JPH04117419U - power transformer - Google Patents

Abstract

(57) [Summary] [Purpose] The power transformer itself suppresses inrush current when the power is turned on. [Structure] In a power transformer, the primary winding 13 and the secondary winding 14 are wound around a wound iron core with a uniform cross-sectional area that forms a closed magnetic path. An iron core is added to the leg part 11 of the wound iron core 10 so that the cross-sectional area is larger than that of the remaining iron core parts. As the cross-sectional area increases, the magnetic resistance of the primary winding part decreases without becoming saturated.
Since magnetic flux in the primary winding is easily generated and input impedance increases, inrush current is reduced.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a power transformer that receives commercial power as input.

0002

[Conventional technology]

When powering on equipment using this type of power transformer, the phase relationship at the time of power-on is This causes the transformer's iron core to become magnetically saturated, causing a large inrush current to flow. these Countermeasures include adding delay characteristics to the power supply fuse of the equipment, and It is necessary to install a zero cross device so that voltage is supplied to the winding from the point of 0 volts. It is being done.

0003

[Problem that the idea aims to solve]

However, the residual magnetism in the iron core of the transformer is affected by the current at power-on. If the magnetization directions are in the same direction, excessive inrush current due to magnetic saturation of the iron core will occur. At the same time, the use of high magnetic flux density iron cores has increased due to the demand for smaller and lighter transformers. In some cases, an inrush current that is 50 times or more than the steady input current may occur. Therefore, the above-mentioned measures alone are no longer sufficient. In view of these points, the present invention uses the power transformer itself to reduce the inrush current when the power is turned on. The purpose is to suppress

0004

[Means to solve the problem]

In this invention, a primary winding and a secondary winding are wound around a wound iron core that forms a closed magnetic path. In a power transformer, the primary winding is wound to achieve the above purpose. An iron core is added to the iron core part so that the cross-sectional area is larger than that of the remaining iron core part. It is characterized by

[0005] When the winding frame around which the primary winding is wound and attached to the winding iron core is formed from a magnetic material, It is possible to give the winding frame an inrush current suppressing effect. This invention uses the same layer in the primary winding. The secondary winding is commonly wound around the iron core of the primary winding. Of course, this applies even if there are.

[0006]

[Effect]

By increasing the cross-sectional area of the wound iron core around which the primary winding is wound, The magnetic resistance of the primary winding decreases without being saturated, generating magnetic flux in the primary winding. The inrush current is reduced due to the increased input impedance.

[0007]

【Example】

FIG. 1 shows a power transformer using a wound iron core according to a first embodiment of the present invention. child As shown in FIG. 2, the wound iron core 10 is formed into one piece or , a plurality of sheet-like silicon steel plates 9 are sandwiched several times to reduce the cross-sectional area to the yoke 12 and It is set to be 30% wider than the leg portion 12a for the secondary winding. And then split into two It is formed as a cut core which is then tightly attached after winding. Leg 11 has commercial A primary winding 13 that is supplied with power from a power source 1 is wound around the leg portion 12a, and a secondary winding 1 is wound around the leg portion 12a. 4 is wound. This prevents the added iron core from becoming saturated. Increases input impedance and reduces inrush current.

FIG. 3 shows test data confirming the effectiveness of the power transformer according to the first embodiment. As for the test conditions, the wound iron core 10 is made of a silicon steel plate as described above, has a cross-sectional area of 19 cm ² , and a capacity of 500 VA. Then, keeping the cross-sectional area of the leg part 11 the same as the others, a magnetic material of the same material whose cross-sectional area gradually increases is added, and each time the power is turned off under the maximum residual magnetization state, which is the most severe condition. The magnetization directions were aligned and the power was turned on at the phase of maximum current. The measured value is an improvement ratio with respect to the inrush current of 130 A when the cross-sectional area of the leg portion 11 is the same as the others. In other words, when the cross-sectional area is increased by 30% as described above, the inrush current ratio is reduced to approximately 50%. After that, it was confirmed that the degree of improvement with respect to an increase in cross-sectional area became smaller, and even if the cross-sectional area was increased by 100% or more, the improvement ratio reached a saturated state, and it was found that increasing the cross-sectional area any further was meaningless. At least as long as the wound iron core is made of a silicon steel plate, the magnetic circuits are considered to be equivalent under high magnetic flux density even if the shape changes, so that the improvement ratio will be almost the same in characteristics.

[0009] FIG. 4 shows a second embodiment, in which the cross-sectional area of the leg portion 21 of the wound iron core 20 is the same as that of the remaining cross-sectional area. area, and a separately prepared attachment to increase the cross-sectional area by, for example, 50%. A plurality of additional silicon steel plates 25 are attached externally to connect the primary winding 23 and the secondary winding 24. It is wound in the same layer. In this case, too, the inrush current is reduced to nearly 30%, corresponding to Figure 3. It can be reduced.

0010 FIG. 5 shows a third embodiment in which the wound iron core 30 has a uniform cross-sectional area as in the conventional case. At the same time, as shown in Figure 6, a winding made of magnetic material is shaped according to the cross section. The primary and secondary windings are wound around the frame 32 and attached to the wound iron core 30. This allows the legs The cross-sectional area of the section is substantially increased to achieve the same effect.

[0011]

[Effect of the idea]

As described above, according to the present invention, the cross-sectional area of the iron core portion around which the primary wire of the wound iron core is wound is widened. By doing so, the expansion of the overall shape of the iron core is suppressed and the inrush current is effectively reduced. It becomes possible to

[Brief explanation of drawings]

FIG. 1 shows the configuration of a power transformer according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing the process of creating a wound iron core of the power transformer.

FIG. 3 is a diagram showing test results for confirming the effectiveness of the power transformer.

FIG. 4 shows the configuration of a power transformer according to a second embodiment of the present invention.

FIG. 5 shows the configuration of a power transformer according to a third embodiment of the present invention.

FIG. 6 is a perspective view showing a winding frame of a winding iron core according to the third embodiment.

[Explanation of symbols]

10, 20, 30 wound iron core 11, 21 Legs 9, 25 Silicon steel plate 32 Reel frame

Claims (4)

[Scope of utility model registration request] Claim 1: A power transformer in which a primary winding and a secondary winding are wound around a wound iron core forming a closed magnetic path,
A power transformer characterized in that an iron core is added to the iron core portion around which the primary winding is wound so that the cross-sectional area is larger than that of the remaining iron core portion. 2. The power transformer according to claim 1, wherein the secondary winding is commonly wound around the iron core portion around which the primary winding is wound. 3. A power transformer in which a primary winding and a secondary winding are wound around a wound iron core forming a closed magnetic path,
A power transformer characterized in that a winding frame around which a primary winding is wound and attached to a winding iron core is made of a magnetic material. 4. The power transformer according to claim 3, wherein the secondary winding is commonly wound around the winding frame around which the primary winding is wound.