JPS62219605A - High-frequency transformer - Google Patents

Abstract

PURPOSE:To restrain heat generation of windings by decreasing a loss resistance of a secondary winding by connecting at least two secondary windings in parallel. CONSTITUTION:As two secondary windings 13a and 13b are connected in parallel, a cross-sectional area of a secondary winding is a sum of the cross-sectional areas of said two windings. To equalize a current density of the secondary winding which is composed at least two windings connected in parallel to that of the secondary winding composed one winding, a thin wire should be used, so that an influence of skin effect can be exceedingly reduced. Accordingly, even if a diameter of the winding is reduced, a virtual current density of the secondary winding of a high-frequency transformer does not increase so much as a cross-sectional area of the winding is reduced and heat generation decreases. Also, an occupation volume of the winding becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency transformer, and more specifically, to an improvement in a power transformer that handles large amounts of power and current.

BACKGROUND OF THE INVENTION Generally, transformers that handle large amounts of power are large because of heat generation in the windings due to copper loss and heat generation in the core due to hysteresis loss. Therefore, various configurations have been proposed to reduce the size, weight, or cost of the device.

FIG. 5 shows a cross-sectional view of a conventional high frequency transformer. In the figure, 1 is ferrite core a, 2 is ferrite core b
and is held down by the fastener 3. 4 is the primary winding of the transformer, and 5 is the secondary winding.

FIG. 6 shows the frequency characteristics of copper loss. As shown in Figure 446, as the frequency increases, resistance increases due to the effect of the skin effect and losses increase, causing the winding to overheat abnormally, causing the insulation film of the wire to burn and making it impossible to maintain insulation between the wires. or Therefore, the influence of the skin effect is reduced by using a so-called Litz wire, which is a bundle of thin copper wires, for the primary winding 4.

On the other hand, the secondary winding 5 has line-to-line withstand voltage and is arranged and wound in multiple layers so as to require less space. A smaller transformer was realized by applying face treatment to increase the withstand voltage between each winding and improve heat dissipation.

Problem 3 to be solved by the invention: However, such conventional high frequency transformers have the following drawbacks.

Power transformers that handle large currents have a problem with heat generation due to copper loss in the high-voltage winding 5, and in order to suppress this problem, it is necessary to take measures such as improving heat dissipation.

For example, an insulating material 6 with good thermal conductivity is used between the core and the high-voltage winding.
It was necessary to use a wire to release heat from the winding to the core, or to increase the cross-sectional area of the winding.

This has resulted in problems in that miniaturization of the transformer has been hindered and costs have also increased. Furthermore, as the handling frequency increases, due to the skin effect, the loss resistance of the winding does not decrease even if the cross-sectional area is increased by increasing the wire diameter, and the life of the transformer is shortened due to carbonization of the winding film due to heat generation, reducing reliability. It had the disadvantage of significantly lowering the

Means for Solving the Problems The present invention has been made to solve the drawbacks of such conventional high frequency transformers, and is a high frequency transformer constructed by the means described below.

That is, the core, the primary winding, and the two
The secondary winding has one or more secondary windings, and the secondary windings are connected in parallel and with the same polarity.

Effects The present invention has the following effects due to the above configuration. That is, in the high frequency transformer of the present invention, by connecting two or more secondary windings in parallel, the loss resistance of the secondary windings can be reduced and heat generation in the windings can be suppressed. Furthermore, when two or more are connected in parallel, thin wires can be used to make the current density of the secondary winding equal to that of a single secondary winding, which greatly reduces the influence of the skin effect. It can be made smaller. Therefore, even if the wire diameter is made thinner, the actual current density in the secondary winding of a high-frequency transformer does not increase as much as the wire's cross-sectional area becomes smaller, resulting in less heat generation and the volume occupied by the winding. Finish.

Since less heat is generated, the winding film only needs to have a low heat resistance, and it can be easily cooled, making it possible to realize a low-cost transformer with improved lifespan and reliability.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

,, FIG. 1 is a sectional view of a transformer according to an example of the present invention.

In the figure, cores 8 and 9 are made of yellowite and have a gap 10 to form a magnetic path. The core 8.9 is fixed with a stop 11. 12 is 1, stolen winding wire, Tsutsu wire! The world is alive. 13a and 13b are connected in parallel with secondary windings. , 1st order,! An insulating material 14 is provided between =1i2 and the secondary winding 13b. Further, an insulation tape 15 is wrapped around the secondary winding, and an insulating material 16 is applied to the creeping surface of the winding.

In the above configuration, since the two wires of the secondary windings 13a and 13b are connected in parallel, the cross-sectional area of the secondary winding is the sum of the cross-sectional areas of the two wires. For example, 0.5φ for the secondary winding.
The sum of the Bakura cut-off products using the copper wire is 6 Heno2 x πX0.252 = 0-39 (mm2).

In order to obtain the same cross-sectional area with one line, it is 0.
A 7φ copper wire is required. As shown in Figure 5, when a high frequency current is passed through a conductor, the resistance increases due to the skin effect, so in the case of an alternating current of 50) 1z, according to the configuration of the present invention, the direct current resistance will increase. If the secondary winding is constructed from one wire, the secondary winding resistance will be approximately 1°17 times as large. Since the loss is proportional to the resistance of the 4m wire, the amount of heat generated is about 1.1 times as shown by the following equation.

1, 17/1.07 = 1.09 Therefore, according to the present invention, the damage or heat generation of the secondary winding is reduced to 10
can be reduced. Figure 2 shows the results of actually measuring the frequency characteristics of the loss resistance of copper wire.

The coil used in the experiment was air-core with a winding width of 10 mm and a coil width of 400 mm.
It is made of turned copper wire. As shown in Figure 2, at high frequencies (10kHz or higher) the diameter of the copper wire is 0.
The loss resistance of 0.6φ (that is, the one with a larger cross-sectional area of 7 heel) is actually larger than that of 3φ. Therefore, reducing the wire diameter of the secondary winding alone is effective in lowering the loss resistance, but as in this example,
If the wire diameter is made thinner by dividing the next winding into two, the current density will not increase, which is effective in further reducing loss.

Less loss means less heat generation, which makes cooling easier, and allows the use of cores, winding coatings, and transformer insulation materials with low heat resistance, making it possible to lower costs and increase reliability. The performance of the transformer is significantly improved, and the efficiency of the transformer is also improved.

One possibility is to use a litz wire to reduce the wire diameter, but since the secondary side of a high-voltage transformer has a large number of turns, it is not easy to wind up a litz wire made of thin wires tied together. However, if the coils are made separately one by one as in this embodiment, it is possible to make them using a general winding machine or a method using an existing production process.

Next, other embodiments of the present invention are shown in FIGS. 3 and 4. Third
Both FIG. 4 and FIG. 4 are cross-sectional views of the transformer, and the same components as in FIG. 1 are given the same reference numerals.

In FIG. 3, the secondary windings j3a and 13b are connected to each other in parallel and with the same polarity, and 13h is wound around the outside of the secondary winding 13&. With such a configuration, it is possible to wind the inner secondary winding 13a and then the outer secondary winding 13b using one winding machine, which facilitates manufacturing.

In FIG. 4, a space 17 is provided along the side surfaces of the secondary windings 13a and 13b, so that when forced cooling of the transformer is performed, the airflow is good and the cooling effect is enhanced. As the frequency increases, the amount of heat generated also increases, so a transformer with a high cooling effect is extremely effective in improving reliability.

As described above, instead of using a Litz wire to reduce the wire diameter of the secondary winding, a compact high-frequency transformer that is easy to manufacture and cool can be realized by dividing the wire into two or more and connecting them in parallel.

Effects of the Invention 9 -\-2 As described above, according to the high frequency transformer of the present invention, the following effects can be obtained.

(1) Since the secondary winding generates less heat, windings with lower heat resistance grades can be used, making it possible to reduce costs.

(21) Since less heat is generated, the current density in the winding can be made higher than before, and a small, low-cost transformer can be realized.

(j) In the case of a transformer that performs forced cooling, the amount of heat generated is small, so a simple cooling configuration can be used.

(4) Since heat loss can be reduced, a transformer with high conversion efficiency can be realized.

(6) Since less heat is generated, the insulating material of the transformer can be made of a material with low heat resistance, resulting in cost reduction.

(6) Manufacture is easy because coils each made of copper wire are connected in parallel.

(7) Since the secondary winding is divided into two or more, the surface area of the winding becomes large and the cooling effect becomes stronger.

[Brief explanation of drawings]

FIG. 1 shows the high frequency t10=- in the first embodiment of the present invention.
. 2 is a frequency characteristic diagram of a copper wire coil loss resistance, FIG. 3 is a sectional view of a high frequency transformer in a second embodiment of the present invention, and FIG. 4 is a diagram of a high frequency transformer in a third embodiment of the present invention. FIG. 5 is a cross-sectional view of a high-frequency transformer in a conventional example, and FIG. 4i46 is a frequency characteristic diagram of increased resistance due to the skin effect of copper wire. 8.9...Core, 12...Primary winding,
13&. 13b...Secondary winding. Name of agent: Patent attorney Toshio Nakao and one other person δ,
? ---Core/2-/Burning/J

Claims (2)

[Claims] (1) A high frequency transformer comprising a core, a primary winding, and at least two secondary windings each configured independently, the secondary windings being connected in parallel and with the same polarity. (2) The high frequency transformer according to claim 1, wherein the secondary windings are arranged in parallel on the core, and a space is provided between each secondary winding.