An isolated composite DC solid-state circuit breaker with three-stage protection function

Abstract

This invention relates to an isolated composite DC solid-state circuit breaker with three-stage protection. The DC input terminal is mechanically isolated by a CB1 rotary double-break operating mechanism and its linked CB1 double contacts. Through the series connection of the mechanical contacts CB1 and the normally closed power electronic switch Q1, the circuit achieves instantaneous short-circuit interruption, short-circuit short-delay interruption, and overload long-delay interruption, thus realizing the three-stage protection function of the DC power distribution system. This device is functionally complete, practical, and highly safe.

Description

Technical Field

[0001] This invention belongs to the field of switching electrical appliances, and specifically relates to an isolated composite DC solid-state circuit breaker with three-stage protection function. Background Technology

[0002] To support the transformation of the power structure, DC distribution networks will serve as an important carrier for the production, transmission, distribution and storage of new energy sources, and will undertake the large-scale access of distributed photovoltaic, electric vehicles and DC energy storage devices.

[0003] While DC distribution networks offer advantages in efficiency and flexibility, their low system impedance leads to extremely rapid current acceleration and the absence of a natural zero-crossing point during short-circuit faults, making fault current interruption extremely difficult. Traditional mechanical circuit breakers, limited by their structure, typically have interruption times in the millisecond range, which is insufficient to meet the rapid fault protection requirements of DC distribution systems. In contrast, DC solid-state circuit breakers based on power electronic switches can achieve fault interruption times in the microsecond range, significantly improving the reliability of DC distribution networks.

[0004] However, most existing DC solid-state circuit breakers only have the function of instantaneous short-circuit breaking, and do not have the functions of short-circuit short-delay and overload long-delay. They cannot form a practical three-stage protection, and it is difficult to configure selective cascading in DC systems. This may cause large-scale cascading tripping and affect the continuity of power supply. They also lack mechanical isolation contacts that can cooperate with electronic switches, resulting in poor safety. In addition, most of them require auxiliary power supply, which makes wiring complicated and inconvenient for engineering applications, thus affecting their promotion. Summary of the Invention

[0005] The purpose of this invention is to provide an isolated composite DC solid-state circuit breaker with three-stage protection function. This device has complete functions, strong practicality and safety.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: an isolation-type composite DC solid-state circuit breaker with three-stage protection function. The DC input terminal is mechanically isolated by the CB1 rotary double-break operating mechanism and its linked CB1 double contacts. The mechanical contacts CB1 and the normally closed power electronic switch Q1 are connected in series to complete the instantaneous short-circuit interruption, short-circuit short-delay interruption, and overload long-delay interruption of the DC system, thereby realizing the three-stage protection function of the DC power distribution system.

[0007] Furthermore, the closing operation is implemented as follows: the operating handle of the double-break operating mechanism of CB1 is rotated to close and lock the contacts of CB1, and the normally closed power electronic switch Q1 is naturally turned on. The DC voltage input at the DC input terminal is directly applied to the load at the DC output terminal through the bimetallic element T1 to supply power to the load. At this time, the system current is not greater than the rated value, the bimetallic element T1 has not undergone sufficient bending, and the circuit can continue to work in the closed and conducting state.

[0008] Furthermore, the instantaneous and short-delay interruption of the short circuit is implemented as follows:

[0009] When a short-circuit fault occurs in the load, the voltage across the drain-source terminals of the power electronic switch Q1, i.e., the DS terminal, rises rapidly, and the fault power supply circuit starts working. The fault power supply circuit consists of resistor R6, Zener diode Z4, adjustable resistor R7, and capacitors C3 and C4. The voltage at the DS terminal charges the voltage divider capacitors C3 and C4 through the adjustable resistor R7. Zener diode Z4 is used to limit the charging voltage of capacitor C4, and resistor R6 is used to limit the minimum regulated current flowing through Z4. The fault power supply circuit draws current from the DS terminal voltage of Q1, and the voltage of capacitor C4 rises rapidly to the limit value of Zener diode Z4, providing auxiliary power for the offline DC / DC fast-start isolation power supply P1. When the voltage of C4 reaches the operating threshold of P1, the isolation power supply P1 begins power conversion, rapidly converting the DS terminal voltage into a stable isolation low voltage V0. V0 is applied to the GS terminal of the electronic switch Q1 through diode D2. Under the negative voltage of V0, the GS terminal of Q1 quickly interrupts the short-circuit current. The entire process from the occurrence of the short-circuit current to its interruption is completed within microseconds.

[0010] After electronic switch Q1 completes the microsecond-level interruption of the short-circuit current, the voltage at the DS terminal becomes the DC power supply voltage. At this time, the CB1 delayed trip circuit starts to work. The CB1 delayed trip circuit consists of the trip coil LCB1 of the CB1 contacts, thyristor Q2, Zener diodes Z2 and Z3, adjustable resistors R4 and R5, and capacitor C2. The CB1 delayed trip circuit also draws current from the DS terminal voltage. Zener diode Z2 is used to set the operating threshold voltage of the delayed trip circuit to prevent false triggering. Resistors R4 and R5 perform voltage division and current limiting to charge capacitor C2. Zener diode Z3 is used to limit the charging voltage of C2. When the voltage of capacitor C2 reaches the conduction threshold of thyristor Q2, Q2 is triggered to conduct. The excitation current flows through the LCB1 trip coil, triggering the trip device in the CB1 rotating double-break operating mechanism to perform the tripping operation. The mechanical contacts of CB1 are disconnected without load, forming a mechanical isolation break. At the same time, the handle of the operating mechanism is reset to the open position.

[0011] This completes the rapid arc-free interruption of short-circuit fault current and the mechanical isolation of the fault.

[0012] By adjusting the adjustable resistor R7 in the fault power supply circuit, the charging speed of capacitor C4 is controlled, thereby adjusting the delay time of short circuit protection and achieving short-circuit short-delay interruption.

[0013] By adjusting the adjustable resistor R4 in the CB1 delay trip circuit, the charging speed of capacitor C2 is controlled, thereby adjusting the delay breaking time of mechanical contact CB1, so that mechanical contact CB1 and electronic switch Q1 can work together better, and quickly form an isolation break after arc-free interruption of fault current.

[0014] Furthermore, the overload long-delay interruption is implemented as follows:

[0015] After closing, the composite DC solid-state circuit breaker continuously supplies power to the load. A bimetallic element T1 is connected in series in the power supply circuit and is linked to the K1 contact, controlling the closing and opening of the K1 contact. When the power supply circuit current is normal, the bimetallic element T1 does not bend sufficiently, and the K1 contact remains open. When an overload fault occurs in the power supply circuit for a period of time, the bimetallic element T1 heats up and bends significantly, causing the K1 contact to close. After the K1 contact closes, the pseudo-short-circuit trigger circuit operates. The pseudo-short-circuit trigger circuit consists of resistors R1 and R2, a Zener diode Z1, and a capacitor C1. R1 limits the charging current of C1 and, together with R2, performs voltage division. 1. Used to limit the charging voltage of capacitor C1; after contact K1 is closed, capacitor C1 charges. When the voltage reaches the trigger threshold of thyristor Q3, the pseudo-short circuit works; the pseudo-short circuit consists of thyristor Q3 and current-limiting power resistor R8. After thyristor Q3 is triggered and turned on, resistor R8 carries a large current similar to a short circuit. This large current causes the voltage at the DS terminal of electronic switch Q1 to rise rapidly, and then the short circuit current is interrupted until the CB1 contact is disconnected without load, forming a mechanical isolation break. At the same time, the handle of the double-break operating mechanism is rotated to reset to the open position; finally, the long-delay interruption of the overload fault is completed, and its long-delay characteristic is determined by the bimetallic element.

[0016] Furthermore, it has a remote normal tripping function, and the remote normal tripping operation is implemented as follows:

[0017] After closing, the composite DC solid-state circuit breaker continuously supplies power to the load. When a remote tripping operation is to be performed, the voltage excitation signal of the remote tripping control circuit is applied to the S1 optocoupler MOSFET. After the S1 optocoupler is turned on, the pseudo short-circuit trigger circuit works, the capacitor C1 is charged, and after the voltage reaches the trigger threshold of the thyristor Q3, the pseudo short-circuit generating circuit works, the resistor R8 flows through the pseudo short-circuit large current, causing the voltage at the DS terminal of the electronic switch Q1 to rise rapidly, and then the pseudo short-circuit current is interrupted until the CB1 contact is disconnected without load, forming a mechanical isolation break. The handle of the double-break operating mechanism is rotated to reset to the tripping position, thereby completing the remote tripping operation.

[0018] Furthermore, it has a local normal manual tripping function, and the local normal manual tripping operation is implemented as follows:

[0019] When performing a local manual tripping operation, press the S2 jog mechanical button. The pseudo-short circuit trigger circuit will activate, capacitor C1 will charge, and once the voltage reaches the trigger threshold of thyristor Q3, the pseudo-short circuit will activate. A large short-circuit current will flow through resistor R8, causing the voltage at the DS terminal of Q1 to rise rapidly. Then, the large short-circuit current will be interrupted until the CB1 contact is disconnected without load, forming a mechanical isolation break. At the same time, rotate the handle of the double-break operating mechanism to reset it to the tripping position, thus completing the local manual tripping operation.

[0020] Compared with existing technologies, this invention has the following advantages: It provides an isolated composite DC solid-state circuit breaker with three-stage protection function. This device has three-stage protection function, and its functionality is complete and highly practical when applied to DC power distribution systems. When used for DC short-circuit protection, this device can achieve arc-free fault interruption at the microsecond level and avoid false tripping caused by system interference. At the same time, the short-circuit delay protection time can be easily adjusted, and it has a short-circuit short-delay interruption function. When used for selective cascade protection, it can isolate the fault within the smallest range and avoid cascading tripping. In addition, in this invention, the power electronic switch and the mechanical contact switch work together to quickly generate a safe and reliable isolation break, while the mechanical contacts always interrupt under no-load, resulting in a long electrical life. Attached Figure Description

[0021] Figure 1 This is a circuit schematic diagram of an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] like Figure 1As shown, this embodiment provides an isolated composite DC solid-state circuit breaker with three-stage protection function. The DC input terminal is mechanically isolated by the CB1 rotary double-break operating mechanism and its linked CB1 double contacts. The mechanical contacts CB1 and the normally closed power electronic switch Q1 are connected in series to complete the instantaneous short-circuit interruption, short-circuit short-delay interruption, and overload long-delay interruption of the DC system, thereby realizing the three-stage protection function of the DC power distribution system.

[0026] In this embodiment, the specific functions of the isolated composite DC solid-state circuit breaker are implemented according to the following principle.

[0027] Closing operation: Operate the operating handle of the double-break operating mechanism of CB1 to close and lock the contacts of CB1. The normally closed power electronic switch Q1 is naturally turned on. The DC voltage input at the DC input terminal is directly applied to the load at the DC output terminal through the bimetallic element T1 to supply power to the load. At this time, the system current is not greater than the rated value, the bimetallic element T1 has not undergone sufficient bending, and the circuit can continue to work in the closed and conducting state.

[0028] Instantaneous Short-Circuit and Short-Delay Breaking: When a short-circuit fault occurs in the load, the voltage across the drain-source terminals (DS terminals) of the power electronic switch Q1 rises rapidly, and the fault-following circuit begins to operate. The fault-following circuit consists of resistor R6, Zener diode Z4, adjustable resistor R7, and capacitors C3 and C4. The voltage at the DS terminals charges the voltage divider capacitors C3 and C4 through the adjustable resistor R7. Zener diode Z4 limits the charging voltage of capacitor C4, and resistor R6 limits the minimum regulated current flowing through Z4. The fault-following circuit draws current from the DS terminals of Q1, and the voltage across capacitor C4 rises rapidly to the Zener diode Z4 limit, providing auxiliary power to the offline DC / DC fast-start isolated power supply P1. When the voltage of C4 reaches the operating threshold of P1, the isolation power supply P1 starts power conversion, quickly converting the voltage at the DS terminal to a stable isolation low voltage V0. V0 is applied to the GS terminal of the electronic switch Q1 through diode D2. Under the negative voltage of V0, the GS terminal of Q1 quickly interrupts the short-circuit current. The entire process from the appearance of the short-circuit current to its interruption can be completed within microseconds.

[0029] After electronic switch Q1 completes the microsecond-level interruption of the short-circuit current, the voltage at the DS terminal becomes the DC power supply voltage, at which point the CB1 delayed trip circuit begins to operate. The CB1 delayed trip circuit consists of the trip coil LCB1 of the CB1 contacts, thyristor Q2, Zener diodes Z2 and Z3, adjustable resistors R4 and R5, and capacitor C2. The CB1 delayed trip circuit also draws current from the DS terminal voltage. Zener diode Z2 is used to set the operating threshold voltage of the delayed trip circuit to prevent false triggering. Resistors R4 and R5 perform voltage division and current limiting, charging capacitor C2. Zener diode Z3 is used to limit the charging voltage of C2. When the voltage of capacitor C2 reaches the conduction threshold of thyristor Q2, Q2 is triggered to conduct, and the excitation current flows through the LCB1 trip coil, triggering the trip device in the CB1 rotating double-break operating mechanism to perform the opening operation. The CB1 mechanical contacts disconnect without load, forming a mechanical isolation break, and simultaneously the handle of the operating mechanism resets to the open position.

[0030] This completes the rapid arc-free interruption of short-circuit fault current and the mechanical isolation of the fault.

[0031] By adjusting the adjustable resistor R7 in the fault power supply circuit, the charging speed of capacitor C4 can be controlled, thereby adjusting the delay time of short circuit protection and achieving short-circuit short-delay interruption.

[0032] By adjusting the adjustable resistor R4 in the CB1 delay trip circuit, the charging speed of capacitor C2 can be controlled, thereby adjusting the delay breaking time of mechanical contact CB1, so that mechanical contact CB1 and electronic switch Q1 can work together better, and quickly form an isolation break after arc-free interruption of fault current.

[0033] Overload Long-Delay Breaking: After closing, the composite circuit breaker continuously supplies power to the load. T1 is a bimetallic element connected in series in the power supply circuit and can be linked with the K1 contact to control the closing and opening of the K1 contact. When the power supply circuit current is normal, the bimetallic element T1 does not bend sufficiently, and the K1 contact remains open. When an overload fault occurs in the power supply circuit for a period of time (the voltage at the DS terminal of Q1 is low, insufficient to activate the fault power supply circuit and the CB1 delay tripping circuit), the bimetallic element T1 heats up and bends significantly, causing the K1 contact to close. After the K1 contact closes, the pseudo-short-circuit trigger circuit is activated. The pseudo-short-circuit trigger circuit consists of resistors R1 and R2, a Zener diode Z1, and a capacitor C1. R1 limits the charging current of C1 and, together with R2, performs voltage division. Z1 limits the charging voltage of capacitor C1. After contact K1 closes, capacitor C1 charges. When the voltage reaches the trigger threshold of thyristor Q3, the pseudo-short-circuit trigger circuit is activated. The pseudo-short-circuit generating circuit consists of a thyristor Q3 and a current-limiting power resistor R8. After the thyristor Q3 is triggered and turned on, a large pseudo-short-circuit current flows through resistor R8. This large current causes the voltage at the DS terminals of the electronic switch Q1 to rise rapidly. Then, according to the short-circuit breaking principle described above, the pseudo-short-circuit current is broken until the CB1 contact is open under no-load conditions, forming a mechanical isolation break. At the same time, the handle of the double-break operating mechanism is rotated to reset to the open position. Finally, the long-delay breaking of the overload fault is completed, and its long-delay characteristic is determined by the bimetallic element.

[0034] Remote normal tripping operation: After closing, the load is continuously powered through the composite circuit breaker. When a remote tripping operation is required, the voltage excitation signal of the remote tripping control circuit is applied to the S1 optocoupler MOSFET. After the S1 optocoupler is turned on, the pseudo short-circuit trigger circuit works, the capacitor C1 is charged, and after the voltage reaches the trigger threshold of the thyristor Q3, the pseudo short-circuit generating circuit works. A large short-circuit current flows through the resistor R8, causing the voltage at the DS terminal of the electronic switch Q1 to rise rapidly. Then, the short-circuit current is interrupted according to the above short-circuit breaking principle until the CB1 contact is disconnected without load, forming a mechanical isolation break. The handle of the double-break operating mechanism is rotated to reset to the tripping position, thus completing the remote triggering tripping operation.

[0035] Local normal manual tripping operation: When performing local manual tripping operation, press the S2 jog mechanical button. The pseudo short-circuit trigger circuit works, capacitor C1 charges, and after the voltage reaches the trigger threshold of thyristor Q3, the pseudo short-circuit generating circuit works. A large short-circuit current flows through resistor R8, causing the voltage at the DS terminal of Q1 to rise rapidly. Then, according to the above short-circuit breaking principle, the large short-circuit current is broken until the CB1 contact is unloaded and a mechanical isolation break is formed. At the same time, rotate the handle of the double-break operating mechanism to reset to the tripping position, thereby completing the local manual tripping operation.

[0036] This invention proposes a DC solid-state circuit breaker with isolation and three-stage protection functions for low-voltage DC power distribution scenarios such as distributed photovoltaic, DC energy storage, and DC charging piles. The device uses a normally closed power electronic switch as the main breaking element of the solid-state circuit breaker. When a short circuit occurs, it automatically draws power to quickly drive the normally closed switch to the breaking state, achieving microsecond-level fault current interruption. After the power electronic switch interrupts the fault current, the electromagnetic trip unit is also quickly energized through fault self-powering, causing the mechanical contacts connected in series with the power electronic switch to disconnect without load, achieving isolation. When the circuit experiences an overload for a period of time, the bimetallic element in series can trigger the power electronic switch to shut off the overload current, after which the mechanical contacts also trip without load, achieving fault isolation. The device also has manual or remote triggering tripping functions, and the fault tripping delay time of the electronic and mechanical switches is adjustable, facilitating better coordinated breaking by the electronic and mechanical switches and constructing cascaded protection, which is convenient for application in DC power distribution systems.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An isolated composite DC solid-state circuit breaker with three-stage protection function, characterized in that, The DC input terminal is mechanically isolated by the CB1 rotary double-break operating mechanism and its linked CB1 double contacts. Through the series cooperation of the mechanical contacts CB1 and the normally closed power electronic switch Q1, the DC system can complete the instantaneous short-circuit interruption, short-circuit short-delay interruption, and overload long-delay interruption, realizing the three-stage protection function of the DC power distribution system. The implementation of instantaneous short-circuit interruption and short-delay interruption is as follows: When a short-circuit fault occurs in the load, the voltage across the drain-source terminals of the power electronic switch Q1, i.e., the DS terminal, rises rapidly, and the fault power supply circuit starts working. The fault power supply circuit consists of resistor R6, Zener diode Z4, adjustable resistor R7, and capacitors C3 and C4. The voltage at the DS terminal charges the voltage divider capacitors C3 and C4 through the adjustable resistor R7. Zener diode Z4 is used to limit the charging voltage of capacitor C4, and resistor R6 is used to limit the minimum regulated current flowing through Z4. The fault power supply circuit draws current from the DS terminal voltage of Q1, and the voltage of capacitor C4 rises rapidly to the limit value of Zener diode Z4, providing auxiliary power for the offline DC / DC fast-start isolation power supply P1. When the voltage of C4 reaches the operating threshold of P1, the isolation power supply P1 begins power conversion, rapidly converting the DS terminal voltage into a stable isolation low voltage V0. V0 is applied to the GS terminal of the electronic switch Q1 through diode D2. Under the negative voltage of V0, the GS terminal of Q1 quickly interrupts the short-circuit current. The entire process from the occurrence of the short-circuit current to its interruption is completed within microseconds. After electronic switch Q1 completes the microsecond-level interruption of the short-circuit current, the voltage at the DS terminal becomes the DC power supply voltage. At this time, the CB1 delayed trip circuit starts to work. The CB1 delayed trip circuit consists of the trip coil LCB1 of the CB1 contacts, thyristor Q2, Zener diodes Z2 and Z3, adjustable resistors R4 and R5, and capacitor C2. The CB1 delayed trip circuit also draws current from the DS terminal voltage. Zener diode Z2 is used to set the operating threshold voltage of the delayed trip circuit to prevent false triggering. Resistors R4 and R5 perform voltage division and current limiting to charge capacitor C2. Zener diode Z3 is used to limit the charging voltage of C2. When the voltage of capacitor C2 reaches the conduction threshold of thyristor Q2, Q2 is triggered to conduct. The excitation current flows through the LCB1 trip coil, triggering the trip device in the CB1 rotating double-break operating mechanism to perform the tripping operation. The mechanical contacts of CB1 are disconnected without load, forming a mechanical isolation break. At the same time, the handle of the operating mechanism is reset to the open position. This completes the rapid arc-free interruption of short-circuit fault current and the mechanical isolation of the fault. By adjusting the adjustable resistor R7 in the fault power supply circuit, the charging speed of capacitor C4 is controlled, thereby adjusting the delay time of short circuit protection and achieving short-circuit short-delay interruption. By adjusting the adjustable resistor R4 in the CB1 delay trip circuit, the charging speed of capacitor C2 is controlled, thereby adjusting the delay breaking time of mechanical contact CB1, so that mechanical contact CB1 and electronic switch Q1 can work together better, and quickly form an isolation break after arc-free interruption of fault current.

2. The isolated composite DC solid-state circuit breaker with three-stage protection function according to claim 1, characterized in that, The closing operation is implemented as follows: The operating handle of the double-break operating mechanism of CB1 is rotated to close and lock the contacts of CB1. The normally closed power electronic switch Q1 is naturally turned on. The DC voltage input at the DC input terminal is directly applied to the load at the DC output terminal through the bimetallic element T1 to supply power to the load. At this time, the system current is not greater than the rated value, the bimetallic element T1 does not bend as set, and the circuit continues to work in the closed and conducting state.

3. The isolated composite DC solid-state circuit breaker with three-stage protection function according to claim 1, characterized in that, The overload long-delay interrupt is implemented as follows: After closing, the composite DC solid-state circuit breaker continuously supplies power to the load. A bimetallic element T1 is connected in series in the power supply circuit and is linked to the K1 contact, controlling the closing and opening of the K1 contact. When the power supply circuit current is normal, the bimetallic element T1 does not bend as set, and the K1 contact remains open. When an overload fault occurs in the power supply circuit for a period of time, the bimetallic element T1 heats up and bends as set, causing the K1 contact to close. After the K1 contact closes, the pseudo-short-circuit trigger circuit is activated. The pseudo-short-circuit trigger circuit consists of resistors R1 and R2, a Zener diode Z1, and a capacitor C1. R1 limits the charging current of C1 and, together with R2, performs voltage division. Z1... Used to limit the charging voltage of capacitor C1; after contact K1 closes, capacitor C1 charges, and when the voltage reaches the trigger threshold of thyristor Q3, the pseudo-short circuit works; the pseudo-short circuit consists of thyristor Q3 and current-limiting power resistor R8. After thyristor Q3 is triggered and turned on, resistor R8 carries a large short-circuit current, which causes the voltage at the DS terminal of electronic switch Q1 to rise rapidly, and then breaks the large short-circuit current until the CB1 contact is disconnected without load, forming a mechanical isolation break. At the same time, the handle of the double-break operating mechanism is rotated to reset to the open position; finally, the long-delay breaking of the overload fault is completed, and its long-delay characteristic is determined by the bimetallic element.

4. The isolated composite DC solid-state circuit breaker with three-stage protection function according to claim 3, characterized in that, It has a remote normal tripping function, and the remote normal tripping operation is implemented as follows: After closing, the composite DC solid-state circuit breaker continuously supplies power to the load. When a remote tripping operation is to be performed, the voltage excitation signal of the remote tripping control circuit is applied to the S1 optocoupler MOSFET. After the S1 optocoupler is turned on, the pseudo short-circuit trigger circuit works, the capacitor C1 is charged, and after the voltage reaches the trigger threshold of the thyristor Q3, the pseudo short-circuit generating circuit works, the resistor R8 flows through the pseudo short-circuit large current, causing the voltage at the DS terminal of the electronic switch Q1 to rise rapidly, and then the pseudo short-circuit large current is interrupted until the CB1 contact is disconnected without load, forming a mechanical isolation break. The handle of the double-break operating mechanism is rotated to reset to the tripping position, thereby completing the remote tripping operation.

5. The isolated composite DC solid-state circuit breaker with three-stage protection function according to claim 4, characterized in that, It has a local normal manual tripping function, and the local normal manual tripping operation is implemented as follows: When performing a local manual tripping operation, press the S2 jog mechanical button. The pseudo-short circuit trigger circuit will activate, capacitor C1 will charge, and once the voltage reaches the trigger threshold of thyristor Q3, the pseudo-short circuit will activate. A large short-circuit current will flow through resistor R8, causing the voltage at the DS terminal of Q1 to rise rapidly. Then, the large short-circuit current will be interrupted until the CB1 contact is disconnected without load, forming a mechanical isolation break. At the same time, rotate the handle of the double-break operating mechanism to reset it to the tripping position, thus completing the local manual tripping operation.

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