JPS61109423A - Cuttent limiter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a device for limiting current flowing from a power source to an electrical device. The concept in this regard is described in claim 1.

This type of current limiting device reduces the cutting power required for interruption and also reduces the
Used to suppress the effects of short circuits. This is because the power distribution network is becoming more and more complex, and in order to maintain a good power transmission situation, it is necessary to maintain a good power transmission situation, and to deal with an increase in short-circuit current due to reasons such as maintenance, management, or unavoidable circumstances.

[Prior Art] A current limiting device as given in claim 1:
It is known from U.S. Pat. No. 3,671,810. The device has a ferromagnetic core with two outer pole pieces and a central pole piece with one free end. The two pole pieces are each equipped with two side-by-side choke coils through which the current to the electrical equipment flows.

The central pole piece has its free end slightly spaced from the yoke. Through this yoke, a magnetic flux flow is guided by the magnetic field of the choke coil through which the current to the electrical equipment flows. A permanent magnet with residual magnetism is placed in the gap between the free end of the central pole piece and the yoke.

This magnet is sufficient to magnetically saturate the ferromagnetic core with the current used by the electrical equipment.

A choke coil with a core made of magnetically saturated ferromagnetic material has only a small actance, so this type of current limiting device exhibits a very small resistance for normal power usage. do not have. However, when a short-circuit current occurs, the magnetic field generated by the choke coil almost eliminates the residual magnetism of the permanent magnet, and the core made of ferromagnetic material becomes unsaturated, so that the choke coil actance reaches its maximum value. Therefore, the current limiting device exhibits a high resistance value to the short circuit current and limits this.

However, in such a current limiting device, the permanent magnet is directly influenced by the magnetic field of the choke coil. This magnet has a shearing effect with its magnetic permeability (μm=1) equal to that of air, and the core made of ferromagnetic material exhibits a significant decrease in magnetic permeability with respect to the coil current. If the current to be limited is alternating current, the permanent magnet itself will be exposed to the alternating magnetic field of the choke coil and will be demagnetized.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a current limiting device that can simply and effectively limit a current of any magnitude.

This object is solved by the concept presented in the characterizing part of patent claim 1.

[Means for Solving the Object] In the current limiting device of the present invention, a magnet that functions to oppose the magnetic field produced by the choke coil through which current flows is arranged in a neutral region of the alternating magnetic field produced by the ferromagnetic core. As a result, the current limiting device of the present invention operates unsupervised and reliably.

Furthermore, it can be installed at a location with a high power supply rate in the power supply network.

Embodiments of the invention are described in the dependent claims.

The features and advantages of this invention will now be explained with reference to the drawings. However, the present invention is not limited to the configuration of the embodiment described below.

[Explanation of Examples]

In the figures, the same symbols indicate members with the same function. In the circuit shown in FIG. 1, the current limiting device 1 of the present invention is connected to an AC power source 2 having a voltage of
It is located between. A power switch 4 is arranged between the current limiting device 1 and the electric device 3. The drive mechanism of this switch is operatively associated with the voltage transformer 5.

However, these are not shown in FIG. Under normal operating conditions, the current limiting device 1 presents only a small impedance to the current flowing from the power supply 2 to the electrical equipment 3. However, if there is a short circuit current, this presents a high impedance and limits the current flowing from the power supply 2 to the electrical equipment 3.

FIG. 2 shows an embodiment of the current limiting device 1 according to the invention, which includes a core 6 made of a ferromagnetic material having four pole pieces 7, 8, 9° 10, two internal yokes 11, 12. The internal yokes 11 and 12 each have two spaced apart cuts 13.14 and 15.16 with their free ends facing each other. There is a gap, for example, 2.3 cm wide between the free ends of the cut portions 13, 14 and 15, 16 of the yoke, and magnets 17, 18 are arranged to fill the cross section of the yoke. has been done. In this magnet, the magnetic flux flow ΦM indicated by the broken line is the magnet 17, the cutting part 14, the pole piece 19, the cutting part 16, the magnet 18, the cutting part 15,
A magnetic circuit consisting of a pole piece 8, a cutting part 13, and a magnet 1 as well.
7, cutting part 14, external yoke 20, pole piece 10, external yoke 2
7, cutting section 16, magnet 18, cutting section 15, external yoke 21
, are arranged to form a magnetic circuit through the pole piece 7, the outer yoke 19 and the cutout 13. This magnet is made of, for example, a permanent magnet with high coercive force and residual magnetism, or an alloy of cobalt and a seed metal. However, it is also possible to use an externally excited electromagnet instead of a permanent magnet.

The yoke 19, the pole piece 8, the yoke 21 and the pole piece 7 form a ring-shaped closed ferromagnetic part 7, 23. On the other hand, the yoke 20, the pole piece 10, the yoke 22 and the pole piece 9 have the cut portions 13.14 and 15.
A closed partial core 24 of ferromagnetic material is formed in the form of a ring spaced apart by 16 mm. A choke coil 25, 26 through which electric current flows is arranged in each of the partial cores 23, 24. These choke coils are connected in series and have equal number of turns and polarity.

The operation of the current limiting device according to the invention is as follows: The residual magnetism of the two magnets 17.18 causes a partial core 25.24 of ferromagnetic material to be set in the choke coil. 25.26 shall be magnetically saturated when there is no current or only a normal operating current is flowing. 25.26 for two choke carp
The reactance XD in each case is then very small. This means that the magnetomotive force θ of the choke coil
This is clear from FIG. 3, which shows the relationship between reactance and reactance XD. The reactance xD means that there is almost no current in the choke coil, so that the partial cores 23, 24 are simply magnets 17.
When it is excited only with a magnetomotive force θ of 18, it is extremely small. When normal operating current flows through the choke coils 25, 26, depending on the polarity of each half-wave of the applied alternating current, the two choke coils will at most
Magnetomotive forces θLM and θR corresponding to the amplitude of the applied current
Since IJ only acts additionally, the reactance XD is quite small. Since the two partial cores 23, 24 of the choke coil 25, 26 are sufficiently magnetically saturated and the reactance XD is small, the voltage drop is the minimum required in the current limiting device of this invention under normal operating conditions. .

When a short circuit occurs, the two choke coils 25 and 26 having a saturation magnetomotive force θ exhibit magnetomotive forces θLK and θRK.

These magnetomotive forces are opposite in direction to the magnetomotive force θM of the magnet 17.1B. Therefore, the magnetic saturation of the partial cores 23, 24 is extremely attenuated or eliminated. The direction of flow is the second
As shown, the pole piece 8.10 and the yoke 20.
22 is made unsaturated by the magnetic flux flow ΦL1ΦR caused by the coil. On the other hand, when the direction of the current is reversed in the next half wave, the pole piece 7.9 and the yoke 19.21 are rendered unsaturated by the magnetic flux flow ΦL1ΦR caused by the coil. In either case, the reluctance in the partial core decreases dramatically and the current increases, resulting in a large alternating voltage UD. This voltage limits the short circuit current.

A cut-off signal to the power switch 4 is issued via the voltage transformer 5 when the permissible set value is exceeded. As soon as the inhibiting current is removed, the current limiting device returns to its normal state.

In the embodiment of FIG. 2, the choke carp A/25.26 was placed on the inner pole piece 8.9, but as shown in FIG. 20.21
and 22.

It is also possible to use just one magnet, as shown as magnet 17 in the embodiment of FIG. 4.5. in this case,
It is necessary that the magnetic flux ΦM of this magnet flows from the partial core 25 to the partial core 24 at the back.

When limiting the alternating current, the magnetic flux flow ΦL1ΦR in the partial cores 23, 24 generated in the choke coils 23, 26 by the electromagnetic action of the electric current is directed in opposing directions with respect to the magnet 17, 18 as shown in Fig. 4. It should be noted that, if present, the magnets 17, 18 are affected by the demagnetizing magnetic field by the choke coils 25, 26. In FIG. 4, such opposing magnetic flux flows ΦL and ΦR are generated by coils whose magnetomotive forces are directed in the same direction. Choke coil 25.26
A good means of protection against the demagnetizing effect of It is to be placed in piece 8.9.

When controlling direct current, the choke coils 25 and 26 are connected in a different direction of the magnetomotive force, contrary to that shown in FIG.

As can be seen from the embodiment of Figure 4.5, the cutting portions 13.14
．． 15 and 16 are removed and the magnet 17 is directly connected to the partial core 2S.
, 24 pole pieces 8.9. magnet 1
The plane A perpendicular to the magnetic flux flow of the core 6 is the ferromagnetism of the core 6 that should be saturated, which is multiplied by the ratio of the saturation induction BI,I of the ferromagnetic material constituting the core 6 and the residual magnetic inductance Br of the magnet material. It is preferable that the cross section perpendicular to the body be equal to or greater than As (A≧BB/Br−A8). In this case, if the magnetic flux flow ΦM branches at the core 6, the cross section As is the sum of the cross sections of the tributaries. In the embodiment of FIG. 2, the magnetic flux flow ΦM of the magnet 17 is not magnetically divided at the back of the cutting part 13, and the pole piece 8
and pass through yoke 19. At this time, the saturated cross section Af3 is the sum of the cross sections of the pole piece 8 and the yoke 19.

As in the embodiment of the invention shown in FIG. 6.7, the ferromagnetic core 6 can also be made simply from a partial core 24 and a relay piece 27. In this case, the relay piece 27 has one end connected to the portion 7. za, and forms a gap with the partial core 24 at the other end, and a magnet 17 (shown by a solid line) is arranged here. It is also possible to define a gap in which the magnets 17, 18 (shown in broken lines) are arranged.

In the current limiting device of FIG. 6, magnet 17 (or magnet 1
7 and 18) magnetic flux flow ΦM ring-shaped closed part,
i! ? 24 and branches from there, one through the pole piece 9 and the other through the yoke 20, the pole piece 10 and the yoke 22.
It flows to the magnetic relay piece 27 via the magnet, and then returns to the magnet 17 again. In the ring-shaped closed partial core 24, the magnetic flux flow ΦM of the magnet 17 (or magnets 17 and 18) and the magnetic flux flows ΦL and ΦR of the choke coils 23, 24 overlap.

As shown in FIG. 6, in the yoke 20, 22 and the pole piece 10, the magnetic flux flows ΦM, ΦL, Φ
The direction of flow of R is opposite, so that the ferromagnetic material in the yoke 20, 22 and the pole piece 10 is demagnetized when a short circuit occurs. When the direction of flow is reversed, the magnetic flux flows ΦM and ΦL1ΦR in the pole piece 9 are directed towards each other, which causes the ferromagnetic material of the pole piece 9 to be demagnetized when a short circuit current occurs. .

In each case, a ring-like closed part, i!, independent of the direction of flow, i! ? 24 pieces are demagnetized and part Z,
The magnetic reluctance of 24 decreases. This increases the magnetic flux flow in the choke coils 25,26.

Then, in response to this large magnetic flux flow, choke coil 2
A large alternating voltage ITD occurs at 5.26 to limit the short circuit current.

Furthermore, as shown in FIG. 7, instead of two (or more) choke coils, a single stubby choke coil 26 can be arranged in the ring-shaped closed partial core 24.

The position of this coil is arbitrary, and it can be provided on the yoke 20, on the yoke 22, or on the pole piece 10 as shown. What is most important in this case is that the partial core 24 is closed in a ring shape, and that the magnet 1
7 (or magnets 17 and 18) to form a magnetic circuit.

[Brief explanation of drawings]

FIG. 1 shows very simply a power circuit with a current limiting device according to the invention. FIG. 2 is a plan view of a first embodiment of the current limiting device shown in FIG. 1, shown briefly and partly schematically, in which two choke coils are connected in series. FIG. 3 is a graph showing the relationship between reactance and magnetomotive force in the choke coil of the current limiting device shown in FIG. FIG. 4 is a partially schematic plan view of a second embodiment of the current limiting device shown in FIG. FIG. 5 is a partially schematic plan view of a third embodiment of the current limiting device shown in FIG. FIG. 6 is a plan view, partially schematically showing a fourth embodiment of the current limiting device in FIG. 1. FIG. 7 is a plan view schematically showing a simple part of the fifth embodiment in FIG. 1: Current limiting device, 2: Power supply, 3: Electrical equipment, 4: Power switch, 5: Voltage transformer, 6: Z17.8, 9, 10
: Pole piece, 11.12: Internal yoke, 13, 14, 15.1
6: Cutting part, 17° 18: Magnet, 19, 20, 21, 2
2: External yoke, 25.24: Partial yoke, 25.26: Choke coil, 27: Relay piece, UD: Voltage, Engineering: Current,
0M: Magnetic flux current of magnet, ΦL, ΦR: Magnetic flux current of choke coil, θ: Magnetomotive force, θLN, θRN 'Amplitude of magnetomotive force due to choke coil operating current, θLK,
θRK 'Amplitude of magnetomotive force due to short-circuit current of choke coil, θM = magnetomotive force of magnet, θ8: saturation magnetomotive force

Claims (1)

[Claims] 1. A device for limiting the current flowing from a power source (2) to an electrical device (3), which comprises a core (6) made of a ferromagnetic material having at least one partial core (for example, 24); ), at least one magnet (e.g. 17) acting on the ferromagnetic core (6) with a magnetic strength sufficient to magnetically saturate at least one partial core (e.g. 24); at least one choke coil (e.g. 26) arranged on said partial core (e.g. 24) and connected between the power source (2) and the electrical device (3);
When a short circuit current occurs, the partial core (e.g. 2
4) has a number of turns that overcomes the magnetic force of the magnet (e.g. 17) and becomes magnetically saturated, and the partial core (e.g. 24) is formed in a closed ring shape. and at least one of the aforementioned magnets (e.g. 17) is placed in the gap of a magnetic circuit provided outside the partial core (e.g. 24), which circuit comprising a partial piece of said partial core (for example 24), which is excited by (for example Φ_R). 2. The device according to claim 1, wherein the core (6) made of a ferromagnetic material includes at least one partial core (for example, 24) and one relay piece (27).
and at least one magnet (for example, 17) is arranged between the partial core (for example, 24) and the relay piece (27). 3. The device according to claim 2, wherein two magnetic relay pieces are provided at both ends of the magnetic relay piece (27) between at least one partial core (for example, 24) and the magnetic relay piece (27). It is characterized by the arrangement of magnets (17, 18). 4. The device according to claim 1, in which the core (6) made of ferromagnetic material is composed of at least two partial cores (23, 24), and at least one magnet (e.g. , 17) are arranged between the two partial cores (for example, 23, 24). 5. The device according to any one of claims 1 to 4, wherein the cross section of at least one magnet (for example 17) perpendicular to the direction of flow of its magnetic flux (Φ_M) is Core (6)
The ratio of the saturation induction B_S in the ferromagnetic material of the core (6) to the residual magnetic induction B_r of the magnet material is determined by at least one choke coil (e.g. 26) in the ferromagnetic material to be saturated in the core (6). The magnetic flux is larger than or equal to the cross section A_S perpendicular to the flow direction of the magnetic flux (for example, Φ_R). 6. The device according to any one of claims 4 to 5, wherein the core made of a ferromagnetic material is a yoke (19, 20, 21, 22
) and the pole pieces (7, 8, 9, 1
0), and the core (6) consists of four pole pieces (7, 8,
9, 10) and four yokes (19, 20, 21, 22), from the above members, respectively external and internal pole pieces (e.g. 7, 8) and four yokes (19, 20, 21, 22). forming one of the two partial cores (for example 23) with each of the two yokes (for example 19, 20) taken out;
and at least one magnet (for example 17) is in contact with both internal pole pieces (8, 9) of the two partial cores (23, 24). 7. A device according to claim 6, characterized in that the inner pole pieces (8, 9) of the two partial cores (23, 24) are provided with at least two cuts (for example 13
, 14) are provided, respectively.
Between these free ends there is at least one magnet (e.g.
17) are arranged. 8. Device according to claim 7, characterized in that the inner pole pieces (8, 9) of the two partial cores (23, 24) are provided with two further cuts (for example 15, 1
6), and a second magnet is arranged between their free ends. 9. The device according to any one of claims 3 to 8, in which the core (6) made of ferromagnetic material is composed of symmetrically arranged partial cores (23, 24). , which is characterized by . 10. The device according to claim 9, characterized in that the two choke coils (25, 26) are arranged at symmetrical positions of both the partial cores (23, 24).