Surge Suppression ICs Surge Suppression ICs (surge suppression integrated circuits) are integrated circuit devices specifically used to suppress transient overvoltage or current surges. They protect sensitive electronic circuits from damage by quickly responding to abnormal voltage/current changes. 1. What are the Core Functions of Surge Suppression IC? <strong>Transient Suppression</strong>: Limit the transient voltage amplitude by clamping or absorbing to prevent the circuit from being damaged by overvoltage (such as lightning strikes and electrostatic discharge). <strong>Fast Response</strong>: The response time can reach nanoseconds (TVS) or microseconds (TSS), ensuring that the action is completed before the surge reaches the protected circuit. 2. What are the Main Types of Surge Suppression IC? 1) TVS (Transient Voltage Suppressor) <strong>Unidirectional/Bidirectional Protection</strong>: Unidirectional TVS only suppresses positive or negative surges, and bidirectional TVS is suitable for AC or positive and negative alternating signal scenarios. <strong>Low Capacitance Design</strong>: Suitable for high-speed signal lines (such as USB and HDMI), reducing the impact on signal integrity. 2) TSS (Semiconductor Discharge Tube) <strong>High Surge Withstand Capability</strong>: Absorbs large current through a semiconductor structure, often used for lightning protection in communication equipment. 3. What are the Key Parameters of Surge Suppression IC? <strong>Clamping Voltage (Vc)</strong>: The maximum voltage value allowed by the device during surge, which must be lower than the maximum withstand voltage of the protected circuit. <strong>Breakdown Voltage (Vrwm)</strong>: The threshold voltage at which the device starts to operate, which must be higher than the normal working voltage of the circuit. <strong>Peak Pulse Current (Ipp)</strong>: The maximum instantaneous current that the device can withstand, which must match the expected surge intensity. 4. What are Surge Suppression ICs Used for? <strong>Communication Equipment</strong>: Protect Ethernet, 5G base stations, etc. from lightning strikes and electrostatic discharge. <strong>Automotive Electronics</strong>: Used for vehicle sensors and battery management systems to prevent failure caused by voltage transients. <strong>Industrial Power Supply</strong>: Suppress voltage spikes in switching power supplies and motor drives. 5. How to Choose the Adaptable Surge Suppression IC? <strong>Signal Type</strong>: For high-speed signals, low-capacitance TVS (such as less than 0.5pF) should be selected, and for ordinary power lines, higher capacitance can be selected. <strong>Working Environment</strong>: In high-temperature scenarios, attention should be paid to the temperature resistance of the device (such as the junction temperature range of the TVS). <strong>Integrated Solution</strong>: Multi-channel array packaging can simplify PCB layout and improve protection efficiency. Through reasonable selection and layout, Surge Suppression ICs can significantly improve the reliability and anti-interference ability of electronic systems. 6. Surge Suppression ICs FAQs 1）What are the Causes of Damage to Surge Suppression IC? <strong>Excessive Energy</strong>: The surge energy exceeds the joule rating of the device (such as insufficient TVS tube Ipp), and a model with higher current capacity needs to be upgraded. <strong>Improper Layout</strong>: The protective device is too far away from the protected circuit, resulting in excessive residual voltage. It is recommended to install it close to the port. 2) What are the Precautions for Designing A Surge Suppression IC? <strong>Ground Consistency</strong>: The reference ground of the protective device must be consistent with the system ground path to avoid potential differences causing protection failure. <strong>Electromagnetic Compatibility (EMC)</strong>: Use spiral inductors or magnetic beads to isolate high-frequency noise and reduce interference with sensitive circuits.
PTC Resettable Fuses PTC Resettable Fuses (Positive Temperature Coefficient Self-Resettable Fuses) are circuit protection components based on polymer materials, which realize overcurrent protection functions through temperature-sensitive characteristics. Its core feature is "self-recovery", that is, it can be reset without manual replacement after the fault is eliminated. It is widely used in consumer electronics, industrial equipment, and new energy fields. 1. Definition and Working Principle <strong>Basic Structure</strong> PTC is composed of a polymer matrix and conductive particles. Under normal conditions, the conductive particles form a chain-like conductive path with low resistance characteristics (usually 10mΩ to 5Ω). <strong>Protection Mechanism</strong> When the circuit has overcurrent or abnormal temperature, the component heats up due to Joule heat, causing the polymer to expand and block the conductive path, and the resistance rises sharply to the kilo-ohm level, thereby limiting the current (the response time can be as short as 8ms). After the fault is eliminated, the material cools and shrinks, and the conductive path is automatically rebuilt. 2. Core Characteristics <strong>Self-recovery Ability</strong>: It can be repeatedly protected tens of thousands of times, which is significantly better than traditional fusible fuses. <strong>Fast Response</strong>: The tripping time is related to the current intensity, and the response is faster in high-current scenarios. <strong>Low Static Power Consumption</strong>: The power consumption is extremely low under normal working conditions (such as the initial resistance of the MF-MSMD050 model is only 0.15Ω). <strong>Wide Temperature adaptability</strong>: The operating temperature range covers -40℃ to 85℃, meeting the needs of harsh environments. 3. Technical Parameters (Typical Values) Parameter Description Reference Value Holding Current (Ih) Maximum continuous current without triggering protection 14mA~50A Breaking Current (It) Critical current for triggering high impedance state Depends on the model Rated Voltage Maximum Allowable Voltage 15V~600V Breaking Time Response time from overcurrent to high impedance state 8ms~90s Reset Time Time required to restore low impedance state after troubleshooting Seconds to minutes 4. Application Areas <strong>Consumer Electronics</strong>: power adapter, USB port, LED drive circuit. <strong>New Energy Equipment</strong>: electric vehicle battery management system, charging pile overcurrent protection. <strong>Industrial Control</strong>: motor driver, communication equipment power module. <strong>Battery Protection</strong>: overcharge/over-discharge protection of lithium battery pack and nickel-metal hydride battery. 5. Selection Points <strong>1) Voltage Matching</strong>: Select a model with a rated voltage higher than the maximum operating voltage of the system. <strong>2) Current Threshold</strong>: Determine the specification based on the normal operating current (Ih) and the maximum fault current (It). <strong>3) Package form</strong>: <strong>Plug-in Type (Radial/Axial Pins)</strong>: Suitable for traditional PCB design. <strong>Surface Mount Type (such as SMD package)</strong>: Suitable for high-density circuit boards (such as hard disk drives and PC motherboards). <strong>Strip Structure</strong>: Dedicated to internal integration of battery packs. 6. Common Model Examples MF-MSMD050: Surface mount type, 15V rated voltage, 0.15Ω initial resistance, suitable for PC peripherals and POS devices. <strong>Polyswitch Series</strong>: A brand under Tyco Electronics (TE), covering all scenarios from microelectronics to industrial equipment. <strong>Summary</strong> PTC Resettable Fuses have become the mainstream solution for modern circuit protection due to their self-healing characteristics and high reliability. When selecting, it is necessary to combine parameters such as voltage, current, package form, and ambient temperature to achieve precise matching.
Lighting Protection 1. Types of Core Protection Devices 1)ESD Protection Components Used to prevent electrostatic discharge from damaging LED and other lighting devices, such as TVS diodes, semiconductor discharge tubes, etc. <strong>Features</strong>: fast response speed (ns level), can accurately clamp voltage, suitable for the protection of high-speed signal lines. 2) Surge Protection Device <strong>Gas Discharge Tube (GDT)</strong>: large flow rate (peak value up to 20kA), low capacitance characteristics (as low as 1.5pF), suitable as a primary protection component. <strong>Varistor (MOV)</strong>: limits overvoltage through nonlinear characteristics, often used for surge absorption of AC power input ports. <strong>Self-resettable Fuse</strong>: has both overcurrent and temperature protection functions, can automatically recover after fault elimination, suitable for LED drive circuits. 3) Transient Voltage Suppressor (TVS) Protects the back-end circuit by quickly clamping transient high voltage, and is widely used in the lightning protection design of vehicle-mounted lighting and communication equipment. 2. Technical Principles and Application Scenarios 1) Protection Mechanism <strong>Switching Devices (such as GDT)</strong>: form a short-circuit path when a surge occurs to transfer energy. <strong>Clamping Devices (such as TVS)</strong>: absorb energy through avalanche effect and limit voltage peak. 2) Typical Applications <strong>LED Lighting System</strong>: ESD protection (to protect chip structure) and surge protection (to deal with power supply fluctuations) need to be integrated at the same time, such as Nichia's blue light LED solution to reduce the voltage sensitivity of white light LEDs through complementary mixing technology. <strong>On-board Equipment</strong>: The instantaneous peak voltage generated at startup needs to be protected by a combination of TVS and MOV. <strong>Communication Base Station</strong>: adopt a multi-level protection architecture (GDT+TVS) to ensure the reliability of equipment under lightning surge. 3. Selection Points Match the device according to the operating voltage, current capacity, and response speed. For example, multi-level protection of GDT+TVS is preferred for high-power lighting scenarios. Considering the impact of environmental factors (such as humidity and temperature) on device life, vehicle-mounted equipment needs to meet wide temperature range requirements. 4. Development Trends With the popularization of smart lighting and IoT devices, protection devices are moving towards miniaturization and integration. For example, ESD and surge protection functions are integrated into a single package module to simplify circuit design and improve reliability.
Inrush Current Limiters (ICL) 1. Definition and Function Inrush Current Limiters (ICL) is an electronic component used to limit the instantaneous surge current caused by power startup or abnormal conditions in the circuit. Its main functions include: <strong>Protect Sensitive Components</strong>: such as capacitors, semiconductor devices, etc., to avoid breakdown or damage due to high current shock. <strong>Reduce Grid Interference</strong>: Suppress voltage drops and harmonic interference caused by current mutations, and improve system stability. 2. Core Function <strong>Limit Peak Current</strong>: At the moment of power startup or load mutation, reduce the current peak through a high impedance or dynamic adjustment mechanism. <strong>Adaptive Switching</strong>: Some designs (such as pre-charge circuits) switch to a low resistance state after completing the initial current limiting to ensure the normal operation of the system. 3. Technical Classification ICL can be implemented in various ways, mainly including the following types: <strong>NTC Thermistor</strong>: Using the negative temperature coefficient characteristic, the initial high resistance limits the current, and the resistance value decreases after self-heating. However, it takes cooling time to restore the protection capability, and it is not short-circuit-proof. <strong>Resonant Solid-state Current Limiter (SSICL)</strong>: Through series/parallel resonant circuit, it provides high impedance at startup and turns to low impedance during normal operation, which is suitable for high-voltage scenarios such as transformers. <strong>Silicon Controlled/Thyristor Control</strong>: Combined with Triacs or SCR components to dynamically adjust the conduction angle and respond quickly to current changes. <strong>Resistor/Inductor Current Limiter</strong>: Limit current through fixed impedance or electromagnetic characteristics, low cost but limited efficiency. 4. Typical Application Scenarios <strong>Power Supply System</strong>: Protect components such as rectifier bridges and filter capacitors in switching power supplies. <strong>Motor Drive</strong>: Suppress instantaneous high-current shocks when the motor starts. <strong>Industrial Equipment</strong>: Equipment that complies with the IEC61000-4-11 standard needs to withstand grid voltage drops. <strong>High-voltage Capacitor Charging</strong>: The pre-charging mode protects the capacitor bank from high current stress. 5. Key Points for Selection <strong>Current and Voltage Range</strong>: Select the withstand voltage/current rating according to the surge current peak and steady-state operating conditions. <strong>Response Time</strong>: In high-frequency scenarios, solutions with no recovery time (such as solid-state current limiters) should be preferred. <strong>Environmental Adaptability</strong>: Consider the impact of temperature and humidity on the performance of components such as NTC thermistors. <strong>Energy Efficiency Requirements</strong>: Resonant or switching solutions can reduce steady-state losses and are suitable for high-efficiency systems. 6. Precautions <strong>Repeated Start Protection</strong>: NTC thermistors need to cool before they can provide protection again. Frequent start-stop scenarios require other solutions. <strong>Short-circuit Protection</strong>: Some ICLs do not have short-circuit protection functions themselves and need to be combined with fuses or overcurrent protection circuits. <strong>Parameter Matching</strong>: The current limiting impedance needs to match the system impedance to avoid insufficient current limiting or excessive losses.
Ground Fault Circuit Interrupter (GFCI) Ground Fault Circuit Interrupter (GFCI) is an electronic protection device used to detect abnormal currents in a circuit and quickly cut off the power supply. It is mainly used to prevent electric shock accidents and leakage risks. 1. Core Principle GFCI achieves protection by real-time monitoring of the current difference between the live wire (Hot) and the neutral wire (Neutral). Under normal circumstances, the currents of the two are equal; if a ground fault occurs (such as leakage or electric shock), the current difference exceeds the threshold (usually 4-6mA), and the GFCI will cut off the circuit within 25 milliseconds. Its internal circuit usually includes an induction coil, an RV4145 amplifier chip, and a thyristor (such as MCR100-6), which detects tiny current differences and triggers the tripping mechanism. 2. Functional Features <strong>High Sensitivity and Fast Response</strong>: Compared with ordinary circuit breakers or RCDs (operating current 30mA), GFCI is more sensitive to tiny leakage and reacts faster. <strong>Surge Resistance</strong>: It can withstand the impact of instantaneous 20,000V high voltage and 10,000A current. <strong>Self-test and Alarm Function</strong>: Some models are equipped with an end-of-life alarm (indicator light or buzzer) and manual test button (Test/Reset button) for regular testing. 3. Application Scenarios <strong>Home Environment</strong>: Kitchen, bathroom, laundry room, and other humid areas to protect electrical appliances such as hair dryers, refrigerators, and water heaters. <strong>Industrial and Commercial</strong>: Handheld power tools, vending machines, pump motors, and other equipment. <strong>Special Requirements</strong>: North America requires the installation of at least 5 GFCI sockets in the above areas. 4. Structure and Installation <strong>Terminals</strong>: Divided into LINE (inlet end) and LOAD (load end), the latter can protect downstream sockets. <strong>Appearance Design</strong>: Contains grounding interface (ground wire), test/reset button, and status indicator light (some models). <strong>Circuit Breaker Type</strong>: GFCI Breaker needs to connect a dedicated neutral line ("small tail" design) in the distribution box to ensure that the complete circuit is disconnected in the event of a fault. 5. Differences from Other Protection Devices <strong>Comparison with RCD</strong>: Both GFCI and RCD are based on the principle of residual current protection, but GFCI has a lower operating current (4-6mA vs. 30mA), and the terminology is used in different regions (GFCI in North America and RCD in Europe). <strong>Comparison with Traditional Circuit Breakers</strong>: Traditional circuit breakers only target overloads or short circuits, while GFCI specializes in ground faults and can protect ungrounded equipment without relying on a grounding system. GFCI significantly improves power safety through precise current monitoring and rapid power-off mechanism, which is indispensable in humid or high-risk electrical environments.
Gas Discharge Tube Arresters (GDT) Gas Discharge Tube Arresters (GDT) is a switching device used for circuit protection. It suppresses transient overvoltage through the principle of gas discharge and is widely used in surge protection in the fields of communication, power supply, etc. 1. Structure and Working Principle 1) Structural Characteristics GDT consists of a sealed ceramic or glass tube filled with inert gas (such as argon and neon), and two or more discharge electrodes. The electrode surface is often coated with an emitter to reduce the breakdown voltage. 2) Working Principle <strong>Normal State (untriggered)</strong>: When the voltage is lower than the breakdown threshold, the GDT maintains a high impedance state (insulation resistance reaches GΩ level) and the leakage current is minimal. <strong>Triggered State</strong>: When the overvoltage causes the inter-electrode electric field strength to exceed the gas insulation strength, the gas is ionized to form a plasma channel, and the GDT turns to low impedance (equivalent short circuit), discharging the surge current to the ground. <strong>Recovery Characteristics</strong>: After the overvoltage disappears, the GDT automatically returns to the high impedance state without external intervention. 2. Main Technical Characteristics 1) Electrical Parameters <strong>Breakdown Voltage</strong>: divided into DC breakdown voltage (triggered at a slope of 100V/s) and pulse breakdown voltage (such as triggered at a slope of 100V/μs or 1kV/μs), the latter of which is usually higher. <strong>Current Carrying Capacity</strong>: can withstand surge currents of tens of kiloamperes (8/20μs waveform). <strong>Junction Capacitance</strong>: extremely low (usually <3pF), suitable for high-frequency signal protection. 2) Environmental Adaptability <strong>Operating Temperature</strong>: the typical range is -40℃ to +85℃, and some models are extended to -55℃ to 125℃. <strong>Life and Reliability</strong>: no aging failure problem, but it is recommended that the operating temperature be controlled at -40℃ to 70℃ to extend the service life. 3. Typical Application Scenarios <strong>Communication System</strong> As the first level of lightning protection, it discharges lightning surge currents (such as base stations and switch power lines). <strong>Power Interface</strong> Used with varistors, etc., to solve the problem of freewheeling and achieve multi-level protection. <strong>High-speed Signal Line</strong> Use low capacitance characteristics (such as less than 1pF) to reduce the impact on signal integrity. 4. Selection Considerations <strong>Voltage Matching</strong> The DC breakdown voltage must be 1.5~2 times higher than the maximum operating voltage of the circuit, and the AC system is calculated as 1.4 times the effective value. <strong>Surge Level</strong> Select a model with flow rate adaptation according to the expected surge current (such as 10kA or 30kA). <strong>Packaging and Installation</strong> SMD or lead packaging, as well as environmental factors such as temperature and mechanical stress, need to be considered. 5. Product Examples Take TDK B88069X0680T as an example: <strong>Nominal DC Breakdown Voltage</strong>: 90V (±20%) <strong>Impact Current Carrying Capacity</strong>: 30kA (8/20μs) <strong></strong> <strong>Operating Temperature</strong>: -40℃ to 90℃, junction capacitance <1pF GDT has become one of the core components of electromagnetic compatibility protection with its high current resistance, fast response and low leakage current characteristics.
Fuses Fuses are core components used for overcurrent or short-circuit protection in electronic circuits. They cut off abnormal currents by fusing themselves to prevent equipment damage or fire risks and play the role of "safety guards" in electronic systems. 1. Basic Structure and Principle 1) Core Composition <strong>Fuse</strong>: The core part, made of materials such as lead-antimony alloy, cuts off the current when it melts. <strong>Electrode</strong>: Connects the circuit, and requires low contact resistance and high conductivity. <strong>Bracket</strong>: Fixes the fuse, and requires high-temperature resistance, flame retardancy, and insulation. 2) Working principle When the current exceeds the rated value or a short circuit occurs, the fuse is heated and melted, quickly cutting off the circuit. 2. Classification and Type 1) By Protection Form <strong>Overcurrent Protection</strong>: Traditional fuse (such as tubular, SMD). <strong>Overheat Protection</strong>: Temperature fuse, used in specific temperature control scenarios. 2) By Appearance and Structure <strong>Tubular/Sheet</strong>: Such as glass tube, ceramic tube fuse. <strong>SMD/Spiral Type</strong>: Suitable for high-density circuit boards or industrial equipment. <strong>Fast-break (F) and Slow-break (T)</strong>: Designed for instantaneous pulses and continuous overloads, respectively. 3) Special Type <strong>eFuse (Electronic Fuse)</strong>: Programmable one-time fuse for chip-level secure startup and data protection. 3. Key Parameters and Selection 1) Core Parameters <strong>Rated Current</strong>: Needs to be derated by 25% according to the circuit load. <strong>Rated Voltage</strong>: Need to match the circuit operating voltage. <strong>Fusing Characteristics</strong>: Including fusing time and withstand energy. 2) Selection Basis Ambient temperature, pulse current, installation size, and certification standards (such as UL and IEC). 4. Application Scenarios <strong>Consumer Electronics</strong>: Overcurrent protection for mobile phones, computers, and other equipment. <strong>Industrial and Power Systems</strong>: Short-circuit protection for distribution cabinets, motor control, and other scenarios. <strong>Automotive Electronics</strong>: On-board circuit protection, such as battery management systems. <strong>Chip-level Protection</strong>: eFuse is used for secure startup, key storage, etc.. 5. Development Trends <strong>Intelligence</strong>: Programmable devices such as eFuse support dynamic adjustment of protection thresholds. <strong>Miniaturization</strong>: SMD fuses meet the needs of highly integrated circuits. <strong>High-performance Materials</strong>: Optimizing fuse materials to improve response speed and voltage resistance.
Fuseholders Fuseholders are circuit protection devices used to fix and install fuses and ensure their reliable operation. Their core function is to provide physical support and electrical connection for fuses while facilitating installation, maintenance, and status monitoring. 1. Core Function <strong>Circuit Protection</strong>: Prevent overcurrent or short circuits from damaging the equipment by stably fixing the fuse. <strong>Installation and Maintenance</strong>: Simplify the replacement process of fuses, and some models support quick plug-in or anti-mistaken touch design. <strong>Status Monitoring</strong>: High-end products integrate blown fuse indication functions (such as LED or mechanical markings) to facilitate real-time detection of fuse status. 2. Structural Design <strong>Adaptability</strong>: Designed according to fuse size and type, such as 5×20mm, 3AG, etc., supporting micro (PICO®), automotive (Blade-Type), and industrial-grade fuses. <strong>Installation Method</strong>: Including panel mounting (Panel Mount), PCB welding (such as HB PCB series) rail fixing, etc., to meet the needs of different scenarios. <strong>Protection Level</strong>: Some models are waterproof and dustproof, suitable for harsh environments. <strong>Material</strong>: High-temperature resistant and flame-retardant materials (such as UL 94V0 certified engineering plastics) are used. 3. Application Areas <strong>Industrial Equipment</strong>: For example, the ABB E90 series supports photovoltaic systems (1500 VDC) and motor control cabinets, providing short circuit and overload protection. <strong>Automotive Electronics</strong>: Manufacturers such as Eaton provide automotive-grade fuse holders to meet the needs of vehicle-mounted circuit protection. <strong>Consumer Electronics</strong>: Miniature fuse holders are used for power adapters, smart devices, etc.. 4. Technical Parameters <strong>Electrical Performance</strong>: The withstand voltage range is usually 250V~1500V, and the rated current ranges from 0.5A to hundreds of amperes. <strong>Environmental Adaptability</strong>: The operating temperature covers -40℃~85℃, and some models are certified by CE, UL, etc.. 5. Main Manufacturers and Series <strong>Littelfuse</strong>: Covers various types such as Inline and Cartridge, supports PCB installation and waterproof design. <strong>ABB E90 Series</strong>: Optimized for high voltage scenarios, equipped with fuse indication and compact structure. <strong>Eaton</strong>: Provides full-category solutions for automotive and industrial grades. The design and application of fuseholders need to be combined with specific circuit requirements, and the appropriate size, installation method, and protection level should be selected to ensure system safety and maintenance convenience.
Accessories 1 Definition and Function <strong>Basic Definition</strong>: Circuit protection accessories are auxiliary components or assemblies designed for use with circuit protection devices (such as fuses, surge suppressors, etc.) to optimize the installation, maintenance, and function realization of protection devices. <strong>Core Function</strong>: By simplifying the installation process of protection devices, improving system reliability, or expanding their applicable scenarios, ensure that the main protection devices work stably under abnormal conditions such as overvoltage and overcurrent. 2 Main Types 1) Installation and Connection Type <strong>Bracket/Base</strong>: Such as fuse base, circuit breaker mounting bracket, etc., used to fix the main protection device and realize electrical connection. <strong>Terminal Blocks and Connectors</strong>: Used to simplify the physical connection between protection devices and circuits, commonly found in high-density circuit boards or industrial equipment. 2) Function extension Type <strong>Monitoring Module</strong>: Such as current/voltage sensor, real-time monitoring of circuit status and linkage with protection devices. <strong>Heat Dissipation Component</strong>: Such as heat sink or thermal pad, to prevent overheating and failure of devices in high current scenarios. 3) Maintenance and Testing Category <strong>Test Tools</strong>: Special test fixtures or simulators to verify the performance of protection devices and system compatibility. <strong>Replacement Kits</strong>: Such as spare fuses and discharge tube replacement modules for quick maintenance. 3 Typical Application Scenarios <strong>Industrial Equipment</strong>: In power systems and automation control cabinets, multi-level protection is achieved through special brackets and monitoring modules. <strong>Consumer Electronics</strong>: For example, TVS diodes in USB ports are equipped with micro heat sinks to prevent static damage. <strong>Communication System</strong>: Gas discharge tubes (GDTs) and lightning protection junction boxes are combined for base station surge protection design. 4 Key Factors in Selection <strong>Compatibility</strong>: The size and electrical parameters (such as voltage/current range) of the main protection device must be matched. <strong>Environmental Adaptability</strong>: For example, accessories made of corrosion-resistant materials are preferred in high-temperature and humid environments. <strong>Cost and Maintenance</strong>: Based on reliability, consider the frequency of accessory replacement and long-term maintenance costs. As the "supporting components" of the protection system, the design and selection of circuit protection accessories directly affect the overall protection effectiveness and operation and maintenance efficiency.
Circuit Breakers 1. Definition and Core Functions Circuit Breakers are core electronic components used for circuit protection. Their core functions include: <strong>Overload Protection</strong>: Automatically cut off the power supply when the circuit current exceeds the rated value to prevent overheating or damage to the equipment. <strong>Short Circuit Protection</strong>: Quickly disconnect the circuit when a short circuit fault occurs to prevent arc or fire risks. <strong>Leakage Protection (some models</strong><strong>)</strong>: Detect leakage current and cut off the circuit to ensure personal safety (such as residual current operated circuit breakers). 2. Classification and Typical Types According to the structure and application scenarios, it is mainly divided into the following categories: <strong>Air Circuit Breaker (MCB/MCCB)</strong>: uses air as the arc extinguishing medium, commonly used in low-voltage distribution systems, such as household air switches (DZ47 series). <strong>Residual Current Circuit Breaker (RCBO)</strong>: Integrated overload, short circuit, and leakage protection functions, used in home and industrial power distribution systems (such as Chint DZ47LE-63 series). <strong>Special Power Relay Circuit Breaker</strong>: Suitable for high current scenarios (such as 300A), with waterproof and moisture-proof characteristics, commonly used in engineering machinery and special vehicles (such as E-T-A MPR20 series). 3. Key Parameters and Selection <strong>1) Rated Current (In)</strong>: Maximum current value for the continuous load (such as C10 means 10A), which needs to be selected according to the load current. <strong>2) Breaking Capacity</strong>: Maximum fault current that the circuit breaker can safely cut off (such as 6000A). <strong>3) Tripping Characteristics</strong>: <strong>Type C</strong>: Suitable for conventional loads (such as lighting and household appliances), the instantaneous tripping current is 5-10 times the rated value. <strong>Type D</strong>: For devices with large starting currents such as motors, with instantaneous tripping currents of 10-20 times the rated value. 4. Typical Application Scenarios <strong>Home and Commercial Buildings</strong>: Protect lighting and socket circuits to prevent overload or leakage accidents. <strong>Industrial Equipment</strong>: Control high-power equipment such as motors and transformers, and support frequent operations. <strong>Special Vehicles and Outdoor Equipment</strong>: Waterproof and corrosion-resistant design is suitable for harsh environments such as construction machinery and agricultural vehicles. 5. Selection and Use Precautions <strong>Matching Wire Specifications</strong>: The rated current of the circuit breaker should be less than the safe current carrying capacity of the wire to avoid overheating of the wire. <strong>Regular Functional Testing</strong>: The leakage protector needs to verify the tripping reliability through the test button. <strong>Distinguishing Between Fuses</strong>: Fuses are one-time protection devices, while circuit breakers can be manually reset and reused. 6. Related Standards and Certifications <strong>International Standards</strong>: such as IEC 60898-1 (household circuit breakers) and IEC 61009-1 (residual current protectors). <strong>Certification Marks</strong>: CCC (China Compulsory Certification), EAC (Eurasian Economic Union Certification), etc.