JPS5843974B2 - Genri Yuusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current limiting device having a short time limit function suitable for selective breaker.

Some circuit breakers are combined with a current limiting device that has a current limiting function in order to increase the breaking ability.

However, conventional current limiting devices such as electromagnetic repulsion devices or devices that utilize phase conversion (solid→liquid→gas) of alkali metals such as sodium and potassium have been put into practical use in various fields. In any of these current limiting devices, when a large current occurs due to a short circuit or the like, a current limiting action occurs before the current reaches the first peak value as shown in FIG. 1a.

For this reason, such a current limiting device is not suitable for being connected in cascade with a breaker to selectively cut off the current.

Selective shutoff in this case means that when it is difficult to distinguish between the fault current and the load current by the maximum value, they are distinguished by the difference in duration and shut off. For example, the rated current is 225AF (L For wiring circuit breakers with a current capacity corresponding to the frame of the circuit breaker, the disconnection time is
1.5 cycles, or 20 to 30 m5ec, whereas conventional current limiting devices require less than 1 cycle, or 10 to 2 m5ec.
Since the current limiting operation was completed within 0 m5ec, it was impossible to perform the above-mentioned selective cutoff with these combinations.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a current limiting device having a short time limit function suitable for selective cutoff.

Two embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

That is, as shown in FIG. 2, numeral 1 is a fixed conductor having a contact point 2 at one end and a fixed conductor-side power supply terminal at the other end, which exhibits a relatively high resistance value at room temperature.

3 has a contact 4 at one end that corresponds to the contact 2 and makes contact with and separates from it.
The movable conductor is provided with a flexible conductor 9 and is electrically connected to one end of the flexible conductor 9 at the other end, is arranged parallel to the longitudinal direction of the fixed conductor 1, and exhibits a relatively high resistance value at room temperature.

Reference numeral 6 denotes a substantially U-shaped supporting conductor consisting of three opposing pieces and a connecting piece connecting one end of each of the three pieces.

The fixed conductor 1 is arranged in the substantially U-shaped portion of the support conductor 6 so as to surround each of the three opposing pieces with an insulating distance between them, and the other end of the three pieces is provided with a The movable conductor 3 is sandwiched between them, and the movable conductor 3 is rotatably supported by a pin 5 with respect to the three pieces.

Here, the support conductor 6, pin 5, and movable conductor 3 are electrically connected.

In the figure, reference numeral 8 denotes a current limiting element, one end of which is electrically connected near the fixed conductor side power supply terminal that is buttoned to the fixed conductor 1, and the other end of which is electrically connected to the other end of the movable conductor 3 through a flexible conductor 9. connected.

The current limiting element 8 is made of, for example, niobium, which has a positive temperature coefficient of resistance, and as shown in FIG.
xio-a, which has a relatively low resistance value, but 2394 °
In the vicinity of , the resistance suddenly exhibits a high resistance value, reaching 5741Ω x 10'' at 1, which is nearly 100 times that at room temperature.

The relationship between the resistance value R1 of the current limiting element 8 and the resistance value R2 of the fixed conductor 1 and the movable conductor 3 is as follows at room temperature: R1
〈〈Selected to be R2.

Next, to describe the operation of the present invention configured as described above, assuming that support conductor 1 is connected to the power supply side electric circuit and fixed conductor 1 is connected to the load side electric circuit, in this state, under normal current Since the current limiting element S exhibits a low resistance, the current at this time flows through the support conductor 6 - pin 5 - flexible conductor 9 - current limiting element 8 - fixed conductor 1 since the movable conductor 3 has a relatively high resistance. flows through.

If a large current due to a short circuit accident etc. flows in the circuit from such a state, the temperature will rise rapidly due to the Joule heat generation of the current limiting element 8, and if the resistance suddenly becomes high near 2394 degrees, at this point Since the circuit passing through the above-mentioned current limiting element 8 has an extremely high resistance and it is difficult for the current to flow, the current flows through the support conductor 6, the pin 5, the movable conductor 3, and the fixed conductor 1.

In other words, a large current due to an accident will flow in different directions between the movable and fixed conductors 3 and 1 arranged in parallel.

Then, an electromagnetic repulsive force is generated between the two conductors 1 and 3, and the movable conductor 3 is rotated clockwise around the pin 5 against the biasing force of the spring γ, so that a force is generated between the contacts 2 and 3. The circuit current is effectively limited and cut off by the arc resistance of the generated arc.

1. The process in step 1 of limiting and cutting off the circuit current after a short circuit occurs is as described above, and this is shown on an oscillogram as shown in Figure 1. After a short circuit occurs, the current is limited after several cycles. It will now initiate the cutoff and will have the short-term functionality necessary for selective cutoff.

Of course, in this case, this time limit can be arbitrarily set by changing the fi2dt capacitance, that is, the cross-sectional area S and length t of the conductor.

If such a current limiting device is combined with a circuit breaker, a circuit breaker capable of selectively disconnecting can be obtained since the current limiting device can provide a short time limit function.

FIG. 4 shows a specific example of this. In this case, the breaker mechanism 11 is housed in the upper part of the case 10, and the above-mentioned current limiting device 12 is housed in the lower part, and these are electrically connected in cascade. , when a short circuit current occurs in the illustrated state, after several cycles have passed, the movable conductor 3 of the current limiting device 11 is first separated from the fixed conductor 1, and then the breaking portion of the upper breaker mechanism 11 is broken, and then the current limiting device 12 is disconnected. The movable conductor 3 is the spring 7
The biasing force automatically returns to the original state and completes the shutoff.

In the above embodiment, the movable conductor automatically returns to its original position due to the biasing force of the spring, eliminating the need to reset the current limiter. However, it is of course possible to employ a structure in which the movable conductor is reversely operated by a toggle spring. It is.

As described above, according to the present invention, a movable conductor having a high resistance value is provided on a fixed conductor having a high resistance value so as to be rotatable so that one end of the movable conductor comes into contact with and separating from one end of the fixed conductor, and the movable conductor has a high resistance value. A current limiting element is provided between the other ends of the movable and fixed conductors, which has a low resistance value at room temperature, but which suddenly becomes a high resistance value greater than the resistance value of the fixed and movable conductors when the temperature reaches a predetermined temperature. The current limiting element short-circuits the movable and fixed conductors, and prevents the current limiting element from becoming high resistance due to the large current that occurs when an accident occurs. Since the repulsion force in the opening direction is generated to cause the circuit to be cut off, the current-limiting cutoff occurs several cycles after the fault current occurs, and the short time-limiting function necessary for selective cutoff can be reliably obtained.

Therefore, if such a current limiting device is used in cascade connection with a breaker to perform selective breaker, a good breaker capable of selective breaker can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram for explaining the conventional current limiting device and the current limiting device of the present invention, and FIG. 2 is a perspective view showing an embodiment of the current limiting device according to the present invention. FIG. 3 is a current limiting device used in the same embodiment. The characteristic diagram of the element, FIG. 4, is a sectional view showing an application example of the current limiting device of the present invention. 1... Fixed conductor, 2, 4... Contact, 3... Movable conductor, 5... Pin, 6... Support conductor, 7... Spring,
8... Current limiting element, 9... Flexible conductor, 10... Case, 11... Breaker mechanism, 12... Current limiting device.

Claims (1)

[Claims] 1. A fixed conductor with a high resistance value, a movable conductor with a high resistance value that is provided parallel to the fixed conductor and is rotatable and has one end connected to and separated from one end of the fixed conductor, and these movable conductors. and a current limiting element that is provided between the other ends of the fixed conductor and has a low resistance value at room temperature, and when a predetermined temperature is reached, the current limiting element suddenly increases to a high resistance value that is greater than the resistance values of the fixed and movable conductors. flow device.