US2575127A - Reverse current responsive device - Google Patents

Description

N0V- 13, 1951 P. J. RHI-SCHNEIDER REVERSE CURRENT RESPONSIVE DEVICE l 1 1.41 JEL' Filed Aug. 18, 19411` Inventor Paul J. Reifschneider;

[j His Attorney Patented Nov. 13, 1951 REVERSE CURRENT RESPONSIVE DEV-ICE raui J. Remwhneiaer. springfield, Pa., mignonto General Electric Company, a corporation ot New York Application August 18, 1949, Serial No. 110,986

s claims. 1

'I'he invention relates to reverse-current responsive devices and provides an improved multipolar m-agnetic trip mechanism for circuit breakers of the direct-acting type having a self polarized amature operable by magneticreaction between reversible magnetic poles with and without a time delay upon reversal oi' the current so as to be suitable for use in a. protective system for multiple-operated direct-current generators or in 'other reverse-current time delay control service.

Hence one object of the present invention is to provide improved means for enabling a permanent magnet self polarized armature to eect an improved selective substantially instantaneous or an inverse time-delay retarded response dependent jointly upon the direction, magnitude and duration of the current.

Thus, whenever the direct-current reverses and Vexceeds a normal maximum reverse value substantially instantaneous response may be obtained. However, reverse currents of lesser values must persist for varying intervals inversely proportional to the value of the reverse current before the time delay retarded response can be obtained. In this way the polarized armature is enabled to ride over many transient current reversals without fully responding While still protecting against continuing unsafe reverse-current conditions.

Another object is to provide an improved inductive current-responsive flux-shifting means for preventing depolarization of the self polarized armature and thereby maintain the armature magnetically eiective to respond in case an I excessive rate of rise should cause the reverse current to exceed the normal maximum value before the amature could otherwise respond substantially instantaneously.

Another object is to provide for automatic reset of the polarized armature of the reverse-current trip mechanism immediately upon the tripping of the circuit breaker.

Further objects and advantages of the invention will appear in the following description of the accompanying drawing in which Fig. 1 is a side view of the improved selective instantaneousv Fig. 3 is an exploded perspective view partially in section indicating more clearly the structure and operating relation of the parts of the lmproved selective reverse-current trip mechanism.

As shown in Fig. 1, the reverse-current responsive trip mechanism indicated generally by the reference character I0 acts directly to trip the latch I I of the circuit breaker indicated generally by the reference character I 2 so as to open the breaker substantially instantaneously when the reverse current exceeds a predetermined value and with an inverse time delay for reverse currents below said value. The reverse current trip mechanism I0 and the circuit breaker mechanism I2 may be mounted on a base I3 preferably formed of molded insulating material and provided with the connection terminals I4 and I5 at the opposite ends of the base I3 for connecting both the trip mechanism and the circuit breaker contacts in the circuit to be protected.

The circuit breaker I2 as shown with its enclosing cover removed is of the well-known tripfree overcenter toggle-operated snap-action type, although it should be understood that the improved reverse current responsive mechanism I0 of the present invention may be applied to trip any suitable type of circuit breaker or in other control service. The circuit breaker I2 has a rectilinearly movable bridging contact I1 operable into and out of engagement with a pair of laterally spaced apart stationary contacts l5, one of which is directly behind the other in Fig. 1 and connected through the conductor I9 with the terminal I4 and the other of which is connected through the conductor 20 and the U-shaped loop conductor 2I of the trip mechanism I0 with the terminal I5 as shown.

The rectilinearly movable bridging contact Il operates inside a pressure arc-suppressing chamber 23 formed in the block 24 of suitable arcresisting material preferably moulded integral with base I3. The plunger 25 that carries the bridging contact I1 extends with a close running iit through the top of the block 24 and in order to obtain the required substantially rectilinear movement is connected by the pivot pin 25 to one end of the lever 21 that in turn is pivoted by means of pin 28 on the guide link 29 that rotates about the stationary pin 30 having its ends xed in parallel side frames 3| mounted by screws 32 on block 24 but the front one of which is not shown in Fig. 1 in order to reveal the operatingr parts carried therebetween.

The toggle links 33 and 34 extend between pivot pin 28 and pivot pin 35 that is carried by the latched yoke member 3i having the latching face 31 engaged by the latching member I I. The yoke 3| is pivotally mounted on the stationary pin 38 so that when the latching face 31 is disengaged by the latch II, the toggle links 33 and 38 can be moved bodily upwardly by the force exerted by the opening bias tension spring 40 having one end connected with pin 28 and the other end anchored on stationary pin 4I. During the initial part of the upward movement of the toggle link, the tension spring 44, having one end connected to the outwardly `bent end 45 of lever 21 and the other end connected to an anchoringv clevis 48 seated in the frame 3|, serves to maintain the bridging contact I1 in firm circuit-closing engagement with the pair of stationary contacts I8. However, as soon as the outwardly bent end 45 of lever 21 engages with the top of the recess 41 formed in the side frame 3|, the continued upward movement of the toggle links 33 and 34 becomes effective to quickly separate the bridging contact I1 from the pair of stationary contacts I8. At the same time, the hump 48 on toggle link 33 engages with pivot pin 38 so as to buckle the toggle and thereby complete the snap action movement of the bridging contact I1 away from the pair of stationary contacts I8. When the toggle buckles, the yoke member 36 is moved automatically by spring 49 to return the face 31 into latching engagement with the latch II.

In order to reclose the circuit breaker I2, the closing lever 50 is operated either manually or by a suitable closing solenoid (not shown) to pivot about its mounting pin 5I so as to engage the nger 52 with the reset pin 53 carried on the overhanging end of toggle link 33 and thereby return the toggle links to their straightened condition since the yoke member 36 has automatically reset the face 31 into latching engagement with the latch II.

Spring 55 serves to return the closing lever 50 to the position in which. it is shown in Fig. 1 after the closing operation is completed. Such re-latching of the trip member 36 and straighteningof the toggle links 33 and 34 serves to move the pin 28 and guide links 29 so that spring 44 becomes effective to bias lever 21 to hold the bridging contact I1 in rm circuit-closing engagement with the pair of stationary contacts I8 through the agency of the plunger 25. With the circuit breaker mechanism I2 in the circuitclosing position as shown in Fig. 1, the finger 54 projecting from the toggle link moves spring 51 to operate a suitable enclosed auxiliary switch 58 that may be connected in a signal lamp circuit for indicating the closed condition of the breaker mechanism.

In order to trip the circuit breaker mechanism I2 upon a reversal of the current in the loop conductor 2i, the improved reverse current responsive selective instantaneous and time delay multipolar magnetic tripping mechanism III is provided in accordance with the present invention. For this purpose a U-shaped magnetic yoke I8 is interlinked with one leg of the direct current U-shaped loop conductor 2I and provided with the pole pieces 6I and 62 to form oppositely aligned pairs of poles 63, 64, 65, 66 in quadrangular spaced-apart relation centrally of the loop. As a result, intersecting oblique ux paths are provided between the diagonally opposite pairs of poles 63, 66 and 64, 65 as will be evident from an inspection of Fig. 2.

A polarized magnetic armature 10 is centrally pivoted by means of a pair of pivot pins 1I adjustably mounted in the opposite legs QI 8, L J- shaped support 12 that is secured to the pole piece 62 by means of the holding screws 13. The polarized -armature 10 is formed with a central permanent magnet straight bar portion 'I5 having the polar extensions 16 and 11 of magnetic material at the opposite ends thereof and provided with a double-arm trip lever 13. 'I'he polar extensions 16 and 11 are suitably joined to the permanent magnet portion 15, preferably by soft soldering and the double-arm trip lever 18 is preferably formed of nonmagnetic material and likewise may be joined in a similar manner to form a unitary polarized armature assembly.

In order to provide for the central pivotal mounting of the unitary armature 10, the trip lever 18 is provided with a central rectangular cutout opening 19 into which a curved pivotal mounting spring member is seated and provided with a central bearing hole for receiving the end of the mounting pivot 1I as shown in the perspective view of Fig. 3. A similar curved spring mounting bearing is similarly seated on the opposite side of the armature 'I0 for receiving a similar mounting pivot 1I so that the armature 10 is suspended for free pivotal movement therebetween. Thus, the polarized armature 1I) can readily tilt from its full-line position to which it is biased by spring 8I and in which the polar extensions 16 and 'I1 are adjacent the diagonally opposite pair of poles 68 and 66 into its dotted-line position as shown in Fig. 2 in which the polar extensions engage with the diagonally opposite pair of poles 6B and 65. Since the centrally pivoted armature 'I0 has its pivot axis at the intersection of the oblique flux paths between the diagonally opposite pairs of poles 63, 66 and 64, 65, the polarized armature 18 will move from one path to the other, i. e., from one polar position to another upon a reversal of the current in the conductor 2l due to the magnetic reaction of the permanent magnet 15 with the ux produced in the magnetic yoke 68 and the pole pieces 6I, 62 by the reverse current ow through the conductor 2i. 'I'hus the magnetomotive forces set up by current ow in the conductor 2I and by the permanent magnet always tend to become cumulative, or in other words the polarized armature 18 always seeks the path of least reluctance as is well known in the art.

The curved trip arm 82 of the lever 18 engages with a nger 83 extending from the circuit breaker latch II that is pivotally mounted on the shaft 84 so as to directly turn the latch II about the shaft 84 to disengage the latch II from the latch face 31 and thereby trip breaker I 0 when the polarized armature 10 is operated into its dotted-lineposition shown in Fig. 2. The latch II is biased to return to the latching position in which it is shown in Fig. l by the spring 85.

In order to enable the reverse current responsive trip mechanism I8 to ride over many transient current reversals without tripping, a timedelay mechanism indicated generally by the reference character is provided with the resil-I ient operating spring connection IIlI for exing to permit a substantially instantaneous movement of the polarized armature 10 from its fullline or normal current position when the reversed current exceeds a predetermined value but retarding the movement of the armature to its dotted-line or reverse current tripping position as shown in Fig. 2 when the reverse current remains below the predetermined value. In the form shown,the time-delay mechanism Il is of the escapement type having a pallet oscillating on the verge 92 upon rotation of the escapement wheel 0 that is turned by engagement of the gear lever 04 with the driving pinion $0. All of these operating parts of the time-delay mechanism 00 are mounted inside the channel frame Il that is secured to oneleg of the magnetic yoke 00 by means of the mounting screws l0. Rivets 01 serve to secure the pole piece 0| to the yoke 00 as shown in Fig. 2. Thus the pivot axis |00 of the gear lever 94 is in quadrature with the pivot axis of the polarized armature 10 and in order to operatively interconnect the two. the spring member |0I is coiled around the pivot axis |00 with one end anchored in a suitable hole |02 formed in the gear lever 94 and the other end hooked into a suitable hole |00 formed in the reset arm |05 extending from the amature trip lever with an intermediate section of the spring I 0| firmly seated upon the projection |00 from the gear lever 94 due to the torque exerted by the coiled portion of the spring.

Thus when polarized armature 10 tends to tilt from its full-line or normal current position to its dotted-line or reverse current position shown in Fig. 2, the spring |0| serves to retard or delay the movement of the armature by rotating the gear lever 94 about shaft |00 and thereby turn the escapement wheel 93 to oscillate the pallet -9| as long as the escapement portion o! wheel 92 engages therewith and the force exerted by the armature 10 is below that required to lift the section of spring |0| away from the projection |06. Consequently, with the force exerted by the polarized armature 10 dependent upon the value of the reverse current below a predetermined normal value an inverse time delay is obtainedbefore the wheel 93 runs free from the pallet 9| to allow trip arm 82 to strike linger 83 and trip the breaker I0. However, whenever the reverse current exceeds the predetermined normal value, spring |0| yields and thereby provides for substantially instantaneous tripping operation of the polarized armature 10 as long as the armature 10 is maintained self polarized by the permanent magnet 1'5.

When the polarized amature 10 is in its dottedline or reverse current tripping position shown in Fig. 2, the permanent magnetization thereof tends to hold the armature in the dotted line position engaging the poles 60 and 65 despite the return bias of the Calibrating spring 8 In order to automatically reset the armature 10 into its full-line or normal current position as soon as the tripping of circuit breaker I0 is accomplished, a lever |01 is pivotally mounted on the pivot axis 30 and provided with an overhanging plate |00 to be engaged by the toggle link 29 during the tripping of the breaker. The finger |00 is carried at the other end of the lever |01 into engagement with the rounded end of the reset lever |05 so as to forceably break away the polarized armature 10 from its dotted-line position shown in Fig. 2 and enable the calibrating spring 0| to dominate thereover to such an extent as to permanently reduce the 'magnetization of the permarient magnet so that it becomes practically ineffective or, in other words, depolarize the magnet. In order to prevent such depolarization and thereby maintain the self polarized armature 10 magnetically eiIective to flex the retarding spring connection |0I, the diagonally opposite pair o! poles 00, l0 are each provided with inductive currentconducting flux-shifting means indicated generally by the reference character ||0 that serves to prevent depolarization of the permanent magnet 10. In the form shown in cross-section in Fig. 2, a facing I of conducting material auch as copper is provided for the pole B3 and an additional current-conducting ring section- I|2 encircles the pole 83 with these parts suitably joined to the pole as by soldering or the like. Thus when the excessively high rate of rise of reverse-current in conductor 2| tends to reverse the flux through the poles 63 and 66 very quickly, the eddy .currents induced in both the facing plate and the ring ||2 serve to shift the flux from these poles into the other poles and thereby maintain the magnetic force eiective to move the polarized armature 10 to the other ux path in which the magnetomotive force produced by the reverse-current in conductor 2| is cumulative with that of the permanent magnet 15.. Furthermore, the facing ||i serves to space the polar projections 16 away from the pole 62 so as to provide a nonmagnetic gap of substantial reluctance therebetween. This is also true o! the -pole 60 which is provided With a facing ||0 and a ring IH of conducting material identical in structure and formation. Thus, whenever an excessively high rate of rise causes the reversecurrent to reachl quickly an abnormally high value, depolarization of the permanent magnet 15 is effectively prevented by the flux-shifting action of the inductive current-responsive means ||2, H3. and ||4 and the armature 10 is maintained magnetically effective to flex the retarding spring |0|.

The reverse-current circuit breaker with the improved tripping mechanism shown in Figs. l, 2, and 3 is particularly adapted for operation in a multiple-connected direct-current generator protective system such, for example, as are used on aircraft in which each generator is driven at vwidely varying speeds by a corresponding one of its speed or stall or a short-circuit or ground should occur. In case of only a transient reduction of the generator operating speed such that the 'magnitude and duration of the reverse current do not exceed predetermined values, the time-delay mechanism will enable the reversecurrent responsive trip mechanism l0 to ride over the disturbance without tripping the circuit breaker mechanism I2. However, in case the generator speed should decrease more rapidly than can be taken care of by the voltage regulator so that the reverse-current exceeds a predetermined normal value, then instantaneous tripping of circuit breaker I2 by trip mechanism |0 will occur due to the exing of the spring connection |0| between the time mechanism 90 and the tilting 'armature 10. In the event of a short circuit or ground-whereby a large value of reverse-current is obtained practically instantaneously. the improved linx-shifting means IH,

ization oi the permanent magnet 1I thereby maintaining the armature 1| magnetically eective at all times. Thus it will be seen that the improvements of the present invention enable the reverse-current trip mechanism Il to successfully meet all of the normal and abnormal instantaneous and time delay operating conditions.

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

1. A reverse-current responsive device having in combination, a direct-current conductor having an interlinking magnetic yoke provided with pole pieces to form oppositely aligned pairs of reversible poles, a centrally pivoted permanent magnet armature having each end thereof magnetically operable between a corresponding pair of said poles when the current in the conductor reverses, and inductive current-responsive conducting rings separately encircling a diagonally spaced one of each pair oi poles for shifting the ilux to the other poles to prevent depolarization of the permanent magnet armature and thereby maintain the armature magnetically effective when the rate of rise of reverse current becomes excessive.

2. A reverse-current responsive device having in combination, a direct-current conductor having an interlinked magnetic yoke provided with pole pieces in opposing alignment to form obliquely spaced pairs of magnetically opposite poles, a centrally pivoted permanent magnet armature having polar extensions at the ends thereof operable by magnetic reaction away from one of said 5 pair oi' poles towards the other pair of poles when the current in the conductor reverses, a facing of conducting material on each of said one pair o! poles for spacing said polar extensions a predetermined distance therefrom, and inductive current-responsive rings separately encircling each of said one pair of poles for cooperating with said conducting facings to shift the ux to the other poles to prevent depolarization of the permanent magnet armature and thereby maintain the amature magnetically eilective when the rate of rise oi reverse current becomes excessive.

3. In combination, a direct-current conductor having magnetic means providing a plurality oi pairs of poles reversible in polarity upon reversal of the current in the conductor, a permanent magnet polarized armature movable from one to another pair of said poles upon reversal of the polarity thereof, time-delay mechanism having a resilient connection with the armature for retarding the movement of the armature between said poles and iiexing to render said time-delay mechanism ineffective when the reverse current in the conductor exceeds a predetermined value and inductive current responsive means interlinking each of said one pair of poles for maintaining the armature magnetically effective to iiex said resilient connection.

4. In combination, a permanent magnet armature provided with pivotal mounting means, direct current electromagnetic means for tilting the rent responsive means engageable by the end of the armature in said one position for preventing depolarization of the permanent magnet of the armature and maintaining the armature magnetically eilective to ex said resilient connection when the rate of rise of the reverse current becomes excessive.

5. A reverse-current responsive device having in combination a direct-current conductor having an interlinked iron yoke provided with pole pieces shaped to form aligned pairs of oprmsite poles, a centrally-pivoted permanent bar magnet having its pivot axis equi-distant from each of said poles and provided with polar extensions in cooperating attractive relation with diagonally opposite pairs of said poles to be moved therebetween when the current in the conductor reverses, and separate conducting rings mounted on each of a diagonal pair ci said poles for engagement by said polar extensions to prevent depolarization of said bar magnet and thereby maintain the magnet eective for movement when the rate of rise oi reverse current through said conductor becomes excessive.

6. A reverse-current responsive device having in combination, a direct-current conductor having an interlinked magnetic yoke provided with pole pieces in opposing alignment to form obliquely spaced pairs of magnetically opposite poles, a centrally pivoted permanent magnetic armature operable magnetically away from one pair of said poles towards the other pair of said poles when the current in the conductor reverses, current responsive members in separate inductive relation with the ux in each of said one pair of poles for shitting the ux to the other poles to prevent depolarization of the permanent magnet armature and thereby maintain the armature magnetically effective when the rate of rise of reverse current becomes excessive, and time-delay mechanism having a resilient connection with the armature to retard the movement of the armature away from said one pair of poles toward the other pair of poles, said connection yielding to provide for substantially instantaneous movement of the armature when the reverse current exceeds a predetermined value.

7. A reverse-current responsive device having in combination, a direct-current conductor having an interlinked magnetic yoke provided with pole pieces to form obliquely intersecting ux paths between diagonally opposite pairs of said poles, a centrally pivoted permanent magnet armature having its axis at the intersection of said ilux paths for tilting movement from one path to the other path when the current in the conductor reverses, an escapement timing mechanism having a pivotally mounted operating gear member with its axis in quadrature with the axis o! said armature, operating connections between said gear member and said armature including a spring to provide an inverse time delay in the tilting of the armature between said paths as long as the reverse current in the conductor is below a predetermined value and flexing to render said time-delay mechanism ineiective when the reverse current in the conductor exceeds said value, and inductive current responsive means interlinking said one path for maintaining the armature magnetically effective to flex said spring when the rate of rise of reverse current becomes excessive.

8. A reverse-current tripping device having in combination, a direct-current conductor in the form of a U-shaped loop, a magnetic yoke inter- 9 v linked with one leg of the loop and provided with pole pieces to form oppositely aligned pairs o! poles centrally of the loop, a centrally pivoted permanent magnet armature having its axis transverse the loop for tilting the amature away from one pair of said poles into engagement with the other pair of said poles when the current in the conductor loop reverses, a double arm lever carried by the armature and having a tripping .arm extending from one side of the loop and a restraining arm extending from the other side of the loop, and an escapement time-delay mechanism having a pivoted gear operating member with its axis normal to the loop and provided with operating connections including a spring connected with said retarding arm to retard the tilting or the armature between said poles and yielding to render said time delay mechanism ineffective when the reverse-current in the conductor exceeds a predetermined value, and inductive current responsive means interlinking 10 each of said one pair of poles for maintaining the armature magnetically eiective to flex said spring when the rate of rise oi reverse current becomes excessive. v

PAUL J. REIFSCHNEIDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 698,027 Knapp Apr. 22,1902 1,158,898 Conrad Nov. 2, 1915 1,248,084 Curtis Nov. 27, 1917 1,837,188 Keller Dec. 22, 1931 1,947,236 Walle Feb. 13, 1934 2,060,492 Dyer Nov. 10, 1936 2,393,736 Bennett et al Jan. 29, 1946 2,439,165 Graves Apr. 6, 1948 2,495,127 Oppel Jan. 17, 1950

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