Method of Reducing Leakage Magnetic Flux for a Shell-type transformer or Inductor

Abstract

A Method of reducing leakage magnetic flux for a shell-type transformer or inductor is disclosed. The magnetic flux density is reduced between flux transitional areas and corner losses are reduced.

Advantageous, the method may also help to reduce the operational temperature of the transformer or inductor (of any size) during normal use. The centre of the ferromagnetic core is cooled. The effective outside area of the core is enlarged. The transformer core is organized to have any number of cooling holes (400.3.1), (400.3.2) without reducing the area for magnetic flux to circulate around the core. Several embodiments are disclosed. Various improvements may be made without departing from the methods and principals disclosed in this patent.

Claims

1) An electric apparatus, comprising: a core (FIG. 2, 200.1), said core constructed from ferromagnetic laminated plates, said core organized to form a closed or substantially closed magnetic circuit, said core organised to have a centre limb (FIG. 2, 200.1.1) and side limbs (FIG. 2, 200.1.2, 200.1.3), one or more electromagnetic coils (FIG. 2, 200.2) organized to encircle said centre limb, said core further organized to have any number of slits (FIG. 2, 200.3; FIG. 3, 300.3) or similar inside the side limbs of said core, said slits organized to have any convenient size, said slits organized to allow air or oil or similar to flow through said slits, said slits further organized to increase the average ferromagnetic path-length, in all laminated plates, during normal operation.

2) An electric apparatus, comprising: a core, said core constructed from E and I type of ferromagnetic laminated plates, the side limbs of said E type of ferromagnetic laminated plates organized to have any number of slits or similar, one or more electromagnetic coils organized to encircle the centre limb of said core, said core further organized to form a closed or substantially closed magnetic circuit, where flux transitional areas between the side limbs of said E type of ferromagnetic laminated plates (700.1.1) of said core and said I type of ferromagnetic laminated plates (700.1.2) of said core are organized to cause a reduction in the magnetic flux density, during normal operation, where said flux is generated by at least one of said electromagnetic coil(s).

3) The core of an electric apparatus, said core constructed from ferromagnetic laminated plates, said core organized to form a closed or substantially closed magnetic circuit, said core organized to have a centre limb and side limbs, said side limbs organised to have any number of slits, the end-sections of said slits (FIG. 3, 300.3; FIG. 5 500.3.1, 500.3.2) organized to be substantially rounded.

4) The core of an electric apparatus, said core constructed from ferromagnetic un-laminated sections, said core organized to form a closed or substantially closed magnetic circuit, said core organized to have a centre limb and side limbs, said side limbs organised to have any number of slits, the end-sections of said slits (FIG. 3, 300.3) organized to be substantially rounded.

5) A process of altering the mechanical impulse transient response of an electric apparatus, during normal operation, via slits or similar, the process including, organizing said electric apparatus to have a ferromagnetic core (FIG. 2, 200.1) constructed from laminated plates, said core organized to form a closed or substantially closed magnetic circuit, said core organized to have a centre limb (FIG. 2, 200.1.1) and side limbs, said core further organized to have any number of slits (FIG. 2, 200.3; FIG. 3, 300.3) or similar inside the side limbs (FIG. 2, 200.1.2, 200.1.3) of said core, one or more electromagnetic coils organized to encircle said centre limb.

6) A transformer bank, constructed from three shell-type transformers, where each of said shell-type transformer comprise: a core (FIG. 2, 200.1), said core constructed from ferromagnetic laminated plates, one or more electromagnetic coils (FIG. 2, 200.2) organized to encircle a centre limb (FIG. 2, 200.1.1) of said core, said core further organized to have any number of slits (FIG. 2, 200.3; FIG. 3, 300.3) or similar inside the side limbs (FIG. 2, 200.1.2, 200.1.3) of said core, said slits organized to have any convenient size, said slits organized to allow air or oil or similar to flow through said slits, said slits further organized to increase the average ferromagnetic path-length, in all laminated plates, during normal operation.

7) The ferromagnetic core of an electric apparatus, said core organized to have a centre limb and two side limbs, said core further organized to have any number of slits (FIG. 3, 300.3) or similar of any convenient size inside the side limbs of said core, said core constructed from laminated E (FIG. 3, 300.1.1) and laminated I (FIG. 3, 300.1.2) type of laminations.

8) Any intermediate component or sub-component of the core of an electric apparatus, where said electric apparatus is organized to function as either a shell-type transformer or as a shell-type inductor, organized in accordance with claim 7.

9) A shell-type transformer with magnetic shunts (FIG. 5, 500.4.1, 500.4.2) organized in accordance with claim 1.

10) A shell-type transformer with magnetic shunts, organized to function as a ferroresonant transformer, organized in accordance with claim 3.

Description

[0181] The invention will now be further described, by way of example, with reference to the following diagrammatic drawings.

[0182] FIG. 1 shows a schematic diagram of a previous art shell-type transformer.

[0183] FIG. 2 shows a schematic diagram of one possible embodiment of a single-phase shell-type transformer, in accordance with the invention.

[0184] FIG. 3 shows a schematic diagram of one possible embodiment of the modified E and I laminations which may be used. Other embodiments are possible.

[0185] FIG. 4 shows a schematic diagram of one possible embodiment of a transformer, with multiple slits in the side limbs, in accordance with the invention.

[0186] FIG. 5 shows a schematic diagram of one possible embodiment of how the ferromagnetic core may be organized if magnetic shunts are used in the design.

[0187] FIG. 6 shows a schematic diagram of one possible embodiment of a large shell-type transformer, constructed in accordance with the invention. An external clamp may be used to keep components in position.

[0188] FIG. 7 shows a schematic diagram of an expanded view of the flux transitional area at one side limb of an “E” lamination in mechanical connection with an “I” lamination.

[0189] It should be noted that in all the diagrams dimensions are not drawn to scale but serves to illustrate the principal of operation. Parameters may be determined experimentally. The drawings are incorporated and forming part of the specifications and together with the description serves to explain the principals involved in the invention.

[0190] Referring to FIGS. 1 to 7 of the drawings, in FIG. 1 the basic configuration of a previous art shell-type transformer is shown.

[0191] In FIG. 2 one possible embodiment of a shell-type transformer, in accordance with the invention, is shown. In FIG. 2 generally referred to by reference numeral 200.0 (see FIG. 2). The ferromagnetic core (200.1) may have a centre limb (200.1.1), encircled by the primary and secondary coils (200.2). In another embodiment (not shown) the primary and secondary coils may be positioned in-line with one another, around the centre limb (200.1.1).

[0192] The two ferromagnetic side limbs (200.1.2) and (200.1.3) may each have one or more slits (200.3) (cavities or similar), cut into the core.

[0193] The effective cross-sectional area of the side limbs (200.1.2), (200.1.3) may be designed to remain unchanged compared to a previous art shell-type transformer with the same power rating. Nuts and bolts (or similar), may be used to keep the assembly in position via mounting holes (200.4), according to known methods.

[0194] The operating principals have already been explained in detail in the description of this patent and are therefore not repeated here again. It will be noted that the side limbs (200.1.2), (200.1.3) and centre limb (200.1.1) may also be refer to as pillars and connecting structures as yokes, in the industry.

[0195] In FIG. 3 one possible embodiment of the modified E and I laminations is shown. In FIG. 3 generally referred to by reference numeral 300.0 (see FIG. 3), an “E” lamination (300.1.1) and an “I” lamination (300.1.2) is shown. The slits (300.3) holes or similar will be noted.

[0196] It will clearly be noted that; other embodiments are possible. For example; any number of slits (300.3) may be punched, laser cut (or similar), into the laminations. It will be noted that the width (or area) of the magnetic flux path is not reduced, by the slit(s) in the core, due to the organization. In larger type transformers the laminations (not shown) may be kept in position by an external clamp (or similar), (not shown).

[0197] In FIG. 4 one possible embodiment of a transformer with multiple slits in the side limbs is shown. In FIG. 4 generally referred to by reference numeral 400.0 (see FIG. 4). A transformer may be organized to have any number of slits (400.3.1), (400.3.2) or similar in the side limbs. The slits (400.3.1), (400.3.2) may be evenly spaced apart, as shown, or any other spacing arrangement may be used, not shown. The electromagnetic coils (400.2.1), (400.2.2) may be positioned in-line with each other or may be wound over each other (not shown).

[0198] In FIG. 5 one possible embodiment of a transformer with slits in the side limbs is shown with magnetic shunts. In FIG. 5 generally referred to by reference numeral 500.0 (see FIG. 5). If required, magnetic shunts (500.4.1), (500.4.2) may be positioned between one or more slits (500.3.1), (500.3.2).

[0199] The slits (500.3.1), (500.3.2) may be made the same size or two different E type laminations may be made (not shown). Magnetic shunts may for example be used in some microwave oven transformers. If required, the core may be designed to accommodate a grounding connection point, thermal sensor, or similar (500.7).

[0200] Welding ports (500.6.1), (500.6.2) may be used in mass produced systems, according to known methods. It will be realised that; if laminations are welded together (in mass produced systems), this may adversely effect generated heat, during normal operation. Advantageous, the cooling holes may be organized to be relative close to welding ports.

[0201] A Ferroresonant transformer with magnetic shunts, (not shown), may be organized in accordance with the invention.

[0202] In FIG. 6 one possible embodiment of a large shell-type transformer is shown. In FIG. 6 generally referred to by reference numeral 600.0, (see FIG. 6). The transformer may be organised to have any number of slits (600.3), in accordance with the invention. The corners of the slits may be organized to be substantially rounded (not shown). An external clamp (600.5) may be used to keep the components in position, according to known methods. The clamp (600.5) may be positioned so that it does not cover the slits (600.3) during final assembly or slits (not shown) may also be cut into the clamp (600.5). Known prior art methods, for example; step-lap mitred cores may be incorporated, etc.

[0203] In FIG. 7 a schematic diagram of an expanded view of the flux transitional area at one side limb of an “E” lamination in mechanical connection with an “I” lamination is shown, In FIG. 7 generally referred to by reference numeral 700.0 (see FIG. 7). Magnetic flux (700.7), generated during normal operation, may jump from the side limb of an “E” lamination (700.1.1) towards an “I” lamination (700.1.2) or vice versa (not shown).

[0204] It will be noted that; the magnetic flux density at the transitional area between the “E” and “I” lamination may be reduced due to an increase in the ferromagnetic area at the flux transitional area. A decrease in the flux density, at the transitional area between laminations, may result in a reduction of leakage flux and magnetostriction forces. This in turn may result in a reduction of noise generated during normal operation of the transformer. By organizing the corners of the slit to be substantially rounded (as shown), corner losses may be reduced, during normal operation.

[0205] With reference to FIG. 2 to FIG. 7, the side limbs of the core structure may be organized to have one or more slits or similar. Many variations may be made; for example: the cross-sectional area of the core may be organized to be round, (according to known methods).