JP3045166B1 - Current limiting device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To connect a plurality of thermal current limiting elements in series on the AC side of a rectifier bridge circuit and to provide a high-resistance thermal current limiting element even if each thermal limiting element has a variation in characteristics. It is possible to prevent the heat-limiting element from being destroyed due to concentrated heat or overvoltage. SOLUTION: An AC terminal of a rectifier bridge circuit is connected in series with an electric power system, a DC reactor is connected between DC terminals of the rectifier bridge circuit, and the temperature of the AC side of the rectifier bridge circuit is increased due to overcurrent. A current limiting device in which a plurality of thermal current limiting elements S1 to Sn that increase resistance by rising are connected in series, and the same number of windings A1 as the thermal current limiting elements S1 to Sn.
To An are tightly magnetically coupled to each other, and each winding A1
To An with the same polarity for each of the thermal current limiting elements S1 to Sn, and when the windings A1 to An are connected in series, the combined inductance value is equal to or lower than the minimum value determined from the current limiting target value. Enlarge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current limiting device, and more particularly, to a current limiting device, which is applied to all electric power systems from low voltage to very high voltage, and suppresses an overcurrent due to a short circuit accident and an inrush current at the time of load application. It relates to a current limiting device.

[0002]

2. Description of the Related Art For example, in all power systems from low voltage to very high voltage, a current limiting device is provided to suppress an overcurrent due to a short circuit accident and an inrush current at the time of load application, and a circuit breaker is provided by the current limiting device. The required breaking capacity is reduced. Conventionally, as this type of current limiting device, there is a device using a rectifying bridge circuit composed of a thermal current limiting element of a positive temperature characteristic (PTC) thermistor or a diode, for example.

[0003] The thermal limiting element of a positive temperature characteristic (PTC) thermistor is composed of a polymer material or a barium titanate material, and generates heat when an excessive current flows, and the temperature rises due to the heat. It has a rapid increase in resistance, has a simple structure and is economical, and has been awarded as a suitable element when a current limiting effect of low-speed response is required.

The current limiting device using the thermal current limiting element has a configuration in which a thermal limiting element S is connected in series between a system power supply 1 and a load 2 of a power system as shown in FIG. For example,
An overcurrent flows due to the occurrence of the short-circuit accident a, and the thermal current limiting element S generates heat and its resistance increases due to its temperature rise. This thermal limiting element S
The overcurrent flowing in the power system is suppressed by increasing the resistance of the circuit breaker 3 while the thermal current limiting element S exhibits the current limiting function.
To disconnect the grid from the power system.

[0005] A current limiting device using a rectifying bridge circuit, as shown in FIG. 5, has AC terminals 5 and 6 of a rectifying bridge circuit 4 bridged by _four diodes D _{1 to} D _4.
Is connected in series with a power system, and a DC reactor 9 is connected between the DC terminals 7 and 8, and is awarded as a suitable one when a current limiting effect of high-speed response is required.

In this current limiting device, if the AC current exceeds the DC current flowing through the DC reactor 9 due to the occurrence of the short circuit accident a, the diodes D ₁ and D ₄ or the diodes D ₂ and D ₃
One of the pairs stops. When viewed from the AC terminals 5 and 6, the DC reactor 9 is inserted in series in the AC circuit during this time, and the terminal voltage of the DC reactor 9 is generated, thereby suppressing the overcurrent flowing in the power system. By opening the circuit breaker 3 while the rectifying bridge circuit 4 is performing the current limiting function, the interconnection of the power system is disconnected.

[0007]

The conventional current limiting device having the thermal current limiting element S and the conventional current limiting device having the rectifying bridge circuit 4 have the following problems.

[0008] In the case of a thermal limiting element of a positive temperature characteristic (PTC) thermistor, the thermal limiting element itself is an economical current limiting element having a simple structure, and generates heat from the element due to an overcurrent at the time of a short circuit accident or the like. It is to get the current limiting effect.
Inevitably, an operation delay of several tens of milliseconds occurs, and there is a disadvantage that a sudden current cannot be suppressed.

On the other hand, in the case of the rectifying bridge circuit 4, an overcurrent at the time of a short circuit fault can be accurately exerted by the inductance of the DC reactor 9 with a current limiting effect, but the DC current flowing through the DC reactor 9 increases every half cycle. For example, during a certain time period, for example, 50 to 100 msec, the cost and the loss are large to expect the current limiting effect, and if the current limiting function is to be maintained for a relatively long time, for example, 50 msec or more after the occurrence of a short circuit accident, The disadvantage is that a larger DC reactor must be installed, which is not economical in terms of cost.

In order to solve these two disadvantages, the thermal limiting element S and the rectifying bridge circuit 4 are combined to complement the characteristics of both, so that when a short-circuit accident a occurs, the sudden current can be reliably reduced by simple means. An economical current limiting device has been proposed which can suppress the current limit and maintain the current limiting function for a relatively long time.

In this current limiting device, as shown in FIG. 6, AC terminals 5 and 6 of a rectifying bridge circuit 4 are connected in series with a power system, and a DC reactor 9 is connected between DC terminals 7 and 8 of the rectifying bridge circuit 4. In addition to the connection, a thermal limiting element S, which generates heat due to an overcurrent and has a high resistance due to a rise in temperature, is connected in series to the AC side of the rectifying bridge circuit 4.

In this current limiting device, the thermal current limiting element S and the rectifying bridge circuit 4 exhibit a function of complementing each other, and when a short circuit a occurs, the rectifying bridge circuit 4 can surely suppress the sudden current. The current limiting effect of the high-speed response is exhibited, and the current limiting function of the thermal current limiting element S can be maintained for a relatively long time, so that the current limiting effect of the low-speed response is exhibited.

Although this current limiting device uses the thermal current limiting element S in a system that can disconnect the interconnection, the thermal current limiting device S may also be used in a system that cannot disconnect the interconnection. is there.
In this case, as shown in FIG. 7, a current limiting reactor 10 is connected in parallel with the thermal current limiting element S, a current always flows through the thermal current limiting element S, a short-circuit current flows, and the thermal current limiting element S has a high resistance. In this case, current is commutated to the current limiting reactor 10 and the thermal current limiting element S is disconnected from the system by the switch 11 to prepare for recovery.

By the way, in the thermal current limiting element S combined with the rectifier bridge circuit 4, only an element having a limited length, in which the partial heat is quickly diffused and the temperature rises uniformly as a whole, can be used. Therefore, the rated voltage is about 100 V per element. Therefore, for example, 2
When applying to a power system of 00V, 400V, 6600V, or the like, it is necessary to share a voltage corresponding to the system voltage at the time of the current limiting operation, so that a plurality of thermal current limiting elements are connected in series.

However, when a plurality of thermal current limiting elements are connected in series, a common short-circuit current flows through each of the thermal current limiting elements. Among the current-limiting elements, only some of the thermal current-limiting elements become high resistance first, and the heat generated by the thermal current-limiting element concentrates, causing thermal breakdown, or overvoltage concentrates, causing a fatal failure. Problem.

Therefore, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to provide a method in which a plurality of thermal current limiting elements are connected in series on the AC side of a rectifying bridge circuit. An object of the present invention is to prevent the heat-limiting element having high resistance from being damaged by the concentrated heat-generating power or overvoltage even if the thermal-limiting element has a characteristic variation.

[0017]

As a technical means for achieving the above-mentioned object, the present invention is to connect an AC terminal of a rectifier bridge circuit in series with a power system, and connect the AC terminal of the rectifier bridge circuit to a DC terminal of the rectifier bridge circuit. Connect the DC reactor and
A current limiting device in which a plurality of thermal current limiting elements, which generate heat due to an overcurrent and have a high resistance due to a rise in temperature thereof, are connected in series on the AC side of the rectifying bridge circuit, and the same number of windings as the thermal limiting elements. Wires with air-core coil structure or gap-shaped iron core rear
The coils are tightly magnetically coupled to each other, and each winding is connected in parallel with the same polarity for each heat-limiting element.
The combined inductance value when each winding is connected in series is equal to or larger than the minimum value determined from the current limit target value.

In the current limiting device of the present invention, a current flows to the thermal current limiting device side in a steady state, but an overcurrent flows due to a short circuit accident or the like and one of a plurality of thermal current limiting devices due to variations in device characteristics. When the resistance of the section increases, a short-circuit current commutates to the winding side installed in parallel with the thermal limiting element having the increased resistance.

At this time, since the windings of each thermal current limiting element are closely magnetically coupled to each other and are connected with the same polarity for each thermal limiting element, the mutual resistance between the windings increases the resistance. In the case of a thermal current limiting element, the element current flows in a direction in which the element current decreases, and in a non-high resistance thermal current limiting element, the element current flows in a direction of increasing the reverse. In the case of a thermal current limiting element that has not been increased in resistance, the element acts to increase the resistance by increasing the element current. This makes it possible to uniformly increase the resistance of each thermal limiting element even if the thermal limiting elements have variations in characteristics.

In the case where the thermal current limiting elements are used in a system in which the interconnection cannot be disconnected, if all the thermal limiting elements have a high resistance and a short-circuit current is commutated to the winding side, these windings will be disconnected. Function as a current limiting reactor in a state of being connected in series.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the current limiting device according to the present invention will be described in detail below. Note that the same or corresponding parts as those in FIGS. 4 to 7 are denoted by the same reference numerals, and redundant description will be omitted.

The current limiting in the embodiment of the present invention shown in FIG.
The device consists of four diodes D₁~ D _FourConfigured with bridge
The AC terminals 5 and 6 are connected in series with the power system,
Rectifier with DC reactor 9 connected between flow terminals 7 and 8
And an edge circuit 4 (see FIG. 6 or FIG. 7). This rectification
A plurality of thermal limiting elements S1 to S are provided on the AC side of the bridge circuit 4.
n are connected in series, and the same number of thermal limiting elements S1 to Sn as
The windings A1 to An are formed by closely magnetically coupling each other.
The windings A1 to An have the same polarity for each of the thermal limiting elements S1 to Sn
It has the structure connected by. These thermal limiting elements S1 to Sn
Is a combination of polymer-based materials and barium titanate-based materials.
A positive temperature characteristic (PTC) thermistor is preferable.
You.

In this current limiting device, by combining the rectifying bridge circuit 4 and the thermal limiting elements S1 to Sn, the characteristics of the rectifying bridge circuit 4 and the thermal limiting elements S1 to Sn complement each other. That is, when a short-circuit accident a occurs, the sudden current can be reliably suppressed by the rectifying bridge circuit 4 to exhibit a current limiting effect of high-speed response, and the thermal current limiting elements S1 to Sn
Accordingly, the current limiting function for a relatively long time can be maintained, and the current limiting effect of the low-speed response is exhibited.

The operation of the current limiting device will be specifically described with reference to FIG.
It will be described in detail. FIG. 2 shows thermal limiting elements S1 and S2 of the same rating.
Are connected in series. In the figure,
A switch, which will be described later, provided for each of the thermal limiting elements S1 and S2 is omitted.
Abbreviated. Resistance of each thermal limiting element S1, S2 (normal operation
Is a minute resistance value corresponding to AC loss).₁, R _Two
Then, the following circuit equation is established.

[0025]

(Equation 1)

[0026]

(Equation 2)

From this equation,

[0028]

(Equation 3)

Substituting this into the above equation gives

[0030]

(Equation 4)

Is obtained. Where the windings for simplicity
The magnetic coupling between A1 and A2 is ideal and leak-free, and L₁L
_Two= M^TwoAnd L₁= L_TwoThen, from the above equation, R₁i₁=
R_Twoi _TwoIs derived.

Therefore, the element resistance at normal time is represented by R,
Short-circuit current i flows, and for example, thermal limiting element S2 is K times higher
In the case of antagonism, ie, K = R_Two/ R₁Then,
The current flowing through each of the thermal current limiting elements S1 and S2 is given by i
_Two/ I₁= R₁/ R_Two= 1 / K, and the windings A1, A2
Mutual induction between the heat-limiting element S2 having a high resistance
In the direction of decreasing the current,
The current element S1 acts to increase the current. But
Therefore, the calorific value of each thermal limiting element is i_Two ^TwoR_Two/ I ₁ ^TwoR₁=
1 / K of the thermal limiting element S1 which has not been increased in resistance.
The calorific value rapidly increased by a factor of K, resulting in an immediate increase in resistance.
You.

Therefore, as shown in FIG. 1, in the steady state, the resistance of the thermal current limiting elements S1 to Sn is almost zero, so that current flows to the element, but a short circuit a (see FIG. 6 or FIG. 7)
When an overcurrent flows due to the occurrence of a current limiter, any one of the plurality of thermal limiting elements S1 to Sn has a high resistance due to variation in element characteristics, and a winding connected to the thermal limiting element. Overcurrent is commutated to the line side.

At this time, the winding A of each of the thermal current limiting elements S1 to Sn
1 to An are magnetically coupled to each other so that each thermal limiting element S1
To Sn, the windings A1 to A
Due to the mutual induction effect between n, the element current flows in the thermal current limiting element having a high resistance, in the direction in which the element current decreases, and in the thermal current limiting element not having a high resistance, the element current flows in the direction in which the element current increases. As a result, the resistance of the thermal current limiting element, which has not been increased, is increased by an increase in element current. In this way, even if the characteristics of the thermal limiting elements S1 to Sn vary, the resistance of the thermal limiting elements S1 to Sn can be increased uniformly.

In this embodiment, as shown in FIG. 1, thermal limiting elements S1 to Sn and self-inductance values L ₁₁ , L ₂₂ ,
..., which are formed by intimately bringing into magnetically coupled to each other winding Al-An of L _nn, expressed a mutual inductance value of each winding Al-An L _12, L _1n, with L _2n, these windings A1 To An are connected in series, the combined inductance value L is L = ΣΣL _ij (i = 1 to n, j = 1 to n), and the combined inductance value L is the value of the power system in which the current limiting device is installed. The minimum value is determined from the impedance required for current limiting. For example, when the thermal current limiting elements S1 to Sn are used in a system that cannot be disconnected, the current limiting reactor 10 (see FIG. 7) ) May be made equal to the inductance value. Further, when the thermal current limiting elements S1 to Sn are used in a system capable of disconnecting the interconnection,
The combined inductance value L may be equal to or greater than the minimum value determined from the current limit target value.

The current limiting device of the present invention is used only when a thermal current limiting element is used in a system that can disconnect the interconnection (there is no current limiting reactor connected in parallel with the thermal current limiting element S) (see FIG. 6). However, the present invention is also applicable to a case where a thermal current limiting element is used in a system that cannot disconnect the interconnection (there is a current limiting reactor 10 connected in parallel with the thermal current limiting element S) (see FIG. 7). ,
Although not shown, the present invention is also applicable to a configuration in which a current limiting reactor is connected in parallel to a series circuit of the rectifying bridge circuit 4 and the thermal current limiting element S.

When the thermal limiting elements S1 to Sn are used in a system in which the interconnection cannot be disconnected, the thermal limiting elements S1 to Sn are generally used.
Although it is necessary to connect a current limiting reactor 10 (see FIG. 7) in parallel with the current limiting elements 1 to Sn, in the case of the present invention, all the thermal current limiting elements S1 to Sn have high resistance, and the short-circuit current is transferred to the winding side. When flowing, these windings A1 to An function as current limiting reactors in a state of being connected in series.
Since it is not necessary to separately provide a current limiting reactor 10 (see FIG. 7) in parallel with Sn, the number of parts can be reduced and the device can be made compact.

In the winding structure of the present invention, the windings A1 to An are formed coaxially as shown in FIG.
If the magnetic coupling of .about.An is high, the structure of the windings A1 to An is not particularly limited. FIG. 3 shows an air-core coil structure, but a reactor having a core structure with a gap may be used.

Further, as shown in FIG.
, The switches C1 to Cn of the thermal current limiting elements S1 to Sn are increased when the resistance of the thermal current limiting elements S1 to Sn is increased by an overcurrent during a short circuit.
To open only the thermal current-limiting elements S1 to Sn so that the short-circuit accident is avoided and then the switches C1 to Cn are turned on to quickly bring the thermal current-limiting elements S1 to Sn into a normal state. Can be restored.

In the above embodiment, the case where the current limiting device is applied to the power system has been described. However, the present invention is not limited to this, and is applicable to general AC circuits other than the power system. Of course.

[0041]

According to the present invention, the same number of windings as the heat-limiting element are provided in the air-core coil structure or in the rear portion having the iron core structure with a gap.
The coils are tightly magnetically coupled to each other, and each winding is connected in parallel with the same polarity for each heat-limiting element.
By setting the combined inductance value when each winding is connected in series equal to or greater than the minimum value determined from the current limiting target value, even if some thermal current limiting elements have increased resistance due to variations in element characteristics Since the short-circuit current is diverted to the winding side and the mutual induction action between the windings allows the other heat-limiting elements, which have not been increased in resistance, to be quickly increased in resistance, each thermal-limiting element is Even if there are variations in characteristics, etc., it is possible to always equalize the increase in resistance of each thermal current limiting element, prevent concentration of overvoltage, prevent thermal destruction of the thermal current limiting element,
The quality and reliability of the device can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a current limiting device according to the present invention.

FIG. 2 is a circuit diagram illustrating a current limiting device in which two thermal current limiting elements are connected in series, for explaining an operation of the current limiting device in the embodiment of the present invention.

FIG. 3 is a configuration diagram showing a structural example of a winding in the current limiting device of the present invention.

FIG. 4 is a circuit diagram showing a conventional example of a current limiting device using a thermal current limiting element.

FIG. 5 is a circuit diagram showing a conventional example of a current limiting device using a rectifying bridge circuit.

FIG. 6 is a circuit diagram showing a current limiting device based on a combination of a rectifying bridge circuit and a thermal current limiting element, which is a premise of the present invention.

FIG. 7 is a circuit diagram showing a current limiting device which is a premise of the present invention using a thermal current limiting element in a system in which interconnection cannot be disconnected.

[Explanation of symbols]

 4 Rectifier bridge circuit 5, 6 AC terminal 7, 8 DC terminal 9 DC reactor S1-Sn Thermal limiting element A1-An Winding

Continuation of the front page (56) References JP-A-9-130966 (JP, A) JP-A-49-45349 (JP, A) JP-A-48-97042 (JP, A) JP-A-56-81039 (JP, A) , A) Patent 2947277 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 9/02 H01C ⁷ /02-7/13 H02J 1/00 309 H01L 39/16 H01H 33 / 59

Claims (1)

(57) [Claims] 1. An AC terminal of a rectifier bridge circuit is connected in series with a power system, a DC reactor is connected between DC terminals of the rectifier bridge circuit, and heat is generated by an overcurrent on an AC side of the rectifier bridge circuit. What is claimed is: 1. A current limiting device in which a plurality of thermal current limiting elements whose resistance is increased by increasing the temperature thereof are connected in series, wherein the same number of windings as the thermal current limiting elements have an air-core coil structure.
Alternatively, the combined inductance value is formed by tightly magnetically coupling each other with a reactor having a core structure with a gap , connecting each winding in parallel with the same polarity for each thermal limiting element, and connecting each winding in series. Is set equal to or greater than the lowest value determined from the current limiting target value.