material, such as brass, may be secured to the ends of members I4, I5 adjacent air gap I6 by any suitable means such as resistance welding. Blocks I9 are preferably tapped in conjunction with members I4, I5 to provide tapped top and bottom walls for the tapped opening between members I4, I5.

A suitable calibrated scale 2| is associated with screw I1 to indicate variations in an operating characteristic of the relay in dependence upon the position of screw I1. As shown, scale 2| is secured to member I4 by a screw 22 and is calibrated in terms of the current required to operate the relay.

The relay further comprises an armature 25 having one end thereof disposed adjacent to, and attractable toward, the pole piece formed by an extension piece I mounted on bridging member I3 in alignment with leg 8. Suitable pivot means are provided to pivotally support armature 25, and such means may comprise a knife edge member 25 secured to member I5 between core leg 9 and magnetic screw I1. A support member 28 of nonmagnetic material is secured to member I through a nonmagnetic spacer by screws 29 and is secured to leg 8 by suitable means (not shown) to provide support for a terminal board 3|. Terminal board 3| is secured to support member 28 by bolts 32 and nuts 33 and is provided with at least two stationary terminal studs 34 to be connected to a circuit to be controlled and having at the lower ends thereof xed contacts 35.

Contacts 35 are adapted to engage a pair of movable contacts 36 carried by a exible conducting member 31 secured to the end of armature by a screw 38 and an insulating support member 38. 'I'he fixed and movable contact assemblies may be enclosed in any suitable dust tight member, such as a transparent cover 4| secured to terminal board 3|. A stud 42 having a spring 43 compressed between board 3| and an adjusting nut 44 extends loosely through terminal board 3| and is secured to armature 25 to control the pickup characteristics of the relay. A

similar stud 45 having a spring 4S compressed between armature 25 and an adjusting nut 41 ex tends loosely through an opening in armature 25 and is secured to terminal board 3| to control the drop-out characteristics of the relay. When the armature 25 is not attracted toward extension IIJ, spring 46 is not compressed, so that only spring 43 holds armature 25 in the deenergized position. When armature 25 is attracted toward the pole piece formed by extension II), spring 46 is compressed so that the force of this spring is added to the force exerted by spring 43 to produce the desired combined spring characteristic.

The relay may be mounted in any suitable manner, and if the relay is to be utilized as a through conductor relay, a mounting bracket 5| secured to core leg 9 by screws 52 may be provided. Bracket 5| is secured to a conductor or conductors, represented by bus bar sections 53, by an insulated bolt 54. Bus bar sections 53 provide parallel paths for the current which it is desired to control and represent energizing means for producing flux in the relay core. If desired, an electromagnetic coil 56 may be provided on the relay core to produce a biasing magnetomotive force in addition to the magnetomotive force produced by the current in bus sections 53.

In operation as a through current relay, the relay is secured to bus sections 53 which carry the current to be controlled. The flux produced in the relay travels through leg 9, member II and leg 8 and then comes to a junction providing two parallel magnetic paths. The first such path includes the extension I0 of leg 8, the working air gap between this extension and armature 25, armature 25 and pivot means 26 to member I5. The second magnetic path includes the adjustable magnetic shunt and comprises member I4, the air gap I6 and screw I1 between members I4 and I5 to member I5.

The division of flux between these two magnetic paths depends upon the relative permeances of the paths, and by adjusting the position of screw I1 in the air gap, the permeance of the second magnetic path may be varied over a wide range. As screw I1 is advanced in the threaded opening, the permeance of the second path is increased to increase the flux in the second path. Thus, by adjustment of screw I1, the current in bus sections 53 or coil 56 at which armature 25 is attracted toward leg 8 is varied to produce operation of the relay at any desired value of magnetomotive force. Screw I1 advances in a direction transverse to the direction of flux in members I4 and I5 increasing the effective cross sectional area of the magnetic path across air gap I6 so that the permeance of the shunt path varies substantially linearly with respect to the advance of screw I1. Thus a substantially linear relationship exists between the travel of the screw |1 and the net magnetomotive force acting upon the relay core at which armature 25 is attracted. The portion of the screw I1 which is engaged in the air gap I6 forms the saturable section of variable cross section mentioned above.

Fig. 6 illustrates an alternate embodiment of the invention in which coil 56 of Fig. l has been replaced or supplemented by a coil 6I) encircling pivot means 26. Pivot means 26 and extension 1|0 have been increased in length so as to accommodate coil `6D between armature 25 and member I3.

The effect on the relay shown in 6 of a given number of ampere turns in coil 60 is greater than the effect of the same number of ampere turns in bus sections 53 or of coil 56 in Fig. l, since in'Fig. 6 coil G5 is in the working magnetic circuit which is traversed by only a portion of the flux produced by the current in bus sections 53 or coil 58. The relay shown in Fig. 6 will trip at a number of ampere turns in coil B0 which is substantially independent of the position of screw I1 and which is always equal to or less than the number of ampere turns in coil 5S or bus sections 53 at which the relay is tripped.

It will be obvious that by suitable modifications, coil 60 may be disposed in other suitable locations in the working magnetic path, such as on extension I0 or around `armature 25.

Fig. 7 illustrates an additional alternate ernbodiment of the invention in which a piece or insert 6I of suitable nonmagnetic material, such as brass, is provided in a portion of the edge of member I4 adjacent air gap I6 and adjacent to the unadvanced position of screw I1. Insert 6| 'is utilized when it is desiredto employY adjustment of an included shunt Vair gap in addition to adjustment of a. magnetic cross section of a portion of the shunt path. Since screw Il must be adparting from-the spirit of the invention or from the scope of the appended claims.

It is claimed and desired A`to secure by Letters Patent:

1. An electromagnetic relay comprising a U-shaped magnetic core having rst and second legs denning a passage for the insertion of a 4current carrying conductor, a magnetic bridging 'member secured across said corelegs, a magnetic armature having one end thereof disposed adjacent to said first core leg, pivot means for pivotally mounting said armature on said bridging member, said armature and said pivot means forming a rst magnetic path, the portion of said bridging member disposed between said first core leg and said pivot means forming a second magnetic path in parallel with said rst path, and adjustable magnetic means in said bridging member for varying the magnetic reluctance of said second magnetic path to vary the division of flux between said first and second magnetic paths.

2. An electromagnetic relay comprising a U-shaped magnetic core having first and second legs defining a passage for the insertion of a current carrying conductor, a magnetic` bridging member secured across said core legs, a magnetic armature having one end thereof disposed adjacent to said rst core leg, pivot means for pivotally mounting the other end of said armature on said bridging member, said armature and said pivot means forming a rst magnetic path, the portion of said bridging member disposed between said rst core leg and said pivot means forming a second magnetic path in parallel with said first path, adjustable magnetic means in said bridging member for varying the magnetic U reluctance of said second magnetic path to vary the division of ilu-X between said first and second magnetic paths, and a calibrated scale associated with said magnetic means for indicating variations in an operating characteristic of said relay in dependence upon the position of said adjustable magnetic means.

3. An electromagnetic relay comprising a U-shaped magnetic core having first and second legs defining a passage for the insertion of a current carrying conductor, a magnetic bridging member secured across said core legs, said bridging member comprising a pair of magnetic members separated by an air gap, the ends of said members adjacent said air gap having tapped surfaces to provide a tapped opening, a magnetic armature having one end thereof disposed adjacent to said rst core leg, pivot means disposed on said bridging member between said second core leg and said opening for pivotally mounting the other end of said armature, said armature and said pivot means forming a nrst magnetic path, the portion of said bridging member disposed betweensaid first core leg and said pivot means forming a second magnetic path in paralle] with said rst path, and a magneticferrous threadedimember engaged in saidtapped opening Vto vary the effective cross sectional area of the ferrous magnetic path provided by said threaded member, whereby movement of said threaded membervaries the permeance of said second magnetic path to vary the division of fiux between said rst and second magnetic paths.

4. An electromagnetic relay comprising a U- shaped magnetic core having 'irst and second legs defining a passage for the insertion of a current carrying conductor, a magnetic bridging member secured across said core legs, said bridging membercomprising a pair of magnetic members separated by an air gap, the ends or said members `adjacent said air gap having tapped surfaces to provide a tapped opening, a 'inagnetic armature having one end thereof disposed adjacent to said first core leg, pivot means disposed on said bridging member between saidsecond core leg and said opening for pivotally mounting the other end of said armature, said armature and said pivot means `forming a first magnetic path, the portion of said bridging member disposed between said first core leg and said pivot means forming a second magnetic path in parallel with said rst path, a ferrous threaded member engaged in said tapped opening to vary the effective cross sectional area of the ferrous magnetic path provided by said threaded member in said air gap, whereby movement of said threaded member varies the magnetic permeance of said second magnetic path to vary the division of flux between said first and second magnetic paths, and a calibrated scale adjacent said threaded member for indicating variations of an operating characteristic of said relay in dependence upon theposition of said threaded member.

5. An electromagnetic relay comprising a U- shaped magnetic core having first and second legs defining a passage for the insertion of a current carrying conductor, a magnetic bridging member secured across said core legs, said bridging member comprising a pair of magnetic members separated by an air gap, a pair of nonmagnetic blocks secured to the ends of said magnetic members adjacent said air gap to secure said magnetic members together, the portions of said blocks adjacent said air gap and the ends or" said members adjacent said air gap having tapped surfaces to provide a tapped opening, a magnetic armature having one end thereof disposed adjacent to said rst core leg, pivot means disposed on said bridging member between said second core leg and said opening for pivotally mounting the other end of said armature, said armature and said pivot means forming a first magnetic path, the portion of said bridging member disposed between said first core leg and said pivot means forming a second magnetic path in parallel with said first path, and la ferrous threaded member engaged in said tapped opening to vary the effective cross sectional area of the ferrous magnetic path provided by said threaded member in said air gap, whereby movement of said threaded member varies the magnetic permeance of said second magnetic path to vary the division of flux between said rst and second magnetic paths.

6. An electromagnetic relay comprising a U- shaped magnetic core having rst and second legs defining a passage for the insertion of a current carrying conductor, a magnetic bridging member secured across said core legs, said bridging member comprising a pair of magnetic mem bers separated by an air gap, a pair of nonmagnetic blocks secured to the ends of said magnetic members adjacent said air gap to secure said magnetic members together, the portions of said blocks adjacent said air gap and the ends of said members adjacent said air gap having tapped surfaces to provide a tapped opening, a magnetic armature having one end thereof disposed adjacent to said rst core leg, pivot means disposed on said bridging member between said second core leg and said opening for pivotally mounting the other end of said armature, said armature and said pivot means forming a rst magnetic path, the portion of said bridging mern ber disposed between said rst core leg and said pivot means forming a second magnetic path in parallel with said rst path, a ferrous threaded member engaged in said tapped opening to vary the effective cross sectional area of the magnetic path provided by said ferrous member in said air gap, whereby movement of said ferrous member varies the magnetic permeance of said second magnetic path to vary the division of flux between said first and second magnetic paths, and a calibrated scale adjacent said ferrous member for indicating variations of an operating characteristic of said relay in dependence upon the position of said ferrous member.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 265,485 Cochran Oct. 3, 1882 1,920,818 Verrall Aug. 1, 1933 2,179,305 Stickney et al. Nov. 7, 1939 2,282,933 Cahill May 12, 1942 2,442,016 Poole May 25, 1948 2,549,371 Fereday Apr. 17, 1951 FOREIGN PATENTS Number Country Date 585,629 France Dec. 12, 1924