Fuse failure is mainly divided into two completely different situations, each of which leads to completely different consequences and is very serious:
When the fuse is blown, it does not melt (it cannot be opened when it fails):
This is the most dangerous situation. When there is an overload (current exceeding the safe value but not reaching the short-circuit level) or short-circuit (current extremely high) fault in the circuit, the fuse fails to melt in a timely manner according to the design requirements to cut off the circuit.
Main consequences:
Wire overheating and fire: Continuous high current can cause circuit wires (wires) to rapidly heat up, far exceeding their safe temperature tolerance. This can cause the insulation layer of the wire to melt and burn, igniting the surrounding flammable materials (such as wooden structures, wall insulation materials, dust, etc.), thereby causing serious electrical fires. This is the most significant and fatal consequence.
Serious equipment damage: Excessive current can directly burn out sensitive equipment such as electronic components, motor coils, transformers, etc. in the circuit. This kind of damage is often permanent and catastrophic, far exceeding the value of the fuse itself. For example, televisions, computers, refrigerator compressors, power tools, etc. may all be burned out.
Increased risk of electric shock: If overload or short circuit causes the equipment casing to become electrified (such as internal circuit insulation damage coming into contact with the casing), and the fuse fails to cut off the power supply, there is a risk of electric shock when the user comes into contact with the equipment casing.
Damage to higher-level protective equipment: If the fuse fails to disconnect, a huge fault current may be conducted to its higher-level distribution system (such as the main switch at home, the distribution box on the floor, or even the transformer), forcing higher-level protective devices (usually circuit breakers) to trip and causing a wider range of power outages.
Fuse when it should not be blown (false fuse/premature aging fuse):
The working current of the circuit is normal and there has been no overload or short circuit, but the fuse has blown, cutting off the circuit.
Main consequences:
Unexpected shutdown of equipment: causing connected appliances or devices to suddenly lose power and stop working.
Production interruption/data loss: In industrial or critical applications, sudden equipment shutdown may cause production line interruption, experimental failure, loss of unsaved data, server downtime, etc., resulting in economic losses or operational inconvenience.
Difficulty in daily life: Important appliances in the home (such as refrigerators, heating/cooling equipment, lighting, security systems, etc.) experience power outages, affecting normal life.
Frequent replacement is troublesome: it requires continuous investigation of the cause and replacement of fuses, which brings trouble and cost.
Common causes of false circuit breakers:
Fuse aging: Long term use, repeated minor overloads, or temperature fluctuations can cause the performance of the fuse to deteriorate and the rated value to decrease.
Selection error: The rated current of the fuse used is too low to withstand the instantaneous current (surge current) required for normal startup or operation of the equipment.
Poor contact/heating: Poor contact of the fuse holder generates additional resistance, leading to local heating and heat transfer to the fuse, causing it to accidentally melt.
High ambient temperature: When a fuse is installed in a high-temperature environment, its actual melting current will decrease.
Mechanical damage: The fuse is subjected to vibration or physical damage.
Summary of key consequences comparison:
|Failure type | Typical cause | Main consequence | Severity|
|Continuous interruption | Aging, poor quality, excessive selection, poor contact | Electrical fire, equipment burnout, electric shock risk, expanding power outage | Extremely high|
|Not meant to be broken but broken | Aging, too small selection, poor contact, high temperature | Equipment shutdown, production interruption, inconvenient life, frequent replacement | Medium to low (but may bring a chain reaction of safety hazards)|
Important Notice:
The failure of 'should be interrupted continuously' is extremely dangerous and must be absolutely avoided. This is one of the main causes of electrical fires.
Never use fuses that do not meet the specifications, and it is strictly prohibited to replace fuses with metal wires such as copper or iron. This is equivalent to completely canceling protection and is extremely dangerous!
If the fuse frequently blows (especially in situations where it should not have been blown but still does), it is necessary to thoroughly inspect the circuit and equipment to identify the real cause (overload, short circuit, poor contact, equipment failure, incorrect fuse selection, etc.), rather than just replacing the fuse. Neglecting this issue may mask potential risks of "continuous interruption" or equipment failure.
Regular inspection and replacement of fuses are necessary preventive measures for important or outdated circuits.
In modern low-voltage distribution systems, circuit breakers (air switches) have basically replaced fuses as the main circuit protection device due to their advantages of reusability, more stable performance, and more precise protection. However, fuses are still widely used in devices, specific electronic circuits, automotive circuits, and some outdated systems.
Therefore, the consequences of fuse failure range from annoying equipment shutdowns to catastrophic fires, and their severity depends on the specific type of failure and the environment in which it occurs. It is crucial to ensure that the fuse selection is correct, installed reliably, and in good condition.