JPH01287908A - Network transformer - Google Patents

Abstract

PURPOSE:To contrive miniaturization and lightweightedness of the title transformer while inverse power breaking characteristics are being secured by a method wherein an iron core, which is constituted by miter-jointing a non- oriented silicon steel plate or an amorphous magnetic band, is used. CONSTITUTION:An iron core 35, which is constituted by miter-jointing non- oriented silicon steel plates 21-34, is used. Also, an iron core 35, which is constituted by miter-jointing using an amorphous magnetic band instead of the non-oriented silicon steel plates 21-34, may be used. Consequently, as the magnetic resistance of the jointed part of the miter-jointing system becomes smaller than that of the jointed part of the lap-joint system, the magnetizing current, which generates magnetomotive flux force, to be used to let magnetic flux to pass through the iron core 35, is attenuated and accordingly, a small type of the iron core 35 performs its function sufficiently. As a result, inverse power breaking characteristics can be obtained without increasing in size of the iron core 35.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a network transformer designed to improve excitation characteristics.

(Prior Art) Typical uninterruptible power distribution systems include a network power distribution system, that is, a spot network power distribution system and a regular network power distribution system.

FIG. 7 shows a schematic single-line connection diagram of the spot network power distribution system. That is, a plurality of, for example three, distribution lines 3 are led out from the substation 1 via circuit breakers 2, respectively. In the customer 4, a disconnector 6. is installed between each of these three distribution lines 3 and the network bus bar 5. A series circuit of a network transformer 7 and a network protector 8 is connected, and a current transformer 9 is disposed between the secondary side of each network transformer 7 and the network protector 8. A network relay (not shown) is connected to the next side.

By the way, there was a short circuit in one of the three distribution lines 3.

If an accident such as a ground fault occurs, the circuit breaker 2 belonging to the faulty distribution line 3 at the substation 1 is disconnected.
At this time, other healthy distribution lines 3 and disconnectors 6. Network transformer7. Faulty distribution line 3 via network protector 8 and network busbar 5
Power flows back to the secondary side of the side network transformer 7.

This backflow power is detected by the network relay via the current transformer 9 provided on the secondary side of the network transformer 7, and thereby the network protector 8 on the side of the faulty distribution line 3 is cut off. Complete separation of the electric wire 3 is completed. In order to perform such reverse power cutoff, the network transformer 7 is required to have excitation characteristics and reverse power cutoff characteristics suitable for the detection sensitivity of the network relay.

FIG. 3 is a vector diagram showing the detection sensitivity characteristics of the network relay, where vN is the voltage vector and IO is the excitation current of the network transformer. Here, if we ignore the charging current of the negative cable, the network relay will operate when it enters the cutoff region shown by diagonal lines. Specifically, the maximum sensitivity angle α is set for the network relay to prevent malfunction, and the excitation 7e:tLl
The current IR projected onto this maximum sensitivity angle α of o is the lowest value 1.
If it exceeds this, it will enter the cutoff region. That is, for a network transformer to have reverse power cutoff characteristics, the current IR projected onto the maximum sensitivity angle α of the exciting current 1o must be at least ff.
It is necessary to set a to a value exceeding tIM.

Therefore, as an iron core used in a network transformer to obtain the above-mentioned reverse power cutoff characteristics, a core made of laminated non-oriented silicon steel plates that can handle a large excitation current is used.

FIGS. 8 and 9 show iron cores used in conventional network transformers. That is, by alternately laminating the silicon steel plates 10 in the combination pattern shown in FIG. 8(a) and the silicon steel plates 11 in the combination pattern shown in FIG. It is composed of an iron core 12.

(Problems to be Solved by the Invention) In a network transformer using a conventional lap joint type iron core 12, for example, when the impedance voltage is large or the capacity is large, the ratio of the excitation current to the load current is Therefore, in order to make the projected current IR larger than the minimum value IM, the current situation is to use a core 12 that is larger than that required during normal operation in which a load current flows.

Originally, when constructing an iron core using a non-oriented silicon steel plate, a silicon steel plate simply cut into a rectangular shape from the material is used because there is little change in characteristics in the rolling direction, that is, there is no need to pass magnetic flux in the rolling direction. Generally, a lap joint method is used, which is easy to manufacture and requires only assembly. However, the core 1 of the conventional network transformer
In the case of 2, since it is necessary to use a larger size than necessary, the economical benefits due to good manufacturability are canceled out, and as a result, as the size of the iron core 12 increases, the overall size increases. Enlarging the size is becoming a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a network transformer that can obtain reverse power cutoff characteristics without increasing the size of the iron core.

[Structure of the Invention] (Means for Solving the Three Problems) The network transformer of the present invention is characterized in that it uses an iron core formed by miter jointing non-oriented silicon steel plates.

Moreover, an iron core constructed by using an amorphous magnetic band instead of a non-oriented silicon steel plate and miter jointing the same may be used.

(Function) According to the network transformer of the present invention, since the magnetic resistance of the miter joint type joint part is smaller than that of the conventional lap joint type joint part, it is possible to pass magnetic flux through the iron core. The magnetizing current that produces the magnetomotive force is reduced, and therefore a small iron core becomes sufficient.

(Example) A first example of the present invention will be described below based on FIGS. 1 to 3.

First, the iron core used in the network transformer of this embodiment will be described according to FIGS. 1 and 2. That is, 21
．． 22 is a non-oriented silicon steel plate forming the left leg, 23.2
4 is a non-oriented silicon steel plate that forms the right leg, 25.26 is a non-oriented silicon steel plate that forms the center leg, 27 to 30 are non-oriented silicon steel plates that form the upper wire part, and 31 to 34 are non-oriented silicon steel plates that form the upper wire part. This is a non-oriented silicon steel plate that forms the underlined iron part. In this case, the silicon steel plates 21 to 26 are formed into an elongated trapezoid shape with both ends sloped at 45 degrees.
and 34 are formed into a short trapezoid shape with one end forming a 45-degree inclined surface and the other end forming a vertical surface, and silicon steel plates 28 .
29, 32 and 33 are formed in a short trapezoidal shape with both ends forming slopes of 45 degrees. And silicon steel plate 21,
23, 25° 27, 29, 31 and 33 with their ends abutting each other in the pattern shown in FIG. 34 are assembled by abutting each other's ends (
By alternately laminating the pattern shown in b), a miter joint type tripod iron core 35 with a predetermined lamination thickness as shown in FIG. 2 is constructed.

Next, the operation of this embodiment will be explained with reference to FIG. 3.

In FIG. 3, Io is the excitation current of the conventional network transformer using the iron core 12, and this is the magnetizing current 1e, which is a component perpendicular to the voltage vN, and the iron loss current IC, which is the component parallel to the voltage vN. It consists of In this case, the magnetizing current 1e is for generating a magnetomotive force for passing the magnetic flux in the iron core 12, and its magnitude is determined by the magnitude of the magnetic resistance of the iron core 12. The magnetic resistance of the iron core 12 depends on the magnetic permeability of the silicon steel plate used and the joint method.

The above also applies to the network transformer of this embodiment using the iron core 35.

Now, assuming that the sizes of the iron cores 35 and 12 are the same and the material of the silicon steel plates used is the same, both have the same magnetic permeability, but the joint portion of the iron core 35 of the miter joint type of this embodiment is The magnetic resistance is significantly reduced compared to the magnetic resistance of the joint portion of the conventional lap joint type iron core 12. Therefore, the magnetizing current 1e'' in the iron core 35 of this embodiment is smaller than the magnetizing current 1e of the conventional example, as shown in FIG.
It will be about 1/3 of that. On the other hand, the iron loss current 1c remains unchanged since both the iron core 35 of this embodiment and the iron core 12 of the conventional example use non-oriented silicon steel plates. Therefore, the exciting current of the iron core 35 in this embodiment is expressed as a combination of the magnetizing current 1e- and the iron loss current 1c as shown in FIG. 3 1o-. When this exciting current 1o- is projected onto the maximum sensitivity angle α of the network relay, the projected current becomes IR-
This becomes larger than the projected current IR of the conventional example. This means that iron core 35 is more IR/I R than iron core 12.
Even if the size is made smaller by (ku1), the projected current IR of the conventional example
This means that a projected current equivalent to can be obtained.

Note that, for convenience, the value of the valley current has been explained above while ignoring the current transformation ratio of the current transformer 9 (see FIG. 6), but the same result can be obtained even if this is taken into consideration.

According to this embodiment, the following effects can be obtained. That is, since the network transformer uses an iron core 35 composed of non-oriented silicon steel plates 21 to 34 in a miter joint method, the magnetizing current 1e- is equal to the magnetizing current of the conventional iron core 12! Therefore, the iron core 35 needs to be small in order to obtain the same projected current IR as the conventional iron core 12, and the network transformer as a whole can be made smaller and lighter. It is also possible to achieve Further, as the iron core 35 is made smaller, iron loss can be reduced, and high efficiency can be achieved, resulting in energy savings.

Note that the network power distribution system, especially the spot network power distribution system, is mainly used for power distribution in buildings, so being able to make the network transformer smaller and lighter as in this example greatly contributes to downsizing the electrical room. However, it has the advantage of reducing building construction costs and making effective use of floor space.

FIG. 4 shows a second embodiment of the invention. That is, 36 is an iron core in place of the iron core 35, and this is constructed by miter-jointing non-oriented silicon steel plates 37 to 43. In this case, the silicon steel plates 37 and 38 for the left leg and the right leg are formed in a long shape with both ends forming an inclined surface of 45 degrees, and the silicon steel plate 39 for the center leg has both ends at right angles. The silicon steel plates 40 and 43 for the upper line iron part and the lower line iron part are formed in a short shape forming an equilateral triangular mountain shape, and both ends of the silicon steel plates 40 and 43 are
The silicon steel plates 41 and 42 for the upper line iron part and the lower line iron part are formed in a short shape with an inclined surface of 5 degrees. It is formed in a short shape with an inclined surface.

FIG. 5 shows a third embodiment of the invention. That is, 44 is an iron core replacing the iron core 35, and this is constructed by miter jointing non-oriented silicon steel plates 45 to 49. In this case, the silicon steel plates 45 and 46 for the left leg and the right leg are formed in a long shape with both ends forming an inclined surface of 45 degrees, and the silicon steel plate 47 for the center leg has both ends at right angles. The silicon steel plates 48 and 49 for the upper line iron part and the lower line iron part are formed in a short shape with equilateral triangular mountain shapes, and both ends thereof are 4
It is formed into a long shape with a 5 degree slope and a V-shaped notch in the center.

The above-described second and third embodiments also provide the same effects as those of the first embodiment.

FIG. 6 shows a fourth embodiment of the present invention. That is, 50 is an amorphous magnetic band of an iron core constructed by a miter joint method, the end of which is formed into a 45 degree inclined surface, and a predetermined number of sheets are stacked so that the end, which is the joint part, forms a step shape. ing.

Recently, research has been underway to use amorphous alloys for iron cores in order to reduce the no-loss loss of transformers. Amorphous alloys are non-crystalline alloys obtained by rapidly cooling molten metal, and essentially have no directionality. Various manufacturing methods have been developed for amorphous alloys, but
Among these, those manufactured by the roll method and having a thickness of about 25 μm are supplied to the market as standard for use in transformer cores. The thickness of general silicon steel plate is 0.23 to 0°35m.
In contrast, since amorphous materials are extremely thin, they are generally used as wound cores. However, if it is to be used in a relatively large capacity transformer, it will be difficult to manufacture a wound core, and a laminated core will have to be used. In this case, since the raw material is too thin and lamination workability is poor, in the fourth embodiment, a plurality of materials are pressed together to form an amorphous magnetic strip 50 having a thickness that facilitates lamination work. When attempting to use an amorphous alloy core constructed by lap-jointing such amorphous magnetic bands 50 for example in a network transformer, the projected current IR as shown in FIG. is so small that even highly sensitive digital network relays cannot detect reverse power. However, when the iron core is constructed using the miter joint method using the amorphous magnetic band 50 as in the fourth embodiment, it has been confirmed that the same effects as in each of the above embodiments can be obtained.

[Effects of the Invention] As explained above, the network transformer of the present invention uses an iron core configured by miter jointing non-oriented silicon steel plates or amorphous magnetic bands.
It has the excellent effect of being able to achieve a reduction in size and weight while having reverse power cut-off properties, and being able to reduce iron loss and save energy.

[Brief explanation of the drawing]

1(a) and (b) are front views of different combination patterns of silicon steel plates in an iron core showing the first embodiment of the present invention, FIG. 2 is a partially enlarged exploded perspective view of the same core, and FIG. 3 is a vector diagram showing detection sensitivity characteristics for explaining the same effect. Moreover, FIGS. 4 and 5 are front views of the core showing the second and third embodiments of the present invention, and FIGS. 6(a) and (b) are front views of the cores showing the fourth embodiment of the present invention. FIG. 2 is a partial side view and a partial front view of a silicon steel plate shown in FIG. FIG. 7 is a single line diagram showing the spot network power distribution system. 8(a) and 8(b) are views corresponding to FIGS. 1(a) and 1(b) showing a conventional example, and FIG. 9 is a view corresponding to FIG. 2 of the same. In the drawings, 21 to 34 are non-oriented silicon steel plates, and 35 is an iron core.

Claims (2)

[Claims] 1. A network transformer characterized by using an iron core constructed by miter-jointing non-oriented silicon steel plates. 2. A network transformer characterized by using an iron core constructed by miter-jointing amorphous magnetic bands.