US1979769A

US1979769A - Constant current transformer

Info

Publication number: US1979769A
Application number: US711413A
Authority: US
Inventors: Pfeil Arthur
Original assignee: RED ARROW ELECTRIC CORP
Current assignee: RED ARROW ELECTRIC Corp
Priority date: 1934-02-15
Filing date: 1934-02-15
Publication date: 1934-11-06
Anticipated expiration: 1951-11-06

Description

Nov. 6, 1934. A. PFEIL 1,979,763

CONSTANT-CURRENT TRANSFORMER Filed Feb. 15, 1934 2 SheetsSheet l JECOIVIIIF) Nov. 6; 1934. A. PFEIL. 1,979,769 I CONSTANT CURRENT TRANSFORMER FiledFeb. 15, 1954 2 Sheets-Sheet 2 FRI/WAR! gwumvbo r/ Patented Nov. 6, 1934 UNITED STATES PATENT OFFICE CONSTANT CURRENT TRAN SFORMIER Application February 15, 1934, Serial No. 711,413

' 7 Claims. (Cl. 171-119) This invention relates to improvements in electric transformers, preferably of the constant current type adapted for use in connection with the illumination of neon or other gaseous lighting tubes or other installations wherever a constant current type of transformer may be suitable.

An important object of my invention comprises providing a transformer of improved conw struction for use in energizing gaseous discharge tubes for illumination, advertising, and other purposes whereby maximum brilliancy and uniform operation of such devices is attained.

Another object of my invention is to provide a transformer in which the primary and secondary coils may be closely coupled so as to attain the necessary high efiiciency for building up the initial high voltage in the secondary coil necessary for starting such gaseous discharge 26* devices. To this end it is one of the objects of my invention to provide an improved arrangement by which an external magnetic shunt return path, by-passing the secondary coils, may be provided without the necessity for interposing the members of such shunt return path between the primary and secondary coils and internally with respect to the transformer core in order that the transformer core may be designed as above noted to permit close coupling of the primary and secondary coils and to have an efficient and effective shape.

The present invention further provides a better distribution and better balancing of the magnetic flux density, particularly in the secondary and a better uniformity in the secondary output.

With the foregoing and other objects in view, the invention consists of a novel construction, combination and arrangement of parts as will be hereinafter more specifically described and illustrated in the accompanying drawings, wherein is disclosed an embodiment of the invention, but it is to be understood that changes, variations, and modifications may be resorted to without departing from the spirit of the claims hereto appended.

In the accompanying drawings forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same:

Figure 1 is a top plan view of a transformer embodying the invention.

Fig. 2 is a side elevational view of the same.

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 1.

5 Fig. 4 is an end view of the transformer.

Fig. 5 is a modification of the invention showing the core with two legs.

Fig. 6 is another form of the invention showing the core with three legs.

In the drawings, especially Figs. 1, 2, 3, and 4, wherein for the purpose of illustration is shown a preferred embodiment of my invention, 7 desighates a transformer core having three legs, a center leg 9 and

outer legs

8 and 10, respectively- Encircling the core cross-wise or at right angles to the plane of the longitudinal dimension thereof is a magnetic shunt path 11 including

magnetic gaps

12 and 13 on opposite sides of the transformer core member 7. The primary coil 14 is mounted on the center leg 9 of the core member 7 and balanced

secondary coils

15 and 16 are mounted on

outer legs

8 and 10, respectively, of the core member 7. The shunt path 11 is as shown in the Figs. preferably designed to have a cross-sectional area not greater than the yoke and secondary legs of the transformer core. In the arrangement shown an all metal magnetic return path is provided for the magnetic flux threading the primary coil 14 and the sec- 30

ondary coils

15 and 16, such return path being in the form of core member 7.

Fig. 5 shows a modification with a single secondary coil 17 encircling leg 18 and a primary coil 19 encircling leg 20. The two legs 18 and 35 20 are connected by yoke portions 21 and 22 to form the complete core of the transformer. Encircling the core of the transformer is a magnetic shunt 23 so positioned with respect to the transformer core as to provide magnetic gaps 24 9i) and 25 between the shunt and the transformer core as shown.' The magnetic shunt as shown preferably encircles the major portion of the transformer core in the plane of the longitudinal dimension of the core in order to eliminate effectively and efficiently stray fields from the transformer core.

In Fig. 6 is shown another form of modification with the shunt path 11 completelyencircling the core 7 in a plane substantially co-incident with the plane of the longitudinal dimension of the transformer core, instead of cross-wise or at right angles thereto as is shown in Fig. 1.

In the use of my improved transformer the current delivered by the secondary coils is arbitrarily limited, being controlled by a regulation of the size of the air gaps between the shunt and core. Preferably the regulation of the size of these air gaps is accomplished by the insertion of brass shims. These shims may be of fiber,

wood or other non-magnetic material or the transformer core and magnetic shunt may be positioned in a container as is usual and the container filled with wax which upon hardening maintains their relative positions. As an impulse of alternating current builds up in the primary coil with the secondary coils connected to a load such as a gaseous discharge tube an induced current is at the same time built up in the secondary coils, my arrangement being very effective for building up such induced current with the high voltage necessary to start the operation of suchgaseous discharge tube because of the close coupling of the secondary coils with the primary coil. This induced current develops a counter magnetic flux pressure resisting the flow of the magnetic flux through the

core members

8, 9 and 10 which soon reaches such proportions as to equal the brake-down resistance of the air gaps with respect to the flow of magnetic flux thereacross in the shunt return paths. As soon as the air gap resistance has been broken down, a greatly increased flow of magnetic flux through the shunt path takes place, serving to by-pass the primary flux from the secondary coils, with the result that there is a sharp drop in the voltage of the induced current flowing through the secondary coils to a normal operating value. This serves also to limit the current flowing through the secondary coils, the maximum current permitted to flow through these coils being that required for establishing the leakage flow of magnetic flux through the shunt paths and across the air gaps. As the magnetic shunt path of my invention extends externally substantially around the core of the transformer as shown in the figures, the shunt operates eflectively to constrain the magnetic flux and .prevent stray fields which ordinarily occur causing heating of the metal container used with such transformers and further undesirable disturbances in the operation of electrical apparatus adjacent to the transformer such as radio receivers. The present embodiment of my invention has been disclosed in considerable detail and in several types merely for the purpose of exemplifies.- tion since in actual practice it attains the features of advantage enumerated as desirable in the statement of the invention and the above description.

It is to be understood that by describing in detail herein any particular form, structure, or arrangement, it is not intended to limit the invention beyond the terms of the several claims or the requirements of the prior art.

Having thus described my invention, what I claim as new is:

1. A constant current transformer comprising, a core member of magnetic material formed to have coil supportinglegs joined by an unbroken yoke, a primary coil on one of said legs, a sec- 1 ondary coil on another of said legs, and a shunt path of magnetic the major portion of said core member and spaced of the flux generated by therefrom to provide air gaps between said core member and said shunt for by-passing a portion said primary coil from said secondary coil.

material externally encircling with a center leg and a plurality of outer legs, a primary coil mounted on said center leg, a secondary coil mounted on each of said outer legs, and a shunt path of magnetic material externally encircling said core member in a plane substantially co-incident with the plane of the longitudinal dimension of said core member and spaced therefrom to provide air gaps between said core member and said shunt for shunting a portion of the flux generated by said primary coil from said secondary coils.

3. A constant current transformer comprising, a core member of magnetic material provided with a center leg and a plurality of outer legs, a primary coil ,mounted on said center leg, a secondary coil mounted on each of said outer legs and a closed shunt path of magnetic material externally encircling said core member and spaced therefrom to provide air gaps between said core member and said shunt for shunting a portion of the flux generated by said primary coil from said secondary coils.

4. A constant current transformer comprising, a core member of magnetic material provided with a center leg and aplurality of outer legs, a primary coil mounted on said center leg, a secondary coil mounted oneach of said outer legs and a closed shunt path of magnetic material encircling said core member in a plane perpendicular to the plane of the longitudinal dimension of said core member and spaced therefrom to provide air gaps between said core member and said shunt for'shunting a portion of the flux'generated by said primary coil from said secondary coils.

5. A constant current transformer comprising, a core member of magnetic material provided with a center leg and a plurality of outer legs, a primary coil mounted on said center leg, a secondary coil mounted on each of said outer legs and a closed magnetic shunt of cross-sectional area throughout not greater than the cross-sectional area of either of said outer legs encircling said core member and spaced therefrom to provide air gaps between said core member and said shunt for shunting a portion of the flux generated by said primary coil from said secondary coils.

6. A constant current transformercomprising, a core of magnetic material formed to have coil supporting legs joined by a yoke, a primary coil on one of said legs, at least one secondary coil on another of said legs, and a shunt pathof magnetic material externally substantially encircling said core and spaced therefrom to provide air gaps between said core and passing a portion of the flux generated by said primary coil.

7. A constant current transformer comprising a core of magnetic material formed to have coil supporting legs joined by a yoke, said yoke and legs having a definite cross-sectional area, a primary coil on one of said legs, at least one secondary coil on another of said legs and a shunt path of magnetic material having a cross-sectional area not greater than that of said yoke 1A and legs encircling a major portion of said core and spaced therefrom to provide air gaps between said core and said shunt for by-passing a portion of flux generated by said p ry coil.

ARTHUR PFEIL. 1

said shunt for by- 13