JPH06245362A - Circuit breaker - Google Patents

Abstract

PURPOSE:To provide a circuit breaker incorporating a microcomputer in which erroneous breaking function due to unstable operation of microcomputer is prevented. CONSTITUTION:The circuit breaker comprises a circuit 12 for varying the output signal when a control power supply voltage exceeds a predetermined level and resetting a microcomputer 6 based on the variation of the output signal, and an AND circuit 11 for producing an output signal based on the logical product of a trip signal and an output signal from the reset circuit. Trigger signal outputted from the microcomputer 6 is invalidated when the control power supply voltage is not normal and when the control power supply voltage reaches a predetermined level for ensuring normal operation of the microcomputer 6, the microcomputer 6 is reset and the output therefrom is validated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker in which a microcomputer is built in and the electric circuit is protected by its control.

[0002]

2. Description of the Related Art FIG. 7 is a block circuit diagram showing an internal circuit of a conventional circuit breaker as disclosed in, for example, Japanese Patent Laid-Open No. 60-223418. In the figure, the current flowing through the circuit breaker contact 1 to the electric circuit 10 is detected by the current sensor 2, and the output current of the current sensor 2 is converted into a voltage by the burden resistor 4. This voltage value is converted into a corresponding digital value by the A / D conversion circuit 5, and the microcomputer 6
Entered in. In the case of an overcurrent, the microcomputer 6 outputs a signal S for driving the switching means 8 according to the input digital value, that is, the magnitude of the output current of the current sensor 2, in the case of an overcurrent. When the switching means 8 receives the signal S and becomes conductive, the tripping device 9 is excited and the breaker contact 1 is opened. Current transformer 3 is circuit 10
A current is supplied to the control power supply circuit 7 by the current. The control power supply circuit 7 internally includes a rectifier circuit 7a and a pair of constant voltage circuits 7b and 7c. The constant voltage circuit 7b supplies a positive constant voltage and the constant voltage circuit 7c supplies a negative constant voltage.

[0003]

In the conventional circuit breaker as described above, the control power supply circuit 7 supplies power based on the current flowing in the electric path 10. Therefore, in order to obtain a normal power supply output, for example, a circuit is used. It is necessary that 10% or more of the rated current of the circuit breaker flows in the electric circuit 10. However, when the circuit breaker is turned on, or when the upper circuit breaker is turned on while the circuit breaker is already closed (hereinafter, simply referred to as power-on), the current flowing through the electric line 10 is If it is smaller than the value of, the output voltage (power supply voltage) of the control power supply circuit 7 becomes unstable. The output of the microcomputer 6 is stable when a predetermined power supply voltage is applied, but the output is unstable at a low power supply voltage of less than 4.5V, for example.
Therefore, there is a problem that the microcomputer 6 may output an erroneous output to open the breaker contact 1 when the power is turned on.

The present invention has been made to solve the above problems, and an object thereof is to provide a circuit breaker which does not cause an erroneous opening / closing operation.

[0005]

A circuit breaker according to the invention of claim 1 is a control power supply for generating a control power supply voltage based on a circuit breaker contact provided in a circuit to be protected and a current flowing in the circuit. A circuit, a current detecting means for detecting a current flowing in the electric circuit, a microcomputer for receiving the control power supply voltage and generating a trip signal according to the output of the current detecting means, and the control power supply voltage having a predetermined value. When the above is reached, the output signal is changed, and the reset means for resetting and starting the microcomputer by the change of the output signal, and the AND for generating the output signal by the logical product of the trip signal and the output signal of the reset means
Means and trip means for opening the circuit breaker contact in response to the output signal of the AND means.
A circuit breaker according to a second aspect of the present invention includes a circuit breaker contact provided on an electric path to be protected, a control power supply circuit for generating a control power supply voltage based on a current flowing through the electric path, and a current flowing through the electric path. A current detecting means for detecting, a microcomputer which is supplied with the control power supply voltage and generates a trip signal according to the output of the current detecting means, and an output signal which is changed when the control power supply voltage exceeds a predetermined value. And a reset means for resetting and starting the microcomputer by the change of the output signal, a delay means for delaying the output signal of the reset means for a predetermined time, and a logical product of the trip signal and the output signal of the delay means. AND means for generating a signal, and trip means for opening the circuit breaker contact in response to the output signal of the AND means. . A circuit breaker according to a third aspect of the present invention includes a circuit breaker contact provided on an electric path to be protected, a control power supply circuit that generates a control power supply voltage based on a current flowing through the electric path, and a current flowing through the electric path. A current detecting means for detecting, a microcomputer which is supplied with the control power supply voltage and generates a trip signal according to the output of the current detecting means, and an output signal which is changed when the control power supply voltage exceeds a predetermined value. Reset means for resetting and starting the microcomputer by the change of the output signal, AND means for generating an output signal by the logical product of the trip signal and the output signal of the reset means, and the output signal of the AND means. Time-delaying operation means for producing a time-delayed output signal and tripping means for opening the circuit breaker contact in response to the output signal of the time-delaying means. When, those having a. A circuit breaker according to a fourth aspect of the present invention includes a circuit breaker contact provided on an electric path to be protected, a control power supply circuit that generates a control power supply voltage based on a current flowing through the electric path, and a current flowing through the electric path. A current detecting means for detecting, a microcomputer which is supplied with the control power supply voltage and generates a trip signal according to the output of the current detecting means, and an output signal which is changed when the control power supply voltage exceeds a predetermined value. The reset means for reset-starting the microcomputer by the change of the output signal, the output signal of the reset means and the trip signal are at predetermined voltage levels, and the potential difference between them is at least a predetermined value. And AND means for generating a predetermined output signal and tripping means for opening the circuit breaker contact in response to the output signal of the AND means. Those were. A circuit breaker according to a fifth aspect of the present invention includes a circuit breaker contact provided on an electric path to be protected, a control power supply circuit that generates a control power supply voltage based on a current flowing through the electric path, and a current flowing through the electric path. Current detecting means for detecting,
A microcomputer which receives the control power supply voltage and generates a trip signal composed of a pulse train according to the output of the current detecting means, and an output signal which changes when the control power supply voltage exceeds a predetermined value, and outputs the output signal. Reset means for resetting and starting the microcomputer by a change in the signal, AND means for generating an output signal consisting of a pulse train by the logical product of the trip signal and the output signal of the reset means, and responding to the output signal of the AND means And tripping means for opening and closing the circuit breaker contact.

[0006]

According to the first aspect of the present invention, the reset means changes the output signal when the control power supply voltage exceeds a predetermined value, and resets and starts the microcomputer according to the change of the output signal. The AND means in claim 1 invalidates or enables the trip signal by taking the logical product of the output signal and the trip signal output from the microcomputer. The delay means of claim 2 delays the output signal of the reset means for a predetermined time and then inputs it to the AND means. The time delay operation means of claim 3 performs the time delay operation by the output signal of the AND means and transmits the output signal to the tripping means. The AND circuit of the fourth aspect generates a predetermined output signal when the output signal and the trip signal of the reset circuit are at predetermined voltage levels and the mutual potential difference is not less than a predetermined value. Conversely speaking, no output signal is generated while the potential difference is less than the predetermined value. The microcomputer of claim 5 generates a trip signal composed of a pulse train.

[0007]

1 is a block circuit diagram showing an embodiment of the present invention according to claim 1. In FIG. In the figure, the current flowing through the circuit breaker contact 1 to the electric circuit 10 is detected by the current sensor 2, and the output current of the current sensor 2 is converted into a voltage by the burden resistor 4. This voltage value is converted into a corresponding digital value by the A / D conversion circuit 5, and the microcomputer 6
Entered in. The microcomputer 6 operates according to the input digital value, that is, the magnitude of the output current of the current sensor 2, and if it is an overcurrent, performs a timed operation and then outputs the output signal S1 (L level) to an AND circuit. Output to 11. The output of the microcomputer 6 is effective at the L level, that is, a trip signal, and normally outputs the H level signal. The current transformer 3 supplies a current to the control power supply circuit 7 by the current flowing through the electric path 10. The control power supply circuit 7 is internally provided with a rectifier circuit 7a and a pair of constant voltage circuits 7b and 7c. The constant voltage circuit 7b supplies a positive constant voltage to the constant voltage circuit 7c.
Respectively supply a negative constant voltage. The reset circuit 12 monitors the voltage of the control power supply circuit 7, and when the voltage exceeds a predetermined value (for example, 4.5 V), the output signal S2 shifts from the L level to the H level. The AND circuit 11 takes the AND logic of the output signal of the microcomputer 6 and the output signal of the reset circuit 12 and outputs it. That is, the output signal S3 of the AND circuit 11 is the L level (trip command) of the output signal S1 of the microcomputer 6, and the output signal S2 of the reset circuit 12 is H level.
When it is at the level (normal power supply voltage), the H level output signal S3 is supplied to the switching means 8. When the switching means 8 receives the H-level signal S3 and becomes conductive, the trip device 9 is excited and the breaker contact 1 is opened.

In the transient state when the power is turned on, the power supply voltage is low as described above, and the output of the microcomputer 6 is unstable. Therefore, at this time, the microcomputer 6 may output an L-level output signal S1 (that is, an erroneous trip signal). However, when the power supply voltage is less than the predetermined value, the output signal S2 of the reset circuit 12 is at the L level, the trip signal is invalid, and the output signal S3 of the AND circuit 11 is at the L level. Therefore, the switching means 8 does not conduct and the tripping operation is not performed. After that, the power supply voltage rises and the output signal S2 of the reset circuit 12 becomes the H level and the output signal S1 from the microcomputer 6 becomes effective only when the power supply voltage reaches a predetermined value. At this time, the output signal S2 of the reset circuit 12 is simultaneously changed to the microcomputer 6
To reset the microcomputer 6. The microcomputer 6 resets and starts from this moment, and operates according to the input from the A / D conversion circuit 5. Next, in a steady state after the power is turned on, when the current flowing through the electric circuit 10 becomes a small current which is less than 10% of the rated current of the circuit breaker, the power supply voltage is divided by a predetermined value and the output of the microcomputer 6 is output. Becomes unstable. At this time, the reset circuit
Reference numeral 12 detects that the power supply voltage is less than a predetermined value and changes its output signal S2 from H level to L level. Therefore, the output signal S1 of the microcomputer 6 becomes L due to an erroneous output.
Even if it is a level (tripping order), it is invalid. After that, when the current flowing through the electric path 10 increases to 10% or more of the rated current, the reset circuit 12 detects the recovery of the power supply voltage and changes the output signal S2 from L level to H level. As a result, the microcomputer 6 is reset and started, and at the same time, the output signal S1 of the microcomputer 6 is validated. In this way, the microcomputer 6 always resets and starts from the moment when the power supply voltage becomes normal, and the output signal S2 becomes valid only while the power supply voltage is normal.

FIG. 2 is a block circuit diagram showing an embodiment of the invention according to claim 2, and FIG. 3 is a block circuit diagram showing an embodiment of the invention according to claim 3. The difference from the embodiment shown in FIG. 1 is that a delay circuit 13 or a time delay operation circuit 14 is provided. In FIG. 2, the delay circuit 13 is provided in the preceding stage of the AND circuit 11.
FIG. 3 shows an example in which the time-delay operation circuit 14 is provided after the AND circuit 11. The delay circuit 13 and the time delay operation circuit 14 are circuits similar to each other, and for example, an integration circuit is used. Other configurations are the same as those in FIG. 1, and the same reference numerals are given and the description thereof is omitted. In FIG. 2, the delay circuit 13 delays only the change of the output signal S2 of the reset circuit 12 from the L level to the H level for a predetermined time and transmits it to the AND circuit 11.
Therefore, the reset of the microcomputer 6 is always performed first, and after the output of the microcomputer 6 becomes the output under the normal operation, it is made effective by the output of the delay circuit 13. In general, the output of the microcomputer 6 is already stable at the voltage (4.5V) at which the output signal S2 of the reset circuit 12 rises, so even if the configuration shown in FIG. The output of 6 is a stable output one step ahead. Therefore, it is unlikely that the output of the AND circuit 11 will erroneously become the H level when resetting. However, since it cannot be guaranteed that there is no variation in the characteristics of the microcomputer 6, the circuit configuration with a slight margin of accuracy is provided by providing the delay circuit 13 in the embodiment shown in FIG. When the output signal of the reset circuit 12 reversely changes from the H level to the L level, the delay circuit 13 does not perform the delay operation and immediately transmits the L level signal to the AND circuit 11 to invalidate the output of the microcomputer 6. To That is, delay circuit 13 is configured to perform a selective delay operation according to a change in signal. In FIG. 3, the time-delay operation circuit
14 does not generate its output unless the output signal from the AND circuit 11 is continuously input for a predetermined time or longer. Therefore, even if the output of the AND circuit 11 temporarily becomes an H level signal due to a precision error of the microcomputer 6 at the moment of resetting the microcomputer 6, the time delay operation circuit 14 does not immediately output the H level signal, Wait for a predetermined time. During that time, the output of the microcomputer 6 returns to a normal state and the input to the time-delay operating circuit 14 becomes L level, so that the switching means 8 is not made conductive.

FIG. 4 is a block circuit diagram showing an embodiment of the invention according to claim 4. The other structure except the AND circuit portion 21 is the same as that of the embodiment shown in FIG. The AND circuit section 21 includes a transistor 21a,
A resistor 21d connected to the collector of the transistor 21a and a constant voltage di-auto 2 connected to the base of the transistor 21a.
It has 1b and a resistor 21c. Next, this AND circuit section 21
The operation of will be described. When the potential difference between the voltage of the output signal S2 of the reset circuit 12 applied to the emitter of the transistor 21a and the voltage of the output signal S1 of the microcomputer 6 exceeds a predetermined value, the base current determined by the resistor 21c flows to the transistor 21a. , The transistor 21a is turned on and the switching means 8 can be turned on. The above-mentioned predetermined value is a voltage when the base current does not flow in the transistor 21a, and is therefore given by the sum of the rated voltage of the constant voltage diode 21b and the base-emitter voltage of the transistor 21a (for example, about 0.6V). It is a value. Therefore, for example, if the 2V constant voltage diode 21b is used, the transistor 21a is turned on while the potential difference between the voltage of the output signal S2 of the reset circuit 12 and the voltage of the output signal S1 of the microcomputer 6 does not reach 2.6V. It never happens. In general, when the power supply voltage supplied from the control power supply circuit 7 is low (for example, 1.0 V or less), the output of the reset circuit 12 may become unstable because the internal electronic circuit does not operate normally. We call it the unstable region. Even if the AND circuit section 21 erroneously outputs 1 V in such an unstable region, the switching element 8 may malfunction if a voltage of 0.6 V is applied to its base. But,
By providing the constant voltage diode 21b as described above, this unstable region is masked (concealed), and the transistor 21
The operation of a, that is, the output signal of the AND circuit unit 21 is stabilized.

FIG. 5 is a block circuit diagram showing an example of the invention according to claim 5. The microcomputer 6 is the same as the embodiment shown in FIG. 1 except that the function of the pulse generator 6a is included, and the same reference numerals are given and the description thereof is omitted. With this configuration, the output signal S1 of the microcomputer 6 becomes a pulse train output with a signal of L level output, for example, a cycle of 100 msec as shown in FIG. Therefore, the AND circuit
Via 11 the switching means 8 is driven by a pulse train. In the first place, the tripping device 9 has a mechanism portion composed of an electromagnet as is well known, and the tripping operation is performed by the movement of the plunger (movable part), but this plunger is caught due to friction and the presence of foreign matter, and is smooth. It may not operate. In such a case, the operation stops even if the power is continuously supplied. However, when the exciting current is intermittently supplied by driving the switching means 8 by the pulse train as described above, the electromagnetic force and the force (force by the spring or permanent magnet) opposite thereto are alternately applied to the plunger. It is highly likely that the cause of the catch will be removed. Since the trip device 9 normally operates when energized for 10 msec, the pulse width is set to several tens msec and the cycle is 100 msec so that the current is not cut off during operation.
And

[0012]

Since the present invention is configured as described above, it has the following effects. In the circuit breaker according to claim 1, the output signal is changed when the control power supply voltage exceeds a predetermined value, and the reset means for resetting and starting the microcomputer by the change of the output signal, the trip signal and the reset means. By providing AND means for generating an output signal by a logical product of the output signal and the control power supply voltage is not normal, even if the trip signal is output from the microcomputer, it is invalidated and the control power supply voltage is changed to the microcomputer. When a predetermined voltage that can guarantee normal operation of the microcomputer is reached, the microcomputer is configured to reset and start to enable its output. Can be prevented. Claim 2
In the circuit breaker described above, the output signal of the reset means is delayed by the delay means for a predetermined time and then input to the AND means, so that there is a possibility that an erroneous trip signal will be momentarily effective at the moment of resetting the microcomputer. The effect according to the invention of claim 1 is further ensured. In the circuit breaker according to claim 3, since the output signal of the AND means is input to the tripping means after being operated by the time-delaying operation means for a timed period, an erroneous trip signal is momentarily output at the moment of resetting the microcomputer. Even if it is done, it eliminates the possibility that it is transmitted to the tripping means, and further secures the effect of the invention of claim 1. According to another aspect of the circuit breaker of the present invention, a predetermined output signal is generated when the output signal and the trip signal of the reset means are each at a predetermined voltage level and the mutual potential difference is a predetermined value or more. By providing AND means, the output signal is not generated while the potential difference is less than the predetermined value.
The unstable region of the operation of the reset means can be masked. According to the circuit breaker of claim 5, in addition to the effect of the invention of claim 1, since the trip signal composed of the pulse train is output from the microcomputer, it is movable during the trip operation of the trip means. Even if there is a problem such as a part being caught, it can be removed and a reliable tripping operation can be performed.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing an embodiment of the present invention.

FIG. 3 is a block circuit diagram showing an embodiment of the present invention.

FIG. 4 is a block circuit diagram showing an embodiment of the present invention.

FIG. 5 is a block circuit diagram showing an embodiment of the present invention.

6 is a diagram showing the waveform of a trip signal output from the microcomputer of the circuit breaker according to the embodiment of FIG.

FIG. 7 is a block circuit diagram showing a conventional circuit breaker.

[Explanation of symbols]

 1 Breaker contact 2 Current sensor 3 Current transformer 4 Burden resistance 5 A / D conversion circuit 6 Microcomputer 7 Control power supply circuit 8 Switching element 9 Tripping device 10 Electric circuit 11 AND circuit 12 Reset circuit 13 Delay circuit 14 Time delay operation circuit 21 AND circuit section

Claims (5)

[Claims] 1. A circuit breaker contact provided on an electric path to be protected, a control power supply circuit for generating a control power supply voltage based on a current flowing through the electric path, and a current detecting means for detecting a current flowing through the electric path. A microcomputer which is supplied with the control power supply voltage and generates a trip signal in accordance with the output of the current detecting means, and an output signal which is changed when the control power supply voltage becomes a predetermined value or more, and a change in the output signal. Reset means for resetting and starting the microcomputer by AND means, AND means for generating an output signal by a logical product of the trip signal and the output signal of the reset means, and the breaker contact in response to the output signal of the AND means. A circuit breaker comprising: 2. A circuit breaker contact provided in an electric path to be protected, a control power supply circuit for generating a control power supply voltage based on a current flowing in the electric path, and a current detecting means for detecting a current flowing in the electric path. A microcomputer which is supplied with the control power supply voltage and generates a trip signal in accordance with the output of the current detecting means, and an output signal which is changed when the control power supply voltage becomes a predetermined value or more, and a change in the output signal. Reset means for resetting and starting the microcomputer by means of: delay means for delaying the output signal of the reset means for a predetermined time; AND means for generating an output signal by the logical product of the trip signal and the output signal of the delay means. A circuit breaker comprising: tripping means that opens the breaker contact in response to an output signal from the AND means. 3. A circuit breaker contact provided on an electric path to be protected, a control power supply circuit for generating a control power supply voltage based on a current flowing through the electric path, and a current detecting means for detecting a current flowing through the electric path. A microcomputer which is supplied with the control power supply voltage and generates a trip signal in accordance with the output of the current detecting means, and an output signal which is changed when the control power supply voltage becomes a predetermined value or more, and a change in the output signal. Reset means for reset-starting the microcomputer, AND means for generating an output signal by the logical product of the trip signal and the output signal of the reset means, and the output signal of the AND means for a timed operation to output the output signal. And a tripping means for opening the circuit breaker contact in response to the output signal of the time-delaying operation means. Circuit breaker. 4. A circuit breaker contact provided in an electric path to be protected, a control power supply circuit for generating a control power supply voltage based on a current flowing in the electric path, and a current detection means for detecting a current flowing in the electric path. A microcomputer which is supplied with the control power supply voltage and generates a trip signal in accordance with the output of the current detecting means, and an output signal which is changed when the control power supply voltage becomes a predetermined value or more, and a change in the output signal. A reset means for resetting and starting the microcomputer by means of the reset means, and a predetermined output signal when the output signal of the reset means and the trip signal are at predetermined voltage levels and the mutual potential difference is a predetermined value or more. And a tripping device that opens the circuit breaker contact in response to an output signal from the AND device. 5. A circuit breaker contact provided on an electric path to be protected, a control power supply circuit for generating a control power supply voltage based on a current flowing through the electric path, and a current detecting means for detecting a current flowing through the electric path. A microcomputer which is supplied with the control power supply voltage and generates a trip signal composed of a pulse train according to the output of the current detecting means, and an output signal which changes when the control power supply voltage exceeds a predetermined value and outputs the output signal. Reset means for resetting and starting the microcomputer by a change in the signal, AND means for generating an output signal consisting of a pulse train by the logical product of the trip signal and the output signal of the reset means, and responding to the output signal of the AND means And a tripping means for opening and closing the circuit breaker contact.