JPH04178111A - Circuit breaker - Google Patents

Abstract

PURPOSE:To prevent thermal deterioration of a semiconductor-element by delivering a signal from an abnormal temperature detecting means for main circuit contact to an overcurrent control means and turning the main circuit contact when a signal is outputted from the control means thereby protecting a microcomputor and semiconductor elements in peripheral circuits against abnormal temperature in the main circuit. CONSTITUTION:At first, a microcomputor 9 decides whether inner temperature of a main circuit 5 is normal or abnormal. If it is normal, a decision is made whether it is a normal overcurrent or not. Upon decision of an overcurrent, main circuit contacts 2A, 2B, 2C are turned OFF. If a decision of abnormal temperature is made at that time, 'counting of abnormal temperature' is executed temporarily. If abnormal temperatures are decided and counted five times continuosly, for example, decision is made that the temperature is abnormal and the main circuit 5 is tripped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a circuit breaker that processes a load current flowing through a main circuit as a digital electrical signal and interrupts the main circuit in the event of an overcurrent.

(Prior art) A circuit breaker that detects the load current flowing through a motor, which is a load, and interrupts the main circuit when it becomes an overcurrent, for example, an overload current, processes and calculates the load current as a digital electrical signal. A microcomputer is provided as a control means for outputting an output signal from an output port when the calculation result is determined to be an overload, and the tripping device is operated by the output signal from the output port of this microcomputer. A static type is available in which a main circuit contact interposed in the main circuit is turned off.

(Problems to be Solved by the Invention) According to the above-mentioned conventional configuration, thermal deterioration of the microcomputer is not considered in the initial stage and the microcomputer operates normally. However, due to abnormal heat generation due to insufficient tightening of screws in current-carrying parts, or repeated cut-off operations due to overload, thermal deterioration occurs in the microcomputer and surrounding semiconductor elements. The following malfunctions may occur.

The present invention has been made in view of the above circumstances, and provides a circuit breaker for the purpose of preventing thermal deterioration of semiconductor elements by protecting semiconductor elements of a microcomputer and its peripheral circuits from abnormal temperatures inside the main circuit. Our goal is to provide the following.

[Structure of the Invention] (Means for Solving the Problem) The circuit breaker of the present invention includes a current transformer that detects a load current flowing through a main circuit contact in a main circuit, and detects a current of the current transformer. A current detection circuit is provided which outputs a voltage corresponding to this, and a control means is provided which processes and calculates the detected voltage of the current detection circuit as a digital electrical signal, and outputs an 8-power signal when the detected voltage is an overcurrent, Furthermore, a signal from an abnormal temperature detection means provided to measure the temperature of the main circuit contact and detect abnormal temperatures that cause thermal deterioration of semiconductor elements is also input to this control means, and the output port of this control means is The main circuit is characterized in that it is provided with a tripping device that turns off the main circuit contact when an output is generated from the main circuit.

(Function) According to the circuit breaker of the present invention, it is possible to detect heat generation in the current-carrying part during overcurrent and abnormal heat generation due to insufficient tightening of screws in the current-carrying part below the overcurrent, and to protect the microcomputer and peripheral semiconductor elements. Turn off the circuit breaker if the temperature exceeds the limit,
Prevents thermal deterioration of microcomputers and surrounding semiconductor elements. Generally, the temperature rise in the main circuit's current-carrying parts is suppressed within the operating temperature range of the microcomputer and surrounding semiconductor elements, but abnormal heat generation due to overcurrent or insufficient tightening of screws, etc. There are many cases where this is not considered. Therefore, as mentioned above, by providing abnormal temperature detection means in the current-carrying part of the main circuit,
This can prevent thermal deterioration of the microcomputer and peripheral semiconductor elements.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

First, the overall configuration will be described according to FIG. That is, LA, IB, and IC are power supply side terminals connected to a three-phase AC power supply (not shown), and these are main circuit contacts 2A,
The main circuit 5 is connected to the load side terminals 4A, 4B, 4C via 2B, 2C and main circuit conductors 3A, 3B, 3C, respectively.
is configured. And load side terminals 4A, 4B, 4
A load such as a three-phase AC motor is connected to C. 6A
.

6B and 6C are current transformers whose primary conductors are main circuit conductors 3A, 3B, and 3C, and these output terminals are connected to the current detection circuit 7.
The currents detected by the current transformers 6A, 6B, and 6C are output as detected voltages with corresponding values, and the - output terminal is connected to the input terminal of the analog/digital (A/D) conversion circuit 8. has been done. The output terminal of the A/D conversion circuit 8 is connected to an input port I of a microcomputer 9 serving as a control means. 10 is a power supply circuit whose input terminal is connected to the current detection circuit 7, and whose power supply terminal and common terminal are connected to a power supply line 11 and a common line 12. Here, the power supply circuit 10 converts the current input to the current detection circuit 7 into a DC constant voltage and outputs it to a power supply line 11, and the power supply line 11 is connected to the power supply terminal VOO of the A/D conversion circuit 8. and is connected to the power supply terminal VDD of the microcomputer 9.

Reference numeral 13 denotes a tripping device, one terminal of which is connected to a power supply line 14 led out from the current detection circuit 7, and the other terminal connected to the common line 12 via a thyristor 15, which is a semiconductor switching element. When the thyristor 15 is turned on, this tripping device 13 causes the power line 14 to
A voltage is applied between the main circuit and the common line 12 to turn off the main circuit contacts 2A, 2B and 2C.

Now, 16 is a temperature detection circuit, which will be described below.

For example, if overcurrent flows from power supply terminals IA, IB, IC to main circuit contacts 2A, 2B, 2C and circuit conductors 3A, 3B, 3
C to load side terminals 4A and 4B.

4C, a temperature sensor 18A, 18B, 18C is placed in each phase to detect the temperature near the main circuit contacts 2A, 2B, 2C and the main circuit conductors 3A, 3B, 3C. This temperature sensor 18A, 18B,
18C as a signal to the microcomputer 9, the A/D conversion circuit 8, and the abnormal temperature detection circuit 16 that determines whether the limit temperature of the semiconductor element of the current detection circuit 7 is abnormal. If the abnormal temperature detection circuit 16 determines that the abnormal temperature is abnormal, it outputs the signal to the port H of the microcomputer 9, and outputs the signal to the output port P of the microcomputer 9. 1, the gate of the thyristor 15 is turned on to drive the tripping device 13 and the main circuit contact 2A
, 2B, and 2C are separated.

Next, the operation of this embodiment will be explained with reference to the flowchart of FIG.

Now, when power is applied to the microcomputer 9 (start), the microcomputer 9 enters the "initialization" processing step S1.

In this processing step S1, the microcomputer 9 performs normal initialization operations such as memory clearing, mode setting, and setting value reading.

Next, the microcomputer 9 enters the input step S2 of "reading current value", in which the output signal from the A/D conversion circuit 8 is read and stored in the memory. In this case, the output signal from the A/D conversion circuit 8 is that the load current flowing through the main circuit 5 is detected by the current transformers 6A, 6B, and 6C.
The current detection circuit 7 converts it into a voltage, and the A/D conversion circuit 8 converts it into a digital electrical signal.

Furthermore, the microcomputer 9 enters a processing step S3 of "arithmetic processing" and performs arithmetic processing for generating a time limit from the signals stored in the memory.

Then, the microcomputer 9 then proceeds to a determination step S4 of "Is the temperature abnormal?" in which it determines whether the internal temperature of the main circuit 5 exceeds the limit set temperature 17 of the semiconductor elements of the microcomputer 9 and peripheral circuits. If there is no temperature abnormality, the answer is "NO" and the next step is "Is it tripping?"
" Judgment step S7. , it is determined whether it is a normal overcurrent or not, and if it is determined that it is an overcurrent, the next "output port P..." is determined.

In step S of "H" output, an "H" output signal is output from P1, 1 of the microcomputer 9.

This high level H output signal is applied to the gate of the thyristor 15, so the thyristor 15 turns on and applies the voltage between the power supply line 14 and the common line 12 to the tripping device 13. Therefore, the tripping device 1
13 operates to turn off the main circuit contacts 2A, 2B, and 2C, thereby performing a tripping operation. Note that when the trip operation is performed, the supply of AC power to the power supply circuit 10 is stopped;
Since a storage element such as a capacitor is provided, power is supplied to the microcomputer 9 for a certain period of time, and the microcomputer 9 proceeds with the program and ends.

Further, if it is determined in the judgment step S6 that the current is less than or equal to the overcurrent, the process returns to the judgment step S2 and repeats the same step again. Here, if it is determined in the judgment step S4 that the internal temperature of the main circuit 5 is abnormal, without immediately proceeding to step S in which a tripping operation is performed, -
First, the microcomputer 9 executes step S of "counting temperature abnormalities" to count the number of temperature abnormalities. For example, if the temperature is determined to be abnormal five times and counted, the microcomputer 9 determines that the temperature is abnormal and executes step S7 to trip the main circuit 5. do. Therefore, when the internal temperature of the main circuit 5 exceeds the temperature limit of the semiconductor elements of the microcomputer 9 and peripheral circuits, the main circuit 5 is tripped. Use can be suppressed.

According to this embodiment, the following effects can be obtained. That is, the temperature sensors 18A, 18B, and 18C detect the internal temperature of the main circuit 5 due to overcurrent and improper tightening of screws in the main circuit conductors 3A, 3B, and 3C, and then the abnormal temperature detection circuit 16 detects pl,' of the microcomputer 9 outputs "H", turns on the thyristor 15, drives the tripping device 13, turns off the main circuit contacts 2A, 2B, and 2C of the main circuit 5, and the microcomputer 9 It also prevents malfunctions due to thermal deterioration of surrounding semiconductor elements.

[Effects of the Invention] According to the present invention, it is possible to detect heat generation during overcurrent inside the circuit breaker and abnormal heat generation due to poor tightening of screws, etc. in the current-carrying part, thereby preventing thermal deterioration of the circuit elements of the control means. To provide a circuit breaker that can prevent frequent failures caused by external noise or malfunctions caused by external noise.

[Brief explanation of the drawing]

The drawings show one embodiment of the circuit breaker of the present invention, and FIG. 1 is an overall electrical configuration diagram, and FIG. 2 is a flowchart for explaining the operation. 2A, 2B, 2C... Main circuit contact, 3A, 3B, 3C... Main circuit conductor, 5... Main circuit, 6A, 6B, 6C... Current transformer, 7... Current detection circuit , 8... A/D conversion circuit, 9... Microcomputer, 10... Power supply circuit, 11... Power supply line, 1
2...Common line, 13...Tripping device, 1
4...Power line, 15...Thyristor, 1
6...Abnormal temperature detection circuit, 17...Temperature set value, 18A, 18B, 18C...Temperature sensor, Sl...
・Initialization processing, S2... Current value reading, S3・
...Arithmetic processing, S4...Temperature abnormality judgment step, S
,... Counting of abnormal temperature values, SL,... Tripping judgment process, S-... Output boat P11. “H” output. Agent Patent Attorney Noriyuki ChikaFigure 1Figure 2

Claims (1)

[Claims] The main circuit is equipped with a current detection means for detecting the load current flowing through the main circuit contacts and outputting an analog voltage signal for each phase at a voltage level corresponding to the load current value of each phase, as indicated by the analog voltage signal. In a circuit breaker that performs a tripping operation based on a load current value, the main circuit contact section is provided with a temperature detection means for detecting heat generation at the contact, and the temperature value detected by this is used as the 1. A circuit breaker characterized in that the circuit breaker is configured to perform a tripping operation when an output is output to a detection means and a predetermined temperature is exceeded.