US2555911A

US2555911A - Variable reactance transformer

Info

Publication number: US2555911A
Application number: US109738A
Authority: US
Inventors: James A Anderson
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-08-11
Filing date: 1949-08-11
Publication date: 1951-06-05
Anticipated expiration: 1968-06-05

Description

June 5, 1951 R J. A. ANDERSON 2,555,911

5 VARIABLE REACTANCE TRANSFORMER Filed Aug. 11, 1949 Fig. 2.

James A. Anderson INVENTOR.

BY MMF% I Patented June 5, 1951 UNITED STATES PATENT ()FFICE VARIABLE REACTANCE TRANSFORMER James A. Anderson, Memphis, Tenn.

Application August 11, 1949, Serial No. 109,738

Claims.

This invention relates to transformers provided with a control of the voltage ratio between the primary and the secondary of the transformer and it has for its general object to provide a variable reactance transformer of a simple and efficient type which is adjustable over a wide range of variation and which is usable in connection with high amperage currents, such as used for welding equipment or for other equipment supplying circuits with heavy and variable loads.

It is a further object of the invention to provide a variable reactance transformer in which the reactance component of the transformer is adjustable at a uniform rate by means of a leakage path which is in parallel to but does not include the cores of the secondary or primary coils of the transformer.

It is a further object of the invention to provide a variable reactance transformer of the above mentioned type in which the variation of the induction in the secondary coil is produced by a closed transformer frame connectible with a leakage path of variable magnetic reluctance which may be finely adjusted at a uniform rate by means of members which are in contact with the closed transformer frame over variable cross sections.

It is a further object of the invention to provide a variable reactance transformer of the above mentioned type in which a leakage path of variable magnetic reluctance is produced by means of a member which is in slidable contact with the two sides of a closed transformer frame, the area of contacts between the leakage path member and the transformer being made adjustable by a relative displacement of the aforesaid members.

It is a further object of the invention to provide a variable reactance transformer of the above mentioned type in which a leakage path of variable magnetic reluctance is formed by means of a secondary core or leakage path member which is movable relatively to the closed transformer frame containing cores for the primary and'secondary coils and which is adapted to divert a portion of the magnetic flux generated in the primary coil through contact surfaces of variable extension and through air gaps of variable width.

A further object of the invention consists in providing a variable reactance transformer of the above mentioned type which is of simple and efficient construction and in which an adjustable member providing a leakage path of variable magnetic reluctance is movably mounted on the transformer frame and is moved towards and away from said frame by simple mechanical means, such as a threaded spindle, said member being in permanent sliding contact with the transformer frame during such adjustment during which the magnetic reluctance of the leakage path is changed by air gaps of variable width and by the change of the extension of the contact surfaces through which the magnetic flux passes from the transformer to the adjustable member, the permanent contact between the transformer and said member during the change of the width of the gaps preventing the appearance of a vibration due to strong magnetic forces acting across the gap.

Further and more specific objects of the in vention will be apparent from the following detailed specification.

The invention is illustrated in the accompanying drawing showing one embodiment thereof by way of example. It is however to be understood that the example shown has been selected in order to explain the principle of the invention and the best mode of applying said principle. Other modes of applying the principle will be obvious to persons skilled in this art. It will therefore be clear that modifications of the example shown in the drawing are not necessarily departures from the essence of the invention.

In the drawing:

Figure 1 is a diagrammatic elevational view of a transformer according to the invention.

Figure 2 is a diagram showing the two main parts of the arrangement in an extreme position.

For welding transformers and for similar transformers carrying heavy load currents and requiring an adjustable voltage and a high reactance in the load circuit variable transformers.

have been proposed regulating the voltage in the secondary or load circuit by adjusting the transformer reactance. Such variable reactance transformers may be considered as a combination between a transformer and a reactor and the reactor part of the transformer with one type of transformer consists in a magnetic path of variable reluctance arranged in parallel to the main magnetic path passing through the primary and secondary coil of the transformer. This parallel path usually includes a magnetic core located in the interior of the secondary coil. The variable reluctance of the magnetic path is customarily obtained by inserting into the same an air gap of adjustable width, this gap being pref-- erably located in the magnetic core inside the secondary coil. This construction has been widely used in connection with transformers the reactance of which is only adjusted occasionally to suit certain permanently prevailing conditions. However this construction is much less suitable for equipment which has to be adjusted during operation. The reason why this construction could not be adapted in a satisfactory manner to variable reactance transformers in which frequent adjustments are to be made during operation resides in difficulties connected with the adjustable air gap the movable member of which, under the heavy magnetic forces produced in connection with heavy amperages, could not be protected against vibrations which lead to noise and to an early destruction of the movable member and of the gap adjustment mechanism.

According to the present invention the difliculties connected with this earlier construction are overcome by the special construction of the transformer. The main characteristic features of the construction according to the invention consists in the use of a magnetic shunt circuit or leakage path to be used in connection with a closed transformer frame, which does not include a core of the primary or secondary coil but which is established solely between the yokes joining the cores of the primary and secondary and adjacent portions and, further, in a special shunt circuit member which is provided with tapering leg members, adapted to slide along the yokes and to con tact them to a variable extent, said member being further provided with shoulders adapted to be brought into contact with and to be removed from the yoke portion of the transformer frame.

The magnetic flux through the leakage path is therefore finely regulable by adjusting the pos'ition of the shunt circuit member and, as part of the said magnetic fiux always passes through surfaces which are in direct contact with each other, the difficulties resulting from the mounting of adjustable members under a heavy variable magnetic stress are avoided. Moreover the structure is greatly simplified as the closed transformer frame is not only the basic structure from which the magnetic flux branches off and is shifted to a secondary path but serves also as a mechanical guide and holder for said branch or leakage path members.

As seen from the figures the adjustable transformer, generally indicated at 5, comprises a closed transformer core or frame 5 consisting of two cores 1, 8 and two yokes 9J9 joining them and forming a closed frame in the well known manner. This structure may be laminated as usual.

The cores and 8 carry the primary coil Hi and the secondary coil l l respectively. The coils are only indicated diagrammatically in the figures but are much larger than indicated in the drawings.

Cooperating with the main transformer structure is the movable secondary or leakage path member l2 which is so arranged that it bridges or shunts the frame 6.

The secondary member which forms a magnetic leakage path essentially consists of an auxiliary core or bridge piece l5, provided with two legs l6, l8 projecting at right angles from the said auxiliary core or bridge piece, which legs are so spaced that their inner surfaces are arranged at a distance which is equal to the distance between the outer surfaces of the yokes 9 and I9. Therefore, said inner surfaces are adapted to slide along the outer surfaces the yoke members 3 and IQ of the transformer frame 6.

The legs [6, l8 have ends 20 tapering off in one direction in such a manner that the cross section of the leg member which, in those portions which are close to the auxiliary core or bridge piece [5 is substantially equal to the cross section of said piece, slowly decreases in said end piece so that.

the ends are approximately linear.

At the junction of the auxiliary core or bridge piece [5 of the leakage path member l2 and the leg members l6, l8 shoulders 2|, 22 are provided with flux carrying surfaces at right angles to the inner surface of the leg members and parallel to the outer surface of the core 7 of the transformer frame 6. These shoulders may be applied against the frame 6 on both sides of the primary coil I0 Which'fits into the space between the two shoulders 2|, 22 when the shunt member [2 is in its extreme position in which there is full contact with the frame 6. When said leakage path member [2 has been moved to this extreme position in which contacts between the frame 6 and the member I 2 has been established to the fullest possible extent a portion of the magnetic flux which has been produced in the core 1 by the primary coil IQ of the transformer and which would otherwise pass through core 8 and yokes 9, I9 is deflected to the leakage path around the core l formed by the member 22 which is now in contact with it along the shoulders 2|, 22 and along the inner sides of the end portion 20 of the legs I6, It.

In order to adjust the leakage path member l2 the transformer frame carries bars 2d, 25 which are riveted or bolted or otherwise secured to the frame 6 and which are joined by a cross piece 26. The cross pieces carries a spindle 30 provided with screw threads which is rotatably mounted within said cross piece in any suitable manner. The spindle is provided with a crank 21 from which a handle 28 projects. The spindle passes through a bore 3| in the member l2, which member also carries a sleeve 29 provided with inner screw threads engaging the screw threads of the spindle 30.

It will thus be clear that a movement of the crank 21' entailing a movement of the spindle 30 will produce a movement of the leakage path member l2 towards and away from the frame 6 according to the direction in which the spindle has been rotated. Each such movement either increases or decreases the extent to which the surfaces of the leg members l6, H3 are in contact with the yokes 9, H3. Likewise, the distance between the shoulders 2 I, 22 and the sides of the yokes of frame 6 is increased or decreased with the movement of the spindle. Obviously the magnetic flux through the leakage path decreases when the member I 2 is moved away from the frame 5. When full contact has been made along the entire inner surface of the leg members and along their adjoining surfaces of the shoulders 2 I, 22 a considerable portion of the magnetic flux produced in the core i will pass through the leakage member [2 thus influencing the inductive transmission from the primary coil to the secondary coil l l, as the magnetic flux generated by the primary coil in the core 1 will be practically divided into two paths which may or may If the leakage path member I2 is gradually moved away from the transformer frame 6 the surfaces through which the leakage path. is closed decrease gradually and the resistance of the gap between the

shoulders

21, 22 and the frame 6 increases. Thereby the distribution of the magnetic flux over the two paths is changed and the reluctance in the shunt or leakage path circuit is increased. As a consequence the magnetic flux which passes to the secondary core increases and the voltage in the load circuit increases proportionately.

It is seen that the above described construction disposes of many of the disadvantages which are inherent in the customary constructions using adjustable leakage paths. The member l2 which forms the leakage path is always firmly held not only by the screw but by the magnetic forces themselves so that these forces assist in producing a stable construction and cannot pr duce vibrations. The air gaps which are used are auxiliary gaps and therefore do not interfere with the operation or cause vibrations as in the customary constructions. It will also be observed that there is always a direct contact between the yokes 9, I9 and the legs l6, 18 through which the magnetic flux may pass while the gaps are widening. In the extreme position shown in Figure 2 in which the legs only touch the transformer frame 6 with their extreme linear ends, the gap between the shoulders and the transformer frame has become so wide that no vibration can be produced. Moreover the member I2 is guided and held by the frame 6 and by the magnetic forces which have to be overcome during adjustment and these forces increase and decrease so gradually during an adjustment that the adjusting operation can be carried out without difficulty.

It will be clear that changes of an unessential nature which are made in the construction shown in the drawing will not affect the essence of the invention.

Having described the claimed as new is:

1. A variable reactance transformer, comprising a closed transformer frame including cores and yokes joining said cores, a primary and a secondary coil mounted on said cores, a movable member including an adjustable auxiliary core piece adapted to form a magnetic shunt provided with contact surfaces sliding on said closed transformer frame on both sides of the aforesaid coils to a variable extent and means for adjusting the area of contact of the contact surfaces of the said movable magnetic shunt memher with the closed transformer frame.

2. A variable reactance transformer, comprising a closed transformer frame including cores and yokes joining said cores, a primary and a secondary coil mounted on said cores, a movable leakage path member including an auxiliary core piece arranged in substantial parallelism with the cores of the closed transformer frame and provided with leg members provided with inner contact surfaces in sliding contact with the yokes of the transformer frame at opposite sides thereof, and means for adjusting the position of said movable leakage path member with respect to the transformer frame.

invention, what is 3. A variable reactance transformer, comprising a closed transformer frame including cores and yokes joining said cores, a primary and a secondary coil mounted on said cores, a movable leakage path member, including an auxiliary core piece, arranged in substantial parallelism with the cores of the closed transformer frame and provided with leg members projecting at right angles to the said core piece from the same, said leg members having tapering ends and inner sliding contact surfaces in contact with the yokes of the transformer frame at opposite sides thereof and means for adjusting the position of the said movable leakage path member with respect to the transformer frame, thus varying the length of the contact surfaces on the legs in contact with the said frame.

4. A variable reactance transformer, comprising a closed transformer frame including cores and yokes joining said cores, a primary and a secondary coil mounted on said cores, a movable leakage path member including an auxiliary core piece, arranged in substantial parallelism with the cores of the closed transformer frame and provided with leg members projecting at right angles to the said core piece from the same, shoulder pieces arranged at the junction of the leg members with the core, said leg members having tapering ends and inner contact surfaces in sliding contact with the yokes of the transformer frame and said shoulder pieces having surfaces adapted to be applied against the transformer frame on opposite sides of a coil carried by the core of the frame, and means for adjusting the position of the said movable leakage path member with respect to the transformer core, thus varying the length of the contact surfaces in active contact with the transformer frame and the gaps between said shoulder pieces and the said frame.

5. A variable reactance transformer, comprising a closed transformer frame including cores and yokes joining said cores, a primary and a secondary coil mounted on said cores, an auxiliary core piece for establishing a leakage path around the cores of the transformer frame, means carried by said auxiliary core piece for maintaining active magnetic contact of said core piece with two sides of the transformer frame along contact surfaces, further means carried by the said auxiliary core piece to produce an air gap traversed by the magnetic flux between said transformer core and said auxiliary core, and means for varying the area of the contact surface while simultaneously varying the width of the air gaps traversed by the magnetic flux.

JAMES A. ANDERSON.

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

UNITED STATES PATENTS Number Name Date 2,206,856 Shearer July 2, 1940 2,437,021 Fries Mar. 2, 1948 FOREIGN PATENTS Number Country Date 693,943 France Nov. 26, 1930