JP2753122B2 - Iron core with gap for transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a core with a gap for a transformer used in a large-capacity semiconductor power converter.

(Conventional technology) A transformer for a converter used in a semiconductor power converter is composed of several unit transformers in which a DC winding and an AC winding are wound around a single iron core, and the DC winding is connected to the transformer. There are several thyristors connected in parallel, and their AC side windings are connected to a power supply or load by connecting several units in series, so-called series multiple voltage type inverters or converters are available. Good characteristics can be obtained with respect to the responsiveness of the operation, the power factor on the power supply side, and the high frequency.

In ordinary transformers, the iron core reduces the gap at the blanked joint of the silicon steel sheet to reduce the magnetic resistance, thereby reducing iron loss, exciting current and vibration noise. Then, for the following two reasons, it is necessary to provide a gap in the iron core and increase the magnetic resistance to some extent.

(1) A DC component current is generated due to a slight shift of the thyristor's ON timing or a shift in control, a difference in impedance characteristics of a circuit including a transformer, or the like. When this DC current flows through the transformer windings, DC bias occurs in the iron core and the iron core is saturated, the exciting current increases, the characteristics of the power converter deteriorate, and the transformer for the converter has a loss. Increase, and the vibration noise increases.

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

Therefore, to satisfy the relationship between the DC current and the amount of magnetization,
The core gap must be designed and engineered.

(2) The operation as a power converter cannot be maintained satisfactorily unless the shared voltages of the AC-side windings connected in series are made uniform, so that the unit transformers have the same excitation impedance, that is, the same magnetic resistance of the iron core. Need to be

It is usually difficult to make the magnetic resistance the same due to variations in the magnetic properties due to the material of the iron core and irregularities in the gaps at the punched joints.However, a gap is provided and the gap length is set for each transformer. By controlling the production so that they are exactly equal, the variation in the excitation impedance can be kept within several percent.

(Problems to be Solved by the Invention) 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. There was no.

However, the static levitation generator using a self-excited inverter for the purpose of stabilizing the power system and the magnetic levitation railway power converter, etc., have a large capacity, so the unit transformer has a large capacity, The number of units to be connected in series increases, and the scale becomes large.

If a large-scale device is used, its iron core becomes large and its work such as adjustment of the gap length becomes difficult. As a converter for a converter, its external dimensions are large and its weight is heavy, so its price is high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to easily adjust a gap length for adjusting a magnetic resistance of an iron core to a specification value, and to configure one unit core for several transformer cores of a unit. It is an object of the present invention to provide a transformer core with a gap that can make a transformer for a converter compact.

[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 on which a DC side winding and an AC side winding are wound, and sides arranged on both sides of the main legs. It is composed of a leg and a lower yoke and an upper yoke which are joined to the main leg via a V-shaped joint, and a gap of a magnetic insulator is provided between the V-shaped joint between the main leg and the upper yoke. It is characterized in that a lap joint seam is provided between the main leg of the upper yoke and between the main leg and the side leg.

(Operation) With such a configuration, the iron core is not independent for each unit transformer, and one unit transformer can be constituted by one main leg, so that a plurality of unit transformers can be integrated into one iron core. Can be made possible. And since the gap is formed in the main leg, the magnetic resistance of the iron core can be increased, the mounting position of the gap is above the transformer winding, and only by removing the upper yoke, the magnetic resistance can be adjusted to the specified value. The gap length can be easily adjusted. Further, since the shape of the gap is provided in accordance with the V-shaped joint between the main leg and the upper yoke, overheating of the iron core, which tends to occur at this joint, can be suppressed.

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

FIG. 1 shows three main legs 3 around which a DC side winding 1 and an AC side winding 2 are wound, side legs are provided on both sides thereof, and these legs are connected to a lower yoke 5 and an upper yoke 6 by a V. And a gap 7 made of a magnetic insulator is attached between the V-shaped joint between the main leg 3 and the upper yoke 6 so as to provide a gap between the main legs of the upper yoke 6 and between the main leg and the side leg. Between each lap joint seams 8 are provided. Then, although not shown, a patch plate is attached to each of the main leg 3 and the side leg 4, and a clamp is attached to the lower yoke 5 and the upper yoke 6, and the bolt is tightened or the bind is tightened with glass tape or the like.

FIG. 2 is an enlarged view of the seam 8 as viewed from above. The upper yoke 6 is formed by stacking punched silicon steel sheets. The joint 8 is formed by lap-joining the punched sheet with a dimension A, and the left and right upper yokes 6 are magnetically coupled with each other. Are configured to be relatively movable.

In the iron core with the gap, although not shown, magnetic attraction acts between the upper and lower surfaces of the gap due to the magnetic flux passing through the gap to generate vibration noise, but the upper yoke 6, the gap 7, the main leg 3, and the lower yoke 5 are not shown. Tighten firmly with fastening studs vertically.

If the upper yoke 6 is a single piece having no seam 8, a compression 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. Due to the above error, a gap may be formed at the joint or the upper and lower yokes may protrude. If there is a variation in the vertical dimensions of the main leg 3 and the side leg 4, the gap 7 cannot be tightened with an appropriate pressure, and vibration noise is generated. May increase.

However, in the present embodiment, the upper yoke 6 has the seam 8 and is divided for each leg. Therefore, the upper yoke 6 can be relatively moved in the vertical direction, so that the above-described errors can be absorbed, and the tightening force can be made uniform. And increase in vibration noise can be suppressed.

Next, a method of adjusting the gap length by this configuration will be described.

First, the main leg 3 and the side leg 4 are connected by a lower yoke 5, and a winding in which the DC side winding 1 and the AC side winding 2 are inserted from above is assembled. 6
Install the clamp and the upper and lower tightening studs 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 specification value, the assembled upper yoke 6 is once removed, the dimension G of the gap 7 is adjusted, and the upper yoke 6 is assembled again to adjust the excitation impedance so as to satisfy the specification value. . By adjusting the dimension G of the gap 7 in this manner, the main landing gear 3
Even if the total height of the gap and the gap 7 is different between the other legs, since the upper yoke 6 has the joint 8, the upper yoke 6 may be relatively moved in the vertical direction.

When the temperature of the iron core is increased by driving, a difference in elongation due to thermal expansion occurs between the main legs and between the side legs due to various conditions, and the upper yoke 6 is pushed or bent, and excessive bending stress or compressive stress is generated. Is generated, the magnetostriction increases, and the vibration noise due to the magnetostriction increases.
No excessive force is generated by the action of the seam 8, so that an increase in vibration noise due to magnetostriction can be suppressed.

FIG. 3 is a diagram showing a magnetic equivalent circuit of the iron core shown in FIG. 1, and Ea, Eb, and Ec in the power supply display indicate an exciting current for flowing a magnetic flux through the main legs and a winding of the exciting current. This is the magnetomotive force obtained by multiplying the number of turns. R ₁ , R ₂ , R ₃ , R ₄ of the resistance display are the magnetic resistance of each magnetic path, R ₁ is the magnetic circuit of the main leg including the gap 7, R ₂ , R ₃ are the lower yoke 5 and the upper yoke 6 And R ₄ is a magnetic circuit component corresponding to the lower yoke 5, the upper yoke 6, and the side leg ₄ between the main leg and the side leg.

Since the resistance R ₁ is with a gap 7, much the value is greater than the no resistance gaps _{R 2, R 3, R 4} . If resistance
If R ₂ , R ₃ , and R ₄ are small and negligible compared to the resistance R ₁ , in FIG. 3, for example, the magnetomotive force Ea is applied only to the left main leg 3.
There Considering the case flows generated magnetic flux phi _a, the magnetic flux phi ₁ flowing through the side leg ₄ of both sides, phi ₄ is increased, the magnetic flux phi ₂ flowing in the middle and right main legs 3, phi ₃ is negligible small become. The flow of the magnetic flux in the case of other main landing gears is the same, and the following can be said.

That is, the magnetic flux generated in one main leg does not flow to the other main leg but flows through the side leg 4, the lower yoke 5, and the upper yoke 6, so that magnetic coupling between the main legs can be ignored, and the conventional This is equivalent to the case where a separate iron core is provided for each unit transformer, and there is no problem even if separate voltage control, that is, a pulse width modulation method is used for the winding of each main leg.

Means for reducing the values of the resistors R ₂ , R ₃ , and R ₄ are as follows: (a) For the side legs 4, the lower yoke 5, and the upper yoke 6, a highly oriented material having high magnetic permeability and better characteristics is used. use.

(B) The cross-sectional area of the lower yoke 5 and the upper yoke 6 may be half the cross-sectional area of the main landing gear for a normal transformer iron core, but is slightly increased so that the magnetic flux density becomes lower.

(C) The joint between the side leg 4, 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 in which the blanks are displaced in a stepwise manner.

These joining means are employed in combination so as to be optimal according to the specification of the iron core.

FIG. 4 is a diagram showing the flow of magnetic flux at the V-shaped joint between the upper yoke 6 and the main leg 3. The direction indicated by arrow 9 is
This is the rolling direction of the grain-oriented silicon steel sheet, and the magnetic flux flows in that direction to reduce the generation loss. Also, for the magnetic flux flowing from the main leg 3 to the upper yoke 6 through the gap 7, the joint between the upper yoke 6 and the main leg 3 is
Since they are joined in a V-shape with an angle of 45 degrees, no component flows in the direction perpendicular to the rolling direction, so that the generation loss at that portion is kept small and there is no danger of causing local overheating.

The present invention is not limited to the above-described embodiment, and the number of main landing gears can be arbitrarily changed, and can be applied within a range that does not change the gist thereof.

〔The invention's effect〕

As described above, according to the present invention, several sets of the DC side winding and the AC side winding can be wound on one polyphase core, and the transformer for the converter can be made compact, In addition, its external dimensions, weight and price can be reduced, and the gap length can be easily adjusted. This provides a reasonable tightening method, so the tightening force is uniform, and the magnetic attraction force and silicon generated in the gap portion It is possible to provide a transformer core with a gap that can suppress vibration noise caused by magnetostriction of a steel plate.

[Brief description of the drawings]

FIG. 1 is a side view of one embodiment of the present invention, FIG. 2 is an enlarged view of a joint of FIG. 1, FIG. 3 is a magnetic equivalent circuit diagram of FIG.
FIG. 4 is an explanatory diagram showing the flow of magnetic flux at the V-shaped joint between the upper yoke and the main leg in FIG. 1,2: DC side winding, AC side winding 3 ... Main leg 4, Side leg 5,6 ... Lower, upper yoke 7 ... Gap, 8 ... Seam 9 ... Rolling direction

Claims (1)

(57) [Claims] An arbitrary number of main landing gears wound with a transformer winding;
In a transformer core composed of side legs arranged on both sides of the main leg and a lower yoke and an upper yoke connecting the legs, a V-shaped joint between the main leg and the upper yoke is provided. A gap iron core for a transformer, wherein a gap of a magnetic insulator is attached, and a seam portion of a lap joint is provided between main legs of an upper yoke and between a main leg and a side leg.