JPH011421A - 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 [Field of Industrial Application] The present invention relates to a circuit breaker equipped with an overcurrent shield.

[Prior Art] This type of circuit breaker is disclosed in, for example, Japanese Patent Application Laid-open No. 60-322.
As disclosed in Publication No. 11 and Japanese Utility Model Publication No. 55-29931, a state in which a load switching contact is closed and power is supplied from the power supply side terminal to the corresponding load side terminal via the load switching contact. In this case, when a fault current flows through the AC line, the current transformer detects the fault current at its own current transformation ratio and induces an output current on the secondary side.

The output signal from the signal conversion circuit is applied to a post-processing circuit, and when it is determined that the fault current is above a predetermined level, the level detection signal is input to the time circuit,
The timer circuit performs a predetermined timer operation based on this signal, triggers the gate of the thyristor, drives the release-type overcurrent tripping coil, opens the load switching contact, and interrupts the electrical circuit.

The above-mentioned time-limited circuit consists of an instantaneous tripping circuit, a short-time exception circuit, and a long-time tripping circuit that operate for a time when the instantaneous tripping current region, short-time exception current region, and long-time tripping current region shown in Fig. 6 are exceeded. Equipped with a timer release circuit.

FIG. 7 shows a conventional long-term interrupt circuit. After the detected voltage corresponding to the fault current is converted to its effective value by an effective value conversion circuit, the output voltage eX is converted to the long-term interrupt circuit (17
0) is input to the comparator (35), and its output 'heavy pressure eX
is for the reference voltage eY of the reference voltage setting circuit (37),
For example, when the number reaches twice, the output switch (36) of the comparator (35) becomes open rather than closed.

This enables charging of the capacitor (38).

Now, when the rated current flowing through the AC line is, for example, 200A, the reference voltage eY of the reference voltage setting circuit (37) is set to, for example, 0.5V, and the output voltage eX from the effective value conversion circuit is twice that value. When the lv is reached, the comparator (3
5) Open the output switch (38) from closed to start charging the capacitor (38). In this case, the fault current flowing through the AC circuit at the start of charging is 400A.

On the other hand, the input voltage eX applied to the input terminal a of the comparator (35) is applied to the voltage-current conversion circuit (44),
It is converted into an output current Ib corresponding to the input voltage eX.

Here, the input voltage eX of the voltage-current conversion circuit (44)
The relationship between the output current Ib and the output current Ib is configured such that their absolute values are equal and their units are different. In other words, when the input voltage eX is, for example, tV, the output current Ib
is configured so that it is converted to lpA.

Therefore, the voltage-current conversion circuit (44) converts the output voltage e x (l V) and current Ib (lpA)
is converted into a capacitor (38
) is charged.

The charging voltage el of the capacitor (38) increases, and the output voltage e of the reference voltage setting circuit (42) for a long time limit operation
When it becomes higher than 2, the comparator (41) outputs a long-time operation time output signal, and if it is 100 seconds, for example, the operation starts immediately.

[Problems to be Solved by the Invention] By the way, when the above circuit breaker is applied to an AC line whose rated current is from 20OA to 400A, for example, when the reference voltage eY of the reference voltage setting circuit (37) is 0.5V, 2
If you try to cut off the fault current in the AC line in such a usage condition where the voltage is set to IV, which is twice as high as IV, the reference voltage eY of the reference voltage setting circuit (37) is lv, so
When a fault current of 0A flows, the output voltage eX from the effective value conversion circuit becomes 2v, which is twice that.

Therefore, the charging current Ib charged from the voltage-current conversion circuit (44) to the capacitor (38) is 2 pA,
Charging current Ib in usage mode with rated current of 20OA (
IuLA), it is twice as long as the long-time intermediate disconnection circuit (1
70) Long-time operation is performed when the rated current is 20OA, and when the rated current is 20OA,
There is a big difference between the case of 00A and the case of 00A.

In order to adjust this, the time constant of the capacitor (38) can be changed, but the long time cutout circuit (170) receives the output signal from the effective value conversion circuit in the effective value, and the effective value is is proportional to the square of the instantaneous value of the fault current, so even if you try to adjust the long-time operation time by changing the time constant of the capacitor (38), it is extremely difficult to make it correspond to the 7+1 current. .

Therefore, in the conventional long-time release circuit (170), when the rated value of the current flowing through the load switching contacts is changed, it is extremely difficult to operate within 125% of the rated value.

This invention was made to solve the above problems, and even if the rated value of the current that causes the load switching contacts to be changed, it is easy to operate within the rated value, and it is possible to easily operate the load switching contacts with accurate long-time operation. The purpose is to provide a circuit breaker.

[Means for Solving the Problems] In the circuit breaker according to the present invention, the long time release circuit includes a comparator that compares each output voltage from the effective value conversion circuit and the reference voltage setting circuit, and an input of this comparator. The present invention is characterized by comprising an arithmetic circuit that calculates a ratio of voltages and outputs a voltage corresponding to the ratio, and a voltage-current conversion circuit that converts the output voltage from the arithmetic circuit into a current.

[Operation] The rA calculating circuit calculates the input voltage eX, eYc7) ratio Z=eX/eY applied to the re-input terminal of the comparator, and outputs the voltage eZ corresponding to the ratio.

Therefore, even if the rated current changes.

Since the input voltage eZ applied to the voltage-current conversion circuit does not change, its output current also does not change, and there is no need to change the time constant of the capacitor that determines long-time operation. Even when the rated value of current is changed, it is easy to operate the single-circuit breaker within the rated value, and accurate timed operation can be achieved.

r Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an example of a circuit breaker according to the present invention.

(21) is a current transformer inserted in the AC line (11), and a rectifier circuit (30) that changes the secondary output current in one direction is connected to the secondary side of this current transformer (21). This rectifier circuit (30) is composed of a series circuit of diodes (31) and (32) and a series circuit of diodes (33) and (34). (500) is a DC constant voltage power supply circuit connected to the positive output terminal of the rectifier circuit (30), which includes a positive terminal (5a), an intermediate terminal (5c) and a negative terminal (5d).
).

The negative terminal (5d) of the power supply circuit (500) is connected to one end of the current detection resistor (40), and the other end of the current detection resistor (40) is connected to the negative connection terminal of the rectifier circuit (30). is connected, and a rectified rectified waveform current corresponding to the load current of the electric path (11) flows through the detection resistor (40).

(60) is a differential amplifier circuit that converts the voltage drop across the current detection resistor (40) into a signal based on the intermediate potential VO of the power supply circuit (500).

The differential amplifier circuit (θ0) is composed of an operational amplifier (63) and four resistors (ea), (e5), (H), and (67). Power for the differential amplifier circuit (60) is supplied from a power supply circuit (500), and an input terminal of the differential amplifier circuit (60) is connected to a current detection resistor (40).

(70) is a time limit circuit, and this time limit circuit (70) includes an instantaneous exception circuit (230), a short time limit release circuit (220), and a long time limit release circuit (170).
0).

The output terminals (220) and (170) are connected in parallel to form the output terminal (7oa) of the one-time circuit (70).

That is, the instantaneous exception circuit (230) is connected to the output terminal of the differential amplifier circuit (80), and the instantaneous exception circuit (230) is connected to the peak value conversion circuit (44) (210) and the short-time exception circuit (230). The series circuit of the disconnection circuit (220), the series circuit of the effective value conversion circuit (211), and the long time disconnection circuit (17G) are connected in parallel.

(80) is an electromagnetic tripping coil connected to the positive output terminal of the rectifier circuit (30), and (12G) is an electromagnetic tripping coil (
80) is connected in series to the switching circuit (1
20) The other end is the negative terminal (5d) of the power supply circuit (500)
It is connected to the. The electromagnetic tripping coil (80) is mechanically linked to the switching contact (120) via a switching mechanism (1oo), and when the switching circuit (120) is switched from open to closed, the above-mentioned The opening/closing contact (120) is configured to be opened.

(50) is an undervoltage operation inhibiting circuit connected between the positive terminal (5a) and negative terminal (5d) of the power supply circuit (500), and (55) is its output switch.

Fig. 2 shows the long time release circuit (17G), which is connected so that the output voltage eX from the effective value conversion circuit (211) is applied to one input terminal a of the comparator (35). has been done. (3B) is an output switch of the comparator (35), which is normally closed and connected to open when an overcurrent occurs.

(37) is a rated current reference voltage setting circuit connected to the other input terminal of the comparator (35), and this reference voltage setting circuit (37) sets the current value of the rated current that is the reference of the comparator (35). This is for setting. (38) is a long time release capacitor connected in parallel to the output switch (36), (39) is a discharge resistor connected in parallel to the long time release capacitor (38), and the effective value conversion circuit (211) ÷
An arithmetic circuit (45) is connected between one input terminal a of the comparator (35) to which the spider output voltage is applied and the connection point between the capacitor (38) and the discharge resistor (39). A series circuit of voltage-current conversion circuits (44) (44) is connected.

The arithmetic circuit (45) calculates the ratio Z of the input voltages eX and eY applied to both input terminals of the comparator (35) = eX/eY (1
) and outputs a voltage eZ corresponding to the ratio.

(41) is a comparator that determines the long time release time, and is connected to one input terminal of this comparator (41) so that the charging voltage e1 of the long time release capacitor (38) is applied. has been done. (42) is a reference voltage setting circuit with a long operating time connected to the other input terminal of the comparator (41), and this reference voltage setting circuit (42) is connected to the other input terminal of the comparator (41).
41) Voltage e2 corresponding to the long-time operation time as the reference
This is for setting.

Next, the operation of the above configuration will be explained.

When current Ia flows through the AC line (11), the current transformer (21
) A secondary current determined by a specific current transformation ratio flows through the secondary winding. This secondary current is converted into a unidirectional current by the rectifier circuit (30), and the output current of the rectifier circuit (30) is
00) and the rectifier circuit (30) through the detection resistor (40).
Reflux to. At this time, a rectified waveform current corresponding to the current Ia of the AC line (11) flows through the power supply circuit (500) and the detection resistor (40).

When a full-wave rectified waveform current flows into the power supply circuit (500), each output terminal (5a), (
5c) and (5d), the potential V of the intermediate terminal (5c)
Voltages (+V) and (-V) based on o are generated.

On the other hand, the power of the differential amplifier circuit (60) is supplied to the power supply circuit (5).
00), and the input of the differential amplifier circuit (80) is supplied from the current detection resistor (40). The gain A of this differential amplifier circuit (BO) is as follows.

The output of the differential amplifier circuit (60) is applied to the corresponding instantaneous tripping circuit (23G), short-time intermediate release circuit (220), and long-time release circuit (170) of the timer circuit (70). Each circuit has an instantaneous trip as shown in Figure 5.

Output signals are outputted to achieve each characteristic operation of short-time release and long-time release.

To explain the characteristic operation of the long time limit, the effective value conversion circuit (211) in the time limit circuit (70)
The output voltage eX from is inputted to the comparator (35) of the long time release circuit (17G) shown in FIG. For example, when it reaches twice, the output switch (3B) of the comparator (35) becomes open rather than closed, and the capacitor (38)
It is possible to charge the battery.

Now, when the current Ia flowing through the AC line (11) is, for example, a rated value of 200 A, if the reference voltage eY of the reference voltage setting circuit (37) is set to, for example, 0.5 V, the effective value conversion circuit (211) The output voltage eX is twice that I
When V is reached, the output switch (36) of the comparator (35)
becomes open from closed, and charging of the capacitor (38) begins. The fault current Ia flowing through the AC line (11) at the start of charging is 40OA.

On the other hand, the input voltages e X and e Y applied to both input terminals of the comparator (35) are
1) The equation is calculated and a voltage eZ corresponding to the ratio is output. That is, from equation (1), this output voltage eZ is as follows: eZ=Ilo, 5V=2V ・-(3
).

Here, the input voltage eZ of the voltage-current conversion circuit (44)
Since the relationship between and output current Ib is configured such that their absolute values are equal and their units are different, input voltage eZ (2V) is converted to output current Ib (2 A).

When the output current Ib charges the capacitor (38) and the charging voltage el rises to become higher than the output voltage e2 of the reference voltage setting circuit (42) for the long time operation time, the time limit circuit (70) Provides an output signal of operating time.

The output signal of the time limit circuit (70) triggers the input of the switching circuit (12G) via the output switch (55) of the undervoltage operation prohibition circuit (50), and the output of the switching circuit (12G) is opened and closed. and excite the electromagnetic tripping coil (80). The electromagnetic tripping coil (80) operates the switching contact (201) from closed to open to cut off the fault current, for example, 100 seconds after the start of the overcurrent.

Next, when the above circuit breaker is used in an AC line (11) whose rated current is from 20OA to 400A, for example, the reference voltage eY of the reference voltage setting circuit (37) is set to 0.
Change the setting to 1v, which is twice 5V.

Under such usage conditions, when a fault current of 80OA flows through the AC line (11), the output voltage eX from the effective value conversion circuit (211) becomes 2V, and the reference voltage setting circuit (37
) is IV, so the arithmetic circuit (4)
The output voltage eZ of 5) is obtained from equation (1), similarly to equation (3), as follows: eZ=2/IV=2V---(4).

Therefore, the charging current Ib charged from the voltage-current conversion circuit (44) to the correductor (38) is 2pA&,
Even if the rated current is 40OA, the usage is similar to that of 200A, and the long-term operation of the timer circuit (70) can be achieved within 100 seconds from the occurrence of the fault current.

Note that when the current flowing through the switching contact (201) is small, about lθ% to 20% of the rated current, the power supply circuit (5
There is a state in which the output voltage of 00) is insufficient for the operation of the time limit circuit (70). In this state, in order to prevent the timer circuit (70) from outputting an incorrect output, the undervoltage operation prohibition circuit (50) is installed.
The output switch (55) of 0) is opened, and the opening/closing circuit (
12G) from closing.

FIG. 3 shows another example in FIG. At this time, a compensation current Id corresponding to the leakage current Ic that leaks little by little from the discharge resistor (39) connected in parallel to the capacitor (38) is supplemented.

Generally, the long-time release circuit (170) has switching contacts (2
It is specified that the current Ia flowing through 01) only needs to operate within 125% of the rated value.

Therefore, by providing the current compensation circuit (43) as described above, the leakage current Ic that leaks little by little from the discharge resistor (38) is compensated for, and the long time release circuit (170)
)-layers can achieve accurate timed operation.

In the above embodiment, the output switch (
36) is not limited to a contact point, but may be a semiconductor switching element consisting of a transistor as shown in FIG.
), and in this case, the transistor (36) is of NPN type.
It is recommended to form the diode (47) in PN type. Thereby, leakage current leaking from the capacitor (38) through each of the above elements to other circuits can be effectively cut off.

Further, in the above embodiment, the voltage-current conversion circuit (44)
is configured such that the relationship between its input voltage eZ and output current Ib is constant, but it may be configured such that as the input voltage eZ increases, the output current Ib also increases.

Further, in the above embodiment, for convenience, a circuit breaker that cuts off a single-phase AC line (11) is described, but it goes without saying that a circuit breaker that cuts off a multi-phase AC line may also be used. do not have.

[Effects of the Invention] As described above, according to the present invention, the ratio Z=eX/eY of the input voltages eX and eY applied to both input terminals of the comparator is calculated by the arithmetic circuit, and a value corresponding to the ratio is calculated by the calculation circuit. Since it outputs the voltage eZ, even if the rated current is changed, the input voltage e applied to the voltage-current conversion circuit (44)
Z does not change.

Therefore, the output current does not change and there is no need to change the time constant of the capacitor, so even if the rated value of the current flowing through the load switching contacts is changed, it is easy to operate the circuit breaker within the rated value. , and accurate timed operation can be achieved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a circuit breaker according to the present invention, FIG. 2 is a circuit diagram of a long time cutout circuit, and FIGS. 3 and 4 are diagrams showing other different examples of the circuit breaker according to the present invention. 5 is a tripping characteristic diagram of a circuit breaker, FIG. 6 is a tripping characteristic diagram for explaining the operation of a conventional circuit breaker, and FIG. 7 is a circuit diagram of a conventional long-time interrupt circuit. It is. (11)...AC line, (21)...Current transformer, (3
0)... Rectifier circuit, (35)... First comparator, (
36)...Output switch. (37)...first reference voltage setting circuit, (38)...
・Capacitor, (39)...discharge resistor, (40)
... current detection resistor, (41) ... second comparator,
(42)...Second reference voltage setting circuit, (44)...
・Voltage-current conversion circuit (44), (45)... Arithmetic circuit, (60)... Differential amplifier circuit, (70)... Time limit circuit, (80)... Electromagnetic tripping coil, ( 100)
... new mechanism, (120) ... switching circuit, (1
70)...Long time limit release circuit, (201)...Load switching contact, (211)...Effective value conversion circuit (44),
(500)...Power supply circuit. In addition, in FIG. 1, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A load switching contact inserted into an AC line, a current transformer that detects the current flowing through this contact, and a current transformer connected to the secondary winding of the current transformer to detect the AC secondary current of the current transformer. A rectifier circuit that converts the current into a unidirectional current, a DC constant voltage power supply circuit connected between the output terminals of the rectifier circuit, and a differential amplifier circuit that amplifies the voltage drop across the current detection resistor that is proportional to the unidirectional current. , a timer circuit that causes a predetermined time delay with respect to a predetermined magnitude of the unidirectional current, a switching circuit that is operated from open to closed by the output of this timer circuit, and an electromagnetic and a cutoff mechanism driven by a tripping coil to change the load switching contact from closed to open, and the timer circuit receives the output signal of the differential amplifier circuit and converts the output signal into an effective value voltage. A first reference voltage setting circuit sets a voltage corresponding to the reference current value of the rated current, and each output voltage from the effective value conversion circuit and the reference voltage setting circuit is compared to determine the fault current. A first comparator for determination, an arithmetic circuit that calculates the ratio of input voltages of this comparator and outputs a voltage corresponding to the ratio, and a voltage-current conversion circuit that converts the output voltage from this arithmetic circuit into a current. , a capacitor charged with an apparent current from the voltage-current converter circuit corresponding to the fault current, a discharge resistor connected in parallel to this capacitor, and a normally closed capacitor connected in parallel to the above capacitor. An output switch of the comparator that opens when an overcurrent occurs, a second reference voltage setting circuit that sets a voltage corresponding to a reference long-time operation time, a charging voltage of the capacitor, and an output voltage of the reference voltage setting circuit. and a second comparator that determines a long-time operation time by comparing the two.