JPH0710146B2 - Circuit breaker - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker, in particular, a current before an overcurrent flows to a main circuit of the circuit breaker before the switching mechanism is tripped. The present invention relates to a circuit breaker capable of detecting an alarm and issuing an alarm before tripping.

[Prior Art] FIG. 4 is a block diagram showing a conventional circuit breaker,
In the figure, 1 is an AC power supply, for example, a three-phase AC power supply, 2 is a load fed by the AC power supply 1, and 3 is a circuit breaker connected between the AC power supply 1 and the load 2. This circuit breaker 3 is provided with an AC power source 1 via an opening / closing mechanism section 4.
Main circuit 5 consisting of three-phase conductors 5a, 5b, 5c connected to each other, current transformers CTa, CTb, CTc connected to the respective phase conductors 5a, 5b, 5c of this main circuit 5, and these current transformers Circuit 6 connected to the secondary side of the converter, maximum phase selection / peak value conversion circuit 7 and maximum phase selection / effective value conversion circuit 8 individually connected to the output side of this rectification circuit 6, and maximum phase An instantaneous circuit 9 and a short time limit circuit 10 individually connected to the output side of the selection / peak value conversion circuit 7, a long time limit circuit 11 connected to the output side of the maximum phase selection / effective value conversion circuit 8, and an instantaneous circuit 9, short time limit circuit 10
And the trigger circuit 12 connected to the output side of the long time delay circuit 11
And a trip coil 13 connected between both ends of the rectifier circuit 6 via the trigger circuit 12, and an overcurrent display LED 14 connected to the long time delay circuit 11. The circuits 7 to 11 described above are made of dedicated ICs.

FIG. 5 is a curve diagram showing the overcurrent trip characteristic of the circuit breaker 3 shown in FIG.

The conventional circuit breaker 3 is configured as described above, and its operation will be described with reference to FIGS. 4 and 5.
Now, suppose that the switching mechanism 4 of the circuit breaker 3 is closed, that is, not tripped, and a current is flowing from the AC power supply 1 to the load 2 through the main circuit 5. Current transformer CTa, CTb,
The CTc causes a secondary current proportional to the main circuit current to flow on its secondary side. The rectifier circuit 6 rectifies the alternating secondary current of each of the three phases. The maximum phase selection / peak value conversion circuit 7 selects the maximum phase rectified signal from the rectified signals of each of the three phases from the rectifier circuit 6 and performs peak value conversion thereof. Similarly, the maximum phase selection / effective value conversion circuit 8 selects the maximum phase rectified signal and converts it into an effective value. The peak-value converted DC signal is the instantaneous characteristic INST, among the overcurrent trip characteristics in Fig. 5, respectively.
The DC signal supplied to the instantaneous circuit 9 and the short time delay circuit 10 having the short time delay characteristic STD and converted into an effective value is supplied to the long time delay circuit 11 having the long time delay characteristic LTD. When the main circuit current exceeds, for example, 100% of the rated current, the long-time circuit 11 turns on the overcurrent indicating LED 14 and changes the effective value of the DC signal, for example, 100% to 1000% of the rated current. After a predetermined time shown in FIG. 5, an output is output and the trigger circuit 12 is turned on. When the trigger circuit 12 is turned on, the trip coil 13 is excited by the rectified output of the rectifier circuit 6 to open the opening / closing mechanism section 4 to cut off the main circuit current. Similarly, when the main circuit current becomes large and exceeds, for example, 1000% and 1700% of the rated current, the short time delay circuit 10 and the instantaneous circuit 9 output, respectively.
Cut off the main circuit current.

[Problems to be Solved by the Invention] The conventional circuit breaker as described above has an overcurrent trip characteristic for disconnecting or disconnecting the main circuit only when the main circuit current is in an overcurrent state. There is no advance warning characteristic for issuing an alarm immediately before the main circuit current goes into an overcurrent state,
In addition, there is a problem that it is not possible to prevent erroneous lighting of the LED for the advance warning operation display.

The present invention has been made in order to solve such a problem, and an object thereof is to obtain a circuit breaker having a pre-warning characteristic and capable of preventing erroneous lighting of the pre-warning operation display LED.

[Means for Solving the Problems] A circuit breaker according to the present invention includes a pre-alarm circuit having a pre-alarm characteristic for issuing an alarm before the current flowing through the main circuit reaches an overcurrent, and the pre-alarm circuit. From the pre-alert circuit, a relay coil excited by the output of the pre-alert output circuit, a relay coil disposed in the vicinity of the relay coil and connected in parallel with the relay coil, and It is provided with a pre-alarm operation display LED that is turned on by the output of the pre-alarm output circuit, and a magnetic shield having a body portion arranged in the vicinity of the relay coil and parallel to its axis and an end portion that covers the end of the relay coil. There is.

[Operation] In the present invention, when the preliminary warning circuit having the preliminary warning characteristic detects the main circuit current before reaching the overcurrent, the preliminary warning signal is generated, and by the output of the preliminary warning output circuit operated by the preliminary warning signal. The relay coil is excited, the buzzer is sounded, and the LED for pre-alarm operation is displayed.
Is also lit.

[Embodiment] FIG. 1 is a block diagram partially showing an embodiment of the present invention in a circuit diagram, in which 1, 2, 4 to 14 are exactly the same as those shown in FIG. Circuit breaker 3A of this invention
Is further connected to the output side of the maximum phase selection / effective value conversion circuit 8 and has a pre-warning circuit 20 having a pre-warning characteristic for detecting a main circuit current before reaching an overcurrent and issuing a warning in advance. And a pre-warning output circuit connected to the output side of the pre-warning circuit 20 and operated by the pre-warning signal
21, a control power supply 23 of, for example, AC 100 V connected to the input side of the pre-alarm output circuit 21 via a voltage drop unit such as a transformer 22, and a relay coil 24 excited by the output of the pre-alarm output circuit 21 and With its normally open contact 24a,
The LED 25 for pre-alarm operation, which is arranged in the vicinity of the relay coil 24 and connected in parallel with it, and which is turned on by the output of the pre-alarm output circuit 21, and between both ends of the control power supply 23 via the normally open contact 24a. A buzzer 26 to be connected and a body portion 27a arranged in parallel with the axis of the relay coil 24 in the vicinity of the relay coil 24 and an end portion covering the relay coil end as is clear from the perspective views of FIGS. 3 (A) and 3 (B). Magnetic shield 2 with 27b
7 and.

FIG. 2 is a curve diagram showing an overcurrent trip characteristic and a pre-warning characteristic of the circuit breaker 3A of the present invention.

In the circuit breaker 3A of the present invention shown in FIG. 1, when the current flowing through the main circuit 5 exceeds, for example, 70% of the rated current, the advance warning circuit 20 causes the maximum phase selection / effective value conversion circuit 8 to change the effective value. A pre-warning signal is supplied to the pre-warning output circuit 21 after a predetermined time, for example 40 seconds, according to the value of the converted DC signal, that is, the pre-warning characteristic PAL of FIG. Then, the pre-alarm output circuit 21 excites the relay coil 24 to close the normally-open contact 24a thereof, and the control power supply 23 urges the buzzer 26 to sound the pre-alarm operation display LED 25. Turn on the light. Since the relay coil 24 is provided with the magnetic shield 27, the magnetic flux due to the main circuit current passes through the magnetic shield 27 and does not pass through the relay coil 24. Therefore, no induced voltage is generated in the relay coil 24. LED25 for alarm action display does not light up by mistake.

[Advantages of the Invention] As described in detail above, the present invention provides a pre-alarm circuit having a pre-alarm characteristic for issuing an alarm before the current flowing through the main circuit reaches an overcurrent, and Pre-warning output circuit operated by the pre-warning signal, a relay coil excited by the output of the pre-warning output circuit, arranged in the vicinity of the relay coil and connected in parallel with the relay coil, and Pre-alarm operation display LED that is turned on by the output of the pre-alarm output circuit,
Since a magnetic shield having a main body portion arranged in parallel with the axis of the relay coil and an end portion covering the end of the relay coil is provided, the switching mechanism of the circuit breaker can prevent overcurrent flowing in the main circuit. Before the trip is triggered, an alarm can be issued to notify the operator, and the erroneous lighting of the pre-alarm operation display LED can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit diagram of an embodiment of the present invention, FIG. 2 is a curve diagram showing characteristics of a circuit breaker of the present invention, and FIG. 3 is a magnetic shield used in the present invention. FIG. 4 is a perspective view, and FIG. 4 is a block diagram showing a conventional circuit breaker,
FIG. 5 is a curve diagram showing the characteristics of a conventional circuit breaker. In the figure, 1 is an AC power source, 2 is a load, 3A is a circuit breaker, 4 is an opening / closing mechanism section, 5 is a main circuit, 9 is an instantaneous circuit, 10 is a short-time circuit, 11 is a long-time circuit, and 13 is a trip. Coil, 20 pre-alarm circuit, 21 pre-alarm output circuit, 24 relay coil, 25 pre-alarm operation display LED, 27 magnetic shield, 2
7a is a main body, and 27b is an end. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A circuit breaker having an overcurrent trip characteristic for detecting an overcurrent flowing in a main circuit between an AC power supply and a load to cut off the main circuit, before the overcurrent is reached. A pre-alarm circuit having a pre-alarm characteristic for detecting an electric current and issuing a pre-alarm, a pre-alarm output circuit operated by a pre-alarm signal from the pre-alarm circuit, and an output of the pre-alarm output circuit A relay coil to be excited and a LE for displaying a pre-alarm operation which is arranged in the vicinity of the relay coil and is connected in parallel with the relay coil and is turned on by the output of the pre-alarm output circuit.
A circuit breaker comprising: D, and a magnetic shield having a body portion arranged in the vicinity of the relay coil and parallel to its axis, and an end portion covering an end of the relay coil.