US2457617A - Time element electromagnetic device - Google Patents

Description

Dec. 28, 1948. L. s. WALLE TIME ELEIERT ELECTROMAGNETIC DEVICE:

Filed Fab. 4, 1947 m Y e a. O m t O n t g v A nw Patented Dec. 28, 1948 UNITEDSTATES PATE T OFFICE 7 TIME nnmanirggraouacmno I as: rears-sire :2

New York Application February 4, 194?, Serial No. 726,866

tromagnetic devices which respond to alternating 10 current, many expedients have been adopted. Some of these have been based on the use of rotary motion embodying. for example, a drag magnet on an induction disk, the inertia of a heavy rotatably mounted member, centrifugal devices, and rotating vane mechanisms. Such devices are costly and more or less difficult to maintain or do not provide a suitable timecurrent characteristic especially where a long time delay is required. Other devices have obtained time delay by movement of fluids ,or small solid particles through a narrow port after the manner of an hourglass or by movement of large solid particlesjin a tortuous path. Belonging to this group broadly are the dashpot devices usually employ- 2 ing oil which is very diflicult to keep confined and which is erratic in performance because of its variation in viscosity with temperature. Some time element devices are of a thermal type based on expansion under heat, but these, generally speaking, do not provide either the time current characteristic desired or the force necessary in a direct tripping device for circuit breakers. An object of my invention is to provide an improved time element electromagnetic device for oscillating current wherein the necessity for complicated movable structure and the use particularly of fluids and the like is eliminated; Another object of my invention is to provide ani-mwhich is responsive to oscillating current and which has a minimum number of movable parts and provides a suitable time current characteristic with suiflcient force at the conclusion oi the desired timing action to act satisfactorily as a direct tripping device for circuit breakers. Still another object of my'invention is to-provlde' a time element electromagnetic device foroscillating current wherein the desired timing action is based on the direct action of magnetic attraction and an opposing action of inductive repulsion which is controlled by a suitable heating eilect.

A further object of my invention is to provide an improved time element electromagnetic devioeior' oscillating currents wherein the directnctiemot 9 Claims. (Cl. 175-372.)

magnetic attraction and the opposing action of ings, and its scope will be pointed out in the appended claims. a

In the accompanying sheet of drawings, Fig. '1 is a vertical side elevation, partly in section, of a hinged armature time element electromagnetic device embodying my invention; Fig, 2 is a front elevation ofthe embodiment of my invention Shown in Fig. 1; Fig. 3 is a side elevation, partly in section, of a modification of the embodiment of my invention shown in Fig. 1 with independent adjustment of the magnetic attraction and inductiverepulsion efiects; Fig. 4 is a front elevation of the embodiment of my invention shown in Fig. 3; Fig. 5 is a side elevation, partly in section, of another embodiment of my invention in a reciprocating armature time element electromagnetic device with independent adjustment of the magnetic attraction and inductive repulsion eflects; and Fig. 6 is a section on the line 6-6 of Fig. 5 looking in the direction indicated by the arrows.

In Figs. 1 and 2, I have illustrated an embodiment ofrmy invention in an electromagnetic device having cooperating stationary and movable magnetic members I and 2, respectively. The

stationary member I is in the form of a core which is suitably secured to a magnetic base member 3 on an extension 4 of which the movable magnetic member or armature 2 is pivotally proved time element electromagnetic device 40' supported at 5. As shown more clearly in Fig. 2,

branch from a common backing member 9 of suitable magnetic material. .The pivotal mount- ;ing oft-he armature 2 includes two nonmagnetic supporting elements H] which are suitably se- .cured; to the armature portions 6 and 8' so asto straddle the extension 4 of .the base member 3.

.The pivotal support or pin 5 passesv through the ,.nonmagnetic supporting .members In and the v baseextension l. The free ends of the armature portionst, 1 and 8 are shaped so as to move freely tqthe attractedpositionjin a notch I l formed in the.. ecre --'I unti1' the free end of the armature 3 enlailesthebose' I: ofthenotclnaswiilbeclclr from Fig. 1. For energising the magnetic members I, 2 and I, there is provided a winding II which when energized by an oscillating current above a predetermined magnitude tends to effect movement of the armature 2 toward the core I.

As shown, the winding II is mounted around the core I on a suitable form such as a spool it which is preferably of nonmagnetic metallic material such, for example, as stainless steel. The flanges ll of the spool I are preferably slotted as at II to restrict the formationof eddy currents. For adjusting the pickup of the device, that is to say at what magnitude of current in the energizing winding I! the armature tends to move to the attracted position, there is provided an adiustably positioned support against which the lower end of the armature 2 abuts. As shown, this support comprises a screw l'l threaded into a nut is which is suitably secured to' an angle bracket 19. This in turn 'is suitably to the magnetic base member I. A lock nut 2| holds the screw ll against movement when it is set for any desired pickup. Withthis arrangement, it

is possible to vary the initial air gap between the free end of the armature 2 and the pole piece l2. With the structure so far described, movement of the armature 2 to the attracted position into engagement with the pole piece or notch I! in the core would be substantially instantaneous. Mounted in the armature 2 to move therewith for controlling operations is a projecting element such as a pin 2i which may be arranged to operate a movable contact or to actuate the latch of a circuit breaker holding mechanism so as to trip the circuit breaker as is well known to the art.

In order to retard or delay the movement of the armature 2 to the attracted position, I'provide, in accordance with my inventibn, means comprising a short circuited winding of positive temperature coefficient of resistivity such, for example, as a closed copper ring 22 which is movably mounted in inductive repulsion relation with the energizing winding I! so as to exert on the armature an effect opposing the movement thereof toward the core I until the heating action of the current induced in the ring increases the resistance thereof s'uificiently for the direct action of the energizing winding to overcome such opposing effect. For the maximum heating action, the central opening of the spool is made large enough to permit the ring 22 to move in the space between the cylinder of the spool and the core I. In order that the inductive repulsion efiect on the winding 22 may oppose the armature 2 directly, the two outside portions 8 and 8 thereof. may be provided with nonmagnetic extensions 23, Also, to center the ring 22 for better freedom of movement relatively to the core I, 1 preferably attach to the ring a guiding ring 24, shown in Fig. 1, of suitable nonmagnetic, noncurrent conducting, heat resistant material such, for example, as an asbestos ring. Further in order to keep the conducting ring 22 out of the magnetic center of the energizing winding II where the repelling action is minimum, I provide a relatively light biasing means such as a compression spring 25 which, as shown in Fig. 1, is positioned-between the magnetic base member I and the ring 24. This spring 2! maintains the ring 22 in engagement with the armature extensions 23 and in the magnetic held due to the winding II at a position-where the inductive repulsion action on 'the ring 22 is approximately maximum.

-. au'miv A movable short circuited winding such as the ring 22 always tends to move so as to enclose the minimum number of magnetic lines of force. Thus the ring 22 tends to hold armature 2 against stop l1 with a force great enough to predominate overthe magnetic attraction thereof. However, it will be appuruit that as the current decreases in the ring 22 in consequence of the heating thereof by the current induced therein, the flux in the magnetic circuit comprising the core I, the base 2 and the armature 2 increases while the inductive repulsion action between the ring 22 and the energizing winding it decreases until finally the magnetic attraction between the armature 2 and its pole piece l2 and also between the armature and the base I is sufficient to overcome the inductive repulsion reversal of predominance of the opposite forces acting on the armature and move the armature to the attracted position. Thus, there is effected an accelerated action in consequence of the reduction of the repulsion action and the increase of the magnetic flux acting on the armature 2 which, of course, tends to move so as to enclose the maximum number of lines of predominance of the attractive over the opposing force. This accelerating force is easily sufficient to control contacts and can readily be made sufiicient to effect the tripping of a circuit breaker. On the basis of the ring 22 being made of copper, its resistance is approximately doubled for a rise of 200 C. in temperature so that the current induced in the winding is approximately halved and the repulsion effect is rapidly decreased.

It wiilwbe clear from the foregoing that the time delay obtained for a given oscillating current in the winding 13 depends upon the initial position of the ring 22 relatively to the winding i3. Thus, when the center line of the ring 22 coincides with that of the winding i3, minimum time is obtained because the repelling action on the ring is substantially zero, whereas with the ring located at the end of the energizing winding ll, maximum time is obtained because in this position the inductive repulsion is at a maximum. It will be clear from the foregoing that any 0s cillating current, either alternating current, pulsating current or the like, may be used to energize the winding ii. The time current character istic of a device such as that shown in Fig. l is, of course, inverse. In general, it has a fairly steep portion for small currents, but for larger currents, the change in the time of operation is not so rapid relatively to the increase in the current. The less steep portion of the characteristic coming as it does in the higher current range enables a more selective setting of relays and tripping devices particularly where it is desirable to arrange several of these in series reiation in a power circuit so as selectively to isolate as little as possible of the circuit in the event of a fault.

In the embodiment of my invention shown in Figs. '3 and 4, the stationary magnetic member, comprising the core i, the base 3' and its extension 4', is laminated with the outer plates flanged at 28 to provide ready means for mounting the device. The armature 2', like the core l, is also laminated. The outside plates of the armature '2 are provided with extensions 21 which straddle the core I and comeyto rest in the unattracted position of the armature preferably against a resiiient stop in order to minimize bouncing. As shown, this stop comprises rubber washers 28 mounted on the core I' near the outer end thereof. The energizing also to obtain substantially instantaneous movement oi the armature to the attracted position independently of the ring under severe current conditions in the nature of a short circuit, the core I is curved with its center of curvature on the pivotal axis of the armature and the ring 22' is mounted for movement'about this axis. For this purpose, the ring 22' is mounted on a generally U-shaped lever 29 which is supported on the pivot 5' and which has a backward extension 39. For adjusting the position of the ring 22' relatively to the armature 2, this lever 29 is provided with a forward projection 3| which abuts a milled cam 32 rotatably mounted on the armature, The face 33 of the cam 32 is suitably graduated, and a pointer 34 mounted on the outer end or the core serves for determining the setting of the ring. H

For maintaining the ring 22 in a predetermined relative position and yet permitting movement of the armature 2' relatively to the ring I! is shown as under currents of short circuit magnitude in the winding i3, I provide a yielding connection between the armature 2' and the lever 29. As shown, this is a resilient connection such as a tension spring 35 which has one end attached to the backard extension 39 of the lever 29 and the other end adjustably attached to a projection 38 at the low'er'end of the armature. Thus at this other end, the spring 35 is secured by a screw 31 which can be turned to vary the tension in the spring.

For varying the pickup of the armature 2, I

provide suitable means such as a relatively heavy counterweight" which is slidably positioned on a milled backward extension 39 of the armature projection 38. This weight 38 is generally U- shaped with channeled grooves 38 inside the bight embracing the edges and a portion of the milled surface ofthe extension 39 on each side thereof. By means of a spring 40, the upper side of each of the grooves 38' in the weight 38 is biased toward the milling on the extension 39 to hold the weight in any given position according to a suitably graduated scale 4| secured to the armature 2 so as to move therewith. Thus, by

pushing up on the bottom of the weight 38 against the bias of the spring 49, the weight can be shifted to any desired position either to increase or decrease the pickup of the armature 2. Then when released, the spring 40 holds the weight 38 in the position to which it was moved. In order to limit the extreme inner movement of the ring 22' relatively to the coil i8, the backward extension 39 of the lever 29may be provided with a stop portion 42 which comes to rest against the back edge of the milled extension 39.

As in the embodiment of my invention shown in Fig. 1, the core i' is notched at H to provide a suitable pole face l2 and the end of the armature 2' is suitably shaped to ride freely in this notch. In order to prevent the armature from sticking against the pole face l2, the inner face of the armature near the end thereof is provided with a nonmagnetic face plate 43.

While this embodiment of my invention operates in a manner generally similar to that of the embodiment of my invention shown in Fig. 1, there are some minor differences based on the armature 2'.

35, the armature will move to the attracted 'posi-- tion. This stretching action of the spring will occur under heavy short circuit currents without any delay for heating the short circuited winding 22 or, in other words, waiting for the inductive repulsion eifect to be reduced by such heating. Consequently, for currents of short circuit value regardless of the magnitude of the repulsion effect on the ring 22', the movement of the armature 2 is not delayed. For currents of overload values and the like which may reasonably be expected to disappear in many cases after a brief interval of time, the relative movement between the ring 22' and the armature 2 does not occur because there' is insuflicient force to produce stretching of the spring 35. Thus, in these cases.

- the time delay action is dependent upon the reduction of the magnetic repulsion effect in consequence of heating of the ring 22 so that the operation is the same as the embodiment of my invention-shown in Fig. 1.

In the embodiment of my invention shown in Figs. 5 and 6, I have illustrated an electromagnetic device wherein the initial repulsion eil'ect and the attractive effect on the armature can be independently adjusted. In this modification of my invention, the stationary magnetic member 44 is generally U-shaped with pole faces 45 at the end of each of the depending legs 45. "Rigidly secured to the inside of the bight of the U-shaped member 44 substantially centrally of the legs 48 is a core member 41 having a pole face 48. Surrounding the core 41 and spaced therefrom is an energizing winding 49, which, as shown, is mounted on a spool 50 of suitable nonmagnetic material such, for example, stainless steel. This spool is secured to the stationary magnetic member 44 on the inside of the bight by suitable means such as bolts 5|. The flanges 52 of the spool and the lower portion of the legs 46 are notched, as shown, at 53 and 54, respectively, to minimize eddy currents.

Projecting through a central bore in the core for a short circuited winding or ring 5l.- For holding an armature 56 in any desired position ontherod 55 so as to control the air gap between the armature and the pole faces and maintain the setting, the armature has a suitable friction holding nut 58. In order to minimize eddy currents, the armature is provided with a plurality of radial slots 58. For adjustably positioning the ring 51 relatively to the magnetic center of the energizing winding 49, the ring is provided with two diametrically aligned supports 60 extending from the inner circumference of the ring toward its center. The adjacent faces of these supports are tapped to fit the thread on the rod 55. In order to insure movement of the ring 51 relatively to the rod 55 when a handle 8i rigidly mounted thereon is turned, the core 41 is provided with two diametrically opposite slots 52, one of which serves as a guideway for a projection 83 secured to the ring 51. The other slot serves to maintain symmetry in the magnetic fleld,'ar'1d the two slots also tend to break up eddy currents in the core. The core '48 may be provided with suitable graduations for setting the position of the ring relatively to the coil by noting where the end of the guiding projection 85 terminates relatively to the core.

In order to prevent unintended rotation of the rod 55 under shocks and the like, I provide suitable holding means such as a spring rod 6 which is arranged to engage a notch in the milled head of the handle 8|. In order to reduce the chatter consequent upon cyclic variation in the current, suitable resilient means such as a rubber washer 55 may be mounted on the rod below the handle 51. latch of a circuit breaker, an operating member 86 is suitably mounted on the lower endoi the rod 55.

In view of the description of the modification of my invention shown in Figs. 1 to 4, inclusive, the operation of the modification of my invention shown in Figs. and 6, in so far as the inductive repulsion and magnetic attraction effacts are concerned, will be apparent except for the matter of controlling the independent adjustments of the two effects. Thus, to control the air gap or magnetic attraction effect, the handle BI is held while the armature is turned on the rod 55 to vary the air gap as desired. For controlling the position of the ring 51 relatively to the coil 49, the handle ii is turned thereby rotating the rod 55 relatively to the ring 51 and thus raising or lowering the ring relatively to the magnetic center of the coil to vary the inductive repulsion eflect.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of my invention.

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

1. In an electromagnetic device, a magnetic circuit having cooperating stationary and movable magnetic members, a winding Ior magnetizing-said circuit when energized by an oscillating current above a predetermined magnitude to tend to effect movement of the movable member toward the stationary member, a short circuited winding of positive temperature coeflicient of resistivity material movably mounted in inductive repulsion relation with said winding and having connections for exerting on said movable member an opposing force greater than the magnetic attractive force thereon to prevent movement of the member toward said stationary member until the heating action of the current induced in the short circuited winding increases the resistance thereof sufficiently to reverse the predominance of said forces.

2. An electromagnetic device having a core, an armature, an energizing winding around said core for attracting said armature when energized by an oscillating current above a predetermined magnitude, and a closed single turn winding of positive temperature coefficient of resistivity material movably mounted around said core in inductive repulsion relation with said energizing winding and having connections with said armature for exerting an opposing force thereon having predominance over the attraction of said armature until the heating action of the current induced in the single turn winding increases the resistance thereof sufficiently to reverse said predominance.

3. A time element alternating current electro- For operating a contact mechanism or the responsive device having cooperating stationary and movable magnetic members in attractive relation, a tubular winding spaced around said stationary member for attracting said movable member when energized by current above a predetermined magnitude, the transverse area of the opening in said winding being materially greater than the cross sectional area of the stationary member, and a short circuited ring of positive temperatine coefflcient of resistivity material encircling said stationary member and movable in the space between the stationary member and the tubular winding under the inductive repulsion action thereof and having connections for preventing movement of the movable member toward the stationary member until the heating action of the current induced in the short circuited ring increases the resistance thereof sufliciently to render said repulsion action ineflective.

4. A time element alternating current electroresponsive device comprising a core, an armature, an energizing winding around said core and spaced therefrom for attracting said armature when energized by an oscillating current above a predetermined magnitude, and a closed single tum winding around said core movable in the space between the core and said energizing Winding under the inductive repulsion action thereof and having connections for eifectively opposing movement of the armature toward the core until the heating action of the current induced in the single turn winding increases the resistance thereof sufliciently to render said repulsion action ineflective.

5. An electromagnetic device having a core, an armature, an energizing winding around said core for attracting the armature when energized by an oscillating current above a predetermined magnitude, a closed single turn winding of positive temperature coeflicient of resistivity material movably positioned around said core in inductive repulsion relation with said energizing winding, and connections between said armature and said single turn winding including a resilient element for causing the force of the repulsion effect on the single turn winding to oppose movement of the armature to the attracted position for a time dependent on the heating effect of the current in said energizing winding, said resilient element being adapted to yield to permit substantially instantaneous movement of the armature to the attracted position when the currentin the energizing winding exceeds a greater predetermined magnitude.

6. An electromagnetic device having a core, a pivoted armature, an energizing winding around said core for attracting said armature when energlzed by an oscillating current above a predetermined magniture, means for delaying movement of the armature to the attracted position including a closed single turn winding of positive temperature coeflicient of resistivity material around said core in inductive repulsion relation with said energizing winding, means pivotally supporting said single turn winding for movement about the pivotal axis of said armature, and connections between said supporting means and said armature including an adjustable element for varying the position of the single turn winding relatively to the armature to control the delay in the attraction thereof, and a resilient element for yielding to permit substantially instantaneous movement 'of the armature relatively to the single turn winding when the current in said energizing winding Q exceeds a greater predetermined magnitude. 7. An electromagnetic device having a core, an armature, an energizing winding around said core for attracting the armature when energized by an oscillating current above a predetermined magnitude. a ring 01 positive temperature coeiiicient of resistivity material positioned around said core in inductive repulsion relation with said energizing windng, and connections between said ring and said armature for opposing movement oi said armature to the attracted position until the heating action of the current induced in the single turn winding increases the resistance thereof sumcie'ntly to render the repulsive action of said ring ineil'ective, said connections including a resilient element for yielding to permit a substantially instantaneous movement of said armature to the attracted position when the current in said energizing winding exceeds a greater predetermined magnitude.

8. An electromagnetic device having cooper- .ating stationary and movable magnetic members,

a winding mounted on .said stationary member to attract said movable member when energized by an oscillating current above a predetermined magnitude, a short circulted winding of positive temperature coeilicient of resistivity material movably mounted in inductive repulsion relation. with said energizing winding and having connec-' tions for exerting on said movable member a D201 so dominant force opposing the attractive force oi the member toward said stationary member l in the short circuited winding increases the resistance thereof suillciently to reverse the predominance of said forces. and means for independently adJusting the initial relative positions of said short-circuited winding and said armature with respect to the energizing winding to control said predominance reversal.

' 9. An electromagnetic device having a core, an armature, an energizing winding spaced around said core for attracting said armature when ener gized by current above a predetermined magnitude, a closed single turn winding of positive temperature coefllcient of resistivity material movable on said core and having connections for opposing the attraction of said armature, means including separate control elements for controlling the attraction of said armature and the inductive repulsion relation 01 said single turn winding with said energizing winding to oppose movement oi the armature to the attracted position, said control elements being individually ad- Justable whereby independently to vary the atuntil the heating action or the current induced traction of the armature and the opposing eflect oi the single turn winding.

LUDWIG 8. WALL]:

REFERENCE! CITED UNITED STATES PATENTS Number Name Date 1,982,385 White Nov. 27, 1984

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