JP2000067710A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-size circuit breaker which suppresses arcs and is unlikely to be depended by an ambient temperature. SOLUTION: In a normal condition, a resistance value of an open circuit operating element 4 is sufficiently smaller than that of a PTC element 5. Thus, an electric current flows little through the PTC element 5. In a state that an electric current flows little through the PTC element 5, a temperature does not rise and a resistance value is low. Thus, a voltage at both ends of the PTC element 5 is kept low, and a voltage operation type excitation coil 6 does not operate and a closed state of the contact 3 is maintained. When an overcurrent flows, the open circuit operating element 4 opens, an electric current flows through the PTC element 5 and rises a resistance value. The rise of a resistance value of the PTC element 5 limits an overcurrent, and the voltage of both ends of the PTC element 5 increases. When the voltage of both ends of the PTC element 5 increases, a voltage of the voltage operation type excitation coil 6 rises, and the voltage operation type excitation coil 6 operates and opens the contact 3 in a state that arks are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker which opens when an overcurrent occurs.

[0002]

2. Description of the Related Art Conventionally, a circuit breaker has a current operation type excitation coil for detecting an overcurrent, and a mechanical contact which is opened by the current operation type excitation coil.

[0003] When an overcurrent is detected by the current operation type excitation coil, a mechanical contact is opened to protect a load or the like from the overcurrent.

[0004] However, due to the presence of an inductor such as a current operation type excitation coil, an arc is generated at the contact when the contact is opened.

[0005] In order to suppress such an arc, it is necessary to provide cooling fins or the like for cooling the arc. When the circuit voltage increases or the overcurrent increases, the arc rapidly increases. The mechanism for cooling becomes large, and the device becomes large.

In particular, in the case of DC, since there is no current zero point unlike AC, it is difficult to extinguish the arc naturally, so that the fins for cooling the arc are enlarged, and it is difficult to reduce the size of the DC circuit breaker. .

[0007] Therefore, as a circuit breaker with a reduced size,
For example, a configuration described in JP-A-4-351825 is known. Japanese Unexamined Patent Publication No. Hei 4-351825 discloses a PTC in series with a mechanical contact for opening a circuit.
(Positive Temperature co-efficient) A circuit breaker to which an element is connected is described.

In this circuit breaker, when an arc is generated, the resistance value of the PTC element rapidly rises to reduce the current, thereby suppressing the arc.

[0009]

However, in the case of the circuit breaker described in JP-A-4-351825,
Since the operation time of the TC element greatly varies depending on the ambient temperature, there is a problem that the operation largely depends on the ambient temperature.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a circuit breaker which suppresses arcing and is less dependent on the ambient temperature and which is reduced in size.

[0011]

According to a first aspect of the present invention, there is provided a circuit breaker in which a PTC element having a positive temperature coefficient, an open-circuit operation element that performs open-circuit operation due to overcurrent, and a voltage-operation-type exciting coil are connected in parallel. It comprises a parallel circuit, and a contact connected in series with the parallel circuit and opened by the voltage-operated excitation coil. Normally, almost no current flows through the PTC element, and the path of the open-circuit operation element and the contact is normally used. When a current flows, the circuit loss is small. When an overcurrent occurs, the open-circuit operation element operates and opens, and when a current flows through the PTC element, the temperature of the PTC element increases and the resistance value increases. The voltage between them rises, and with this rise in voltage, the contacts are opened by the voltage-operated excitation coil,
In this case, since the resistance value of the PTC element is sufficiently high, the current flowing through the contact is sufficiently limited to suppress the arc of the contact, and the overcurrent is cut off. However, since the overcurrent is commutated to the PTC element without interrupting the PTC element and the interrupting ability is not required, the open-circuit operating element can be applied to a circuit exceeding the rated voltage.

According to a second aspect of the present invention, there is provided a circuit breaker according to the first aspect, wherein the PTC element is made of a polymer, and generally has a low resistance and a small heat capacity. The device can operate.

According to a third aspect of the present invention, there is provided a circuit breaker according to the first aspect, wherein the PTC element is made of a ceramic material, and the breakdown voltage of the PTC element is sufficiently increased.

According to a fourth aspect of the present invention, in the circuit breaker according to any one of the first to third aspects, the open-circuit operation element is connected in series with the current operation type excitation coil and the current operation type excitation coil. This is a breaker having a contact opened by a mold excitation coil, and a general breaker can be easily used.

According to a fifth aspect of the present invention, in the circuit breaker according to any one of the first to third aspects, the open-circuit operation element is a circuit protector, thereby simplifying a circuit configuration.

A circuit breaker according to a sixth aspect of the present invention is the circuit breaker according to any one of the first to third aspects, wherein the open-circuit operation element is made of a bimetal, thereby forming a circuit at low cost.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the circuit breaker according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a circuit breaker 1 is connected to a DC power source E.
The load 2 is connected via the.

The circuit breaker 1 includes a contact 3, an open-circuit operation element 4 such as a circuit protector that performs an open circuit that opens a circuit due to an overcurrent, and a polymer-based positive temperature co-efficiency (PTC) having a positive temperature coefficient, for example.
ent) The element 5 and a parallel circuit of a voltage-operated excitation coil 6 for opening the contact 3 are connected in series, and the open-circuit element 4 and the PTC element 5 constitute a current limiting mechanism.

Next, the operation of the above embodiment will be described.

First, at a normal time when the current is within a normal range,
Since the resistance of the open-circuit operation element 4 is sufficiently lower than that of the PTC element 5, almost no current flows through the PTC element 5, most of the current flows through the open-circuit operation element 4, and the circuit loss is reduced. In addition, since almost no current flows through the PTC element 5, the temperature of the PTC element 5 does not rise, and the resistance value is low, the voltage across the PTC element 5 is kept low. It does not operate and keeps the contact 3 closed.

On the other hand, when an overcurrent having a current value equal to or more than a predetermined value flows, the open-circuit operation element 4 is opened, a current flows through the PTC element 5, the temperature of the PTC element 5 rises, and the resistance value of the PTC element 5 increases. To rise. The open-circuit operation element 4 is a PTC element 5
Are connected in parallel, no arc is generated at the time of the opening operation, and no reactivation voltage is applied.
The contact distance may be a distance that does not cause dielectric breakdown.
Also, by using the polymer-based PTC element 5,
The temperature of the PTC element 5 can be raised in a short time to cause a trip, and the increase in the resistance value of the PTC element 5 limits overcurrent and increases the voltage across the PTC element 5. When the voltage between both ends of the PTC element 5 rises, the voltage of the voltage-operated excitation coil 6 rises and operates, and the contact 3 is opened in a state where the arc is suppressed. Therefore, a fin for cooling the arc is not required, and the size of the apparatus can be reduced. When the contact 3 is opened, the arc is suppressed by limiting the overcurrent flowing through the contact 3 by the PTC element 5.

Here, the effect of the current limiting mechanism constituted by the open-circuit operation element 4 and the PTC element 5 will be described using the preliminary experiment circuits shown in FIGS. 2 and 4, and the results of this preliminary experiment will be described.

First, as shown in FIG. 2, only the open-circuit operation element 4 is used.
As a circuit protector with a current of 3.15 A and a resistance of 13 mΩ, the power supply voltage is 130 V DC and the rated current is 1
When a current of 00 A was supplied, the waveform became as shown in FIG. 3, and the circuit protector could not withstand a power supply voltage of DC voltage of 130 V and was broken. However, as shown in FIG. 4, the open-circuit operation element 4 has a trip current of 2 A and a P value of 130 mΩ.
In the case of the open-circuit operation element 4 in which the TC elements 5 are connected in parallel, for a similar DC voltage of 130 V and a current of 100 A,
The waveform shown in FIG. 5 was obtained, and the current commutated to the PTC element 5 was limited, and the operation was performed without any trouble.

Next, as shown in FIG.
An experimental result using the circuit breaker 1 using the PTC element 5 and the voltage operation type excitation coil 6 will be described. The circuit breaker 1 shown in FIG. 1 uses a circuit protector having a DC voltage of 32 V, a current of 3.15 A and a resistance value of 13 mΩ as the open-circuit operation element 4, and a PTC element 5 having a trip current of 2 A and a resistance value of 130.
mΩ, and an operation voltage of 30 V is applied to the voltage operation type excitation coil 6.
In the case of a resistance value of 40Ω, a DC voltage of 130 V and a current of 12 V
The waveform shown in FIG. 6 was obtained when the current was 0 A, and the operation was performed without any trouble. Here, the operation of the circuit breaker 1 will be described with reference to FIG. 6. At point A, the circuit breaker 1 starts to be energized, at point B the open circuit operation element 4 starts operating, and at point C, the open circuit operation element 4 starts operating. Is opened and current flows through the PTC element 5,
The temperature of the PTC element 5 rises, the resistance value rises, the overcurrent is limited, and a voltage is applied to the voltage operation type excitation coil 6. At the point D, the voltage operation type excitation coil 6 starts to be excited. At E, the contact 3 is opened by the voltage operation type exciting coil 6, and the contact 3 is opened in a state where the arc is suppressed by the current limiting action of the PTC element 5, and the operation is completed by interrupting the circuit current. The current flowing through the PTC element 5 has a small current value equal to or smaller than the value obtained by dividing the voltage of the DC power supply E by the resistance value of the PTC element 5 if the load 2 and other impedances are not considered.

The operating time of the circuit breaker 1 can be arbitrarily set by selecting the electrical characteristics of the open-circuit operation element 4, the PTC element 5, and the voltage-operation type excitation coil 6.

In the steady state, the resistance value of the open-circuit operation element 4 is sufficiently smaller than the resistance value of the PTC element 5;
Almost no current flows through the TC element 5, and even if the ambient temperature fluctuates, there is no effect on the current-carrying performance. Since the time required to excite the type excitation coil 6 hardly changes, the operating time of the circuit breaker 1 can be kept constant without changing much.

In the above-described embodiment, a circuit protector is used as the open-circuit operation element 4. For example, a current-operation type excitation coil and a current-operation type excitation coil are connected in series with this current-operation type excitation coil. Similarly, the arc of the contact 3 can be suppressed by using a general breaker having a contact opened by the above or by using a bimetal switch. The open-circuit operation element 4 does not need to interrupt the overcurrent, but only needs to commutate the overcurrent to the PTC element 5. Therefore, the open-circuit operation element 4 is not required to have an interrupting ability, and the open-circuit operation element 4 is used for a circuit exceeding the rated voltage. Applicable.

Further, by using the ceramic PTC element 5, the withstand voltage of the PTC element 5 can be increased.

Further, since a cooling fin or the like for cutting off the generated arc is not required, the size of the apparatus can be reduced.

[0031]

According to the circuit breaker of the first aspect, almost no current flows through the PTC element at normal times, current flows through the path of the open-circuit operation element and the contact, and the circuit loss is small.
When an overcurrent occurs, the open-circuit operation element operates and opens, and PT
The current flows through the C element, the temperature rises, the resistance increases, the current is limited, and the voltage between both ends of the PTC element rises, and the contacts are opened by the voltage-operated excitation coil. In addition, since the open-circuit operation element does not interrupt overcurrent but commutates the overcurrent to the PTC element and does not require the interrupting capability, the open-circuit operation element can be applied to a circuit exceeding the rated voltage.

According to the circuit breaker of the second aspect, the first aspect
In addition to the circuit breakers described, the operating time can be shortened because the PTC element is of a polymer type.

According to the circuit breaker of claim 3, claim 1 is provided.
In addition to the circuit breaker described above, the PTC element is of a ceramic type, so that the withstand voltage can be increased.

[0034] According to the circuit breaker of the fourth aspect, the first aspect is provided.
In addition to the circuit breaker according to any one of (3) to (3), since the open-circuit operation element is a breaker having a contact opened by a current operation type excitation coil, a general breaker can be easily used.

According to the circuit breaker described in claim 5, claim 1 is provided.
In addition to the circuit breaker according to any one of (3) to (3), since the open-circuit operation element is a circuit protector, the circuit configuration can be simplified.

According to the circuit breaker of claim 6, claim 1 is provided.
In addition to the circuit breaker described in any one of (3) to (3), since the open-circuit operation element is bimetal, a circuit can be formed at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a state in which a circuit breaker according to an embodiment of the present invention is connected.

FIG. 2 is a circuit diagram showing a preliminary experiment circuit according to the first embodiment;

FIG. 3 is a waveform diagram showing a circuit current of the circuit shown in FIG. 2 and a voltage between terminals of the circuit protector.

FIG. 4 is a circuit diagram showing another preliminary experiment circuit according to the first embodiment;

FIG. 5 is a waveform chart showing a circuit current of the circuit shown in FIG. 4 and a voltage between terminals of the circuit protector and the PTC element.

FIG. 6 is a waveform diagram showing a circuit current and a voltage between terminals of the circuit protector, the PTC element and the voltage operation type excitation coil when the circuit protector, the PTC element and the voltage operation type excitation coil are connected in parallel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Breaker 3 Contact 4 Open circuit operation element 5 PTC element 6 Voltage operation type excitation coil

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsugaki Itagaki 8050 Igarashi Ninomachi, Niigata City, Niigata F-term in Niigata University (reference) 5G028 AA08 FB05 FC02

Claims (6)

[Claims] 1. A parallel circuit in which a PTC element having a positive temperature coefficient, an open-circuit operation element that performs an open-circuit operation due to an overcurrent, and a voltage-operation type excitation coil are connected in parallel. And a contact opened by a voltage-operated excitation coil. 2. The circuit breaker according to claim 1, wherein the PTC element is made of a polymer. 3. The circuit breaker according to claim 1, wherein the PTC element is a ceramic type. 4. The open-circuit operation element is a breaker having a current operation type excitation coil and a contact connected in series with the current operation type excitation coil and opened by the current operation type excitation coil. Item 6. The circuit breaker according to any one of Items 1 to 3. 5. The circuit breaker according to claim 1, wherein the open circuit operation element is a circuit protector. 6. The circuit breaker according to claim 1, wherein the open-circuit operation element is a bimetal.