US2200109A - Current limiter - Google Patents

Description

K. W. WILCKENS CURRENT LIMITER May 7, 1940.

Filed May 23, 1934 2 Sheets-Sheet 1 R O T N E V m ATTORNEY.

5 N E K c w W w K CURRENT LIMITER Filed May 23, 1934 2 Sheets-Sheet 2 INVENTOR. 222%? M fiew ATTORN.

"(Patented May 7, 1940 ,UNITED- STATES 2,200,109 I CURRENT LIMITER Kurt w. Wilckens, Philadelphia, 1a., assignor, by mesne assignments, to Heinemann Circuit- Breaker Company, Trenton, N. J., a corporation of New Jersey Application May 23, 1934, Serial 727,113

4 Claims.

My invention is a circuit breaking device which will be equally efiective in a number of diflerent positions regardless of the weight of the movable members.

6 My invention further provides a circuit breaker which is simple in construction and certain and accurate in operation, and affords positive protection in the event of short circuits.

In the preferred embodiment of my invention 10 a circuit controlling switch is actuated by current as the result of the flow of current through an electromagnet comprising a plurality of turns of conductor.

The intensity of the magnetic flux and its attraction for the armature is regulated by the movement in the magnetic field of a bridge member or magnetically permeable core which varies the reluctance of the magnetic circuit of the electromagnet and varies the width of an air gap or gaps in such magnetic circuit. Such bridge member is moved relatively to the magnetic field, by the magnetic attraction thereof, under control of retarding mechanism which pref erably consists of a fluid tight fluid container I in which the core is housed and is movable axially against the retarding action of fluid which slowly seeps from one portion to another portion of the fluid container upon the movement of the core. The electromagnet utilized in the preferred 80 embodimentoi my invention consists of a hol-' low tube containing a magnetically permeable core movable axially within the tube and normally spring-biased away from the magnetic field and toward one end of the tube. The tube contains a liquid or gas which seeps slowly between the periphery of the core and the inner wall of the tube on movement of the core longitudinally within the tube against the action of 'the biasing spring. Or the liquid or gas may pass 4o quickly from one end of the tube to the other end thereof through a bore or passage through the core, such passage or bore being controlled by a non-retum valve. Consequently, the core is movable quickly in the direction toward which 4.5 it is biased by the spring and is movable slowly in the opposite direction.

The tube has wound on the periphery thereof, along a portion of its length, a number of turns of electrically conducting wire connected with terminals or electrodes.

It is important that the armature be attracted on the occurrence of an overload, in excess of the rated capacity for which the device is set, only in the event such overload is so excessive or so long continued as to cause damage. If, for instance, the overload is but momentary, it may be harmless it it does not exceed say ten times the rated capacity for which the device is set, but harmful if such an overload is long continued. If the overload exceeds s'ay ten times 5 the rated capacity for which the device is set, it may be harmful no matter how brief its duration.

The core member is normally so positioned in the tube as to leave an air gap in the magnetic l0 circuit within the coil between poles of the electromagnet. The reluctance of the magnetic circuit is so increased by the gap that a momentary flow'of current through the electromagnetic coil in excess of the rated capacity for which 15 the device is set, but less than say ten timessuch rated capacity, creates insufficient magnetic flux to operate the switch-controlling armature until the coreis moved into the magnetic circuit so as to bridge or decrease the air gap and decrease 20 the reluctance of the circuit. When the vcore is so positioned that it decreases or closes the air gap in the magnetic circuit within the coil between the pole pieces of the electromagnet, the magnetic flux or number of lines of magnetic 26 force resulting from the flow of a given current through the electromagnet windings is so increased that the switch operating armature may be actuated upon the flow of current slightly in excessisay, 125%) of the rated capacity for 30 which the device is set.

The windings of the electromagnet are so designed that; with the maximum reluctance of its magnetic circuit, there will be suflicient magnetic flux to attractthe armature and operate 35 the switch when the current is so much in excess of the rated capacity for which the device is set as to be dangerous to apparatus in the circuit, say in excess of ten times the rated capacity for which the device is set.

. Should the intended maximum rate of current consumption be exceeded for any. substantial time, even tothe extent of only 125%, the circuit is automatically broken. If the intended rate of consumption is exceeded only momen- 45 tarily, as for instance during the time required for heating lamp filaments or starting a motor, the circuit is not interrupted. If there is an accidental or intentional slight overload of undue duration, the magnetic flux will be increased by the closing of the air gap in the magnetic circuit, the armature will thereupon be attracted and the switch will be operated to open the circuit. If there is a heavy overload, the armature will be immediately attracted and the switch II operated to open the circuit regardless of the set-.

ting oi the device.

The characteristic features and improvements of my invention will further appear from the following description and the accompanying drawings bf an illustrative embodiment of my improvements.

In the drawings, Fig. 1 is a front elevation of a current limiter embodying my improvements; Fig. 2 is a front elevation of the same device with the cover removed from the Operating parts and the connections of the line and load terminals indicated in dotted lines; Fig. 3 is a fragmentary transverse sectional view taken longitudinally of Fig. 2 and Fig. 4 is an enlarged transverse sectional view through the electromagnet and its armature.

In the embodiment of my invention illustrated in the drawings, a cylindrical brass tube l is brazed or soldered to a magnetically permeable metal sheet 2 forming a pole piece. A magnetically permeable metal sheet 3 is secured on the tube l between its ends and has a flange 4 extending normally thereto in the direction of theaxis of the tube so as to form a pole piece complementary to and in the plane of the pole piece 2.

The pole piece 2 has the ears 5 bent therefrom or secured thereto and providing bearings for a shaft 6 on which is journalled the bearings 1 of a non-magnetic lever 8. The lever 8 is so bent as to form a bell crank having an arm 9 adjacent to the projecting boss I of a link II which forms with the link l2 a toggle through which the handle l3 operates and positions the switch arm l4 normally biased to open position by a spring IS.

The lever 8 has an armature I 9 fixed thereto by a screw 20, the armature being movable toward and from the end of the tube I. The lever and armature are normally biased away from the pole pieces 2 and 4 by the spring l6 wound on the shaft 8, such movement being limited by the stop I! fixed to the pole piece 4 and preferably of non-magnetic material.

The pole piece 2 has fixed thereto the nonmagnetic guide pin 2| which fits loosely within a hub 23 of the magnetically permeable core 24 and has coiled thereon an expansion spring 22 by which the core is biased away from the pole piece 2.

The core 24 contains an axial bore or passage 25 having in the one end thereof a hemispherical valve seat 26 with which coacts the ball valve 21 whose movement away from its seat is limited by the pin 28. The pin 28 limits the movement of the valve 21 without materially impeding the flow of fluid through the bore when the valve is unseated from the valve seat 26. The core 24 makes a slip fit with the tube, such fit being sufficiently loose to permit the slow seepage 01' oil or other fluid from one end to the other end of the chamber 29 within the tube when the core 24 is moved axially in the tube. The outer end of the tube is sealed by a cap 30, and the chamber 29 formed by the tube I, the pole piece 2, and the cap 30 is preferably liquid tight so that the devicemay be mounted in any desired position when-liquid is used as the retarding medium.

The tube I has wound thereon a number of turns of insulated wire forming a coil 3|, 3|.

A conductor 42 has its end connected with the switch terminal 45 adapted to be contacted by one leg 46, 01' a bifurcated switch blade 41 fixed to the switch member l4. The other leg 48 of the switch blade is adapted to contact with a terminal 49 connected with the line terminal 50. A

conductor is connected with the load terminal 52.

As the current flow increases, the magnetic flux created by the electromagnet causes the core 24 to move toward the pole 2, thereby decreasing the reluctance of the magnetic circuit. The rate of movement of the core 24 may be regulated by the viscosity of the fluid in the chamber 29. When a rapid movement of the core proportionately to the magnetic flux is desired, the fluid in the chamber 29 may be air, a gas or a, light liquid. When a slower movement of the core 24 is desired, a more viscous liquid, such as an oil, may be used in the chamber 29. If the potential 01 the current passing through the winding should' be greatly increased, as by a short circuit, the magnetic flux would be sufficiently great to attract the armature l9 and thereby cause the arm 9 to break the toggle and permit the opening of the switch 41. If the overload is insuflicient to immediately attract the armature 18, such overload will cause the core 24 to move gradually toward the pole 2 and shorten the air gap in the magnetic circuit, with a resulting increase in the magnetic flux. When the reluctance of the magnetic circuit has been so decreased that the magnetic flux attracts the armature IS, the arm 9 will break the toggle and permit the operation of theswitch.

It will, of course, be understood that the core 24 is moved by the spring 22 away from the pole piece 2 as soon as the circuit through the electromagnet is broken by the opening of the switch. The movement of the core 24 by the spring 22 imseats the ball 2'! from its seat and permits the substantially unimpeded flow of the retarding fluid in the tube I through the passage 25.

In each setting of the device, the magnetic flux created by a heavy overload will be sumcient to attract the armature l9 irrespective of the position of the core 24. As the core 24 moves horizontally in the tube I in any of the usual positions of the current limiter, its action is unaffected by the force of gravity.

By my improvements there is provided a switch-controlling mechanism comprising a conducting coil adapted to create a magnetic flux upon the passage, of current therethrough. A path for such magnetic flux is provided by a magnetically permeable member extending from one end of the coil externally thereof to a point adja cent to the other end of the coil and adjacent to a plate of magnetic material extending transversely to the axis of the coil so as to form a short air gap across which pass lines of force generated by current flowing through the coil. A pivotally mounted magnetically permeable armature swings toward and from such plate and member and bridges the air gap when it contacts with the plate and member, and the movement of such armature operates a switch-controlling device.

Having described my invention, I claim:

I. In a circuit breaker of the tripping toggle type, an electro-magnetic trip mechanism comprising a tube having an end closure of magnetizable material forming a pole piece, a magnetizable member between the ends of said tube and forming a second pole piece, an electro-magnetic coil wound .on said tube between said magnetiz able member and said end closure, a magnetizable core magnetically movable into engagement with said end closure and extending therefrom to said magnetizable member, and an armature magnetically movable into magnetically bridging contact with the said pole pieces to operate the tripping toggle.

2. In a circuit breaker of the tripping toggle type, an electro-magnetic trip mechanism comprising a tube having an end closure of magnetizable material forming a pole piece, a magnetizable member between the ends of said tube and forming a second pole piece, an electro-magnetic coil wound on said tube between said magnetizable member and said end closure, a magnetizable core magnetically movable into engagement with said end closure and extending therefrom to said magnetizable member, a spring movable telescopically to said core and biasing said core away from said end closure, and an armature magnetically movable into magnetically bridging contact with said pole pieces.

3. In a circuit breaker of the tripping toggle type, an electro-magnetic trip mechanism comprising a substantially L-shaped magnetizable bracket, a tube supported by one arm of said bracket and extending along the other arm of said bracket, an electro-magnetlc coil wound on said tube, a magnetizable bracket fixed to the free end of said tube, and a substantially L-shaped lever fulcrumed on said second bracket and including a magnetically operable member magnetically bridging the space between said first named bracket and second named bracket to operate said toggle.

4. In a circuit breaker of the tripping toggle type, an electro-magnetic tripping mechanism comprising a substantially L-shaped magnetizable bracket, a tube fixed to one arm and extending along the other arm of said bracket, a substantially L-shaped bracket fixed to the free end of said tube, a toggle-operating handle tulcrumed on one arm of said second bracket and a magnetically operable toggle actuating lever fulcrumed on the other arm of said second bracket.

KURT W. WILCKENS.

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