Transformers

Abstract

Electric transformers, such as for spot welding machines and the like, which have at least the secondary winding divided into sections of less than one turn so as to obtain a large current at a low voltage, such as one-half, one-third or one-fourth turns.

Description

In the function of an electric welder such as a spot welding machine, important is the current value but not the voltage. For example, a large current is required to work on material of large thickness.

It is evident in general that a definite electric power can serve to obtain a large current when it is transformed to a low-voltage condition.

In this type of conventional transformers, however, large transformer dimensions are inevitable to obtain a great current for welding because the minimum limit of the secondary winding is one turn.

The present invention is designed to provide a constitution of a transformer in which the secondary windings are divided into minute components less than one turn to obtain a large current with a low voltage.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to electric apparatus, and more particularly, transformers employable for electric welders such as spot-welding machines and the like which are required to furnish a large current with a low voltage for a great power output.

This type of conventional transformers could not have the secondary winding portion less than one turn because of the structural constitution. If the number of turns of the primary coil is diminished for a countermeasure, the secondary voltage or output voltage rises and a very large input power is necessary to obtain a great current. For example, when a transformer of a welding machine for the input power 500 KVA is designed, the voltage of power source 200 V requires eight turns of primary winding, and one turn of secondary coil corresponds to 25 V.

Provided an instantaneous welding current of 50,000 amp. is required, the necessary instantaneous input will be 1,250 KVA and the primary current 6,250 amp. These data suggest a great uneconomy with a transformer requiring a large current at a low voltage such as an electric welder.

On the other hand, when the coil and the iron core of this type of transformer are constructed, it is normal to wind the coils and have oblong iron sheets cross them, the coils being connected in series, so that these iron sheets may be overlapped to form a frame work as a magnetic core. However, in order that the iron sheets cross the coils, connected in series to construct a coil-pile, at least one seam or junction had to be formed and, therefore, the resulting magnetic resistance, produced by the jointing gap, inevitably deteriorated the function of transformer. On the other hand as regards the case of employing a spiral core, disadvantages similar to those as above mentioned have been found because the winding process was practised by cutting off the spiral core, fitting the coil on the spiral core and joining the cut sections.

One object of the present invention is to furnish an improved transformer of the above mentioned structural type, applicable to a wide field of utilization, and more particularly, in which the combination of coil windings and iron cores is improved so that the length of the turns in the secondary winding is reduced to less than one turn, for example, one-half turn, one-third turn or one-fourth turn, which has not yet been realized, thereby increasing the output current produced from the same input power.

Another object of the invention is to form coil sections from plural winding components by dividing equally the secondary winding of the mentioned type of transformer into quotients of one turn, wherein the winding components are crossed in series by the core blocks of the same shape, and the electric powers of equal voltage corresponding to a winding component less than one turn are supplied from the terminals of each winding component of the secondary winding so that the output voltage may be optionally selected by connecting these winding components appropriately in series and in parallel.

Further object of the invention is to furnish a transformer of which each winding component for the primary and secondary coils can be formed by one stamping strike from a sheet material which is a good electric conductor, piled alternatingly with isolating sheets to be fastened into one assembly block, and connected in respective adequate manner whereby the apparatus can be minified, the magnetomotive force may not be large, the power factor can be improved, and the leakage flux can diminish so as to provide an apparatus of high efficiency.

Furthermore an object of the invention is to propose a transformer of the mentioned type of which the iron core is composed of seamless component sheets to make a closed magnetic circuit and which can save exciting current.

Another object of the invention is to propose an apparatus of the mentioned type which produces magnetic fluxes as many as possible with a definite magnetomotive force to improve efficiency so that the produced fluxes may cross the secondary windings in series efficiently, thereby curtailing the mean magnetic circuit of the iron core constituting magnetic circuit to reduce the magnetic resistance.

Other objects, characteristics and advantages of the present invention will be demonstrated in the following description, the attached claims and enclosed drawings, in which:

FIG. 1 is a plan view of an exemplary embodiment of the transformer of the invention;

FIG. 2 is a side elevation for the transformer of FIG. 1;

FIG. 3 (1) to (4) shows side elevations of iron core components for the transformer of FIG. 1;

FIG. 4 and 5 are plan views of primary and secondary winding components for the transformer of FIG. 1;

FIGS. 6 and 7 are plan views of other examples of respective winding components;

FIG. 8 shows another example of the invention and is a side elevation of a transformer constructed with a ring-type wound iron core;

FIG. 9 shows another example of the invention and is a side elevation of a transformer constructed with a rhombic wound iron core; and

FIG. 10 shows a further example and is a side elevation of a transformer constructed with a pyramidal wound iron core.

To illustrate with reference to the drawings, an exemplary embodiment of the transformer of the invention is generally represented with numeral 10. This apparatus is composed of a iron core 12 of the iron enclosure type and a coil or winding section 14.

Iron core 12 is constructed of blocks 16, 18, 20 and 22, which are formed by the combination of iron cores of different dimensions so that every side of square coil sections 14 may be crossed in series by said iron cores, and which are disposed abutting against each other to build a cross structure.

As shown in FIG. 3 (1) - (4), respective iron cores for forming the core blocks 16, 18, 20 and 22 are constructed in the manner that a predetermined numbers of iron core components 24, 26, 28 and 30 of the same dimensions among those components of different dimensions are piled separately with respective openings punched in the centers of seamless rectangular iron sheets.

On the other hand, the coil section 14 is constructed in the manner that, when the iron core components 24, 26, 28 and 30 have been piled separately, respective primary and secondary coil or winding components 34, 36, composed of electroconductive sheet material divided uniformly along each side of a square frame-shaped space 32a, which was formed by the penetration of punch hole 32, are disposed in the shape of said frame-shaped space 32 (see FIG. 3) and these components for the primary and secondary coils are alternately piled with inserted insulating sheets. Terminal lugs 38 and 40 are provided respectively at both ends of the primary and secondary coil components 34, 36. It should be noted from FIGS. 4 to 7 and others that all coil components are continuous or seamless, the terminal lugs constituting the points of electrical interconnection.

The mentioned iron core 12 and coil section 14 may be constructed as follows: A predetermined number of either the primary or secondary components 34 or 36 (herein the former components will be considered) are piled together, are successively penetrated with punch hole 32 for the iron core components 24, 26, 28 and 30 to heap up to predetermined thicknesses and build iron cores, and the resulting members are combined to form respective iron cores 16, 18, 20 and 22.

Then each secondary coil component 36 is inserted together with insulating material layer such as glass fiber between adjacent primary coil components 34, and the resulting structure is fastened together with insulating rods or the like. Terminal lugs 38 and 40 are appropriately connected to constitute the primary coils and the secondary coils.

After then these prepared members are disposed in a square shape to complete the winding section 14. The iron core blocks 16, 18, 20 and 22 are abutted against one another to form a cross shape. They are brought to close contact together to fill the square space enclosed by the core frame of the winding section 14, thus building iron core 12. In this construction, each core block 16, 18, 20 or 22, connected with iron core 12, crosses successively each side of square winding section 14, i.e. each primary and secondary coil component 34 or 36 in the same condition of arrangement so that the primary and secondary coil components 34 and 36 are firmly enclosed into the frame-shaped space 32a penetrated by the punch hole 32 whereby the average magnetic circuit is much shortened. Therefore the characteristics of transformer are improved to obtain larger output of the secondary coil with smaller magnetomotive force.

In addition to the improvements of the characteristics of the transformer, the compact combination of iron core 12 with coil or winding section 14 and the exclusion or surplus iron core sections can assure a weight reduction of conventional transformers as compared to the same capacity.

Furthermore, since iron core 12 is composed of the iron laminate structure piled together with core components 24, 26, 28 and 30 of which four sides are continued without seam, so the magnetic circuit becomes a completely closed magnetic circuit so that the exciting current may be reduced.

Now the function of the inventive transformer 10 will be explained: Primary coil components 34 are connected together in series to amount to the predetermined number of turns, and secondary coil components 36 are connected appropriately in series or in parallel, so that very low voltage corresponding to less than one coil turn such as one-fourth, one-half or three-fourths turn may be obtained from the secondary coil and also voltages corresponding to one, five-fourths or three-halves turns may be taken out. Particularly, in the former case the same primary input as that applicable to conventional apparatus can produce a larger current with a lower voltage.

For example, in a transformer of a welding machine for an input of 500 KVA, the power source of 200 V requires eight turns of primary winding to yield 25 V per one turn of secondary winding, but because one turn is divided into quarters one-fourth turn corresponds to 6.25V. Therefore, if 50,000 amp. is obtained with this voltage, 200,000 amp. can be taken out of the secondary coil. Suppose that 50,000 amp. are sufficient for the welding current, then primary current may be 1.562 amp. This fact will be particularly desirable for power source equipments and control apparatus etc.

The transformer of the above-described example is constituted in the manner that each side of square winding section 14 is divided.

However, as shown with another example in FIG. 6, both or one of the primary and secondary coil components 34 and 36 may be disposed to form a substantial rectangle together with a coil component 42 so that the two adjacent sides make an L-combination, or otherwise as shown in FIG. 7 the rectangle may be composed of a U-shaped coil component 44 with three consecutive sides and said component 34 or 36.

Furthermore, the primary coil component also may be electrically interrupted only at one point but have four sides continued together.

Hereinbefore the examples were described in the case that the primary and secondary coils were arranged alternatively. In the present invention, however, concentrated type or the type of the primary and secondary coils being respectively collected are practicable, too, and moreover the secondary coil may be composed of the coil constructing components formed in an entirely collective structure of secondary coil components.

Finally, iron core 12 may be constructed in the shape of a ring-form wound or circular core 12a as shown in FIG. 8, in the shape of a rhombic wound core 12b as shown in FIG. 9 and in the shape of a L-form wound or triangular core 12c as shown in FIG. 10. The two latter variants constitute polygonal arrangements.

Claims

What I claim Is :

1. A transformer comprising an iron core and thereon primary and secondary coils constituted by electrically interconnected discrete coil sections, said iron core being formed of laminates in the shape of a framework, said coil sections being electrically divided into mechanically continuous, seamless plural coil components which successively cross said iron core, said components in the primary coil section being at least one full turn while said components in the secondary coil section are less than one turn in length, thereby generating in said secondary coil section a large current at a low voltage.

2. The transformer as defined in claim 1, wherein said coil components are equally divided into portions of less than one turn, each component being crossed by said iron core in an equal arrangement.

3. The transformer as defined in claim 1, wherein said coil components are made of electroconductive sheet material, and an appropriate number of said components is successively piled together in the direction of their thickness.

4. The transformer as defined in claim 1, wherein said iron core includes seamless component sheets having substantially identical central openings, piled together so that said openings overlap in coincidence, each coil component being allotted to a respective portion of said framework and inserted through said openings.

5. the transformer as defined in claim 1, further comprising seamless component sheets having central openings of substantially identical outline, said sheets being wound in shapes to constitute said iron core, each coil component being allotted to a respective portion of said framework and inserted through said openings.

6. The transformer as defined in claim 1, wherein said iron core encloses said coil sections and is constructed of plural shapes of blocks having different dimensions so as to fill an opening inside said framework.

7. The transformer as defined in claim 1, wherein said framework has a polygonal shape.

8. The transformer as defined in claim 1, wherein said framework has a substantially circular shape.