JPH0219611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a feed-through current transformer having a structure in which a secondary winding is divided, and particularly to a structure for reducing the size and weight of the current transformer.

[Prior art]

Figure 1a is a side view of a conventional feed-through current transformer, with part of the cross section taken, Figure 1b is a sectional view taken along line A-A' in Figure 1a, and Figure 2 is a wiring diagram of each divided winding. shows. In each of the above figures, the current transformer has an annular iron core 2 provided around a bus bar 1 which is a primary conductor, an insulating tape 3 wrapped around the entire surface of the iron core 2, and a secondary Divided windings 4a to 4c obtained by dividing the winding 4 into six parts
(The other three divided windings are omitted in the above figures)
The above-mentioned divided windings 4a to 4
c is connected in series and has a predetermined number of turns as a secondary winding.

In this way, the conventional current transformer has secondary windings 4a to 4a.
4c is divided and wound around the iron core 2, an induced secondary current i ₁ is generated in the secondary windings 4a to 4c.
When , a leakage magnetic flux φL that does not interlink with the bus bar 1 is generated in the magnetic flux due to the induced secondary current i ₁ . For this reason, the magnetic flux passing through the iron core 2 increases locally,
In other words, the magnetic flux density differs between the parts of the core 2 around which the divided windings 4a to 4c are wound and the other parts, and in order to achieve a predetermined magnetic flux density that does not cause magnetic saturation in the core 2, the cross-sectional area of the core must be changed. Therefore, the shape of the current transformer itself had to be made large.

In addition, the iron core 2 is a wound iron core made by winding a long silicon steel strip without cutting it, for example, and because the silicon steel strip is bonded and fixed with insulating tape, it is extremely vulnerable to external mechanical forces. However, the shape and structure of the core 2 itself is distorted due to external forces such as vibrations during assembly or use, resulting in deterioration of magnetic properties.

[Summary of the invention]

The present invention has been made in view of the above-mentioned drawbacks, and it is possible to reduce leakage magnetic flux and minimize the core cross-sectional area, thereby preventing deterioration of magnetic properties and achieving size and weight reduction. This provides a current transformer that can

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in Figs. 3a, b and 4.
This will be explained in detail based on FIGS. Figure 3a
3b is a sectional view taken along line BB' in FIG. 3a, FIG. 4 is a winding connection diagram, and FIG. FIG. 5 is an enlarged view showing the direction of the magnetic field regarding one divided winding. In each of the above figures, a current transformer according to an embodiment of the present invention has six divided windings 5 wound around the peripheral edge of an annular core 2 with a predetermined gap in the direction of the magnetic path of the annular core 2.
windings having windings a to 5c (the three on the right half are not shown) and wound in the opposite direction to the divided windings 5a to 5c on the inner side of the central part of each of the divided windings 5a to 5c. First leakage flux reduction windings 6a to 6c (hereinafter referred to as first reduction windings) for canceling the leakage flux generated by the divided windings 5a to 5c (hereinafter referred to as first reduction windings), and only 6b is shown, 6a, 6c is not shown), and the winding direction is the same as that of the divided windings 5a to 5c, and the first reduction windings 6a to 6c are provided on both sides of the first reduction windings 6a to 6c. Second reduction windings 7a to 7a are formed of the same number of turns and are used to cancel leakage magnetic flux together with the first reduction windings 6a to 6c.
7c (only 7b is shown, 7a and 7c are not shown).
By providing second reduction division windings 7a' and 7a'', 7b' and 7b'', and 7c' and 7c'', each of which is divided into two parts (the same applies hereinafter), the above-mentioned division windings 5a to 5c and the first reduction The windings 6a to 6c and the second reduction division winding constitute the secondary winding 5 as a whole.The division windings 5a to 5c, the first reduction division winding 6a to 6c,
The second reduced division windings 7a′ to 7c′, 7a″ to 7c″ are
Since they are each connected in series to form the secondary winding 5, the current i ₂ flowing through each winding is in the same direction. That is, the number of windings of the same direction windings of the divided windings 5a to 5c and the second reduction divided windings 7a' to 7c', 7a'' to 7c'' is larger than that of the reduction windings of the opposite direction windings. Since the number of windings is greater than that of the wires 6a to 6c, the first reduction windings 6a to 6c are reversely wound, so even though a secondary current is generated in the opposite direction by the action of the magnetic flux from the bus bar 1. First, current i ₂ flows in the same direction as the divided windings 5a to 5c.

Moreover, between the iron core 2 and the secondary winding 5,
A shield container 8 made of a non-magnetic good conductor such as copper or aluminum is provided over almost the entire circumference of the surface of the iron core 2 in an insulated state by interposing insulation tapes 3 and 10 between the iron core 2 and the secondary winding 5. ing.

Next, in the current transformer configured as above,
The relationship between the leakage flux generated by the divided winding 5b, the first reduced winding 6b, and the second reduced divided windings 7b' and 7b'' will be explained based on FIG. The magnetic flux related to the boundary between the wire 6b and the second reduction divided windings 7b' and 7b'' is, as shown in the figure, the leakage magnetic flux φ5b due to the divided winding 5b, the leakage magnetic flux φ6b due to the first reduction winding 6b and the second reduction magnetic flux φ5b. Reduced split winding 7
The leakage magnetic fluxes φ7b′ and φ7b″ due to b′ and 7b″ are in the opposite direction, and the leakage magnetic fluxes φ5b, φ6b, φ7
b', φ7b'' cancel each other out and the leakage magnetic flux is reduced.Therefore, the first reduction winding 6b and the second reduction divided winding 7b', 7b'' are connected to the inside of the secondary winding 5. As a whole, the leakage magnetic flux φ5b generated by the divided winding 5b is reduced, and as a result, the above-mentioned iron core 2
The magnetic flux passing through the iron core 2 is prevented from increasing locally, and the iron core 2 has a predetermined magnetic flux density that does not cause magnetic saturation, and the cross-sectional area of the iron core 2 can be kept to a minimum.

Furthermore, the leakage magnetic flux due to the divided winding 5b outside the secondary winding 5 is prevented from passing through the shield container 8 to the outside of the shield container 8, and all the leakage magnetic flux generated by the divided winding 5b is It will be further reduced. In addition, since the shield container 8 covers the iron core 2 with metal such as copper or aluminum, it is possible to improve the mechanical strength against external forces such as vibration during assembly or use. By eliminating distortion in the shape and structure of 2 itself, deterioration of magnetic properties is prevented.

The shield container 8 is provided with a slit 9 consisting of a groove-shaped opening all around the inner circumference in the longitudinal direction of the circumference, through which an induced current generated by the excitation magnetic flux passing through the magnetic path formed by the iron core 2 flows. This is prevented by the slit 9. This shield container 8
Insulation between the iron core 2 and the divided windings 5 is achieved by insulating tapes 3 and 10 wound inside and outside.

Note that the ratio of the number of turns of each winding that constitutes the secondary winding 5 can also be changed to an arbitrary ratio that cancels out the leakage fluxes. In the above embodiment, the first reduction windings 6a to 6c and the second reduction windings 7a to 7c are provided inside the divided windings 5a to 5c, but they may be provided outside. Further, the slit 9 of the shield container 8 may be provided anywhere above or below, as long as it is provided over the entire circumference in the longitudinal direction.

〔Effect of the invention〕

As explained above, the present invention employs a configuration in which the secondary winding is formed by the divided winding, the first reduction winding, and the second reduction winding, so that leakage flux can be reduced. Therefore, it is possible to prevent the magnetic flux passing through the iron core from increasing locally and to minimize the cross-sectional area of the iron core corresponding to a predetermined magnetic flux density without causing magnetic saturation of the iron core. This has the effect of reducing weight.

[Brief explanation of drawings]

Fig. 1a is a front view showing a conventional current transformer, Fig. 1b is a sectional view taken along line A-A' in Fig. 1a, Fig. 2 is a connection diagram of a split winding, and Fig. 3a is a diagram of the present invention. A front view of a current transformer according to an embodiment of the present invention, FIG. 3b is B- of FIG. 3a.
B' sectional view, FIG. 4 is a wiring diagram of each winding constituting the secondary winding, and FIG. 5 is an enlarged view showing the direction of the magnetic field regarding one divided winding. 1: Bus bar, 2: Iron core, 3, 10: Insulating tape,
4, 5: Secondary winding, 4a, 4b, 4c, 5a, 5
b, 5c: split winding, 6a, 6b, 6c: first reduction winding, 7a, 7b, 7c: second reduction winding,
7a', 7b', 7c', 7a'', 7b'', 7c'': second reduced division winding, 8: shield container, 9: slit.

Claims (1)

[Scope of Claims] 1. An annular iron core is provided around a bus bar which is a primary conductor, and split windings in which a secondary winding is divided are wound around the periphery of the iron core in the magnetic path direction with a predetermined gap therebetween. In the current transformer, a first leakage flux reducing winding wound near the center of each of the divided windings in a direction opposite to the winding direction of the divided winding, and the first leakage flux reducing winding. A second leakage flux reducing winding is formed at both ends of the winding in the same direction as the winding direction of the divided winding and having the same number of turns as the first leakage flux reducing winding. 1. A current transformer comprising a secondary winding having a secondary winding. 2. A shielding container made of a non-magnetic electrically conductive material such as copper or aluminum is provided between the iron core and the secondary winding via an insulating tape, covering almost the entire circumference of the surface of the iron core. A current transformer according to claim 1.