Ceramic tube fuse is a very common overcurrent protection device, and its core structure is a tubular shell made of ceramic material, which encapsulates the fuse element (fuse) inside.
Here are its key features and components:
Core structure:
Ceramic tube: This is the outer shell of the fuse, usually made of high-purity alumina or other ceramic materials. The selection of ceramic materials is crucial as it provides:
Excellent insulation: ensuring that current only flows through the internal fuse.
Extremely high heat resistance: able to withstand the high temperature arc and gas generated when the fuse is blown, without softening or breaking.
High mechanical strength: able to withstand internal pressure (gas pressure generated during melting) and external impact.
Good chemical stability: not easily reacting with metal vapors or fillers generated by melting.
Fuse link (fuse): usually made of conductive materials such as silver, copper, copper alloy, tin alloy, etc., with precise geometric shapes (such as straight lines, wavy lines, spot welded balls, etc.) and cross-sectional areas. This is the path through which current flows, and also the part that truly 'melts'. Its resistance characteristics and thermal capacity determine the rated current and melting characteristics of the fuse.
End cap/electrode: usually made of conductive metals such as brass, tin plated copper, nickel plated copper, etc., welded or crimped at both ends of the ceramic tube. They are the contacts that connect fuses to external circuits.
Filler: Many ceramic tube fuses (especially those with high breaking capacity) are filled with high-purity quartz sand inside. The function of quartz sand is to:
Absorb the heat generated during melting.
Help quickly extinguish the arc generated at the moment of melting.
Limit the diffusion and splashing of metal vapor.
Improve the breaking ability of fuses to safely cut off very large fault currents.
Working principle:
When the current flowing through the fuse exceeds its rated value and lasts for a certain period of time (the length of time depends on the degree of overload and the melting characteristics of the fuse, such as fast break, slow break, and extremely slow break), the temperature of the fuse link increases due to Joule heating.
When the temperature reaches the melting point of the fuse material, the fuse melts at its thinnest point (as designed).
An arc will be generated at the moment of melting. The ceramic shell and internal quartz sand (if any) work together to rapidly cool, absorb energy, elongate, and ultimately extinguish the arc, thereby safely and thoroughly cutting off the circuit and preventing further damage to equipment or fire hazards caused by fault currents.
Main advantages:
High safety: The ceramic shell is resistant to high temperatures and has high strength, which can effectively prevent the tube from bursting, spraying, or catching fire during melting, especially suitable for high voltage and high current applications.
High breaking capacity: The design filled with quartz sand can safely cut off very large fault currents (up to thousands or even tens of thousands of amperes), with extremely strong protection capabilities.
Stable and reliable: Ceramic materials have stable performance, are not easily aged, and their melting characteristics are relatively less affected by the environment.
Impact/Vibration Resistance: High mechanical strength, suitable for harsh environments.
Good isolation: After melting, ceramic tubes can provide reliable electrical isolation.
Difference from glass tube fuses:
Shell material: ceramic vs glass.
Heat resistance/strength: Ceramics are far superior to glass and can withstand higher temperatures and internal pressures.
Breaking ability: Ceramic tubes (especially those filled with quartz sand) usually have higher breaking ability than glass tubes of the same size.
Safety: Ceramic tubes are less likely to burst and have higher safety when overloaded or short circuited.
Visualization: After the glass tube is blown, the blown fuse can usually be directly seen for visual inspection; Ceramic tubes are opaque and cannot be directly seen for their internal state, requiring other methods (such as multimeter measurement) to determine.
Cost: Ceramic tube fuses are usually more expensive than glass tubes.
Common applications:
Power supply: Switching power supply (AC/DC input/output terminal) UPS、 Inverter and charger.
Industrial control: PLC, motor drivers, control transformers, distribution panels.
Household appliances: high-power appliances such as air conditioners, refrigerators, washing machines, and microwaves.
Electric tools.
Automotive electronics (some types).
Any overcurrent protection situation that requires high security, high reliability, and high breaking capacity.
In summary:
Ceramic tube fuse is a type of fuse that uses ceramic materials as the outer shell. It is a safety device that uses an internal fuse to melt during overcurrent and relies on the ceramic shell and filler (quartz sand) to safely extinguish the arc and cut off the circuit, thereby protecting subsequent electronic and electrical equipment from damage caused by overcurrent (overload and short circuit). It is characterized by high security, high breaking capacity, and high reliability, and is widely used in demanding industrial and consumer electronics fields, especially suitable for protecting high-power or critical equipment. When the safety or breaking capacity of glass tube fuses cannot meet the requirements, ceramic tube fuses are usually a better choice.