JPH07120586B2 - Iron core with gap for transformer - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial Application) The present invention relates to a gapped core of a transformer for use in a large capacity semiconductor power converter.

(Prior Art) A transformer for a converter used in a semiconductor power converter includes:
It consists of several unit transformers in which a DC side winding and an AC side winding are wound around one iron core, several thyristors are connected in parallel to the DC side winding, and several AC side windings There are those for so-called series multiple voltage type inverters or converters that connect the two in series to the power supply or load, but this method has good characteristics in terms of the speed of operation, power factor on the power supply side and high frequency. Is obtained.

In a typical transformer, its iron core reduces the magnetic resistance by reducing the gap at the blank joining part of the silicon steel sheet, and the iron loss,
Although the exciting current and the vibration noise are further reduced, in the above transformer for transformer, it is necessary to form a gap in the iron core and increase the magnetic resistance to some extent for the following two reasons.

A direct current component is generated due to a slight shift in the on-timing of the thyristor, a shift in control, a difference in the impedance characteristics of the circuit including the transformer, and the like. When this DC current flows through the transformer windings, DC bias is generated in the iron core, the iron core is saturated, the exciting current increases, and the characteristics of the power converter deteriorate, and the transformer transformer loss And the vibration noise increases.

Since it is difficult to completely prevent this DC bias magnetization phenomenon, by providing a gap in the iron core, the magnetic resistance of the iron core is increased, the amount of bias magnetization is reduced, and a DC current of about 1% of the rated current is generated. Make sure that the iron core does not become saturated even if it flows.

Therefore, the iron core gap must be designed and machined so as to satisfy the relationship between the direct current and the amount of magnetic deviation.

If the shared voltage of the AC side windings connected in series is not made uniform, the operation as a power conversion device cannot be maintained well, so the unit transformers have the same excitation impedance, that is, the magnetic resistance of the iron core. Need to

It is usually difficult to make the magnetic reluctance the same, because there are variations in the magnetic characteristics due to the material of the iron core and the gaps in the blank plate joints are not uniform, but a gap is added.
By controlling the manufacturing so that the gap length is exactly the same in each device, it is possible to make the variation of the excitation impedance within several percent.

(Problems to be Solved by the Invention) However, in the conventional power converter, the required capacity of the unit transformer is small, and the number of units to be connected in series is small. Therefore, the iron core of each unit transformer is independent. But there was no particular problem.

However, the magnetic levitation type power converter for railways, which has recently attracted attention, and the static reactive power generator using a self-excited inverter for the purpose of stabilizing the power system, etc., have a large capacity, so the unit used The capacity of the transformer is large, the number of units connected in series is large, and the entire device becomes large-scale. And if it becomes a large-scale device, it is unavoidable that the transformer for the converter also becomes large in size, and the iron core also becomes large and heavy along with it, making it difficult to adjust the gap length. It was

The present invention has been proposed in order to solve the above-mentioned problems, and it is possible to easily adjust the gap length to match the magnetic resistance of the iron core with the specification value, and yet to provide one unit transformer core for several units. An object of the present invention is to provide an iron core with a gap for a transformer, which is made of an iron core and enables downsizing of the transformer for a converter.

[Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a plurality of main legs for winding a DC side winding and an AC side winding, and a main leg of the main leg. It is provided with side legs arranged on both sides and a lower yoke and an upper yoke for joining the legs, a gap of a magnetic insulator is attached between the main leg and the upper yoke, and between the main legs of the upper yoke. Further, a structural feature is that a seam portion for lap joining is provided between the main leg and the side leg.

(Operation) Since the iron core of the present invention having such a configuration is provided with a plurality of main legs for winding the DC side winding and the AC side winding, one winding for one unit transformer is provided. It can be wound around the main landing gear, and a plurality of unit transformers can be configured with one iron core. Since the magnetic insulator gap is formed in the main leg, the magnetic resistance of the iron core can be increased, and the mounting position of the magnetic insulator gap is above the transformer winding. The gap length for adjusting the magnetic resistance to the specified value can be easily adjusted simply by removing the.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the iron core of the present embodiment is provided with three main legs 3 around which a DC side winding 1 and an AC side winding 2 are wound, and side legs 4 are provided on both sides thereof. ing. These three main legs 3 and the side legs 4 on both sides are joined by a lower yoke 5 and an upper yoke 6, and in particular, a magnetic insulator gap 7 is attached between each main leg 3 and the upper yoke 6. ing. Further, a seam 8 for lap joining is provided between the main legs 3 of the upper yoke 6 and between the main legs 3 and the side legs 4.

Then, although not shown, a backing plate is attached to each surface of the punched plates forming the main leg 3 and the side legs 4, and a clamp is attached to the punched plates forming the lower yoke 5 and the upper yoke 6. The binding is tightened with bolts or glass tape. Further, in the iron core with a gap as in this embodiment, the magnetic flux passing through the gap 7 causes a magnetic attraction force between the upper and lower surfaces of the gap 7 to generate vibration and noise. 6, the gap 7, the main leg 3, and the lower yoke 5 are firmly fastened in the vertical direction by fastening studs.

Further, as shown in the enlarged plan view of FIG. 2, the upper yoke 6 is formed by stacking punched plates of silicon steel sheets, and the seam 8 of the punched plates is lap jointed with the dimension A, and the left and right upper yokes are joined. 6 is magnetically bonded, but is configured to be relatively movable in the vertical direction.

The iron core with a gap of this embodiment has the above-mentioned structure, and its operation will be described below.

If the upper yoke 6 is a single piece without the seam 8, a compressive force is applied to the main leg 3 and the side leg 4 by tightening the lower yoke 5 and the upper yoke 6 up and down. If there are gaps in the joints due to tolerances or errors in assembly, the upper and lower yokes are stretched, and the vertical dimensions of the main leg 3 and side legs 4 vary, the gap 7
May not be tightened with proper pressure, and vibration and noise may increase. However, in this embodiment, the upper yoke 6 has the seam 8, and the seam 8 is divided for each leg and can be relatively moved in the vertical direction. The force is applied uniformly, and the increase in vibration and noise can be suppressed. In particular, when the temperature of the iron core rises when the transformer is operated, a difference in expansion occurs between the main legs and between the side legs, causing the upper yoke 6 to be pushed or bent, which may cause excessive bending stress or compressive stress. The generated magnetostriction increases and the vibration / noise due to the magnetostriction increases. However, in the configuration of the present embodiment, since the force of the joint 8 of the upper yoke 6 does not generate an unreasonable force, the vibration / noise due to the magnetostriction is increased. Can be suppressed.

Next, a method of adjusting the gap length in this embodiment will be described. First, the main leg 3 and the side leg 4 are joined by the lower yoke 5, the DC side winding 1 and the AC side winding 2 are inserted from the upper side to assemble the winding, and the gap 7 is attached to the upper side of the main leg 3. , Assemble the upper yoke 6, attach the clamp and the vertical stud, and tighten. Then, an AC power supply is connected to the DC side winding 1 or the AC side winding 2, and the excitation impedance of each leg is measured. If the measured excitation impedance does not satisfy the specified value, the assembled upper yoke 6 is removed, the size G of the gap 7 is adjusted, and the upper yoke 6 is reassembled so that the excited impedance satisfies the specified value. adjust. By adjusting the dimension G of the gap 7 in this manner, even if the total height of the main leg 3 and the gap 7 is different between the other legs, the upper yoke 6 has the seam 8, so that
It suffices to move the upper yoke 6 relatively in the vertical direction.

Furthermore, the iron core of the present embodiment performs the same action as when the conventional plurality of unit transformers are used as separate iron cores, with reference to FIG. 3 and FIG.

That is, FIG. 3 is a diagram showing a magnetic equivalent circuit of the iron core shown in FIG. 1, and Ea, Eb, and Ec on the power supply display are exciting currents for flowing magnetic flux to the main legs and the exciting currents. It is the magnetomotive force obtained by the product of the number of winding turns. Resistance display R ₁ , R ₂ , R ₃ , R
₄ is the magnetic resistance of each magnetic path, R ₁ is the magnetic circuit of the main leg including the gap 7, R ₂ and R ₃ are the magnetic circuits corresponding to the main leg between the lower yoke 5 and the upper yoke 6, and R ₄ Is a magnetic circuit portion corresponding to the lower yoke 5, the upper yoke 6 and the side leg 4 between the main leg and the side leg. Here, since the resistor R ₁ has the gap 7,
It is much larger than the resistors R ₂ , R ₃ and R ₄ without gaps. If the resistances R ₂ , R ₃ and R ₄ are small and can be ignored compared to the resistance R ₁ , a magnetomotive force Ea is generated only in the left main leg 3 in FIG. , The magnetic fluxes Φ ₁ and Φ ₄ flowing to the side legs 4 on both sides become large, and the magnetic fluxes Φ ₂ and Φ ₃ flowing to the main leg 3 on the center and the right side.
Will be small and negligible. The flow of magnetic flux in the case of the other main landing gears is the same, and the following can be said.

That is, since the magnetic flux generated in one main leg does not flow in the other main leg but through the side leg 4, the lower yoke 5, and the upper yoke 6, magnetic coupling between the main legs can be ignored, and This is equivalent to the case where separate iron cores are used for the unit transformers, and there is no problem even if the windings for each of the main legs have separate voltage suppression, that is, a pulse width modulation method.

In this case, in order to make the values of the resistors R ₂ , R ₃ , and R ₄ smaller, the side leg 4, the lower yoke 5, and the upper yoke 6 are made of a highly oriented material having a large magnetic permeability and good characteristics. To do.

The cross-sectional area of the lower yoke 5 and the upper yoke 6 may be half the cross-sectional area of the main leg in the case of an ordinary transformer iron core, but it should be made slightly larger so that the magnetic flux density becomes lower.

The joint between the side leg 4 and the lower yoke 5 and the upper yoke 6 may be a frame-shaped lap joint, and if necessary, a so-called step lap structure may be employed in which the blanks are staggered and joined.

These means are used in combination to optimize the iron core specifications.

(Other Embodiments) The present invention is not limited to the above-described embodiments, and the number of main legs can be arbitrarily changed, and the configuration of other portions does not change the gist of the present invention. It can be changed with.

For example, in FIG. 1, the direction indicated by the arrow 9 is the rolling direction of the grain-oriented silicon steel sheet, and in the above-mentioned embodiment, the magnetic flux flows in that direction to reduce the generated loss. With respect to the magnetic flux flowing from 3 to the upper yoke 6 through the gap 7, there is a component that flows in the direction perpendicular to the rolling direction in the upper yoke 6, so that the loss generated at that portion becomes large and causes local overheating. . Therefore, when the applied device becomes larger and the iron core size becomes large, or when it is necessary to particularly reduce the generated loss, as shown in FIG. Install the right triangle punch plate 10. That is, the upper yoke 6 which is in contact with the gap 7 is cut out in a triangular shape, and a punched plate is cut in that portion.
10 is installed so that the rolling direction 9 is vertical.
With such a structure, the gap 7 can be formed from the main landing gear 3.
The magnetic flux flowing through to the upper yoke 6 smoothly flows through the punched plate 10 and is improved so that the magnetic flux flows in the rolling direction at any place, and the above-mentioned increase in loss is reduced,
Effective in preventing local overheating.

[Advantages of the Invention] As described above, according to the present invention, an arbitrary number of main legs and side legs on both sides thereof are joined by the upper and lower yokes, and a gap is attached between each main leg and the upper yoke. Moreover, despite the simple means of providing lap joint seams between the main legs of the upper yoke and between the main legs and the side legs, several sets of DC side windings and AC side windings are provided in one multi-phase core. A transformer gap that can be wound, is small as a transformer for transformers, can easily adjust the gap length, and can suppress the magnetic attraction force generated in the gap and the vibration and noise due to the magnetostriction of the silicon steel sheet. An iron core can be provided.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an iron core with a gap for a transformer according to the present invention, FIG. 2 is an enlarged plan view of a joint 8 portion in FIG. 1, and FIG. 3 shows the operation of the embodiment shown in FIG. FIG. 4 is a magnetic equivalent circuit diagram for explaining, and FIG. 4 is a front view showing a joint portion between an upper yoke and a main leg in another embodiment of the present invention. 1 ... DC side winding, 2 ... AC side winding, 3 ... Main landing gear, 4
...... Side legs, 5 ... lower yoke, 6 ... upper yoke, 7 ...
… Gap, 8 …… Seam, 9 …… Rolling direction, 10 …… Triangle upper yoke blank.

Claims (1)

[Claims] 1. A transformer comprising a plurality of main legs around which transformer windings are wound, side legs arranged on both sides of the main legs, and a lower yoke and an upper yoke joining the legs. In the iron core with a gap, a magnetic insulator gap is attached between the main leg and the upper yoke, and lap joint seams are provided between the main legs of the upper yoke and between the main leg and the side legs. An iron core with a gap for a transformer.