US2175039A

US2175039A - Transformer with a closed magnetic circuit

Info

Publication number: US2175039A
Authority: US
Inventors: Soulary Pierre
Original assignee: Air Liquide SA
Current assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 1935-10-25
Filing date: 1936-10-15
Publication date: 1939-10-03
Anticipated expiration: 1956-10-03
Also published as: BE418072A; GB474781A; NL45295C; FR817690A

Description

Oct. 3, 1939. P. sou;Y ARY TRANSFORIER WITH A CLOSED MAGNETIC CIRCUIT Filed 001;. 1955 2 Sheets-Sheet l MOVHLE CU/L STAND/WWP CO/L MOVIQHLE PP/MMV COIL Attorney Oct. 3, 1939. P. soULARY 2,175,039

TRNSFORIER WITH A CLOSED MAGNETIC CIRCUIT Filed Oct. l5, 1936 2 Sheets-Sheet 2 im 31k 56, MOI/AggL/ PRIN/)ky Inventor Attorney Patented Oct. 3, `1939 UNITED STATES PATENT OFFICE TRANS-FORMER WITH A CLOSED MAGNETIC CIRCUIT France Application October 15, 1936, Serial No. 105,769 In Germany October Z5, 1935 3 Claims.

The present invention relates to transformers with a closed magnetic circuit and a controllable magnetic leakage obtained by stepless displacing of one of the windings with respect to a stationary Winding. These transformers are used in the cases in which a reactive voltage drop is to be obtained, for instance in electric arc Welding or in resistance welding.

In electric arc Welding it is necessary that it o should be possible to make the intensity of the welding current to assume all values between the limit values which it is desired to have available according tothe nature of the metal and the bulk of the Work to be Welded, the diameter of the il Welding rods and the nature of their coating, etc. In the same way in resistance Welding the trans.. formers of this kind can be advantageously used as they permit the control of the welding current, particularly according to the thickness to the i nature of the metal of the work.

In the transformers of this kind heretofore manufactured, the windings of the primary and secondary circuits are wound around a closed magnetic circuit, of rectangular or annular shape s and their relativefposition is changed by displacing one of the windings with respect to the other, which is stationary. The rectangular construction requires a relatively large space in order to obtain all the desirable current ranges and D the annular construction in practice has the same drawback. Further the latter presents certain diiliculties in manufacture or requires the entirely curvilinear cutting of the sheets of the core, which increases the costI of manufacture and in-- 'i volves sheet wastes which are practically useless.

The transformers designed according to the present invention avoid all these drawbacks and in particular occupy a small space and are easy to manufacture. The transformer is characterized in that its closed magnetic circuit is constituted on one hand by an incurvated part, along `which the movable winding can be displaced, and, on the other hand, by one or more rectilinear parts, which bridgesor bridge-the ends of this incurvi ated part.

Preferably the incurvated part ofthe magnetic circuit is so shaped that it renders possible the displacement of the movable winding along an arc of a circle and for example along a half-circle i and the rectilinear parts are constituted by two parallel cores and by a yoke perpendicular to these cores. Y l

In order to obtain a predetermined range of controlled currents with the minimum expendin 5 ture of raw material it is advantageous to reduce (Cl. T11-119) the magnetic circuit.

The invention is illustrated by way of examples in in the accompanying drawings in which:

Figure l is a transformer intended for use in electric arc welding,

Figure 2 is a modied form with an incurvated core of progressively varying section,

Figure 3 is a transformer in which one of the circuits includes a stationary winding and a movable winding, connected in series,

Figure 4 shows a device which allows the movable winding to assume elastic displacements, and 2o Figure 5 shows a transformer for electric arc welding and resistance welding.

In the Figure 1 the magnetic circuit consists of a semi-circular part 'l and of two cores 4 and 8; a yoke 9 closes this magnetic circuit. The Wind- 5 ing which is stationary with respect to the magnetic circuit is shown at l and surrounds the core 4. It forms the secondary Winding of the transformer and is connected to the electrode 4 and to the workpiece 3. so

The second winding 5, which is therefore the primary winding, is connected to a network; it can rotate about an axis 6 and surrounds the semi-circular part 1 of the magnetic circuit. This axis can coincide, as in the case of the figure, with the centre of the semi-circular part of the magnetic circuit, or not. The winding 5 is so manufactured and disposed that, during its rotation, it can be displaced from a position of maximum coupling with the winding I to a position of minimum coupling. In Figure 1, the movable winding 5 is represented in full lines n its position of maximum coupling and in dotted lines inits position of minimum coupling. These two limit values of the coupling correspond to an angular displacement of of the movable winding.

Owing to this arrangement of the magnetic circuit a very, tight maximum coupling and a very loose minimum coupling are obtained and the space required is reduced. o

The transverse sections of the magnetic circuit s can be square or rectangular or present any shape ascertained as advantageous from the point of view of the utilization of the raw materials or oi the ease of manufacture. The area of these u sections he cons" vary in continuous dis l e.. particularly if it is o advantage to cre sones ci" a more or less high saturation. along the may netic circuit, in order to obtain modes ci distribution ci the values of the secondary cu:-

in relation with the angular displacemogt of movable wind igure 2 the magnetic circuit coy parallelopipedic yoke l@ and two cores l the transverse sectionsY of which are un tl e core having the grea'er section. c. curva-ted piece bridges the ends of ese cores and its transverse section is progressively im duced 'troni the transverse section oi? the core li transverse action or the core i3, rrhe sec-1 tion of ie il is crosseshaoed, vantageous connection v surface to he wound. The stationary ing situated at lll', around movable winding is shown at displacement of the movable winding in tion oi the arrow, the free space between and the movable winding pr gressiv creases, which'oers the advantage, as against a magnetic circuit with a constant section, that the current value changes less rapidly in the regions oi tight coupling and therefore in the range of the higher current intensities, and changes more rapidly in the range o the lower current intensities.

in the Figure 3, relating to a transiormer in which one of the circuits includes a winding a movable winding, connected series, the magnetic circuit is constituted by semi-circular yoke i6, two cores and and a rectilinear yoke lil. rThe primary is formed by two coils connected in series: the one No is sta ticnary and wound around the core il; the other 2l is movable and can rotate about the which, in this illustrated construction, coincides with the axis of the semi-circular part of the magnetic circuit. The secondary coil is shown at It is to be noted that the highest leakage e'ect, which is obtained when thetwo primary windings ill and 2l are in the nearest relative position, principally depends on the total nurnber oi the primary turns, whereas the lowest leali'.- age effect, which is obtained when the winding 2l is in its nearest position in relation to the stationary secondary winding, principally depends on the respective numbers of turns oi the windings 2li and 2l. t is therefore possible, by properly choosing these numbers of turns, to obtain the maximum and minimum desired values ci the secondary current and to simultaneously maintain an angular movement oi itil" o the movable winding, if this is deemed useful.

lllhis disposition Jfurther affords the advantage or" reducing the dimensions and the weight of the movable part and involves a better utilisation o the free space in the opening of the magnetic circuit.

The transformers according to the invention can be provided with windings having a number of taps to allow the obtaining of several ranges of control or several values oi no load voltage. lt is also possible to associate these transformers with other appliances such as reactance coils, capacities, resistances, or choke coils or three phase-single phase systems, current rectiiiers, etc. One can also use simultaneously several of these transformers to constitute polyphase systems, for example the three phase- ,Wo phase system for electric arc Welding,

the core l i, vthe Through the e direc is advantageous ior certain tions `oil these leakage tran rmers, to use a support o' the movable winding so constructed that under the inuence oi the electromagnetic repulsion, the movable winding assumes an elastic displacement in relation to its equilibrium position of no load. conditions, which permits the usc, during a very brief space oi' time when the output circuit is put under load, oi current higher than the current necessary when under load. For this purpose, the mecha nical device that connects the winding to the di ving axle can either be flexible in the direction of the angular displacements and assume elastic-deformations of position, or can be pro vided with a system articulations and springs, the latter being adj1 table if necessary. When the utilisation circuit is under load, the current intensity attains a predetermined value which corresponds to the equilibrium position ci no load conditions, then it progressively decreases until the winding assumes new equilibrium position., under the simultaneous influences of its ertia, of the electromagnetic repulsion, ci the elastic tension exerted on the support and evenu tually of gravity.

Figure e shows diagrammatically a device which allows the movable winding to assume elastic displacements in relation to its equilibrium position oi no load conditions. The support oi the winding movable along the magnetic ciru cuit is provided with a piece Eil, that rotates about the axle under the action o the driving means of this support, and with a piece 2 to w ich is fastened the movable winding and which. is articulated at on the piece lill. This piece "IC can rotate between two stops tu and Cil. i pri*- g Si? biases the piece 2d against the stop 35i; he tension oi this springis adjustable by dislacing in a slot 33 of the piece 26 the block. to which is attached an end o this spring. weight lil is fixed to the piece for increasing the inertia o the 'whole device which rotates about the axle 2d. when the utilisation circuit is put under load, the electromagnetic repulsion exerted on the coil dfi has the eirect oi causing it to rotate about this articulation in the direction indicated by the arrow. rlhe internal dimensions of the winding maires this displacement possible.

Transformers in which current circuits are provided for several purposes which involve different electric characteristics can also be constructed according to the invention. One and same transformer can for instance be constructed for clectric arc welding and for resistance Welding. One can, in this case, use windings with several taps, the sections of which, in their different parts, correspond to the required current intensities. One can also use several primary and secondary Windings, the movable parts of these windings being then preferably attached to the same support.

lin the Figure 5, relating to a transformer for electric arc Welding and resistance welding purposes, the apparatus is provided with a .single primary winding constituted by the stationary coil 35 and the movable coil 36, which are connected in series. rThe secondary Winding used for electric arc welding is illustrated in 31: it is wound on the core opposite the core on which the stationary primary winding is wound. A second secondary winding 38, independent of the 'lirst one, is wound concentrically with the winding 35. The number of its turns and their section cor respond to the voltages and current intensities involved in resistance welding.

1t is to be noted that this transformer functions for electric arc welding in an identical manner to the transformer illustrated in Figure 3. The minimum coupling corresponds to the position in which the two coils of the primary winding are nearest one to the other. On the other hand, in resistance welding, the maximum coupling and therefore the highest current intensity is obtained in the position where the two primary coils are nearest one to the other.

What I claim is:

1. In a closed magnetic circuit transformer, an incurvated core, two straight core legs in alignment with the end parts of' the incurvated core, a yoke bridging the ends of said core legs, a primary winding movable along said incurvated part, a first stationary winding mountedvaround one of the straight core legs and providing the secondary of an external utilisation circuit and a second stationary winding electrically independent from the rst stationarywinding, mounted around the second of the straight core legs and providing the secondary of a second external utilisation circuit.

2. A transformer of the character described, comprising a closed-magnetlc-circuit core having a semi-circular portion, straight core extensions projecting contiguous with the opposite ends of said semi-circular portion, a yoke bridging the free ends of said core extensions, a stationary coil mounted upon one of said core extensions and a movable coill displaceable arcuately on said semicircular portion about an axis corresponding substantially to the radial center of said semiable coil being disposed around said semi-circular core portion and movable through a full 180 arc, whereby said movable coil can be closely coupled to either of said stationary coils.

PIERRE SOULARY.