JPH0720334B2 - Circuit breaker - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a circuit breaker, and more particularly to an electronic circuit breaker having an improved long-time trip circuit.

[Prior Art] FIG. 3 is a block diagram showing an example of a well-known electronic circuit breaker. In the figure, 1 is an AC power supply, for example, a three-phase AC power supply, and 2 is a load fed by the AC power supply 1, for example, a motor. Reference numeral 3 is a circuit breaker connected between the AC power supply 1 and the load 2. The circuit breaker 3 includes three-phase conductors 5a, 5b, which are connected to the AC power source 1 via the opening / closing mechanism section 4.
The main circuit 5 composed of 5c and the phase conductors 5a, 5b,
The current transformers CTa, CTb, and CTc respectively connected to 5c, the rectifier circuit 6 connected to the secondary side of these current transformers, and the maximum phase selection and individually connected to the output side of the rectifier circuit 6 The peak value conversion circuit 7 and the maximum phase selection / effective value conversion circuit 8, the instantaneous trip circuit 9 and the short time delay trip circuit 10 individually connected to the output side of the maximum phase selection / peak value conversion circuit 7, and the maximum The long time delay trip circuit 11 connected to the output side of the phase selection and effective value conversion circuit 8 and the output side of the instantaneous time trip circuit 9, short time delay trip circuit 10 and long time trip circuit 11 were connected. It is provided with a trigger circuit 12, a trip coil 13 connected across the rectifier circuit 6 via the trigger circuit 12, and an overcurrent display LDE 14 connected to the long-time trip circuit 11. The circuits 7 to 11 described above are made of dedicated ICs.

FIG. 4 is a curve diagram showing an overcurrent trip characteristic of the circuit breaker 3 shown in FIG.

The circuit breaker 3 is configured as described above, and its operation will be described with reference to FIGS. 3 and 4. Now, let us say that the switching mechanism section 4 of the circuit breaker 3 is closed, that is, the circuit breaker 3 is not tripped, and current is flowing from the AC power supply 1 to the load 2 through the main circuit 5. Current transformer
CTa, CTb, CTc are proportional to the main circuit current on the secondary side.
Apply the next current. 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 DC signal with the converted peak value is the instantaneous trip characteristic of the overcurrent trip characteristic in Fig. 4.
INST and short time delay trip circuit 9 having short time delay trip characteristics STD, respectively, are supplied to the short time delay trip circuit 10, and the DC signals whose effective values have been converted are long time time trip circuit 11 having long time delay trip characteristics LTD. Is supplied to. When the main circuit current exceeds, for example, 100% of the rated current, the long time delay trip circuit 11 causes the value of the DC signal converted into an effective value, for example, 100% to 1% of the rated current.
Depending on 000%, an output is output after a predetermined time shown in FIG. 4, the trigger circuit 12 is turned on, and the overcurrent display LED 14 is turned on. When the trigger circuit 12 turns on, the trip coil 13
Is excited by the rectified output of the rectifying circuit 6 to open the opening / closing mechanism section 4 to cut or cut off the main circuit current. Similarly, when the main circuit current increases and exceeds, for example, 1000% and 1700% of the rated current, the short-timed trip circuit 10 and the instantaneous trip circuit 9 respectively output to cut off the main circuit current.

FIG. 5 is a circuit diagram showing, in a partial block diagram, a conventional long-time trip circuit 11 used in the circuit breaker 3 of FIG. In this long time delay trip circuit 11, one input terminal − is connected to the output side of the maximum phase selection / effective value conversion circuit 8 and the other input terminal + sets a reference voltage corresponding to, for example, a rated current of 100%. A first comparator 112 for a long time delay trip pickup connected to a first reference voltage setting circuit 111, and a voltage-current conversion circuit for converting the effective value voltage from the maximum phase selection / effective value conversion circuit 8 into a constant current. 113, a switching transistor 114 whose collector is connected to the output side of this voltage-current conversion circuit 113, whose emitter is connected and whose base is connected to the output terminal of the first comparator 112, and of this switching transistor 114. A backflow prevention diode 115 and a long-time trip capacitor 116, which are connected in parallel with the collector-emitter circuit and in series with each other between the output side of the voltage-current conversion circuit 113 and the ground, and this capacitor. Capacitors 1
A resistor 117 having a large resistance value that is connected in parallel with 16 and has a thermal time constant, and one input terminal − of which is connected to the connection point of the diode 115, the capacitor 116, and the resistor 117 and the other input terminal + Includes a second comparator 119 for generating a long time delay trip signal, which is connected to a second reference voltage setting circuit 118 for setting a reference voltage corresponding to the long time delay trip operation time.

In the long time delay trip circuit 11 configured as above, the output level of the first comparator 112 is high while the effective value voltage is lower than the reference voltage of the first reference voltage setting circuit 111, so that switching Transistor 114 is turned on and thus capacitor 116 is shorted and not charged, so that no trip signal is provided externally from output terminal 120 of long time trip circuit 11. However, when the RMS voltage exceeds the reference voltage described above, the output level of the first comparator 112 becomes low and the switching transistor 114 is turned off. Then, the capacitor 116
Is gradually charged by the constant current from the voltage-current conversion circuit 113 through the diode 115, and when the charging voltage exceeds the reference voltage of the second reference voltage setting circuit 118, the second comparator 119 outputs the first voltage from the output terminal 120. A trip signal is supplied to the trigger circuit 12 and the LED 14 shown in FIG. At the same time, the capacitor 116 is discharged through the resistor 117, but its discharge constant is so long that it may be charged again before it is completely discharged.

[Problems to be Solved by the Invention] In the above-described conventional long-time-delay trip circuit, the discharge time constant of the capacitor is extremely long. Therefore, if the long-time trip test is continuously performed many times, the capacitor becomes There was a problem in that a charge was accumulated and charges were accumulated before the discharge was completed, resulting in a time error.

Therefore, the present invention has been made in order to solve the above problems, and an object thereof is to obtain a circuit breaker having an improved long-duration trip circuit that does not cause a time error even if a long-duration trip test is continued. And

[Means for Solving the Problems] A circuit breaker according to the present invention is provided with an improved long-time trip circuit having a transistor having a collector-emitter circuit connected in parallel with a long-time trip capacitor. is there.

[Operation] In the present invention, since the long-timed trip circuit generates the trip signal and at the same time the trip signal turns on the transistor, the charge load of the capacitor connected in parallel with the transistor is immediately discharged. It

[Embodiment] FIG. 1 is a circuit diagram showing a partial block diagram of a long time delay trip circuit used in the present invention. In the figure, 111 to 120
Is exactly the same as that shown in FIG. The long-time trip circuit 11A used in the present invention is the long-time trip circuit 11 of FIG. 5 provided with a transistor 121 for immediately discharging the discharge load of the capacitor 116. This transistor 121 has its collector-emitter circuit connected in parallel with the capacitor 116 and its base via the drive circuit 122 at the output side of the second comparator 119, that is, the output terminal.
Connected to 120.

In the long-time delay trip circuit 11A configured as described above, at the same time that the second proportional circuit 119 outputs the trip signal,
The trip signal is supplied to the drive circuit 122, and as a result, the drive signal is supplied from the drive circuit 122 to the base of the transistor 121 to turn on the transistor 121.
The charge of the capacitor 116 is discharged, and the long-timed trip test can be immediately performed without causing a time error.

When the output side of the first proportional circuit 112 is connected to the base of the transistor 121 by the external connection 123, the main circuit current is reduced to 100% or less of the rated current as shown in FIG. When the output level returns to high level,
Since the transistor 121 is turned on, the capacitor 116
The electric charge of is immediately discharged, and the characteristics with respect to an intermittent load can be changed immediately.

EFFECTS OF THE INVENTION As described above in detail, since the present invention includes the improved long-time trip circuit having the transistor in which the collector-emitter circuit is connected in parallel with the long-time trip capacitor, The capacitor is completely discharged at the same time as the generation of the disconnection signal, and the retest can be performed immediately without causing a time error.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a partial block diagram of a long time delay trip circuit used in the present invention, FIG. 2 is a waveform diagram for explaining the operation of the long time delay trip circuit shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing an example of a known electronic circuit breaker, FIG. 4 is a curve diagram showing the overcurrent trip characteristics of the circuit breaker and circuit breaker shown in FIG. 3, and FIG. It is a circuit diagram which shows a part of block diagram of a time delay trip circuit. In the figure, 1 is an AC power supply, 2 is a load, 3 is a circuit breaker, 11A is a long-time trip circuit, 116 is a long-time trip capacitor, 121 is a transistor, and 122 is a drive circuit. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A circuit breaker having a long-time trip circuit for detecting an overcurrent flowing in a main circuit between an AC power supply and a load to shut off the main circuit. Collector in parallel with long time delay trip capacitor
A circuit breaker having a transistor to which an emitter circuit is connected, the transistor being driven by a trip signal output from the long-time trip circuit.