JPH08148346A - High frequency transformer - Google Patents

Abstract

PURPOSE: To obtain a simple, compact and high performance cooling structure by resin molding the ring core, the cooling water tube, the primary winding, the secondary winding and the insulation tape. CONSTITUTION: A ring-like cooling water tube 24 is disposed concentrically to a tubular ring core 23 while touching the outer circumference thereof. The ring core 23 and the cooling water tube 24 are applied with a secondary winding 22 through an insulation tape 25. The secondary winding 22 is formed of a litz wire. The insulation tape 25 is wound around the secondary winding 22 which is then applied with a primary winding 21 through the insulation tape 25. The primary winding 21 is formed of a litz wire. The primary winding 21 is wound, similar to the secondary winding 22, along a route of the inner circumferential face of the ring core 23→upper end face of the ring core 23 and the cooling water tube 24→outer circumferential face of the cooling water tube 24→lower end face of the ring core 23 and the cooling water tube 24. The ring core 23, the cooling water tube 24, the primary winding 21, the secondary winding 22 and the insulation tape 25 are molded of an epoxy resin 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency transformer, which is devised so as to reduce the size of the structure and improve the performance.

[0002]

2. Description of the Related Art In an induction heating apparatus, a high frequency transformer (matching transformer) for impedance matching is provided between an oscillator and an induction heating coil. As an oscillator, a vacuum tube oscillator (output frequency 30 to 5
00kHz, output voltage 6 ~ 7kV) was used, but with the recent high frequency and large capacity of semiconductors, frequency converter using semiconductors (output frequency 30 ~ 50)
0 kHz, output voltage 200-2000 V) is used.
With a frequency converter using semiconductors, the output voltage is low (20 V) even if the output frequency is high frequency (30-500 kHz).
0-2000V).

When the above frequency converter is used, the primary voltage is lowered, so that the insulation between the primary winding and the secondary winding of the matching transformer can be facilitated and the corona countermeasure can be lightened. There is. However, since the primary voltage is low, the degree of coupling of the matching transformer must be high. This is because if the degree of coupling is low, the power loss is large and the efficiency is deteriorated. Especially, when the primary voltage is low, the efficiency deterioration due to these adverse effects becomes a problem.

A high frequency transformer 01 shown in Japanese Utility Model Publication No. 3-14795, which has a high degree of coupling, will be described with reference to FIGS. Note that FIG. 13 is a perspective view showing a frame omitted, FIG. 14 is a plan view, and FIG. 15 is X of FIG.
It is a -X sectional view.

As shown in FIGS. 13 to 15, in this high-frequency transformer 01, three ferrite core units 02 formed by assembling ferrite cores in a frame shape are arranged side by side, and the legs of these ferrite core units 02 are elliptical. A primary winding 03 and a secondary winding 04 having a shape are wound. Primary winding 03
Is a serial winding, and the secondary winding 04 is a parallel winding. As shown in FIG. 15, the primary winding 03 and the secondary winding 0
4 are alternately arranged one by one to increase the degree of coupling.

Frames 05 and 05 are arranged at both ends of the ferrite core unit 02, and cooling water pipes 06 (06a, 06a, 06a, 06a, 05b) are provided between the ferrite core units 02 and between the ferrite core unit 02 and the frame 05, respectively.
06b) is interposed. Then, the ferrite core unit 02, the cooling water pipe 06 and the frame 05 are
7 assembled together.

As shown in FIG. 15, the cooling water pipe 6a has a straight line shape with both ends bent, and the cooling water has an inlet 6a.
enter from _in out of the exit 6a _out. On the other hand, the cooling water pipe 6b
Is bent in a zigzag manner, and the cooling water enters through the inlet 6b _in and exits through the outlet 6b _out .

[0008]

When a high frequency current is supplied to the above high frequency transformer 01, the ferrite core unit 02 generates heat due to iron loss, and the windings 03 and 04 generate heat due to the high frequency current flowing. In order to effectively cool the heat generation of these two systems, the cooling water pipes 6 of the two systems are conventionally used.
a, 6b are required, and the cooling water pipes 6b must be arranged in a zigzag manner, and the cooling structure is complicated.

Further, since there is a voltage difference between the legs of the ferrite core unit 02 and the windings 03 and 04, an insulation is put between them to secure the insulation. Compaction was hindered.

Further, when copper pipes having a function as a flow path for passing cooling water are used as the windings 03 and 04,
The amount of copper used is higher than when only high-frequency current is passed. More specifically, the high frequency current flowing through the winding (copper tube) flows within the current penetration depth δ represented by the following equation (1).

[0011]

[Equation 1]

For example, a copper tube is used as the winding wire, and 100 [kH
z]], the current penetration depth δ is about 0.2.
It becomes 2 [mm]. However, the copper pipe must withstand water pressure because it flows cooling water, and the thickness of the pipe is 1-2 [mm].
Is required. Therefore, there is a drawback that the weight of the winding (copper tube) is heavy because the thickness of the tube is inevitably thicker than the thickness required to pass an electric current.

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and an object thereof is to provide a high-frequency transformer having a simple and compact structure and high performance.

[0014]

Means for Solving the Problems A first method for solving the above problems is described below.
According to the configuration of the present invention, the ring-shaped cooling water pipe is arranged concentrically in contact with the outer periphery of the cylindrical ring core, and the inner peripheral surface of the ring core, the ring core and the upper end surface of the cooling water pipe, the outer peripheral surface of the cooling water pipe, and the ring core. And the primary winding and the secondary winding made of litz wire are wound around the ring core and the cooling water pipe with the route along the lower end face of the cooling water pipe as a winding route, and the ring core, the primary winding and the secondary winding are connected. An insulating tape is provided between each of them, and the ring core, the cooling water pipe, the primary winding, the secondary winding, and the insulating tape are molded with resin.

According to the second aspect of the present invention, ring-shaped cooling water pipes are respectively arranged in contact with the upper end surface and the lower end surface of the cylindrical ring core, and the inner peripheral surface of the ring core, the upper end surface of the upper cooling water pipe, The Litz wire primary winding and secondary winding are wound around the ring core and the cooling water pipe, with the route along the outer peripheral surface of the ring core and the lower end surface of the lower cooling water pipe as a winding route. An insulating tape is provided between the secondary winding and the secondary winding, and the ring core, cooling water pipe, primary winding, 2
It is characterized in that the next winding and the insulating tape are molded with resin.

The third aspect of the present invention is characterized in that the ring core is formed of a silicon steel plate or a ferrite core.

A fourth aspect of the present invention is characterized in that the resin is an epoxy resin.

The structure of the fifth aspect of the present invention is characterized in that the diameter of the fine wire constituting the litz wire is smaller than the current penetration depth of the high frequency current flowing in the litz wire.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

1 to 3 show a high frequency transformer 1 according to a first embodiment of the present invention, FIG. 1 is a front view (partially cut away and shown), FIG. 2 is a side view, and FIG. It is a top view.

In this high frequency transformer 1, a casing 3 is provided on a lower base 2, and an upper base 5 is mounted on the casing 3 with insulating bolts and nuts 4.
A transformer main body 20 (the detailed structure of which will be described later) is housed in the casing 3, and primary terminal bolts 6U, 6V, secondary terminal bolts 7U, 7V, a common terminal bolt 8 and a tap terminal are provided on the upper base 5. Bolts 9a, 9b, 9c, 9d are provided.

As shown in FIG. 4, the primary terminal bolt 6U is
It is connected to the secondary winding 21, the primary terminal bolt 6V is connected to the common terminal bolt 8, and the tap terminal bolts 9a, 9b, 9
c and 9d are connected to the primary winding 21, and the secondary terminal bolt 7
U and 7V are connected to the secondary winding 22. A power source (for example, a semiconductor type frequency converter) is connected to the primary terminal bolts 6U and 6V, and a load (for example, an induction heating coil) is connected to the secondary terminal bolts 7U and 7V. The switching plate 10 allows the common terminal bolt 8 and the tap terminal bolt 9
One bolt of a-9d is connected. The voltage generated in the secondary terminal bolts 7U and 7V can be switched in four stages depending on which of the tap terminal bolts 9a to 9d is selected.

Next, FIGS. 1 and 5 are sectional views taken along the line aa of FIG.
Referring to FIG. 6 which is a bb cross section of FIG. 5, the transformer main body 20
The configuration of will be described. As shown in these figures, a ring-shaped cooling water pipe 24 is concentrically arranged in contact with the outer periphery of a cylindrical ring core 23, and the ring core 23 and the cooling water pipe 2
Insulation tape 25 is wound around 4. In addition, the set of the ring core 23 and the cooling water pipe 24, around which the insulating tape 25 is wound in this manner, is vertically stacked in three stages. Insulation tape 2 is formed on the outer circumference by integrating the three-stage set.
5 is rolled. The ring core 23 is made of a silicon steel plate or a ferrite core.

The secondary winding 22 is wound around the ring core 23 and the cooling water pipe 24 via an insulating tape 25.
The secondary winding 22 is formed by a litz wire (details of this wire will be described later). The winding path of the secondary winding 22 is a path along the inner peripheral surface of the ring core 23 → the upper end surface of the ring core 23 and the cooling water pipe 24 → the outer peripheral surface of the cooling water pipe 24 → the lower end surface of the ring core 23 and the cooling water pipe 24. The secondary winding 22 is wound in one row.

An insulating tape 25 is wound around the outer circumference of the secondary winding 22, and a primary winding 21 is wound around the secondary winding 22 via the insulating tape 25. The primary winding 21 is formed by a litz wire (details of this wire will be described later). The winding path of the primary winding 21 is the same as that of the secondary winding 22,
Inner peripheral surface of ring core 23-> upper end surface of ring core 23 and cooling water pipe 24-> outer peripheral surface of cooling water pipe 24-> ring core 23
And the route along the lower end surface of the cooling water pipe 24
The next winding 21 is wound in one row.

Insulating tape 2 is further provided on the outer circumference of the secondary winding 25.
5 is rolled. The ring core 23, the cooling water pipe 24, the primary winding 21, the secondary winding 22, and the insulating tape 25.
Are molded with an epoxy resin 26 (see FIG. 1). The transformer main body 20 thus configured is attached to the insulating bolt / nut 4.

The primary winding 21 has primary terminal bolts 6U, 6
A voltage is applied from a power source via V, and the voltage generated in the secondary winding 22 is supplied to the load via the secondary terminal bolts 7U and 7V. In addition, a cooling water nipple 27 is provided in the cooling water pipe 24.
Cooling water is flowed through.

The structure of the primary winding 21 and the secondary winding 22 will be described with reference to FIGS. 7 and 8. The windings 21 and 22
Have the same configuration. The windings 21 and 22 are half-wrapped with a 0.13 mm-thick insulating tape 28 on a wire formed by twisting a large number of thin copper wires (one half width of the tape is overlaid).
It is a litz wire wound around. The diameter of each thin wire is
The penetration depth of the high-frequency current flowing through the windings 21 and 22 is made smaller.

In the litz wire, since the diameter of each thin wire is small, the electric resistance characteristic to high frequency current is good. That is, as shown in FIG. 9, when a high-frequency current is applied, the smaller the diameter of the fine wire, the closer the ratio of the direct current resistance R _DC to the alternating current resistance R _AC becomes to 1 and the smaller the effect of the skin effect. An electric current effectively flows through the cross section of the line. Further, as shown in FIG. 10, the resistance value decreases as the number of twisted wires increases. That is, as compared with the winding of the copper tube, the winding using the litz wire can reduce heat generation (copper loss) due to energization. Furthermore, since the litz wire is a twisted wire, it is easy to wind.

As described above, in this embodiment, (1) the cooling water pipe 24 is arranged in contact with the ring core 23,
Since the windings 21 and 22 are wound around the ring core 23 and the cooling water pipe 24, the cooling water pipe 24 can linearly cool the ring core 23 and the windings 21 and 22. Also, the cooling water pipe 2
The arrangement structure of 4 is simple, and since the ring core 23 and the windings 21 and 22 can be cooled by the cooling water pipe 24, the cooling structure is simple. (2) Between the ring core 23 and the winding 22, the winding 2
Since the insulation between the 1 and 22 is performed by impregnating the insulating tape 25 and the epoxy resin 26, the space required for the insulation is reduced and the overall size is reduced. (3) Further, since the litz wires are used as the windings 21 and 22, heat generation is reduced and the winding amount is reduced. (4) Since the epoxy resin 26 is molded, the thermal conductivity can be several times higher than that of natural cooling, and the cooling capacity is improved also from this point. Also, by molding, it is possible to prevent leakage due to dew condensation.

Next, the main part of the second embodiment of the present invention is shown in FIG.
And FIG. 12 will be described. In the second embodiment, ring-shaped cooling water pipes 24, 24 are arranged in contact with the upper end surface and the lower end surface of the ring core 23, respectively, and the configuration of the other parts is the same as in the first embodiment. Also in the second embodiment, the cooling structure can be simplified, the size can be reduced, and the heat generation can be reduced. The cooling water pipe 24 may be installed between the ring cores 23.

Next, specific performance of the high frequency transformer 20 according to the embodiment will be described. However, the specifications of the high-frequency transformer 20 which has been subjected to the performance test are as follows. Capacity 33kV, frequency 25-35kHz, primary voltage rated value 220V. The secondary winding has 7 turns and the secondary voltage is 194V, 17
The primary winding corresponds to 9, 10, 11, 11 and 12 turns respectively for 4 steps of 5V, 159V and 145V. Again 1
The secondary winding uses one litz wire and the secondary winding uses two litz wires in parallel. For the winding, 44 springs of fine wire having a diameter of 0.3 mm were twisted to form a cross section of about 22 mm ² . Ferrite was used as the ring core.

The following results were obtained in the short circuit test for measuring copper loss. The short circuit test is a test in which the secondary side of the transformer is short-circuited and a voltage is applied to the primary side, and the current I and the input power P are obtained. This input power P indicates copper loss on the primary side and the secondary side.

Short circuit test results Primary tap: 9 turns Primary voltage: 89V Primary current: 150A Frequency: 28.3 kHz Cooling water inlet temperature: 18.1 ° C Cooling water outlet temperature: 19.2 ° C Cooling water flow rate: 3.65 l / min Loss: 320W Maximum temperature: 88 ℃

The following results were obtained in the no-load test for measuring iron loss. Note that the no-load test is a test in which the secondary side circuit of the transformer is opened and no load is applied, and a voltage of the rated frequency is applied to the primary side. Iron loss is obtained by subtracting the copper loss on the secondary side.

No-load test results Primary tap: 12 turns Primary voltage: 221V Primary current: 1.91A Frequency: 30.0 KHz Cooling water inlet temperature: 18.0 ° C Cooling water outlet temperature: 18.7 ° C Cooling Water flow rate: 3.65 l / min Loss: 196W Maximum temperature: 22 ° C

As shown in the above two test results, the capacity is 3
It was confirmed that it could be sufficiently used as a high frequency transformer of ³ kVA (= 220 V × 150 A × 10 ⁻³ ). Also, the efficiency η
Is 98.4 [%] as shown by the following equation, which is higher in efficiency than the efficiency (96%) of the conventional transformer. η = [{33− (320 + 196) × 10 ⁻³ } ÷ 33]
× 100 = 98.4 [%]

The high frequency transformer of the present invention can be used not only for induction heating devices but also for various high frequency application products such as ozonizers and plasma generators.

[0039]

According to the present invention as specifically described above with reference to the embodiments, the cooling water pipe is arranged in contact with the ring core, and the winding is wound around the cooling water pipe and the ring core.
The ring core and the winding can be directly cooled by the cooling water pipe, and the cooling effect is improved. Also, the cooling structure becomes simple.

Further, in the present invention, since the winding is a litz wire, heat generation is small and the amount of winding is reduced. This improves the cooling effect and reduces the size.

Furthermore, since insulation is provided by the resin and the insulating tape, the space for insulation is reduced, and the overall size is reduced.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of a high frequency transformer according to a first embodiment of the present invention.

FIG. 2 is a side view showing the high frequency transformer of the first embodiment.

FIG. 3 is a plan view showing a high frequency transformer of the first embodiment.

FIG. 4 is a connection diagram showing a winding connection state of the high frequency transformer of the first embodiment.

5 is a cross-sectional view showing a cross section of the transformer main body taken along the line aa in FIG.

6 is a cross-sectional view showing a bb cross section of FIG. 5;

FIG. 7 is a cross-sectional view showing a winding.

FIG. 8 is a configuration diagram showing a winding.

FIG. 9 is a characteristic diagram showing an AC resistance increase rate of a litz wire.

FIG. 10 is a characteristic diagram showing AC resistance of a litz wire.

FIG. 11 is a cross-sectional view showing a transformer main body of a high frequency transformer according to a second embodiment.

FIG. 12 is a cross-sectional view showing a C-C cross section of FIG. 11.

FIG. 13 is a perspective view showing a conventional high frequency transformer.

FIG. 14 is a plan view showing a conventional high frequency transformer.

FIG. 15 is a sectional view showing an XX section in FIG. 14;

[Explanation of symbols]

 01 high frequency transformer 02 ferrite core unit 03 primary winding 04 secondary winding 05 frame 06, 06a, 06b cooling water pipe 07 bolt 1 high frequency transformer 2 lower base 3 casing 4 insulating bolt / nut 5 upper base 6U, 6V 1 Next terminal bolt 7U, 7V Secondary terminal bolt 8 Common terminal bolt 9a, 9b, 9c, 9d Tap terminal bolt 10 Switching plate 20 Transformer main body 21 Primary winding 22 Secondary winding 23 Ring core 24 Cooling water pipe 25 Insulating tape 26 Epoxy resin 27 Cooling water nipple 28 Insulating tape

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Hanamoto 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Kuniyuki Kajisai Kannon Shin-cho, Hiroshima City, Hiroshima Prefecture 4-6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Research Institute (72) Inventor Taketoshi Eguchi 2-3-4 Jonanjima, Ota-ku, Tokyo Eguchi High Frequency Co., Ltd.

Claims (5)

[Claims] 1. A ring-shaped cooling water pipe is arranged concentrically in contact with the outer periphery of a cylindrical ring core, and the inner peripheral surface of the ring core, the upper end face of the ring core and the cooling water pipe, the outer peripheral surface of the cooling water pipe, the ring core and the cooling. The Litz wire primary winding and secondary winding are wound around the ring core and the cooling water pipe, with the path along the lower end surface of the water tube as the winding path, and between the ring core, the primary winding, and the secondary winding. A high-frequency transformer characterized in that the ring core, the cooling water pipe, the primary winding, the secondary winding, and the insulating tape are molded with resin by including an insulating tape. 2. A ring-shaped cooling water pipe is arranged in contact with an upper end surface and a lower end surface of a cylindrical ring core, respectively, and an inner peripheral surface of the ring core, an upper end surface of the upper cooling water pipe, an outer peripheral surface of the ring core, and a lower side. The primary winding and the secondary winding made of litz wire are wound around the ring core and the cooling water pipe with the route along the lower end face of the cooling water pipe as the winding route, and the ring core, the primary winding and the secondary winding are A high-frequency transformer characterized in that an insulating tape is provided between each of them, and the ring core, the cooling water pipe, the primary winding, the secondary winding, and the insulating tape are molded with resin. 3. The high frequency transformer according to claim 1, wherein the ring core is formed of a silicon steel plate or a ferrite core. 4. The high frequency transformer according to claim 1, wherein the resin is an epoxy resin. 5. The high frequency transformer according to claim 1, wherein a diameter of the fine wire constituting the litz wire is smaller than a current penetration depth of a high frequency current flowing through the litz wire.