US1948099A - Electromagnet for circuit breakers and the like - Google Patents

Description

Feb. 20, 1934. R. c. DICKINSON ELECTROMAGNET FOR CIRCUIT BREAKERS AND THE LIKE Filed Jan. 19, 1928 Fig. 3.

Fig.2.

INVENTOR Raberf C Dickinson.

AITTORNEY Patented Feb. 20, 1934 ELECTROMAGNET FOR CIRCUIT BREAKERS AND THE LIKE Robert C. Dickinson, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application January 19, 1928. Serial No. 247,829

Claims.

My invention relates to circuit interrupters, and more particularly to electro-magnets for maintaining them in their closed positions.

One object of my invention is to provide a 5 circuit interrupter with an electro-magnet that shall operate to open the circuit very quickly after the occurrence of an overload or other abnormal circuit condition.

Another object is to provide an electromagnet responsive to a maximum value of either alternating current or direct current.

Another object of my invention is to provide a circuit interrupter with an electro-magnet that shall be adapted to open the circuit upon the occurrence of an overload on either an alternating-current or a direct-current circuit.

A further object of my invention is to provide a circuit interrupter with an electro-magnet that shall be adapted to permit it to move to its open position with great rapidity when actuated by an increase of current in the circuit.

Heretoiore, certain circuit interrupters intended for use on direct-current circuits have been provided with electro-magnets having a separately excited winding for holding the circuit-interrupter in closed position and which are operated to release the circuit interrupter upon the occurrence of an overload in the circuit, by reason of being provided with a second winding energized to oppose the first-mentioned winding and neutralize its holding efiect. By properly proportioning the two coils, such balance may be obtained that an armature may be released when the current in the neutralizing winding has attained a certain value. Attempts to apply this principle to alternating currents have been more or less unsuccessful for the reason that it was necessary to employ either rectifiers or electromagnets having cumbersome magnetic circuits to produce release of the armature member.

In practicing my invention, I am able to construct a holding electro-magnet that employs no polarized magnets and that, accordingly, may be operated on either an alternating or a directcurrent circuit to open the circuit when an increase of current occurs in the circuit.

Referring to the drawing:

Figure 1 is a diagrammatic view of a particular embodiment of my invention in which the holding electro-magnet is energized from a directcurrent source.

Fig. 2 is a sectional view of a particular embodiment of my core member showing the parallel path traversed by the line-current circuit in the device shown in Fig. l.

Fig. 3 is a diagrammatic view showing the flux distribution in the core member and the armature when normal current is flowing in the two circuits.

My invention comprises, in general, a circuit 50 interrupter 1 that is held in closed position by latch The latch 2 is controlled by an armature 3 which engages the magnetic core 4 of a holding electro-maghet 5.

The core 4 is or" E shape, that is to say, it comprises a central leg 6 and two end legs 7 and 8. A winding 9 is located about the lower portion of the central leg 6 and may be energized any constant source of potential, such as the battery 11. The upper half of the central 7 leg 6 is provided with arms 12 and 13 that provide a shunt path for the flux induced in the core 4 by the line current, in a manner that will be more fully explained hereinafter. Channels 14 and 15 are thus provided in the upper part of the core 4 through which the bars 17 and 18 extend. .The bars 1*. and 18 are traversed by the main-circuit current which thus divides near the core 4 into these two paths, passing between the outside legs and the central leg of the core 4. In Fig. l, the bars 17 and 18 are shown connected to one side of a current transformer 19, although they may beconnected to a direct-current source 21, in the manner indicated in Fig. 2.

The armature 3 is biased to open position by a spring 22 and is pivotally supported upon a lever 23 that is supported near its center on a fixed pivot 24. The other end of the lever 23 contains a latching means 25 for holding the circuit interrupter l in closed position.

The circuit interrupter 1 comprises an operating arm 26 that is biased by the spring 27 to open position against stop member 28 and is pivotally supported on a fixed pivot 29. A bridging member 31 is connected to the upper end of arm 26 and is employed to bridge contact members 32 and 33 to complete a circuit in the main line 34.

A spring 35 is connected between the operating member 26 and the latch 2 to bias the latter into engagement with t. e latch 25. Stop member 36 is provided on the operating member 26 to prevent the member 2 from being drawn too far downward, thereby ensuring its engagement with the latch 25 upon the closing of the circuit interrupter 1.

Referring to Fig. 3, the circles enclosing crosses indicate, by a familiar convention, that the current in the parallel circuits 1'7 and 18 is flowing in the same direction. This current may be supplied from either an alternating-current or a di-' 110 rect-current source. A normal holding flux, indicated by the arrows 37, is produced in the magnetic circuit by the winding 9 that is energized by the battery 11 or any other source of invariable energy. The strength of the coil 9 is so chosen that the flux 37, induced thereby in the magnetic circuit formed by the armature 3 and the core 4, is sufiicient to produce saturation in the iron of the armature 3. The current supplied by the line to the paths 17 and 13 produces fipxes in the same direction in the armature 3, as indicated by the arrows 38.

The arms 12 and 13 provide a magnetic circuit encircling the bars 17 and 18, thereby increasing the magnitude of the fluxes 38.

It will thus be seen that, if the current in the paths 1'7 and 18 is sufficiently increased, the fiux produced by the current in bar 18 will, as shown in Fig. 3, be in the opposite direction to the flux 37 normally present therein and will reduce the net flux in the adjacent end of the armature 3.

On the other hand, the flux 38 induced by the current in bar 17 has the same direction as the flux 37 and will tend to increase the number of lines of force on the other end of the armature 3. Because of the saturated condition of the armature 3, however, little or no increase in the holding force on the right hand end of armature 3 will result. The sum of the next fluxes through the two ends of armature 3 is, therefore, decreased and, if the current in the parallel conductors 17 and 18 reaches a certain value, the spring 22, shown in Fig. 1, will operate to pull the armature 3 to its open position.

The same result will be obtained if an overload occurs while the direction of the current in the circuit is reversed. The flux about the path 18 will then assist, and that about the path 17 will oppose the normal flux 37. The only change produced by reversal of current is, therefore, that the other end or" the armature 3 is the one in which the flux decreases. The effect on releasing armature 3 will be no diiferent from that just described.

As the armature 3 moves to its open position, the latch 25 moves from under the trigger 2, releasing the operating arm 26 of circuit interrupter l. The arm 26 is quickly drawn over against the stop member 28 by the energy stored in the spring 27. This movement of the arm 26 moves the bridging member 31 away from the contact members 32 and 33 and thus opens the circuit of the main line 34.

In closing the circuit interrupter, the armature 3 is first moved to its circuit-closing position, that is to say, into engagement with the core member 4. Member 4 being energized by the winding 9, holds the armature 3 in that position. The operating arm 26 of the circuit interrupter 1 is next moved forward until the bridging member 31 engages the contact members 32 and 33, at which time the trigger 2 engages latch 25 and is drawn downwardly into engaged position by the spring 35. The circuit-interrupter is thus latched in closed position.

This method of employing a latch to operate the bridging member is used only as an illustration, and it will readily be seen that other connections may be made without departing from the scope of the invention. As an example, the armature 3 could be shown connected directly to the bridging member 31, and the latch 25 would be omitted.

It will thus be seen that I have provided a hold ing magnet for a circuit interrupter that is adapted to open the circuit interrupter when the holding electro-magnet is excited from either an alternating or a direct-current source. My invention is further novel in that no polarized electromagnets are employed in its operation, and the release of the armature is obtained by the employment of current coils that produce uni-directional fluxes in the magnetic circuit.

It is' to be understood that such changes in the form, arrangement and connection of component parts of my invention may be made as shall fall within the scope of the appended claims.

I claim as my invention:

1. An electromagnet comprising a core member and anarmature, a normal magnetizing winding saturating the core member to retain the armature in closed position, a conductor that divides on passing through the core member to form parallel current paths one of which produces a magnetizing force that assists, the other a magnetiz- .ing force that opposes, the normal magnetic flux in the armature in such manner that a predetermined increase ofcurrent in said conductor releases the armature from engagement withthe core member.

2. An electromagnet comprising a core member and an armature, means normally exciting the core member to retain the armature thereagainst in engagement therewith against the pull of a. bias means, the said exciting means being of such strength that the armature is highly saturated, a pair, of conductors associated with the core member in parallel relation to produce fluxes in those parts of the core member and armature associated with each conductor, in addition to the flux produced by the first said exciting means, and so disposed as to reduce the flux on one end of the armature but not to increase the flux in the other end because of its saturated condition, thereby producing the release of the armature on a predeterminedincrease in current in said conductor.

3. An electromagnet for circuit interrupter-s and the like comprising an E-shaped core and an armature biased away from the core, a. coil about the middle leg of the E-shaped core adapted to supply sufficient magnetizing force to highly saturate the armature, and'a circuit that comprises parallel conductors on each side of the middle leg of said E-shaped core, said conductors being so arranged relative to each other that one opposes and the other assists the magnetizing force of said coil, whereby, upon increase beyond a predetermined value of current, said armature will be released.

4. An electromagnet responsive to either direct or alternating current and comprising core means, armature means, means biasing the armature means away from the, core means, means for normally exciting the core means to draw the armature means thereto against the force of the biasing means, the exciting means being of sumcient strength to substantially saturate the core means, and current conducting means arranged to produce two fluxes, one of which reduces a part of the flux produced by the excitingmeansand the other of which tends to increase another part of said flux but is substantially inefiective because of the saturated condition of the core means, whereby, when the current flowing through the conducting means exceeds a predetermined value, regardless of direction offiow, thetotal effective flux will be reduced and permit the biasing means to move the armature means away from the core means.

fluxes, one of which reduces a part of the flux produced by the exciting means and the other of which tends to increase another part of said flux but is substantially ineffective, because of the saturated condition of the core means, whereby, when the current flowing through said circuit exceeds a predetermined value, the total efiective flux will be reduced and permit the biasing means to move the armature means away from the core means.

ROBERT C. DICKINSON.

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