US2636935A - Electromagnetic relay with multiple inverse time relationships - Google Patents

Description

Patented pr. 28, 1953v ELECTROMAGNETIC RELAY WITH MULTI- PLE INVERSE TIME RELATIONSHIPS John H. Michael', West Allis, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application January 25, 1951, Serial No. 207,746

Claims.

This invention relates to improvements in automatic circuit protective devices and more particularly to a new and improved delayed action overcurrent electromagnetic relay.

The usual type of electromagnetic relay has a characteristic fast action which is not adapted to certain circuit arrangements, such as are involved in switchgear circuit breaker practice. These applications require a relay with a time delayed action. The period of time during which electric equipment can be subjected to abnormal conditions, such as high currents or short circuit currents, is ordinarily variable depending upon the character or intensity of such abnormal con ditions. In some cases it is desirable to permit the electric system to remain intact for a period of time that varies with the value of an abnormal condition. At high values of overload currents or short circuit currents, it is desirable that the circuit be interrupted after a time interval which is comparatively small but which, nevertheless, insures freedom from interruption due to momentary disturbances.

Power distribution systems are frequently protected by a number of serially connected circuit breakers which operate in a predetermined sequence. Each serially connected breaker is adjusted to trip at a different predetermined interval of time, thereby sequentially isolating segments of the electric circuit in accordance with the location of the disturbance, the length of time the disturbance continues or the character of the disturbance. Heretofore, time delay relays have been used to sequentially trip serially connected circuit breakers but these relays have not been capable of accurate settings for such short time intervals as are desirable for clearing circuit faults with a minimum of burning of connections and connected apparatus.

`In accordance with the invention claimed, a new and improved delayed action overcurrent electromagnetic relay is provided for circuit breaker operation which has a given current time characteristic for currents up to a predetermined value and diierent current time characteristics for currents above that predetermined value.

In the preferred embodiments of the invention the magnetic relay embodies an armature which actuates a switch operating rod. The rod is retarded by a pair of suction disks from moving into switch actuating position in a time varying inversely of the force exerted on the rod. This force varies with the current traversing the winding of the relay as long as the magnetic circuit of the relay remains unsaturated. For currents (Cl. F-372) below a predetermined value the armature remains in the position shown adjacent the relay core structure to provide an air gap of a predetermined value, and for currents above a certain value the armature is actuated to provide one or more positions which define air gaps of smaller values.

In order to accurately calibrate the electromagnetic relays so as to trip a plurality of serially connected circuit breakers, the relay is provided with means for varying the tension on the springs arranged between the armature and a flange provided on the switch actuating rod without varying the size of the original air gap.

It is, therefore, one object of the present invention to provide a new and improved delayed action overcurrent electromagnetic relay in which the relay has a given current time characteristic for overload currents up to a predetermined value and different current time characteristics for currents above that predetermined value.

Another object of this invention is to provide a new and improved delayed action relay which is adjustable for operation at predetermined current values with predetermined periods of time delay.

A further object of this invention is to provide a new and improved delayed action magnetic relay with multiple inverse time relationships which provide for adjustments of the point of changeover from one relationship to the other.

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

Fig. 1 is a diagrammatic view of a circuit breaker and a delayed action overcurrent electromagnetic relay therefor embodying the present invention;

Fig. 2 is a view in axial cross section through a modified embodiment of the armature and controlling structure used therewith illustrated in Fig. l;

Fig. 3 is a graph of the current time characteristics of the electromagnetic relay illustrated in Fig. 1 and a graph of a current time characteristic of a relay similar to the one illustrated in Fig. 1 but embodying the armature and controiiing structure iiiustrated in r'ig. 2.

Reieiring more particularly to the drawing by characters oi' reierence, Fig. 1 illustrates an electric circuit 6 provided with a circuit interrupter or breaker l and a time delay overcuirent eiectromagnetic relay 8 for controlling its actuation at predetermined overloads. The relay comprises a magnetizing winding il connected to one phase conductor of the electric circuit t. Winding t may be connected in series with the associated phase conductor, or may be connected therewith through a current transformer, as is well known. The relay further comprises a core structure li. and an armature li. Armature li is or" cylindrical forni and is provided with a central opening l2 into one end of which a nut i3 is screwed. The armature is disposed adjacent core structure it to form therewith a magnetic circuit having a given air gap.

A core lil extending through the central portion of armature li is threaded therein, and another core lil is threaded in core l2. Core it is arranged within armature Il and core lll but extends beyond core it.

The armature ii, nut i3, core lli and core lil are provided with aligned openings loosely receiving a rod it for actuating the circuit breaker switch arm it. rthe rod i6 is provided with a flange portion i9 enclosed Vwithin armature Ill and Ahaving a sliding nt therewith. rllhe lower end of the rod it is threaded into a nut 2Q which is, in turn, suitably secured to one of a pair of suction disks. Nut may be `pinned to rod le to lock it in piace, if so desired. A resilient means such as a spring A2i is arranged within armature il about rod it for opposing movenient of armature l l relative to rod it. Spring 2i is mounted between harige it and a nut 22. Nut 2E is threaded into armature il land 'may be used for adjusting the tension of spring 2l without changing the relative position of armature il and core structure il?, thereby retaining the size of the original air gap. 'Nut 22, further, may be used to lock in position core lit, and a nut 25, as illustrated, will provide Ya definite arrangement between cores it and i5.

Another resilient means such as a spring '23 is arranged within armature ll about rod i6 for opposing movement of armature il relative to rod it. Spring 23 is arranged between ilange it on rod it and a -flange 2d lmounted on core Hl.

A rigid cylinder 2l surrounds the` lower `end of armature l l and is suitably secured to core structure it and acts as a guiding means `or bearing for the armature. Flange i9 ci rod l5 acts as a guiding means for the upper end of armature i i, and a rigid cylinder 28 suitably secured to core structure le acts as a guiding means .or bearing `for the upper portion of rod It and also a stop for armature i l.

The suction disks are arranged inan Oil bath withthe upper disk 2s secured torod It and the lower disk 3c secured to thefbottom .of a 4container Si which houses the oil.

Circuit breaker i as illustrated in the drawing comprises stationary arcing contacts 32 and movable arcinsr contacts The movable arcing contacts 33 are connected to a rod 31% which is actuated to circuit open .position Yloy -a toggle mechanism.

The toggle mechanism 35 .comprises a link 36 which is pivotally mounted/atl 3l `and a link 32 which is pivotally. mounted at a point te on rod 34. A spring biases-toggle mechanismt to circuit .open position. Link 36 carries a lug t3 which is engaged by a catch dll. Catch M is mounted .on one end ci pivotally mounted lever arm it and is held in its operative position against .a stop i5 by means of a spring lit, Lever arm i8` is actuatedby rod it when the latter is actuated to switch opening position by armature il.

Fig. 2 is an enlarged diagrammatic view of a modification ci' the armature and controlling structure therefor, illustrated in Fig. l. By adding a resilient means such as spring ill, acting between a flange i3 which forms a part of core i5 and flange i9, the operation cf relay 8 may be varied to obtain a series of different time delay characteristics.

'n Fig. 3 curve ABC illustrates a time current curve of the usual prior art current responsive relay. The curve ABDE illustrates the time current curve of the `electronriagnetic relay illustrated in Figi, and the curve ABE-G illustrates a time current curve of a relay of the type illus- .trated in Fig. -l but `incorporating the armature and controlling structure shown in Fig. 2. These curves are plotted with current as abscissas and time as ordinates. All of the curves are plotted on 'the basis of the relay being set for ltripping only on'values ci current above 106% load. Fig. 3 illustrates diagrainmatically the manner in which the relay incorporating the armatures illustrated in Figs. i and 2 may operate and is not intended to set any limits within which-this invention must be restricted.

"in operation, the circuit breaker i being closed as indicate-d in Fig. l, current flows through the arci-ng contacts S2, 33 andthe inagnetizing winding il, For all line currentsbelow Aa certain value the parts ofthe relay remain in ytheI position indicated. Upon the occurrence of an overload line current through magnetizing winding il below a predetermined value, the upward .attraction of armature il is insufficient to lcompress springs 25, 2S. owever, the springs transmit the thrust vexerted by the armature to rod i6. liter a predetermined delay the disks separate and armature ii,springs 2i, 23 androd it move as a unita-nd actuate arm it to trip vthe circuit breaker i Operation of the relay illustrated in Fig. l for overload currents belogwgsuch predeterminedvalue may be illustrated by curve AB in Fig. 3. This type of linverse time' delay is characteristic o f the prior art lrelay structures wherein'the time delay is inversely proportional `to the Vcurrent owingthrough the magnetizing winding for the full overload current range of the relay.

In order to permit thev relay'to `operate 'faster for overload currents above a predetermined value `the vrelayV illustrated in Fig. l is provided with an `armature which, when the current reaches the predetermined value, .moves relative to the switch'actuating rod it from a rstposition to a second position Whereat the .Spfng 12! and 2S are gradually compressed a predetermined distance depending on the current intensity. 1n the second position of armature il, the air gap between the armature and the upper part of .core structure is smaller.

The inverse time-relation for a ygiven .relay Setting for Vcurrents above the predetermined ,over- `loadvalue is represented by curve BD. Therefore, the relay illustrated in 1 operates for all 'overload currents below a predetermined value on the curve 'AB and for all overload rcurrei'lts above the predetermined value on thecurve BID.

By providing relay d with threaded cores l and l5 the tensions of springs 2i and'tt1 maybe changed without changing the relative position of armature ll with respect to core structure lil. By varying the `tensions of springs il and 23,`the inversetime relationship of `the` relay inthe medium current range is changed, and the point of' changeover from one relationship to theother has been varied. When thel tensions of springs 2i and 23 have been reduced by varying the relative 'positions of core i4 and.4 nut 22 with reference to armature il the position of changeover from curve ABC to curve ABD, namely point B, will have been moved higher up on the curve ABC, i. e., to a higher time lower current position. Similarly, by increasing the tensions of springs Sil and 23 the position of point B of curve ABD be moved to a lower position on the curve ABC, i. e., to a higher current lower time position. When the line current reaches or exceeds a second predetermined value, armature i i moves into engagement with stop 2S. In that position of armature Il, springs 2l, 23 transmit to rod it a force which is independent of the value of the line current. In the high current range therefore rod it actuates arm I8 in a constant time regardless of the value of the line current. The operation of the relay in that range is accordingly represented by a horizontal line DE. This type or" operation is desired when the line current exceeds the interrupting capacity of the circuit brealrer and therefore should be interrupted by a faster back. up circuit breaker oi higher rating.

Curve ABF@ is the time current curve of relay when the relay incorporates the armature and controlling structure illustrated in Fig. 2. By providing spring il? between flange 153 and nange the armature ii must operate during part of its movement against the combined aotions of springs 2i, 23 and fil. Spring 4'1 ts loosely into the armature assembly and is compressed only after armature I l has moved a predetermined. distance in switch actuating direction. Until spring all is compressed the relay operates as above set forth and as represented by curve ABD. However, when the relay reaches an operating point such as point F on curve ABD, the upward movement of armature li is arrested by spring di. The energy absorbed by spring 41 in compressing under the upward movement of armature Il is stored by spring 47 to be applied toward breaking the suction oi disks 29 and 361 and toward accelerating rod i6. The operation of the relay in that range is represented by curve FG.

By changing the position of core l5 relative to armature il the distance that armature li may move before compressing spring 47 may be varied. When the distance of travel of armature Il before compressing has increased over that illustrated in the drawing, the point F on curve ABFG will be moved lower down on the curve, i. e., to a lower time high current relationship. By decreasing the distance of travel of armature Il before it starts to compress spring 4l the position of point F will be moved to a lower current higher time relationship.

The position of point B on curve ABFG may also be varied in a manner similar to point B on curve ABD by varying the initial tension on springs 2l and 23. Thus, a variety of time current relationships may be obtained from the same relay by simply varying the tension on the springs without varying the relative positions of armature and core structure.

Although but two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modications may be made therein without departing from the spirit of the invention' or from claims.

It is claimed and desired Patent:

to secure by Letters 1. A time delay relay comprising a core strucy ture, an armature'disposed adjacent said coreA structure to form therewith a magnetic circuit having a given air gap, a magnetizing winding for producing a magnetic flux in said magnetic circuit, an operating rod having a fiange ar-A nut for opposing movement of said armature relative to said rod, and means for varying the position of said nut relative to said cylinder for varying the tension of said resilient means without changing the length of said air gap.

2. A time delay relay comprising a core structure, an armature disposed adjacent said core .structure to form therewith a magnetic circuit having a given air gap, a magnetizing winding for producing a magnetic iiux in said magnetic circuit, an operating rod having a ange arranged to be actuated by said armature, means for retarding the movement of said rod into actuated position in a time varying inversely of the value or the current traversing said winding, said armature comprising a cylinder and a nut threaded within said cylinder, said cylinder enclosing said flange, a core threaded in said cylinder for movement therewith in an adjustable position, a rst resilient means acting between said flange and said core for opposing movement of said armature relative to said rod, and a second resilient means acting between said flange and said nut for opposing movement of said armature relative to said rod, adjustment of the positions of said core and said nut relative to said cylinder varying the tensions of said rst and second resilient means, respectively, independently of each other and without changing the length of said air gap.

3. A time delay relay comprising a core structure, an armature disposed adjacent said core structure to form therewith a magnetic circuit having a given air gap, a magnetizing winding for producing a magnetic iiux in said magnetic circuit, an operating rod to be actuated by said armature, means for retarding the movement of said rod into actuated position in a time varying inversely of the value of the current traversing said winding, resilient means acting between said armature and said rod for opposing movement of said armature relative to said rod from a first position to a second position, and a second resilient means acting between said armature and said rod for opposing movement of said armature relative to said rod from said second position to a third position depending on the value of said current, said armature moving relative to said rod from said rst position to said second position when the current traversing said winding reaches a predetermined value and from said second position to said third position when said current exceeds said predetermined value, said movement of said armature relative to said rod varying the inverse time relation between rod actuation and the value of said current.

4. A time delay relay comprising a core structure, an armature disposed adjacent said core the scope of the appended aeeegees,

structure to form therewith a/magrretie circuit having a given air gap, a magnetizing windingior producing a magnetic nuxin said magnetic circuit, an operating rod having a ange arranged to be actuated by said armature,izneans for retardine the' movement of said rod into actuatedpos-ition in a time varying inversely cr" the value oi the current traversingsaid Winding,said armature comprising a cylind r `anni a threaded within said cylinder, said` Vcylinder enclosing said ange, a core threaded Within Vsaid cylinder for movement therewith inana'djustabie position, a second core threaded. wit-nin. saidnrst core for movement therein ein env adjusta'oie position, a it ineens acting; between said; flange and. saidinest coreforonposing movement of said armature relative to seid rod, e second resiiient means acting between said iiange said nut for opposing nieve-ment oi said. armature relative tok said i' e, and e third esiiient means arranged between 4seid. Second core and said flange ior opposing movement oi saidarmatnre relative to said only after said arm-attire hes traveled a predetermined. distance, said armature moving said predetermined distance relative to said rod from Ya. first position to a second position when the current traversing said winding reaches a predetermined vaiue and :trom said second position to a third position depending on the value of said current when. said einrent exceeds said predetermined vaine, said movement of said armatore relative to said rod varying the inverse time relation between rod actuation and the vaine ot said current.

5. A time delay relay comprising a core sti'ucture, an armature disposed adjacentsaid core structure to form therewith o, magnetic circuit a. e. having a given air gan, o megnetizing' winding` for producing a magnetic fiux in .said magnetic circuit, an operating 'rod having a ange arranged to be actuated by said armature, means for retarding the movement of said rod into actuated position in a time varying inversely of the vaine' of the current traversing said Winding, a first resilient means :acting between said armature andsaid rod for opposing movement of said armaturereietive tosaid rod from 'a first position to a second position, said armature moving` relative to said rod 'from said 'first position to-said second position when the current traversing said winding; reaches a predetermined valuesaid movement of said armature relative to said rod varying the inverse time rLeIat-ion betvveen'rod actuation the vaine of seid current, and 'a second resilient means acting between said armature and said rod; for opposingmovement of said armature relative to said rod and becoming operativ'eat e point intermediate said rst and second positioif-i` thereby varying the inverse .time relation betweenrod actuation end the value oi said currentt 03N MICHAEL.

References Cited in the le of this patent UNITED STATES PATENTS

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