US2188803A - High speed permanent magnet electroresponsive device - Google Patents

Description

Jan. 30, 1940. w, BQEHNE 2,188,803

HIGH SPEED PERMANENT MAGNET ELECTRORESPONSIVE DEVICE Original Filed Aug. 4, 1936 Z Figl.

Inventor: Eugene W. Boeh e,

b WW7 6. A

y His Attorney.

opening of the breaker. The control of many n p e to a fa t n i ion in the high ten- 5 Patented Jan. 30, I

HIGH SPEED PERMANENT MAGNET ELECTRORESPONSIVE DEVICE.

Eugene W. Boehne, Yeadon, Pa., assignor to General Electric Company, a, corporation of New York Original application August 4, 1936, Serial No. 94,220. Divided and this application March 24, 1938, Serial No. 197,873

1 Claim. (Cl. 175339) My invention relates to high speed electroret o ed by a t pp g m et 3, which 18 in t n sponsive releasing devices, such as for example controlled by a relay 4 and current transformer 5. those applied to the tripping mechanism of an he operation n g a s S il r o the electric circuit breaker for initiating high speed ven ional me hod of ipp n e a r, a is other high speed operations, such as the quick o power line S as a Short circuit for automatic application of breakers to rotating ample, the Current transformer causes e e q pment is also contemplated. tion of the relay 4, which in turn energizes the In high tension power systems operating at tripping or releasing means 3 for opening the commercial frequencies, the duty of quickly isoeaker I.

latin a. fault, such as a, short circuit for ex- The operation and arrangement of the rel y ample, falls upon the circuit breakers controlling system which comprise no part of the present inthe affected part of the system. It is, therefore, vention are specifically described and claimed in essential that the circuit breaker completely clear my patent for Protective control devices and sys the circuit within a few cycles at the most in t n No- 2,130,370, a ted ep e 1933 15 order that the stability of the system shall not and assigned to the same assignee as the present be upset. The operation of a high tension oil cirinvent on. cuit breaker for example to clear the circuit may The relay 4 comprises a perm ne t ma 6 be divided into several stages; namely, disenav ng So o p e P s 7 n a ooao ng a 30 gagement of the tripping or releasing mechanism mature 8 carried on a pivoted contact arm 9. 20 in response to a fault condition, initiation .of The operation of the armature 8 controls the opening movement of the breaker Contact struccontacts of the relay switch indicated at S. The ture in response to release thereof, and opening magnetomotive force produc d by he permanent movement of the contacts coincident with the magnet 5 normally maintains the armature 8 in arc-interrupting operation. The present inventhe closed magnetic circu t posi i n Sho a a 25 tion is primarily concerned with the first stage .the bias of spring l0. When this magnet'omotive of operation, the last two stages relating more force Overcome y t e sp ing lo, the relay specifically to the circuit breaker and its opswitch Sis closed.' For the purpose of controlling erating mechanism. release of the armature 8, a solenoid or tripping A principal object of my invention, therefore, i coil II is related to the magnetic circuit above 30 the provision of an improved high speed tripping described so that energization of said coil from or releasing device which is efiective appreciably the direct current control source l2 causes reto reduce the tripping time over that heretofore ase f he a e 3 n closing of the e y ttained, switch S. To this end the current transformer 5 5 Thisis a division of my Patent No. 2,130,871, causes in response to predetermined current in granted September 20, 1938 for High speed the line 2 actuation of the solenoid I3 for closing tripping system. the control circuit at l4. The relay control cir- My invention will be more fully set forth in cuit also includes a current limiting series rethe following description referring to the accomsistance I5 and a capacitance 16 connected across 40 panying drawing, and the features of novelty the coil II when the contacts at M are closed. 40 which characterize my invention will be pointed It will, therefore, be apparent from the above out with particularity in the claim annexed to description that predetermined energization of and forming a part of this specification. the current transformer 5 is eifective to cause Referring to the drawing, Fig. 1 is partly actuation of the relay 4 andclosing of the relay diagrammatic view of a circuit breaker operating Switch S. 45

system including a tripping magnet embodying The np g r releasing d v ,'w is the present invention; Fig. 2 is a view of the controlled by the relay 4, also includes a permatripping magnet embodying my invention gennent magnet l1, soft iron pole pieces I8 and I9 erally shown in Fig. 1 and Fig. 3 is a perspective andan armature 20 of similar material. The ar- 5 view illustrating the structure of the magnet mature 20 is carried at 2| by a latch member 22 shown by Fig. 2. pivoted at 22 and biased by a tension spring 23 The circuit breaker operating system illustrated away from the magnet. The latch 22 is provided by Fig. 1 comprises an electric circuit breaker at its opposite end with an abutment 24 arranged generally indicated at l for the high tension to engage and hold as generally indicated, the

power circuit 2, the circuit breaker being conoperating rod l of the circuit breaker in the 55 not shown) and the latch 22. Since the relay closed circuit position. Normally, the magnetomotive force produced by the permanent magnet I1 is effective to hold the armature 20 in the closed magnetic circuit position against the bias of spring 23.

The tripping magnet 3, as in the case of relay 4 includes a tripping solenoid or coil T which is arranged when energized from the control source l2 to produce a flux in the magnetic circuit of the magnet opposing that produced by the permanent magnet in that portion of the magnetic circuit including the soft iron armature 20. This relationship is such that energization of the trip coil T so weakens the holding force at the armature 20 that the armature spring 23 rotates the latch 22 in a counterclockwise direction, thereby releasing the breaker operating rod l' and permitting opening of the breaker. This general type of tripping device is shown for example by Tritle Reissue Patent No. 15,441 of August 29, 1922.

Energization of the trip coil T may be effected when the breaker l is closed by closing the relay switch S. The control circuit so established includes the control source I2, relay switch S, auxiliary switch 25, which is controlled by the breaker l and assumes similar circuit controlling positions thereto, magnet trip coil T,'auxiliary switch 26 which is controlled by the latch 22 so that it is closed in the holding position of the latch and vice versa, and series resistance R which is chosen in accordance with the characteristics of the tripping circuit.

Immediately upon release of the latch 22 in response to a tripping impulse, the latch controlled auxiliary switch 26 is opened, instantly deenergizing the trip coil T. Also, the circuit breaker in moving to open circuit position causes opening of the auxiliary switch 25, which is also in series with the relay switch S. The latch controlled auxiliary switch 26 operates considerably faster than the breaker controlled auxiliary switch 25, the latter serving more as a back-up switch for insuring that the circuit of the trip coil is open when the breaker is open.

The breaker also controls auxiliary switch contacts at 29 included in the control circuit of the resetting coil 30 of the relay 4. Likewise included in the circuit of the resetting coil 30 are contacts indicated at 3| controlled by a solenoid 32 which is in turn energized'from the control source l2 through another auxiliary latch controlled switch at 33. Accordingly, release of the latch 22 causes closing of the auxiliary switch at 33, energizing of the solenoid 32 and closing of the control circuit at 3|. Therefore, when the circuit at 29 is also closed the resetting coil 30 is energized from control source I 2, thereby attracting the armature 8 to the holding position shown. In this position the relay switch S is open.

If desired, the permanent magnet I! may be provided with an exciting coil 34 which is but momentarily energized from the control source 12 by the breaker controlled auxiliary switch at 35. That is, in moving to the closed circuit position the breaker rod I causes momentary closing of the exciting coil circuit at 35 so that the permanent magnet is recharged, so to speak, to its original magnetoniotive force. I

The resetting of the latch 22when thecircuit breaker is to be reclosed can be accomplished in any suitable manner, such as by a mechanical connection (not shown) operatively interconnecting the breaker closing mechanism (also 4 is immediately reset after the circuit opening operation, the magnet trip coil T cannot again be energizedprior to another actuation of the relay 4. The latch 22 can also be manually tripped if desired.

Referring more particularly to the tripping device 3, the permanent magnet portion H in carrying out my invention is preferably composed of a magnetic alloy comprising a precipitation hardened product, basically an iron-nickelaluminum alloy, and specifically a nickel-ironaluminum and cobalt alloy of the character described and claimed in Ruder Patents 1,947,274 and 1,968,569. This magnetic alloy has certain highly desirable qualities for a permanent magnet material, such as for example magnetomotive force greatly in excess of that of ordinary permanent magnets. The pole pieces [8 and I9, referring to Figs. 2 and 3, are composed of soft iron laminations, and are designed so as to col-,

lect the flux produced by the permanent magnet and concentrate it at that portion of the magnetic circuit including the soft iron armature 20; The flux produced by the permanent magnet I! in the closed magnetic circuit including the armature 20 can be generally designated by the flux arrows l1.

The trip coil T, which includes a soft iron laminated core 36 spaced by non-magnetic members 31 from the pole pieces l8 and I3, is positioned in shunt with respect to the aforesaid magnetic circuit so that when the coil T is energized from the control source 12 the flux produced thereby tendsto take two paths, namely the path including the armature 20 indicated by the flux arrows 38, and a path through the permanent magnet indicated by the flux arrows 39. Therefore, the flux produced by the coil T is in the same direction as the main flux in the magnetic circuit including the permanent magnet thereby having a magnetizing effect on the permanent magnet, and in the opposite direction in that part of the circuit including the armature 20. Accordingly, the holding flux at the armature 20 is weakened a predetermined extent so that the spring 23 is effective to pull the armature away from the magnet.

In designing the magnetic path of the magnet including the armature 20, the force required to move the latch 22 is primarily taken into account.

In the present instance, wherein the latch is' used for tripping a large high tension power breaker, the spring 23 is designed for a'pull of approximately 300 pounds. Accordingly, in the holding position the magnet must exert a pull in excess of this, such as 500 pounds for example. Knowing the required pull at the armature, the magnetomotive force and the size of the permanent magnet'are chosen and the optimum area of the armature for maximum pull determined in accordance with known design.

Since the magnetomotive force of the permanent magnet material is definitely known, the soft iron laminated pole-pieces I8 and I9 are designed to collect the flux from the inherently low density area at the abutting surface of the magnetic alloy and concentrate it at a comparatively small high density area at the armature. This is determined by'the formula F=.014 3 A, where F is the force in pounds, A is the armature area in square inches and B is the flux density in kilolines per square inch. Knowing the most efficient point for operation on the saturation curve, the optimum area of the armature for maximum force may readily be computed.

Heretofore tripping magnets of the character in question utilized an electromagnet energized from a direct current source rather than a permanent magnet, hence soft iron comprised the main, if not the entire part, of the magnetic circuit including the armature. with the present invention, part of the magnetic circuit includingthe 'ineifective path of the trip coil flux has comparatively high reluctance so that the tripping flux is concentrated at the armature where it is most effective. Since the division of tripping flux between its two paths 38 and 3% (Fig. 2) depends on the reluctance of these paths, it will be seen that a high reluctance path through the permanent magnet and a comparatively low reluctance path through the armature 20 are desirable. This is accomplished by using the precipitation hardened magnetic alloy of the character above described for the permanent magnet since this alloy has a permeance of 2 as compared with 1 for air and 1000 to 2000 for iron. This practically amounts to an open circuit for that part of the trip coil flux 39-.

Referring again to Fig. 2, it will therefore be apparent that the flux indicated at 39 would be weak as compared with the magnet bucking flux at 38. This insures faster building up of the bucking flux in the armature to a tripping value. Also the soft iron laminated pole pieces i8 and I9, which are particularly designed for low losses form for the trip coil flux 38 a path permitting a high rate of flux build-up.

Accordingly, by varying the permeance of various parts of the magnetic paths in the manner above disclosed, the tripping flux is used in a far more emcient and effective manner than heretofore proposed.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit 01 my invention.

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

A high speed tripping magnet for releasing instantly a large force comprising a precipitation hardened permanent magnet portion having a pair of pole arms, said permanent magnetportion having very high reluctance and magnetomotive force, a soft iron laminated pole piece supported by each of said pole arms and a relatively movable armature of similar material likewise having very low reluctance completing with said permanent magnet portion and said pole pieces a magnetic circuit, the holding'surface area'of said armature coacting with said pole pieces being an optimum with respect to the flux holding said magnet in closed magnetic circuit position, means biasing said armature away from said pole pieces towards an open magnetic circuit position, and an armature releasing coil having a magnetic core compactly disposed between said laminated pole pieces and adjacent to said armature adapted to be energized to produce a flux to effect the release of said armature, said core forming with said pole pieces and armature a low reluctance, low loss, circuit of small length, said small circuit and optimum area jointly contributing to increased efliciency of the releasing coil flux, the releasing flux produced by said coil traversing both a high reluctance circuit and said low reluctance circuit, said high reluctance circuit including said permanent magnet portion wherein the releasing flux is in the same direction as the flux produced by said permanent magnet portion, the releasing flux in said low reluctance circuit traversing said pole pieces and armature in a direction opposite to that of the flux produced by said permanent magnet portion, the ratio of the reluctanoes-of said circuits being such that substantially all the flux produced by said coil traverses said armature at said optimum holding areas to oppose said holding flux sufliciently to cause high speed release of said armature.

EUGENE w. BOEHNE.

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