US 2781433 A
Description (OCR text may contain errors)
1957 K. w. WILCKENS ELECTRO'MAGNETIC CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed Dec. 23, 1950 mmvrozz.
KURT W WILCKENQ BY HIS ATTORNEY K. w. WlLCKENS 2,781,433
ELECTRO-MAGNETIC CIRCUIT BREAKER Feb. 12, 1957 Filed Dec. 23, 1950 2 Sheets-Sheet 2 IN V EN TOR.
KURT W. Wucuaus B HIS ATTORNEY United States Patent 2,781,433 ELECTRO-MAGNETIC CIRCUIT BREAKER Kurt W. Wilckens, Morrisville, Pa., assignor to Heinemann Electric Company, Trenton, N. J., a corporation of New Jersey Application December 23, 1950, Serial No. 202,541
Claims. (Cl. 200-88) My invention is an improved circuit breaker comprising a switch blade operatively associated with an electromagnetic trip mechanism having an armature operable, on overload, by a change in the flux of an electro-magnet under the influence of an element of the magnetic circuit which is abnormally demagnetized (as compared With the remainder of the circuit) by being heated responsively and proportionately to the flow of current controlled by the breaker.
In my improved breaker, the thermal demagnetization of the flux regulating element lags behind the rise in current flow producing the demagnetizing heat, and thereby provides a time delay preventing operation of the breaker as a result of a momentary rush of current when a motor or lights are turned on. The rate of heating of the fiux regulating element will vary with the rate of rise of the heating current, and consequently, the lag in the operation of the breaker will vary proportionately 'to the increase in current.
In a preferred embodiment of my invention, a tripping armature is operatively associated with an electro-magnet comprising a solenoid coil and a core and frame forming a closed, or substantially closed, magnetic circuit or flux path which is magnetically permeable throughout at normal temperatures but which includes an element or a section which is gradually demagnetizable at temperatures resulting from deleterious overloads. The resulting interruption of the closed metallic flux path causes lines of magnetic force to fiow through the air to and through the tripping armature, which is thereby rocked to trip a toggle or the like and permit the opening of the switch blade.
The principles of my invention, and the best mode in which I have contemplated putting such principles into practice will further appear from the following description and the accompanying drawings in illustration thereof.
In the drawings, Fig. 1 is 'a perspective view of a single pole circuit breaker embodying my improvements; Fig. 2 is a transverse sectional view taken on the line 22 of Fig. 1; Fig. 3 is a fragmentary sectional view taken on the line 33 of Fig. 4; Fig. 4 is a fragmentary sectional view taken on the line 44 of Fig. 2; Fig. 5 is a fragmentary sectional view showing a modified form of the electro-rnagnetic mechanism of the breaker shown in Fig. 1; Fig. 6 is a fragmentary view taken on the line 66 of Fig. 5; Fig. 7 is a fragmentary sectional view of a further modification of the electro-magnetic mechanism of the breaker shown in Fig. 1; Fig. 8 is a fragmentary sectional view taken on the line 88 of Fig. 7; and Fig. 9 is a fragmentary sectional view taken on the line 9--9 of Fig. 7.
In the embodiment of my invention, shown in Figs. 1 to 4, a frame 1 is provided with slides 2 which are seated in grooves 3 of an insulating casing 4. The frame is pro vided with ears 5 containing slots 6 forming seats for a pintle 7 on which a switch blade 8 is rockable into and out of engagement with a contact 9 connected with a line terminal 10.
The blade 8 is rockable through pivoted links 11 and 12 by a handle 14 rockably mounted on cars 15 of the frame 1.
The links 11 and 12 form an over-center toggle which may be held rigid by the engagement of a tooth 16 on the link 12 with the peripheral face of a shaft 17 mounted in the link 11, as set forth in my Patent No. 2,360,922. The shaft 17 may be turned, by rocking the arm 18 thereof, to bring its flat face into juxtaposition to the tooth 16 and permit the movement of the tooth past the fiat face. This results in the collapse of the toggle and the movement of the blade 8 away from the contact 9 as a result of the biasing action of its spring 19.
The arm 18 is rockable by a bent finger 20 of an armature 21 pivoted by the pintle 22 on the ears 15. The armature 21 is mounted in operative relation to a pole piece 23 forming one end of a magnetically permeable core or bar 24 which is encircled by the solenoid coil 25. The coil has one end connected by a pig tail 26 with the switch blade 8 and the other end connected with a load terminal 27, so that when the switch blade 8 engages the contact 9 current flows through the solenoid coil to generate a magnetic flux.
The core 24 is held by the bolt 24 in close contact with a face of the magnetically permeable leg 28 of the frame 1. A magnetically permeable leg 29, integral with and at right angles to the leg 28, extends along the exterior of the coil 25, parallel with the core 24, and has an end forming a pole 30 complementary to the pole piece 23 and in operative relation to the armature. The core and frame thus constitute a U-shaped magnet and form with the coil an iron-clad tractive bar electro-m'agnet or solenoid.
A bridge 31, preferably consisting of an annulus tightly encircling the pole piece 23 and welded to or at least making close contact with the pole piece 30, may act as a spacer between the poles 23 and 31 or as a flux path between the poles, depending upon the temperatureof the bridge.
The bridge 31 is composed of a metal whose magnetic reluctivity increases with increases in temperature much more rapidly than does the reluctivity of the core 24 and frame 1. Such metals are preferably iron-nickel or ironmanganese alloys having a relatively high content of nickel or manganese and which lose their magnetism gradually as they are heated and regain it as they cool. Preferably, an alloy is selected whose magnetic permeability will approximate that of the core 24 and frame 1 at tempera tures resulting from normal current flow or permissible overload, but which will become virtually non-permeable at a temperature indicative of danger to or deterioration of the device to be protected or of the circuit breaker. The nickel-iron alloys should contain at least 29% nickel so that for each temperature there is a characteristic permeability value.
When the breaker is designed for use at ordinary atmospheric temperatures, the nickel content of the alloy may exceed one-half and approximate 65%.
So long as the bridge 31 is at a relatively low temperature, the magnetic flux generated by the coil 25 will flow in the closed circuit formed by the core 24, bridge 31 and frame 1, and consequently, there will be insufficient flux density in the air to attract the armature 21. When, however, the temperature of the bridge 31 rises so that it is substantially impermeable, the magnetic flux will flow from the pole piece 23 through the air and armature 21 to the pole 30 thereby attracting the armature 21 and rocking the finger 20 and arm 18 to unlatch the toggle and permit the opening of the blade 8.
Figs. 5 and 6 show a modification of my invention in which the bridge 31 is eliminated but the pole piece 23' of the core 24 is connected with the leg 28 of the framel by a bridge consisting of the magnetically permeable brackets 32 and 33 contacting the pole piece 23' and leg 28 and connected by a core 34 and bolt 35. The core 34 and bolt 35 are composed of an alloy such as above described having high magnetic permeability when cold and high magnetic reluctivity when hot. W The core 34 is encircled with an inductive coil 36 in series with, and preferably of finer wire than, the coil 25 and is connected With the load terminal 27.
The coils 25 and36 are so wound as to create magnetic fluxes tending to flow counter to one another, as indicated by the arrows adjacent to the ends of the respective coils, and of substantially the same flux densities, so long as the core 34 is at a temperature at which is'is desired that theswitch blade 8 remain closed. The oppositely flowing fluxes flow in a closed circuit and so, diminish the flux in the air adjacent to the pole piece23 that the armature 21 is not attracted. When, however, a detrimental overload flows through and heats the coil 36, the core 34 is heated to a temperature at which itbecomes magnetically impermeable and consequently little or no flux is generated to flow from the coil 36 through the brackets 32 and 33 and the magnetic reluctivity of the core 34 forms a gap between the brackets 32 and 33 preventing the flow of flux therethrough from the coil 25 and core 24. Consequently, the flux generated by the coil 25 flows from the pole piece 23 through air and the armature 27 to the pole 30, thereby attracting the armature 21 and tripping the toggle to release the switch blade 8.
In the form of the invention illustrated in Figs. 7 to 9, a magnetically permeable core 37 is substituted for the leg 29 of the frame 1 and has one end seated in the leg 28 and the other end seated in an extension 31' of the bridge 31. A coil 38 is wound on the core 37 in series with the coil 25 and is connected with the load terminal 27. The coils 25 and 38 are so wound that the ends of the cores, 24 and 37 adjacent to the armature 21 form opposite poles.
When the blade 8 is closed current flows through the coils 25 and 33 to form a U-shaped electro-magnet having a coil on each leg and having the north pole of the core 24 adjacent to but spaced from the south pole of the core 37. These poles are magnetically bridged 'by the bridge 31 and extension 31 so as to form a closed magnetic circuit so long as the temperature of the members 31 and 31' is below their demagnetization temperature. So long as the magnetic circuit is thus closed, it will not attract the armature 21. But when the members 31 and 31 are heated to a dem'agnetizing temperature, the magnetic flux flows from the pole of the core 24 through the air and the armature 21 to the pole of the core 37 thereby rocking the armature and tripping the toggle to release the switch blade.
Having described my invention, I claim:
l. The combination of an electromagnetic coil tending to heat on passage of current therethrough, a metallic frame in the flux field of said coil and including a core in said coil, said frame being composed entirely of stationary members all of which have a high magnetic per- 4 r meability at normal atmospheric temperatures and which form a closed metallic magnetic circuit when at normal atmospheric temperatures, one of said members having much greater flux reluctivity than the other members when heated by abnormal current flow through said coil above normal atmospheric temperatures, and means interrupting the flow of heating current through said coil when said member of greater flux reluctivity is heated thereby and including an armature attracted by flux diverted by the reluctance of said last named member, said armature closing a metallic magnetic path for flux generated by said coil when said member of greater flux reluctivity is abnormally heated.
2. A combination as set forth in claim 1 in which the interrupting means includes a movable blade in series with said coil and a toggle controlling said blade and operable by said armature to break the circuit through said coil when said member of greater flux reluctivity is abnormally heated.
3. A combination as set forth in claim 1 and having a second coil wound on said frame in series with said first coil, said coils being wound to produce opposite fluxes in said frame upon flow of current through said coils in series, said armature being attracted to the core of said first coil when there is little or no flow of flux from the second coil. I
4. A combination as set forth in claim 1 and having a second coil wound on the member of high reluctivity when heated, said first and second coils being in series with one another and wound to produce opposite fluxes insaid frame upon flow of current through said coils in series, said armature being attracted to the core of said first coil when there is little or no flow of flux from the second coil.
5. A combination as set forth in claim land having a second coil wound on a member of said frame and in series with said first coil, the member on which said secondcoil is wound having a pole piece adjacent to said armature, and said coils being wound to form poles of opposite polarity adjacent to said armature in said core andlast named member when current flows through said coils in series.
References Cited in the file of this patent UNITED STATES PATENTS 1,330,094 Simon Feb. 10, 1920 1,440,879 Lee Jan. 2, 1923 1,561,386 White Nov. 10, 1925 1,608,872 Wallis NOV. 30, 1926 1,655,847 Siebs Jan. 10, 1928 1,901,708 Ellingson Mar. 14, 1933 1,960,402 Wilckens May 29, 1934 1,968,971 Sullivan Aug. 7, 1934' 1,985,033 Hudson Dec. 18, 1934 2,347,018 Armstrong Apr. 18, 1944 2,360,922 Wilckens Oct. 24, 1944 FOREIGN PATENTS 561,904 France Oct. 30, 1923 578,611 Great Britain July 4, 1946