A disposable fuse (non resettable fuse) is a circuit protection component whose core function is to forcibly cut off the current path by self melting in the event of overcurrent, short circuit, or abnormal power surge in the circuit, thereby protecting the backend equipment from permanent damage. Its "one-time" feature determines that it needs to be manually replaced after melting, making it irreplaceable in the following scenarios:
Typical application scenario analysis
Main circuit protection for high-power equipment
In high current scenarios such as switch mode power supplies and industrial motor controllers, disposable fuses achieve graded protection through precise melting characteristics (such as slow break/fast break models). For example, in the primary circuit of a power adapter, a glass tube fuse can withstand short-term surge currents and quickly melt when subjected to continuous overload, preventing the transformer from overheating and catching fire.
Security sensitive electronic systems
The core power supply module of medical equipment (such as defibrillators and ventilators) often uses micro patch fuses, which can achieve millisecond level overcurrent response without causing fatal risks due to the delayed action of self recovering fuses. The automotive ECU control board also relies on ceramic fuses to ensure the certainty of protection actions under harsh working conditions.
Cost sensitive consumer electronics
Despite the popularity of resettable fuses (PPTC) in smart devices, axial lead fuses are still widely used in white goods control boards. Its core advantage lies in the fact that the cost of 0.03 yuan/piece is only 1/10 of PPTC, and there is no need to consider the current oscillation problem during reset, making it particularly suitable for scenarios such as microwave ovens and air conditioning compressors that require absolute power-off protection.
Key parameters for technical selection
Rated current: usually taken as 1.5 times the normal operating current of the circuit (combined with the ambient temperature derating curve)
Breaking ability: Select 10 × In for household circuits, and achieve a breaking level of 20kA for industrial scenarios
Fuse characteristics: fast melting type (semiconductor protection) vs slow melting type (motor starting shock resistance)
Packaging form: Surface mount (SMD) suitable for automated production, tube type (5 × 20mm) easy to maintain and replace
The essential difference from resettable devices
The melting mechanism of disposable fuses is based on the irreversible phase transition of metal conductors, and their action threshold stability is better than PPTC that relies on phase transition of polymer materials (error ± 20% vs ± 50%). In scenarios where precise protection thresholds are required (such as overcharge protection circuits for lithium battery packs) or where physical isolation is necessary after a fault (anti reverse protection for photovoltaic inverters), disposable fuses remain the only compliant option.
This kind of "circuit breaker termination" protection logic essentially constructs the last line of defense for circuit safety. When the system encounters anomalies beyond its design tolerance, it achieves fault isolation through self sacrifice, and this deterministic protection mechanism is the fundamental reason why it has been widely adopted for hundreds of years.