JPH10256055A - Low-voltage large-current transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a transformer, reduce a manufacturing cost, and improve an efficiency and a radiation property by constituting the transformer with a plurality of cores, a primary winding that is wound around each core, and a secondary coil winding that is folded back so that the primary winding can be pinched. SOLUTION: A low-voltage large-current transformer 1 is constituted of, for example, three primary windings 2, a secondary winding 3, and a three cores 4 being provided for the number of the primary windings. In the secondary windings 3, a copper plate 3a is flexed as a band-shaped conductor by press machining, thus forming an arc-shaped part 3b along the outer periphery of the three primary windings 2 and a flat part 3c that is overlapped while pinching an insulation sheet 5 in between. The cores 4 are formed by two members that can be separated and are especially in EE type. More specifically, the cores 4 have three legs 4a-4c and can be separated into left and right precisely at the central part so that square-shaped θ can be formed by joining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-voltage large-current transformer used for, for example, resistance heating or high-frequency induction heating.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional structure of a low-voltage large-current transformer 10. In this figure, a low-voltage high-current transformer 10 includes a large shell-type ferrite core 11, a primary winding 12 wound around the core 11, and a secondary winding wound around the outside of the primary winding 12. It consists of line 13. And
A low-voltage, large-current transformer 10 incorporated in a power supply generally used for resistance heating (for example, carbon crucible heating)
For example, it is necessary to supply electric power for flowing a secondary current of about 1000 A at a low secondary voltage of about 7 V, that is, about 7 kVA.

[0003]

However, in the low-voltage large-current transformer 10 described above, in order to obtain a desired output power and secondary voltage, the winding is wound around a large core 11 having a weight of, for example, 60 kg. It was necessary to wind 12,13. In other words, in order to obtain a large power, the special core 11 must be used, which makes it difficult to obtain, and has the disadvantage of being expensive.

In order to apply a large current to the secondary side, the secondary winding 13 is formed, for example, by drawing a copper plate 13a having a width of 80 mm and a thickness of 2 to 3 mm and silver brazing to both ends in the length direction thereof. The secondary winding 13 must be wound around the large core 11 several times from above the primary winding 12. Therefore, it is difficult to wind the secondary winding 13 from above the primary winding 12 without any gap, and the operation is troublesome. Further, the workability of drawing out the lead wire 13b from the copper plate 13a was very poor. In addition, the gap generated between the windings 12 and 13 causes leakage of magnetic flux and causes a reduction in efficiency. In addition, since the copper plate 13a is wound in a pile, there is a disadvantage that the heat generated in the inner copper plate 13a cannot be radiated.

The present invention has been made in view of the above-mentioned circumstances, and is easy to manufacture, has low manufacturing cost, and has good efficiency and heat dissipation despite a large current flowing at a low voltage. It is an object to provide a high voltage current transformer.

[0006]

To achieve the above object, a low-voltage high-current transformer according to the present invention comprises a plurality of cores, a primary winding wound on each core, and a primary winding. It is characterized by comprising a secondary winding folded back so as to sandwich it. The secondary winding may be configured to have an arc-shaped portion capable of separately accommodating the primary winding, or the secondary winding may be folded in a U-shape.

[0007] The low-voltage, large-current transformer does not require a high-level manufacturing technique, despite being a low-voltage, large-current transformer. In other words, regardless of the amount of output power, an easily available and inexpensive core can be used, and the secondary voltage is the same as when a secondary winding is wound once around a transformer having a single core and a primary winding. Multiple times the next voltage can be obtained. Therefore, an optimal primary winding can be used depending on the operating frequency and the core material regardless of the magnitude of the secondary voltage.
In addition, the area of the secondary winding in contact with the air is larger than in the case where the secondary winding is wound around the core in a stacked manner, so that the secondary winding can be cooled well.

Further, since the secondary winding is formed by pressing a strip-shaped conductor, it is not necessary to draw a lead wire from the secondary winding. That is, since the secondary winding is formed in advance, the workability of assembly is very good.
Further, when the core is formed of two members that can be separated from each other, the work of assembling the low-voltage and large-current transformer involves inserting the independently wound primary winding into the integrated secondary winding. In addition, it is only necessary to insert the divided core at the center thereof, and the assembly can be performed extremely easily.

The primary windings may be connected in parallel, may be connected in series, or may be connected in a combination of parallel and series. The connection of the primary winding can be arbitrarily selected according to the magnitude of the voltage and current supplied to the primary side.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show a first embodiment of the present invention. First, in FIG. 1, a low-voltage large-current transformer 1 comprises, for example, three primary windings 2 and 1 Secondary windings 3
And three cores 4 provided in accordance with the number of the primary windings 2.

Similar to the primary winding of a general transformer, the primary winding 2 is adapted to the characteristics of each core 4 determined by the frequency at which the low-voltage large-current transformer 1 operates and the material of the core 4. Thus, the optimum wire 2a can be used. A substantially square hole 2b for inserting a core 4 to be described later is formed in the center of the primary winding 2.

The secondary winding 3 is a strip-shaped conductor, for example, a copper plate 3a having a thickness of 3 mm and a width of 80 mm is bent by press working to form an arc-shaped portion 3b along the outer periphery of the three primary windings 2. And a flat portion 3c that overlaps with the insulating sheet 5 interposed therebetween. That is, sheet metal processing is performed so that the secondary windings 3 corresponding to the three primary windings 2 are connected in series by half the number of turns. As described above, the secondary winding 3 is bent so as to form an arc-shaped portion 3b that can be inserted between the plurality of primary windings 2 so as to sandwich the primary winding 2 with the copper plate 3a. It is formed so that the gap with the primary winding 2 is minimized.

The arc-shaped portion 3b and the flat portion 3c of the secondary winding 3 are provided with insulating properties by means of an insulating paint. I have. Then, power is supplied to the load 9 (see FIGS. 5 and 6) of the heating device, for example, via the terminal 3d. Needless to say, the copper plate 3a may be provided with an insulating property by covering with an insulating coating. Further, the insulating sheet 5 may be omitted.

The core 4 is formed of two separable members.
In this embodiment, the EE type is particularly used. In other words, the core 4 has three legs 4a to 4c, and has a shape that can be separated right and left at the center just so that the core 4 has a substantially "sun" shape at the time of joining. Each core 4 may be fixed with a band or an adhesive as necessary.

[0015] The low-voltage high-current transformer 1 in the above embodiment.
When assembling, the primary windings 2 are inserted into the respective arc-shaped portions 3b of the integrated secondary windings 3 and divided into the holes 2b formed at the center of the respective primary windings 2. It is only necessary to insert the first leg 4 a having a substantially square cross section of the core 4, and it is troublesome to wind the secondary winding so as to be in close contact with the primary winding and to draw out the lead wires from both ends of the secondary winding 3. No work is required. That is, since the secondary winding 3 is formed in advance, the workability of assembly is very good.

FIG. 2 shows a low-voltage high-current transformer 1 according to the first embodiment.
FIG. 4 is a plan view showing an assembled state of the first embodiment. In order to obtain an output of, for example, a voltage of 7 V and a current of 1000 A on the secondary side, the primary side is divided into three parts. Therefore, when the output power on the secondary side is 7 kVA as described above, each core 4
May be about 2.3 kVA. The wire 2a of the primary winding 2 wound around each core 4 is, for example, a coated lead wire 2c.
To form a composite low-voltage / high-current transformer 1 as a whole.

According to the first embodiment, a high-capacity low-voltage / high-current transformer 1 can be easily formed by using an easily available and inexpensive core 4, and a high-level manufacturing technique is not required. , The low-voltage large-current transformer 1 can be easily manufactured.

Also, since almost all of the secondary winding 3 is exposed to the outside, the cooling of the secondary winding 3 can be reduced as compared with the conventional case where the secondary winding 3 is wound in a stack. Very good. Therefore, even if a large current is applied to the low-voltage large-current transformer 1 to generate heat, the heat is reliably released and the efficiency is improved accordingly. The cooling efficiency may be further improved by providing cooling auxiliary fins outside the secondary winding 3 or attaching a water cooling hose or the like. Of course, forced air cooling may be performed by a fan.

Further, although the secondary winding 3 of the above embodiment is formed integrally by pressing a strip-shaped copper plate 3a, the present invention is not limited to this.
May be formed by joining a pair of upper and lower copper plates 3a formed by press working by screwing or silver brazing. That is, the present invention does not limit the shape of the secondary winding 3, and the secondary winding 3 is folded back so as to sandwich the plurality of primary windings 2 even if the secondary winding 3 is interposed therebetween. It should just be.

FIGS. 3 and 4 show a second embodiment of the low-voltage and large-current transformer 1 according to the present invention. In FIGS. 3 and 4, members denoted by the same reference numerals as those in FIGS. 1 and 2 are the same or equivalent members, and thus detailed description thereof will be omitted.

In FIG. 3, the secondary winding 6 is formed as a strip-shaped conductor, for example, a copper plate 6a having a thickness of 3 mm and a width of 80 mm bent in a U-shape. And a terminal 6c with the copper plate 6a exposed.

The shape of the core 7 in this embodiment is of the EI type.
That is, the core 7 is composed of an E-shaped member 7d having three legs 7a to 7c and an I-shaped member 7e connected to the E-shaped member 7d. The members 7d and 7e are configured to be separable.

Therefore, when assembling the low-voltage large-current transformer 1, the primary winding 2 is inserted so as to be sandwiched between the integrated U-shaped secondary windings 6. Thereafter, the first leg 7a of an E-shaped member 7d having a substantially square cross section is inserted into a hole 2b formed at the center of each primary winding 2, and an I-shape is inserted into the E-shaped member 7d. It is only necessary to join the member 7e in the shape of a circle.

Alternatively, the first leg 7a is inserted into the hole 2b of each primary winding 2, and the core 7 is joined by connecting the E-shaped member 7d and the I-shaped member 7e. Then,
The terminal 6c of the U-shaped secondary winding 6 is inserted between the first leg 7a and the second leg 7b of the core 7 and between the first leg 7a and the third leg 7c, so that the primary winding is performed. The low-voltage high-current transformer 1 may be assembled so as to sandwich the line 2. In any case,
Since the secondary winding 7 is formed in advance, the workability of assembly is very good.

The secondary winding 7 of the low-voltage high-current transformer 1
Is a copper plate 6a bent in a U-shape, so that the bending operation is easy, there is no need to perform sheet metal processing, and the manufacturing cost of the low-voltage large-current transformer 1 can be further reduced.

FIG. 4 is a plan view showing an assembled state of the low-voltage and large-current transformer 1 of this embodiment. In this embodiment, three cores 7 are used to obtain, for example, an output of 7 kVA. . Therefore, the capacity of each core 7 may be about 2.3 kVA, and since the core 7 that is easily available is used, the low-voltage large-current transformer 1 can be easily manufactured. Also,
The wires 2a of the primary winding 2 are connected in parallel in the present embodiment, and form a single composite low-voltage / high-current transformer 1 as a whole.

As can be seen from FIG. 4, almost all of the secondary winding 6 is exposed to the outside. Therefore, the cooling of the secondary winding 6 can be performed satisfactorily, and the efficiency of the low-voltage large-current transformer 1 is improved. It should be noted that cooling auxiliary fins are provided outside the secondary winding 6,
It goes without saying that the cooling efficiency may be further improved by attaching a water cooling hose or the like. Of course, forced air cooling may be performed by a fan.

In each of the above-described embodiments, the EE type and the EI type are illustrated as examples of the cores 4 and 7. However, the present invention is not limited to this, and other shapes such as an EIR type and an EER type may be used. Needless to say, the core may be used. Further, the capacity of the power supplied from each primary winding 2 may be adjusted by using the cores 4 and 7 in an overlapping manner.

Further, the low-voltage high-current transformer 1 of the present invention
Is not limited to the above-described tripod core, and may be a two-leg core. Further, the present invention can be carried out regardless of whether the core is an outer iron type or an inner iron type.

In addition, the thicknesses and widths of the secondary windings 3 and 6 in each of the above-described embodiments are merely examples, and are not limited to these values, but may vary according to the magnitude of the output current. Can be set arbitrarily. Also, as for the material, although strip-shaped copper is used as an example, the present invention is not limited to this. For example, a litz wire arranged in a strip, that is, formed by bundling a plurality of wires each insulated. The wire may be used as a secondary winding to prevent the secondary winding from having a resistance when a high-frequency current flows.

In each of the above embodiments, each primary winding 2
Although the example in which the wires 2a are connected in parallel by the lead wires 2c is shown, the present invention is not limited to this, and it goes without saying that the wires 2a may be connected in series. This will be described below.

FIGS. 5 and 6 show a part of a power supply circuit of a heating apparatus using the low-voltage / high-current transformer 1 of each of the above embodiments. In these drawings, members denoted by the same reference numerals as those in FIGS. 1 to 4 indicate the same or equivalent members, and thus detailed description thereof will be omitted.

In FIGS. 5 and 6, reference numeral 8 denotes an inverter serving as a power supply necessary for heating. The primary winding 2 of the low-voltage and large-current transformer 1 of each of the above-described embodiments is provided on the output side of the inverter 8.
Are connected. The secondary winding 3 (the secondary winding 6 in the case of the embodiments of FIGS. 3 and 4) of the low-voltage high-current transformer 1 is connected to, for example, a load (for example, a carbon crucible) 9. Therefore, heating can be performed by converting the output power of the inverter into low-voltage and high-current power by the low-voltage / high-current transformer 1 of the present invention and supplying the power to the load 9.

In the embodiment shown in FIG. 5, all of the primary windings 2 of the low-voltage high-current transformer 1 are connected to the inverter 8 in parallel. This is an example in which the wires 2a are connected in parallel by the lead wires 2c as shown in FIGS. 2 and 4, and is effective when the output voltage of the inverter 8 is low and a large output current can flow.

On the other hand, in the embodiment shown in FIG. 6, all the primary windings 2 of the low-voltage large-current transformer 1 are connected in series to the inverter 8. This shows a state in which the lead wires 2c shown in FIGS. 2 and 4 are rearranged so that the respective wires 2a are connected in series. Connecting in series in this way
This is effective when the output current of the inverter 8 is small and the output voltage is high.

Although not shown, the primary winding 2
It is needless to say that the connection can be made in accordance with the output voltage and the output current of the inverter 8 by partially connecting them in series and partially connecting them in parallel.

In each of the above-described embodiments, three primary windings 2 are used as an example of the plurality of primary windings 2. However, the present invention is not limited to this. Needless to say, the number can be arbitrarily selected according to the required capacity. For example, to obtain a capacity of 7 kVA, it is possible to use 14 inexpensive cores for 500 VA and 14 primary windings 2. In this case, 14 times the output power and output voltage obtained by the single core and the primary winding 2 can be obtained on the secondary side.

Further, the low-voltage high-current transformer 1 of the present invention
It is also possible to increase the output power by driving the primary winding 2 by a plurality of inverters.
FIG. 7 is a block diagram showing an example in which the low-voltage large-current transformer 1 of the present invention is driven by a plurality of inverters. In this embodiment, N inverters 8 are provided on one printed board.
a, a drive circuit 8b, an oscillator 8c for controlling them, and a pulse width control unit 8d.
a by connecting N primary windings 2 corresponding to
The configuration is such that double output voltage and output power can be supplied to the load 9.

[0039]

As described above, according to the low-voltage / high-current transformer of the present invention, although it is a low-voltage / high-current transformer, it does not require advanced manufacturing technology, A high voltage and high current transformer can be easily manufactured. In other words, regardless of the amount of output power, an easily available and inexpensive core can be used, and the secondary voltage is obtained by winding the secondary winding once around a transformer formed using a single core and the primary winding. An integral multiple of the secondary voltage at the time can be obtained. Therefore, an optimum primary winding can be easily used depending on the frequency used and the core material regardless of the magnitude of the secondary voltage. In addition, the area of the secondary winding in contact with the air is larger than in the case where the secondary winding is wound around the core in a stacked manner, so that the secondary winding can be cooled well.

When the secondary winding is formed by pressing a strip-shaped conductor, the assembling work becomes extremely easy since the secondary winding is formed in advance. Further, when the core is formed of two members that can be separated from each other, the assembling work of the low-voltage high-current transformer involves inserting the primary winding into the secondary winding, and further dividing the core into the center. , It is possible to assemble the low-voltage high-current transformer more easily.

When the primary windings are connected in parallel, a sufficient secondary voltage can be obtained even when the primary voltage is low. When the primary windings are connected in series, the primary current is reduced. Even in a small case, a sufficient secondary current can be obtained. That is, it is possible to correspond to the magnitude of the voltage and current on the primary side by the connection method of the primary winding.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a low-voltage high-current transformer according to a first embodiment of the present invention.

FIG. 2 is a plan view of the low-voltage / high-current transformer.

FIG. 3 is an exploded perspective view of a low-voltage high-current transformer according to a second embodiment of the present invention.

FIG. 4 is a plan view of the low-voltage / high-current transformer.

FIG. 5 is a diagram showing a power supply circuit of a heating device using the above-described low-voltage and large-current transformer.

FIG. 6 is a diagram showing another power supply circuit of a heating device using the above-described low-voltage and large-current transformer.

FIG. 7 is a diagram showing another embodiment of a power supply circuit using the above-described low-voltage and large-current transformer.

FIG. 8 is a perspective view showing an example of a conventional low-voltage / high-current transformer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Low voltage large current transformer, 2 ... Primary winding, 3, 6 ... Secondary winding, 3b ... Arc-shaped part, 4, 7 ... Core.

Claims (7)

[Claims] 1. A low-voltage, large-current transformer comprising a plurality of cores, a primary winding wound around each core, and a secondary winding folded so as to sandwich the primary winding. vessel. 2. The low-voltage high-current transformer according to claim 1, wherein the secondary winding has an arc-shaped portion capable of separately accommodating the primary winding. 3. The low-voltage high-current transformer according to claim 1, wherein the secondary winding is folded in a U-shape. 4. The low-voltage high-current transformer according to claim 1, wherein the secondary winding is formed by pressing a strip-shaped conductor. 5. The low-voltage and large-current transformer according to claim 1, wherein the core is formed of two members that can be separated from each other. 6. The low-voltage high-current transformer according to claim 1, wherein said primary windings are connected in parallel. 7. The low-voltage high-current transformer according to claim 1, wherein the primary windings are connected in series.