Complete Guide to Selection and Application of Ceramic Tube Fuses
introduction
Ceramic tube fuses are widely used in power distribution systems, industrial control applications, and the protection of electronic equipment, thanks to their outstanding pressure resistance, heat tolerance, and arc-quenching capabilities. These fuses can quickly interrupt circuits in the event of a short circuit or overload, while also withstanding high-energy surges to ensure system safety. This article provides a comprehensive overview of ceramic tube fuses to help you select and apply them efficiently and accurately.
What is a ceramic tube fuse?
Ceramic tube fuses are composed of built-in fuses and ceramic tube bodies, with copper or nickel alloy end caps installed at both ends. When in operation, if the current exceeds its rated value, the internal fuse melts rapidly. The ceramic powder inside the tube absorbs the arc energy and extinguishes the arc, thereby achieving circuit protection.
- Ceramic casing: High-strength insulation, heat resistance, flame retardancy, capable of withstanding the high temperature and electric arc during melting.
- Fuse structure: Different materials (copper, silver alloy or copper-nickel alloy) are selected according to the application to determine the melting characteristics.
- End caps and fillers: The end caps are responsible for electrical connections and are filled with quartz sand or alumina powder to quickly absorb arc energy.
Main types and structural differences
| Type | Appearance Features | Typical Applications |
|---|---|---|
| Fast-Blow | Thin fuse element; reacts quickly | Semiconductor protection, precision instruments |
| Time-Delay (Slow-Blow) | Thick fuse element; tolerates inrush current | Motors, power supply filter capacitor circuits |
| High-Voltage Type | Longer fuse body with high insulation and voltage withstand | Medium- to high-voltage power supplies, inverter inputs |
| Standard Low-Voltage Type | Common sizes like 5×20mm, 6×30mm | Household appliances, industrial control panels |
Key performance parameters
rated current
The maximum current that is allowed to pass through for a long time without melting.
It is recommended to leave a margin of 20% to 50% when selecting the model.
nominal voltage
The maximum working voltage that a fuse can withstand when it is disconnected.
Common grades: 250V, 500V, 600V, etc.
Melting characteristic curve
Describe the melting time of the fuse under different overcurrent multiples.
The fast type usually melts within milliseconds when the overcurrent exceeds 200%. The delayed type can withstand short-term surges.
breaking capacity
It indicates the maximum short-circuit current (kA) that can be safely cut off.
In industrial Settings, ≥10kA is usually required to prevent arc prolongation caused by high fault current.
Heat resistance and mechanical strength
Ceramic tubes can withstand temperatures above 250℃ and are not prone to falling off under welding stress and vibration conditions at the end caps.
Filling material inside the pipe
Siliceous or silicon nitride powder is commonly used for energy absorption, which can accelerate arc extinction
Modem
Clarify the protected objects
Before selecting the type, it is necessary to first be clear about which part of the circuit or equipment the fuse is used to protect:
Precision electronic components (such as ics, MOSFETs) : It is recommended to use fast-breaking ceramic fuses, which can quickly respond to overcurrent and prevent device damage.
Inductive loads (such as motors, relays) : It is recommended to choose a ** slow-melting type (delayed type) ** fuse, which can tolerate the inrush current during startup.
Power input terminal protection: Fuses with high breaking capacity can be adopted to prevent short circuits caused by large currents from damaging the system.
Determine the electrical performance parameters
This is the core of fuse selection, which requires precise calculation or reference to the system design indicators.
Rated Current
The fuse should be capable of withstanding the maximum continuous operating current of the protected circuit, and usually a safety margin of at least 1.25 times should be considered.
If the normal operating current of the equipment is 4A, a fuse with a rated current of 5A can be selected.
Rated Voltage
The fuse must be capable of safely cutting off any overcurrent below the maximum working voltage. Common grades include 125V, 250V, 500V, etc. When selecting the type, it should be equal to or higher than the actual voltage of the circuit.
Breaking Capacity
It indicates the maximum fault current that the fuse can withstand and safely disconnect. For industrial power supplies or equipment, it is recommended that the breaking capacity be no less than 10kA.
Melting characteristic (I-T curve)
Select the appropriate fuse characteristic curve based on the protected target: fast type, delayed type, medium speed type, etc. This characteristic determines the operating speed of the fuse under different overcurrents.
Consider the size specifications and installation methods
Common sizes:
- 5×20mm: Suitable for small equipment with limited space
- 6×30mm: Suitable for high-power household appliances and industrial control cabinets
- 10×38mm and above: Suitable for high-power equipment and high-voltage applications
Make sure that the size of the fuse you purchase exactly matches the reserved position on the fuse socket or PCB to avoid poor contact or inability to install due to size mismatch.
Evaluate environmental and reliability factors
Different usage environments have different requirements for the performance of fuses
Temperature: In a high-temperature environment, the current capacity of the fuse will decrease. The temperature derating curve should be taken into consideration.
Vibration and shock: Select models with reinforced structures and firm welding to enhance mechanical resistance.
Humidity/Pollution: It is recommended to choose models with more sealed packaging and nickel-plated end caps to enhance corrosion resistance.
Confirm the standards and certification requirements
High-quality fuses should have international certifications to ensure that their performance complies with relevant safety standards:
- UL (USA)
- IEC (International Electrotechnical Commission Standard)
- RoHS (Environmental Compliance)
- Regional certifications such as CSA, TUV, and CCC
The use of certified fuses helps the entire system obtain compliance certifications such as CE and UL
Match with the fuse base and other components
Fuse selection: Excessive current will cause an increase in contact resistance. High-quality fuses that match the fuse specifications should be selected.
Supporting protection design: Pay attention to the coordination with components such as TVS, NTC, and inductors to avoid misoperation or protection delay.
It is recommended to collaborate with the supplier
When the selection is uncertain or the application is special (such as high altitude, high impact, rapid current switching), it is recommended to cooperate with a regular manufacturer or technical support team, providing information such as load type, current/voltage/temperature conditions, and certification requirements, and having them assist in providing a recommended solution.
Installation and maintenance suggestions
Operation after power failure: Be sure to disconnect the main power supply and lock it first, and then replace the fuse.
Installation torque: For models with threaded end caps, tighten according to the recommended torque in the manual to avoid poor contact.
Regular inspection: Confirm the integrity of the fuse by visual inspection or measurement with a multimeter; Check whether there are cracks, discoloration or burn marks on the pipe body.
Thermal imaging monitoring: Infrared thermal imagers can be used for high-power circuits to promptly address any abnormal heating.
Standby inventory: It is advisable to have sufficient commonly used specifications to shorten maintenance time.
Typical application scenarios
Industrial control cabinet: Motor drive, PLC power protection;
Power adapter: Inverter, UPS input side overcurrent protection;
Consumer electronics: High-power chargers, home appliance panels;
Transportation equipment: Track signals, elevator control systems.
common problem
Q: Can a ceramic tube fuse that has already blown be reused?
A: No, after it melts, the internal powder has absorbed energy and the fuse has broken. A new one needs to be replaced.
Q: Why does my fuse blow faster than what is indicated in the manual?
A: It's possible that the ambient temperature is too high or the circuit surge is large. Please check the actual working conditions and appropriately reduce the rated selection.
Q: Can the fast type and the delayed type be interchanged?
A: It is not recommended to replace at will, otherwise it may lead to accidental tripping or failure to provide timely protection.
conclusion
Ceramic tube fuses are widely used in various electrical systems due to their high-temperature resistance, strong breaking capacity and high reliability. Through reasonable selection, correct installation and regular maintenance, the safety of equipment and personnel can be effectively guaranteed.