The difference between a fuse resistor and fuse blowing

Resistors have a certain limit to their load. When the current passing through a resistor exceeds this limit, it can burn out, causing the resistor to appear as an open circuit. Resistors also have a function similar to a fuse—that is, they can cut off the current when the circuit is overloaded, acting somewhat like a fuse—but this is very different from the protection provided by a fuse.

A fuse must fulfill three functions simultaneously: protection, load-bearing, and safety. A fusible resistor is unable to perform well in any of these three areas.

The protective function includes overload protection and short-circuit protection. When the circuit experiences an excessive current or a short-circuit current beyond the permissible limit, the fuse must operate within a specified time frame to protect the circuit or components. However, the start time and action duration of a fusible resistor cannot match the precision of a fuse, making overload current protection unreliable; it can only provide very limited protection against short-circuit currents.

The load-bearing function of a fuse is ensured by its melting heat energy, allowing it to withstand energy pulses from a certain number of switch operations. This requires calculation and evaluation when selecting a fuse. A fusible resistor, on the other hand, does not have similar technical specifications. If it is too small, it may be blown by a pulse; if it is too large, it loses any protective function.

The safety function of a fuse is guaranteed by rated voltage, breaking capacity, and other indicators, especially verified through authoritative third-party safety certifications. Fusible resistors, however, are not safety components and do not require safety certification. Therefore, their safety is questionable. Their protective function is already insufficient, and during the burnout process, it is difficult to ensure that no hazardous conditions affecting the surroundings will occur.