Design of Circuit Breaker Hardware Function Module

1 Power Module Design

The power supply in this study is directly connected to the neutral and live wires, and converted through the lnk306 chip. The 13V voltage required by the control module is obtained by adjusting the resistance value, realizing the direct conversion from 220V to 13V [6], so there is no need to provide separate power supply to the circuit breaker. Since the microprocessor system requires a 5V voltage supply, it is converted through the 78M05 chip.

2 Design of signal sampling module

This study uses a zero-sequence current transformer on each neutral and live line to collect the real-time current on the neutral and live lines, converts it into a voltage signal that can be recognized by a controllable microcontroller, and adjusts the sampling accuracy through the amplification factor of LM358.

3 Design of microprocessor system module

The microprocessor system module mainly includes Atmega16 microcontroller [7], JTAG port, and 3 lights that display different situations. The program can be burned in and modified through the JTAG port. The changes of the 3 lights can show the current status of the circuit.

4. Design of control module

Because it is a large current control, the traditional relay cannot be used. Here, a bidirectional thyristor is used to achieve it. It can pass large currents, and the bidirectional thyristor can be easily closed and disconnected. Due to the high risk of large current operation, the author used an optocoupler for isolation. The author used a triode as a switch, and controlled the conduction and disconnection of the triode through a single-chip microcomputer to achieve the conduction and disconnection of the optocoupler, thereby achieving the purpose of controlling large currents with small currents. This study uses a bidirectional thyristor to replace the traditional circuit breaker release, which can also avoid the generation of high-voltage arcs caused by the connection and disconnection of the line. The arc is generated because when the circuit breaker cuts off the circuit with current, as long as the power supply voltage is greater than 10V~20V and the current is greater than 80mA~100mA, an arc will appear in the contact gap at the moment when the moving and static contacts are separated. At this time, although the contacts have been separated, the current in the circuit continues to flow. Only when the arc is extinguished can the circuit be truly disconnected. If a bidirectional thyristor is used to replace the traditional release, the generation of arcs can be avoided. First, the thyristor is a contactless switch without contacts; secondly, the bidirectional thyristor can only be disconnected when the voltage in the circuit passes through zero, that is, at the moment of disconnection of the thyristor, there is no current in the circuit, so as to avoid the generation of arcs. Finally, the medium of the bidirectional thyristor is a semiconductor, which also has a certain inhibitory effect on the generation of arcs. Therefore, this study can successfully avoid the generation of arcs in the circuit by using bidirectional thyristors. In a series of tests, the thyristor withstood the impact of 20A to 3000A currents, and no arcs were generated. At the same time, the thyristor itself was not damaged, and the safety was very high.

5 Design of wireless communication module

Finally, the author will apply the product to household appliances and bind it to the electric meter. This will not only protect household appliances, but also facilitate the management of the electric meter by the power supply bureau. The wireless coverage range is 200m. A terminal can be set up in each community to control all the circuit breakers in the community through this terminal. Commands are issued through the terminal, the wireless module receives the commands, and passes the commands to the microprocessor system. The microprocessor system receives the commands and performs corresponding operations.

6 Design of interface display module

To facilitate user operation, I will design a user-friendly interface display. I use LCD 1602 as the display screen, equipped with 9 numeric keys to perform corresponding operations. In the display screen, I will have the following functions: Normally, the interface will display the leakage current value and overload value in the current circuit. If I need to operate it, at the beginning, I will perform a self-check of the device connection status. If the connection is normal, the interface will show that it is normal, and then enter the main page. The main page has the following items: ① Leakage current value setting; ② Overload current value setting; ③ Password setting; ④ Delete record; ⑤ Network setting; ⑥ Self-check.