JP2869264B2 - Circuit breaker with advance alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker with a pre-alarm, and more particularly to a circuit breaker with a pre-alarm in which a pre-alarm starting current and an overcurrent trip starting current have exactly the same value.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a configuration of a conventional circuit breaker with a pre-alarm. In the figure, U, V, and W are each phase of an AC power supply (not shown), 1 is a main circuit composed of phase conductors connecting each phase to a load, 2 is a breaker contact provided in the main circuit 1, 3 Is a trip coil that opens the circuit breaker contact 2 via the breaking mechanism 3A when excited and closes the circuit breaker contact 2 when demagnetized, and 4 denotes a primary winding for each phase conductor of the main circuit 1. Current transformers 5 are circuit breakers with pre-alarm connected to the secondary windings of these current transformers 4.

[0006] Reference numeral 6 denotes a rectifier circuit for converting alternating current of the main circuit 1 connected to the current transformer 4 to direct current, 7 denotes a power supply circuit connected to the rectifier circuit 6 and supplies required voltages to various circuits described later, 8 is an electronic switch connected in series with the trip coil 3 between both ends of the power supply circuit 7, and 9 is an AL output for outputting an alarm signal (hereinafter referred to as AL) connected between both ends of the power supply circuit 7. The circuit 10 is an AL output relay connected to the AL output circuit 9 and operated by AL.

[0004] Reference numeral 11 denotes an air-core coil coupled to each phase conductor of the main circuit 1, and 12 is connected to the air-core coil 11 to reproduce an overcurrent of the main circuit 1 and a current signal proportional to a current before the overcurrent. The current signal reproducing circuit 13 is connected to the air-core coil 11 in parallel with the current signal reproducing circuit 12,
A ground fault signal reproducing circuit for reproducing a ground fault signal proportional to the ground fault current of the main circuit 1 is a rectifying signal circuit for rectifying the current signal reproduced by the current signal reproducing circuit 12.

[0005] Reference numerals 15A and 15B denote rectified signal circuits 14, which are connected in parallel with each other at the output side to select the maximum phase rectified signal from the rectified signals of the respective phases.
Reference numeral 7 denotes a peak value conversion circuit and an effective value conversion circuit for converting the rectified signal selected by the maximum phase selection circuits 15A and 15B into a peak value and an effective value, respectively.

Reference numeral 18 denotes a long time delay for outputting a trip signal when the rectified signal converted into an effective value from the effective value conversion circuit 17, that is, the detected voltage exceeds the long time trip characteristic of the overcurrent trip characteristics shown in FIG. It is a removal circuit. Reference numeral 19 denotes a long time operation display circuit which is activated by a trip signal from the long time trip circuit 18.

Reference numeral 20 denotes a characteristic setting circuit for setting characteristics of each trip circuit including the long time trip circuit 18 and a pre-alarm circuit, 21 denotes an effective value conversion circuit 17, and a long time trip circuit 19
And an effective value conversion circuit 1
A pre-alarm circuit that outputs a pre-alarm signal when the above-described detected voltage from 7 exceeds the pre-alarm characteristic of FIG. 5, and 22
Is a pre-warning output circuit which is activated by the pre-warning signal from the pre-warning circuit 21 to turn on an LED or a lamp. Since other circuits are not directly related to the present invention, the description thereof is omitted here.

FIG. 4 is a circuit diagram showing the internal configuration of the characteristic setting circuit 20 and the long time trip circuit 19. The characteristic setting circuit 20 includes a reference power supply 20a and a buffer amplifier 20 having a gain of 1.
b, and variable resistors 20c to 20e. The variable resistor 20c is connected between the reference power supply 20a and the ground, and its tap is connected to one input terminal + of the buffer amplifier 20b. The output terminal of the buffer amplifier 20b is connected to the other input terminal of the buffer amplifier 20b and is grounded via a variable resistor 20d. The variable resistor 20e is connected between the output terminal of the reference power supply 20a and the ground.

On the other hand, the long time trip circuit 18 includes a V / I ² converter 18a and a long time (LTD) pickup comparator 1
8b, timed operation transistor 18c, diode 18
d, capacitor 18e, discharge resistor 18f, switch 18
g, and a long time (LTD) timer comparator 18h, the V / I ² converter 18a further includes a voltage converter 18a1 for converting the detection voltage V from the effective value conversion circuit 17 into V ² ,
Consists transistor pair 18a4 consists of transistors 18a2 and 18a3, the respective base transistor pair 18a4 is connected to the V ² output side of the voltage converter 18a1, the emitter resistance between each emitter and the power supply are connected respectively 18a5 , 18a6.

The collector of one transistor 18a2 of the paired transistors 18a4 is connected to the collector and emitter circuit of the timed operation transistor 18c and the diode 18d.
And a series circuit including a capacitor 18e and a series circuit including a switch 18g and a discharge resistor 18f, which are grounded in parallel through three loops. L
The comparator 18b for TD pickup has one input terminal + to which the detection voltage from the above-described effective value conversion circuit 17 is applied, and the other input terminal-from the tap of the variable resistor 20c in the characteristic setting circuit 20 to the LTD pickup. A reference voltage is applied, and its output terminal is connected to the timed operation transistor 18c to keep the transistor 18c normally on.

Further, a diode 18d and a capacitor 18
e and the connection point between the switch 18g and the discharge resistor 18f are both connected to one input terminal + of the LTD timer comparator 18h, and the other input terminal is connected to the reference power source 20a in the characteristic setting circuit 20. Output terminal.

Similarly, the advance warning circuit 21 operates in advance (PA
L) Pickup comparator 21a, timed operation transistor 21b, diode 21c, capacitor 21d, discharge resistor 21e, switch 21f, and advance (PAL)
It includes a timer comparator 21g.

The collector of one transistor 18a3 of the pair transistor 18a4 is connected to the collector and emitter circuit of the timed operation transistor 21b and the diode 21c.
And a series circuit including a capacitor 21d and a series circuit including a switch 21f and a discharge resistor 21e, which are grounded in parallel through three loops.

The PAL pickup comparator 21a has one input terminal + to which the above-mentioned detection voltage is applied and the other input terminal to the variable resistor 20 in the characteristic setting circuit 20.
The PAL pickup reference voltage is applied from the tap of d, and its output terminal is a timed operation transistor 21b.
To keep the transistor 21b normally on.

Further, a diode 21c and a capacitor 21
The connection point d and the connection point between the switch 21f and the discharge resistor 21e are both connected to one input terminal + of the PAL timer comparator 21g, and the other input terminal is connected to the variable resistor 20e in the characteristic setting circuit 20. Connected to the tap.

Next, the operation of the conventional circuit breaker with pre-alarm will be described. If the current in the main circuit 1 is small flows and whose value is the detection voltage V corresponding to this small current is converted to V ² by the voltage converter 18a1, thereby paired transistor 18a4 is turned on. In addition,
The emitter resistance 18a5 of the pair transistor 18a4
And the relative value of 18a6 determines the ratio of the time of the advance warning characteristic to the long time trip characteristic of FIG.

Since the detection voltage V is smaller than the reference voltages of the PAL pickup comparator 21a and the LTD pickup comparator 18b, the time-limited operation transistor 21
b and 18c are both turned on, and the I ² collector current of paired transistor 18a4 flows to ground through these timed transistors 21a and 18c.
Therefore, the pre-warning circuit 21 does not generate the pre-warning signal, and the long time trip circuit 18 does not generate the trip signal.

However, when the value of the current flowing through the main circuit 1 increases (corresponding to the point A in FIG. 5) and the corresponding detection voltage V exceeds the PAL pickup reference voltage, P
Since the timed operation transistor 21b is turned off by the output of the AL pickup comparator 21a, the other transistor 18a3 of the pair transistor 18a4 is turned off.
I ² collector current from charging the capacitor 21d through a diode 21c, the its charging s pressure exceeds the reference voltage of the comparator 21g for PAL timer, PAL timer comparator 21g generates a pre-alarm signal.

Similarly, when the value of the current flowing through the main circuit 1 further increases (corresponding to the point B in FIG. 5) and the corresponding detection voltage V exceeds the LTD pickup reference voltage, the pickup LTC comparator 18b since timed operation transistor 18c is turned off by the output, I ² collector current from one transistor 18a2 in the pair transistor 18a4 charges the capacitor 18e through the diode 18 d, the comparator for the charge s pressure LTD timer 18h , The comparator 18h for the LTD timer generates a trip signal.

Conversely, the value of the current flowing through the main circuit 1 decreases (corresponding to points B and A in FIG. 5) and the capacitor 18
When the charging pressures of the e and 21d become lower than the reference voltages of the LTD timer comparator 18h and the PAL timer comparator 21g, respectively, the LTD timer comparator 18h does not generate a trip signal and the PAL timer comparator 21g No pre-warning is issued.

The above-mentioned capacitor charging pressure is discharged through the discharging resistors 18f and 21e, respectively. At this time, since the time operation transistors 18c and 21b are turned on, if the switches 18g and 21f are closed here, the capacitors 18e and 21d are rapidly discharged through the time operation transistors 18c and 21b, respectively.

[0022]

In a conventional circuit breaker with a pre-alarm, the overcurrent trip start current and the pre-alarm start current are set to be exactly the same current, and the pre-alarm start and the overcurrent trip start are made the same. In this case, the reference voltage of each comparator for pickup is set to be the same, and a comparison signal is output to each transistor for timed operation at the same time. However, since the comparator for pickup is composed of an operational amplifier, an offset voltage is applied to the output. May have appeared. Therefore, even if the reference voltage is the same, the comparison signal is not always output from each pickup comparator at the same time. In some cases, the relationship between the pre-warning characteristic and the long time trip characteristic in FIG. There was a problem that it would.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an advance warning characteristic and a long time limit trip characteristic.
Easy to start each operation while maintaining the relationship with the performance
An object is to obtain a circuit breaker with a pre-alarm that can be adjusted .

[0024]

SUMMARY OF THE INVENTION A circuit breaker with a pre-alarm according to the present invention detects an overcurrent flowing in a main circuit between an AC power supply and a load, and trips the overcurrent for breaking the main circuit. Characteristics, and in a circuit breaker with a pre-alarm having a pre-alarm characteristic for detecting a current before reaching the overcurrent and generating an alarm in advance, an overcurrent reference voltage and a response to the main circuit current A reference voltage setting means for setting a pre-alarm reference voltage; a voltage detection means for detecting a voltage corresponding to the main circuit current; and a detection voltage detected by the voltage detection means being set by the reference voltage setting means. Outputs a signal when exceeding the current reference voltage is detected
And the overcurrent tripping means for generating a trip signal after a predetermined time, if more than a pre-alarm reference voltage set the detected voltage by said reference voltage setting means, the trip
Pre-alarm generation means for generating an alarm signal after a predetermined time before signal generation, and operating the pre-alarm generation means based on a signal output from the overcurrent trip means, simultaneously with the start of the overcurrent trip operation And a pre-warning operation means for starting a pre-warning operation.

[0025]

In the circuit breaker with pre-alarm according to the present invention, when the overcurrent tripping means reaches the operation start condition, the start condition is transmitted to the pre-alarm generation means by the pre-alarm operation means and the overcurrent tripping operation is performed. By starting the pre-alarm operation at the same time as the start, the operation start timing can be adjusted without individually adjusting the start condition of each means.

[0026]

[Embodiment 1] FIG. 1 is a block diagram showing an overall configuration of a circuit breaker with a pre-alarm according to the present embodiment. In the drawing, the same reference numerals as those in FIG. 3 indicate the same or corresponding parts. In the figure, reference numeral 18A denotes a long time-limit trip circuit in the present embodiment,
0A is a characteristic setting circuit in this embodiment, and 21A is a pre-alarm circuit in this embodiment. FIG. 2 shows a characteristic setting circuit 2
0A, long time limit trip circuit 18A and advance alarm circuit 21
FIG. 2 is a circuit diagram showing an internal configuration of A. In each circuit, the same reference numerals as those in FIG. 4 indicate the same or corresponding parts. Note that the characteristic setting circuit is a reference voltage setting circuit, the effective value conversion circuit is a voltage detecting means,
The long time trip circuit constitutes an overcurrent trip circuit, and the pre-warning circuit constitutes a pre-warning means.

In the characteristic setting circuit 20A, the LTC pickup comparator 18 provided in the long time trip circuit 18A is provided.
b, each of the variable resistors 20c, 20d and 20e for providing a reference voltage to the PAL pickup comparator 21a and the PAL timer comparator 21g provided in the advance alarm circuit 21A is connected between the output terminal of the reference power supply 20a and the ground. I have.

Further, the comparator 18b for the LTD pickup
Between the output terminal and the base of the timed operation transistor 18c.
The output current limiting resistors 18R and 21R are inserted between the output terminal of the PAL pickup comparator 21a and the base of the timed operation transistor 21b, respectively, and the timed operation is performed with the output terminal of the LTD pickup comparator 18b. A diode D is connected between the bases of the transistors 21b as a pre-alarm operation means having a cathode connected to the output terminal and an anode connected to the base.

Next, the operation of the first embodiment of the present invention shown in FIG. 1 will be described. First, if a trip signal is output from the long time trip circuit 18 to the electronic switch 9 after the prior warning signal is generated from the prior warning circuit 21 as in the conventional case, the reference voltage applied to the PAL pickup comparator 21a is set to the LTD pickup. The characteristic setting circuit 20 is set to be lower than the reference voltage given to the comparator 21a.
Of the variable resistors 20c and 20d are adjusted.

Next, the LTC pickup comparator 18b
When the pre-warning circuit 21A is operated by the low level output from the controller and the trip signal is output from the long time trip circuit 18A simultaneously with the pre-warning output, PAL
The variable resistors 20c and 20d of the characteristic setting circuit 20 are adjusted so that the PAL pickup reference voltage given to the pickup comparator 21a is set higher than the LTD pickup reference voltage given to the LTD pickup comparator 18b.

As a result, the value of the current flowing through the main circuit 1 increases (corresponding to the point B in FIG. 5), and when the corresponding detection voltage V exceeds the LTD pickup reference voltage of the LTD pickup comparator 18b, LTD The output of the pickup comparator 18b changes from High to Low.
At this time, the output of the PAL pickup comparator 21a is H
Since it is at the high level, the diode D is connected to the base of the timed operation transistor 21b connected to the output terminal of the PAL pickup comparator 21a via the resistor 21R.
, A current flows to the LTD pickup comparator 18b.

When a forward current flows through the diode D in this manner, 0.6 V is applied between the anode and the cathode of the diode D.
Is generated, and the generated voltage causes the base-emitter voltage of the timed operation transistor 21b to be 0.
6V is offset. As a result, the timed operation transistor 21
b turns off. Thereafter, similarly to the conventional circuit, the other transistor 18a3 in the pair transistor 18a4
I ² collector current from charging the capacitor 21d through a diode 21c, the its charging s pressure exceeds the reference voltage of the comparator 21g for PAL timer, PAL timer comparator 21g generates a pre-alarm signal.

When the pre-alarm circuit 21A operates,
The timed operation transistor 18c is also a pickup LTD.
Since it is turned off by the output of the comparator 18b, one of the pair transistors 18a4, 18a4
The I2 collector current from ² charges capacitor 18e through diode 18d. When the charged voltage exceeds the reference voltage of the LTD timer comparator 18h, the LTD timer comparator 18h generates a trip signal. Therefore, as shown in FIG. 5, it is possible to shift the starting point A of the advance warning characteristic to the starting point B of the long time trip characteristic.

[0034]

As described above, according to the present invention, an overcurrent tripping characteristic for detecting an overcurrent flowing in a main circuit between an AC power supply and a load and shutting off the main circuit, and the overcurrent In a circuit breaker with a pre-alarm for detecting a current before reaching and generating an alarm in advance, an overcurrent reference voltage and a pre-alarm reference voltage in response to the main circuit current are set. a reference voltage setting means for, voltage detecting means for detecting a voltage corresponding to the main circuit current, than the overcurrent reference voltage detected voltage detected by the voltage detecting means is set by the reference voltage setting means super
Over the outputs a signal if the detected overcurrent tripping means for generating a trip signal after a predetermined time, if more than a pre-alarm reference voltage set the detected voltage by said reference voltage setting means, the trip signal A pre-alarm generating means for generating an alarm signal after a predetermined time before the occurrence, and the pre-alarm generating means are operated based on a signal output from the overcurrent tripping means. With the pre-alarm operation means for starting the alarm operation, if the overcurrent tripping means has reached the operation start condition,
By transmitting the start condition to the pre-alarm generation means by the pre-alarm operation means and starting the pre-alarm operation simultaneously with the start of the overcurrent tripping operation, the pre-alarm characteristic can be obtained without individually adjusting the start condition of each means. There is an effect that each operation start timing can be easily adjusted while securely maintaining a relationship between the operation start timing and the long time limit trip characteristic.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a circuit breaker with advance alarm according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a characteristic setting circuit, a long time limit trip circuit, and a pre-alarm circuit in the present embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional pre-alarm circuit breaker.

FIG. 4 is a circuit diagram showing a configuration of a conventional characteristic setting circuit, long time trip circuit, and prior alarm circuit.

FIG. 5 is a characteristic curve showing general characteristics of a circuit breaker with a pre-alarm.

[Explanation of symbols]

 17 Effective value conversion circuit 18A Long time limit trip circuit 20A Characteristic setting circuit 21A Pre-alarm circuit D Diode

Claims (1)

(57) [Claims] 1. An overcurrent tripping characteristic for detecting an overcurrent flowing in a main circuit between an AC power supply and a load to cut off the main circuit, and detecting an overcurrent before the overcurrent is detected to detect an overcurrent. A pre-alarm circuit breaker having a pre-alarm characteristic for generating an alarm, wherein a reference voltage setting means for setting an overcurrent reference voltage and an advance alarm reference voltage in response to the main circuit current; and voltage detecting means for detecting a voltage corresponding to the current, outputting a signal if the detection voltage detected by the voltage detecting means detects an excess than the over-current reference voltage set by the reference voltage setting means
And the overcurrent tripping means for generating a trip signal after a predetermined time, if more than a pre-alarm reference voltage set the detected voltage by said reference voltage setting means, the trip
Pre-alarm generation means for generating an alarm signal after a predetermined time before signal generation, and operating the pre-alarm generation means based on a signal output from the overcurrent trip means, simultaneously with the start of the overcurrent trip operation A circuit breaker with a pre-warning, comprising: a pre-warning operation means for starting a pre-warning operation.