US 2548179 A
Description (OCR text may contain errors)
April 10, 1951 o. J. UNDERWOOD TRANSFORMER Filed June 1, 1948 //70N WI FE fifCO/VD/IF Y WINDING COPPER Wl/PE FINN/71?) WINDING d n e/K (Ittorneg Patented Apr. 10, 1951 TRANSFORIHER Orville J. Underwood, Minneapolis, Minn., as-
signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application June 1, 1948, Serial No. 30,347
5 Claims. 1
My invention relates to transformers of the leakage type. Transformers of this type generally require a special core lamination in which provision is made for a leakage flux path. These leakage flux paths are generally made of a higher reluctance material than the core structure or if the same type of magnetic material is used an air gap is provided to vary the reluctance through the leakage path. Difiiculty arises in the manufacture of such a core structure when difierent materials are used for the magnetic core structure, or if an air gap is required, there is difiiculty in the assembly of the core structure to maintain the minimum required air gap.
The present invention is directed to a leakage type transformer in which a conventional transformer lamination is used without provision for a leakage path, that feature being provided for in the secondary winding of the transformer.
It is therefore an object of this invention to provide an improved transformer of the leakage type.
It is also an object of this invention to provide a leakage type transformer in which the secondary winding is made of an electrical conductive and magnetic material which will form a leakage path for the transformer as well as provide for an electrical circuit for the current induced therein.
It is a further object of this invention to provide a leakage type transformer which employs a conventional transformer lamination, there being no required leakage path therein.
Another object of this invention is to provide a leakage type transformer which is simple to manufacture, and is easily assembled at a reduced cost.
These and other objects of this invention will become apparent with the reading of the accompanying specification and drawings wherein:
Figure l is side elevation view of the transformer with parts broken away, and
Figure 2 is a plan view of the transformer with parts broken away.
The present transformer includes a magnetic core structure generally indicated at which is composed of a stack of thin laminations of magnetic material, such as soft iron. Each of the laminations II is rectangular in shape having an opening 12 therein wherein the primary windin 13 and the secondary winding [4 are positioned. Two of the surfaces on the opening of the rectangular lamination have semicircular notches l punched therein. The core structure I 0 further includes a rectangular shaped cross (Cl. I'll-242% member or le 16 whose extremities are rounded or semicircular to fit in the semicircular notches I5 in the outer rectangular shaped core lamination II. The centrally disposed cross leg is also a laminated structure and serves to mount the primary winding [3 and secondary winding M in a conventional manner.
The core structure I0 is formed by stacking the rectangular shaped outer laminations II and the inner cross leg laminations It in a manner which can best be seen in Figure 2, the laminations being held together by rivets ll or any other suitable fastening means. The rivets I! extend through a cylindrical bore or aperture I8 positioned at a point where the semicircular ends of the centrally disposed member l6 fits into the semicircular notches is of the outer rectangular core lamination H. The heads of the rivets I! are flattened out to extend over both portions of the laminations of the core structure l0 and thereby securely hold or form the laminations into a solid core structure.
. Prior to the assembly of the core structure ID, the centrally disposed laminations l5 are formed in a stack and the primary winding [3 which is wound on an insulating spool 20 is mounted on the stack. Primary winding I3 is formed of any conventional electrically conductive material, such as copper. The secondary winding I4 is similarly wound on an insulating spool 2i and is formed of a magnetic material, preferably iron which is also a good electrically conductive material. The secondary winding is also positioned on the stack of laminations forming the cross leg [6 and is positioned abutting or in near abutting relationship to the primary winding l3. The material and number of turns on the primary winding, as well as the number of turns on the secondary winding, are so chosen that the diameter of each of the primary c-oil i3 and secondary coil I4 will be such that they will fit into the aperture [2 in the core structure I0.
It will be noted that there is no provision in the core structure Ill for a leakage path. However, the secondary winding, when formed of a magnetic material, provides such a leakage path from the centrally disposed leg [6 to the outer core laminations I I. Because there is certain spacing or air gap between each turn of iron Wire on the secondary winding due to winding tolerances and further because each turn of wire has a certain amount of insulation thereon, the required air gap or section of higher reluctance in the leakage path is thereby obtained to give a leakage path of higher reluctance than the normal flux path for the core structure I. The secondary winding must be so shaped that it substantially fills the opening l2 in the outer core laminations H so that no further air gap will be present between the iron wires and the magnetic core laminations H of the core structure. The insulating bobbin 2| for the secondary winding 14 is also so chosen that a minimum of air gap is present between the iron wire turns on the secondary winding l4 and the laminated centrally disposed leg 16.
In the present leakage transformer design, the requirements for the special leakage path in the laminated structure is eliminated and the tolerances in assembly of the laminations to insure a minimum air gap in the leakage. path. is further.
eliminated. The present transformer operates as a conventional leakage type transformer, the leakage flux traversing the magnetic path of the secondary winding in such a manner that .it-will not thread both windings equally. This leakage flux is composed of the main energizing flux creamed by the energized primary winding and-the counter flux createdby the induced current in the secondary winding. By providing the secondary winding with iron wire, a wire of a magnetic material, as well as electrically conductive material, a flux path for this counter flux between the main leg of the core and the outer portion of the frame is obtained. This reduces the affect of the counter flux on the primary winding, thereby reducing the current flow in the primary winding and eliminating the necessity of a leakage path integral with the laminated core structure.
In-considering this invention it should be kept in mind that the present disclosure is intended to be illustrative only and that changes may be made in the types, of materials and the form of the core structure. The scope of the invention should be determined 1 only by the appended claims.
I claim as my invention:
1. A leakage transformer. having a continuous magnetic circuit with a primary winding and a secondary winding in inductive relationship mounted thereon, said secondary winding being made of a magnetic material to shunt a portion of said ..continuous magneticcircuit and provide a path for the leakage flux such that. it does not equally thread bothof said windings.
L12. leakage transformer having a continuous core member of magnetic material including a centrally disposed leg, a primary winding and a secondary winding positioned on said leg in inductive relationship thereto, said secondary winding being made of a magnetic material to provide a leakage flux path from said centrally disposed legto said continuous core member.
3. A leakage type transformer having a continuou magnetic circuit and including a secondary winding made of a magnetic material and conductively independent of a primary winding which provides a magnetic path through said secondary winding to'said continuous magnetic circuit and independent of said primary winding.
4. A transformer comprising a continuous core member of. laminated magnetic material, a primary energizingwinding on said core member, a secondary winding of magnetic and electrically conductive material on said core member and conductively independent of said primary winding and said core'member, said secondary winding being disposedrelative tosaid primary winding and said coreto provide a magnetic shunt path around said primary winding.- 7
5; A transformer comprising a magnetic core continuous in form with a centrally disposed leg of magnetic:material, a primary winding positioned'onsaidcentrally disposed leg, a secondary winding positioned on said centrally disposedleg adjacent to said primary winding, said secondary winding being made Of a magneticmaterial and being conductively independent of said primary winding. g I
ORVILLE J UNDERWOOD.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS