JPH0260409A - Circuit breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a circuit breaker, particularly before an overcurrent flows in its main circuit and the opening/closing mechanism is tripped. This invention relates to a circuit breaker that has an improved advance warning circuit for detecting and issuing a warning before tripping.

[Conventional technology]

FIG. 3 is a block diagram showing a part of a conventional circuit breaker. In the figure, 1 is an AC power source, for example, a three-phase AC power source, 2 is a load, such as a motor, which is supplied with power by this AC power source IK, and 3 is a block diagram of these. This is a circuit breaker connected between an AC power source 1 and a load 2. This circuit breaker 3 includes a three-phase conductor 5a connected to an AC power supply IK via a switching mechanism section 4;
A main circuit 5 consisting of 5b and 5c, and a current transformer CT connected to each phase conductor 5a, 5b, and 5c of this main circuit 5, respectively.
a rCTb, CTc, a rectifier circuit 6 connected to the secondary side of these current transformers, a maximum phase selection/peak value conversion circuit 7 and an interpersonal phase selection connected individually to the output side of this rectification circuit 6. The instantaneous circuit 9 and the short-time circuit 10 are individually connected to the output side of the effective value conversion circuit 8 and the maximum phase selection and peak value conversion circuit 7, and the output side of the interpersonal phase selection and effective value conversion circuit 8 is connected to the output side of the effective value conversion circuit 8. The connected long time circuits 11 and these instantaneous circuits 9
, a trigger circuit 12 connected to the output sides of the short time limit circuit 10 and the long time limit circuit 11, and a tripping coil 13 connected between both ends of the rectifier circuit 60 via the trigger circuit 12;
The overcurrent display KED 14 is connected to the long time limit circuit 11. Note that the circuits 7 to 11 described above are dedicated ICs.
Made with.

The conventional circuit breaker 3 is further connected to the output side of the maximum phase selection and effective value conversion circuit 8, and has advance warning characteristics for detecting the main circuit current before it reaches an overcurrent and issuing a advance KV alarm. an advance warning circuit 20 having a
A photocoupler 27 consisting of a light emitting diode 27a connected to the output side of the light emitting diode 27a and a phototransistor 27b optically coupled to the light emitting diode, and a phototransistor 27b connected to the output side of the photodiode 27b.
A pre-warning output circuit 21 is connected to the output side of the pre-warning circuit 20 and is operated by the pre-warning circuit from the pre-warning circuit 20. The example given is a control power supply 23 of AC 100 volts, a relay coil 24 and its normally open contact 24a excited by the output of the advance warning output circuit 21 on the output side of the advance warning output circuit 21, and a circuit connected in parallel with the relay coil 24. An LED 25 for indicating advance warning operation as a warning means that is lit by the output of the front warning output circuit 21 is connected to the control power source 2 through a normally open contact 24a.
+V buzzer connected between both ends of 3 as a means of reporting 2
6.

FIG. 4 is a curve diagram showing the overcurrent-side disconnection characteristics and front-loading/time-signaling characteristics of the conventional circuit breaker 3.

The conventional circuit breaker 7 and disconnector 3 are constructed as described above, and their operation will be explained with reference to FIGS. 3 and 4.

Assume now that the switching mechanism section 4 of the circuit breaker 3 is closed, that is, it is not tripped, and current is flowing from the AC power source 1 through the main circuit 8 to the load 2. current transformer CTa,
CTb and CTc allow a secondary current proportional to the main circuit current to flow through their secondary sides.

The rectifier circuit 6 rectifies the AC secondary current of each of the three phases. The maximum human aspect selection and peak value conversion circuit 7 is a
The maximum phase eruption signal is selected from among the egress signals of each phase and converted to a peak value. Similarly, the interpersonal phase selection and effective value conversion circuit 8 selects the maximum phase band current signal and converts it into an effective value.

The peak value-converted DC signal has the instantaneous characteristic lN5T and short-time characteristic STD among the overcurrent bow removal characteristics shown in Fig. 4, respectively.
The signal is supplied to an instantaneous circuit 9 and a limit circuit 10 having an effective value, and the +i4 current signal converted into an effective value is supplied to a long time limit circuit 11 having a long time limit characteristic LTD.

When the current flowing through the main circuit 5 exceeds 70% of the rated flow, the advance warning circuit 20 outputs the value of the blood flow signal converted to the effective value from the maximum phase selection and effective value conversion N path 8, that is, the value shown in FIG. After a predetermined time according to the advance warning characteristic PAL, the advance warning signal is sent to the advance warning output circuit 21 through the photocoupler 27
supply. Then, this advance warning output circuit 21 excites the relay coil 24 to close its normally closed contact 24a, and the control power supply 23 energizes the buzzer 26 to sound it and lights up the advance warning operation LED 25. let

Figure 5 shows the advance warning circuit 2 shown in the block diagram in Figure 3.
0, and FIG. 6 is a circuit diagram of this advance warning circuit 2.
FIG. 2 is a waveform diagram for explaining the operation of 0.

In the advance warning circuit 20 shown in FIG. 5, V+, 5GND and ■- are power supply terminals, Vref is a reference voltage supply terminal for a timer comparator to be described later, and VRref is a variable reference voltage supply terminal for a comparator for advance warning generation to be described later. , the terminals VRref and 5G are terminals to which the DC signal converted to an effective value is supplied from the maximum phase selection and effective value conversion circuit 8 shown in FIG.
A first fixed resistor Rh potentiometer VR and a second fixed resistor R2 for setting an advance warning generation level are connected in series between ND and ND.

As the second fixed resistor R2, a high-precision resistor is used which has a special resistance value and is therefore expensive in order to obtain accuracy at the maximum and minimum times of the advance warning generation V bell. Terminal ■
The first comparison means connected between + and V-, that is, the pre-warning generation comparator COI, has a non-inverting input terminal (- is connected to the arm of the potentiometer VR, and an inverting input terminal - is Connected to RMS+.Terminal Vr
Between ef and 5GND, resistor R3 and capacitor C7!
II'' - connected in series, and in parallel with this series circuit further resistors R4 and R5 are connected in series.Capacitor C
A normally closed switch Ql is connected in parallel with , and a resistor R6 is also connected thereto. A second terminal connected between terminals V+ and V-
The comparison means, that is, the timer comparator CO2 has its non-inverting input terminal - connected to the connection point between resistors R4 and R5, and its inverting input terminal - connected to the connection point between resistor R3 and capacitor C. A light emitting diode 27a of a photocoupler 27, a resistor 7, and a normally open switch Q2 are connected in series between the terminals 2+ and V-.

Next, the operation of the advance warning circuit 20 configured as described above will be explained with reference to the waveform diagram of FIG. 6. First, the variable reference voltage of the advance warning generation comparator COI, that is, the antenatal warning generation level, is set to a predetermined value according to the rated current.

For example, if the rated current is 40OA, it is set to 4■, which corresponds to 280A, which is 70% of the rated current, and when it is 200A, it is set to 2■, which corresponds to 140A, which is 70% of the rated current. At time t1, when the DC signal proportional to the effective value of the main circuit current exceeds the advance warning circuit level, the advance warning generation comparator COI outputs an output and turns off the normally closed switch Q1. Make it.

Therefore, the RC timer consisting of resistor R3 and capacitor C starts operating, capacitor C is gradually charged and its voltage increases little by little. However, time t2
When the above-mentioned DC signal becomes smaller than the pre-warning generation level, the pre-warning generation comparator COI does not output an output and the normally closed switch Q1 returns to ON, so the capacitor C is instantly It discharges and therefore its voltage becomes zero. At time t3, the DC signal exceeds the advance warning circuit level and this state remains for a predetermined period of time, for example, 40
If the capacitor voltage continues for more than a second, the timer comparator C
Since the reference voltage of O2, which corresponds to the alarm output operation level, exceeds 2.5■ at time t4, the timer comparator CO2 outputs an output and turns on the normally open switch Q2. Therefore, a current flows from the terminal V+ to V- through the light emitting diode 27a, the resistor R7, and the normally open switch Q2 which is turned on. That is, the advance warning circuit 20 supplies the advance warning signal to the advance warning output circuit 21 through the photocoupler 27.

Returning to FIGS. 3 and 4, when the main circuit current exceeds, for example, 100% of the rated current, the long time circuit 11 converts the effective value converted DC signal value, for example, from 100% to 100% of the rated current. 1000%, output is output after a predetermined time shown in FIG. 4 to turn on the trigger circuit 12 and light up the overcurrent indicating LED 14. When the trigger circuit 12 is turned on, the tripping coil 13 is excited by the rectified output of the rectifying circuit 6 and opens the bending/closing mechanism 4 to cause the main circuit current to flow to 'F flal'. Similarly, when the main circuit current becomes thicker and exceeds, for example, 1000% or 1700% of the rated current, the short time limit circuit 10 and the instantaneous circuit 9 are disconnected, respectively, and the main circuit current is cut off.

[Problem to be solved by the invention]

In the advance warning circuit used in the conventional circuit breaker as described above, a special second fixed resistor is used for setting the advance jurisdiction occurrence level in order to obtain the maximum and minimum accuracy of the advance warning circuit level. There is a problem in that a high-precision resistor having a high resistance value and therefore being expensive is required.

The present invention was made to solve these problems, and an object of the present invention is to provide a circuit breaker that does not require a high-precision resistor and uses an improved advance warning circuit.

[Means to solve the problem]

In the circuit breaker according to the present invention, a general-purpose resistor is used as the second fixed resistor for setting the advance warning generation level, and another general-purpose resistor is connected to this resistor and a variable resistor.

[For production]

In this invention, the accuracy of the maximum and minimum pre-warning generation level is adjusted by the parallel resistance values of the second fixed resistor, which is a general-purpose product, and another resistor, which is a general-purpose product.

〔Example〕

FIG. 2 is a block diagram showing a partial circuit diagram of an embodiment of the present invention.
is exactly the same as shown in FIG.

The circuit breaker 3A of the present invention includes an advance warning circuit 2OA having the same advance warning characteristics as shown in FIG. 4, the details of which are shown in the circuit diagram of FIG. The advance warning circuit 2OA is different from the advance warning circuit 20 shown in FIG. 5 in that, instead of the high-precision second fixed resistor R2, it is made up of general-purpose resistors with standard resistance values and are connected in parallel with each other. Second fixed resistor R
2A and another resistor R2B. With this configuration, it is possible to select various partial resistance values and adjust the maximum and minimum levels of the occurrence level.

Note that the excessive tif flow disconnection operation and the ante-mortem warning operation of the circuit breaker 3A of the present invention and the operation of the advance warning circuit 20A are as described for the conventional example.

〔Effect of the invention〕

As described above, the present invention outputs an output when the current before reaching an overcurrent exceeds a predetermined value, and turns the normally closed switch to zero.
Since a general-purpose resistor is used as the second fixed resistor in the first comparison means for FFK, and another general-purpose resistor is connected in parallel with this resistor, there is an advantage that a high-precision resistor is not required.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an advance warning circuit used in this invention, Fig. 2 is a block diagram showing an embodiment of this invention partly as a circuit m+, and Fig. 3 shows a part of a conventional circuit breaker. A block diagram shown in a circuit diagram, Fig. 4 is a curve diagram showing the characteristics of a conventional circuit breaker, Fig. 5 is a circuit diagram showing an advance warning circuit used in a conventional circuit breaker, and Fig. 6 is a curve diagram showing the characteristics of a conventional circuit breaker. FIG. 3 is a waveform diagram for explaining the operation of the advance warning circuit shown in the figure. In the figure, 1 is the AC side L2 is the load, 3A is the circuit breaker, 4 is the switching mechanism, 5 is the main circuit, 9 is the instantaneous circuit, 10
is a short time circuit, 11 is a long time circuit, 13 is a tripping coil, 20A is an advance warning circuit, CO1 is a comparator for generating advance warning, R1 is the first fixed resistor, VR is a potentiometer, R
2A is the second fixed resistor, R2B is another resistor, Ql is a normally closed switch, C is a capacitor, CO2 is a timer comparator, Q
2 is a normally open switch. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A circuit disconnector having an overcurrent tripping characteristic for detecting an overcurrent flowing in a main circuit between an AC power supply and a load and disconnecting the main circuit, and furthermore, the overcurrent occurs. When the previous current exceeds a predetermined value, it outputs an output and turns the normally closed switch to O.
a first comparison means for turning the FF into an FF; a capacitor connected in parallel with the normally closed switch and generating a voltage corresponding to the current exceeding the predetermined value; and a capacitor that outputs an output when the capacitor voltage continues for a predetermined time or more to switch the normally open switch. an advance warning circuit having a second comparison means that generates an advance warning signal by turning ON the first comparison means, the first comparison means includes a comparator for generating advance warning and a first fixed one for setting the level of generation of advance warning. In the circuit/breaker comprising a resistor, a potentiometer, and a second fixed resistor, a general-purpose resistor is used as the second fixed resistor, and another general-purpose resistor is connected in parallel with this resistor. Circuit break or break.