30 Amp Fast Acting 437 Cross SM 125V Thin Film Surface Mount Fuses 1206

A resistor is available for a certain load. If the current flowing through the resistor goes beyond the limit, it will be burned and the circuit will be open. At this point, a resistor is similar to a fuse, i.e., the current can be interrupted upon overcurrent. This seems like a fuse function. In this way, some manufacturers change the fuse in its original design to cheap fuse resistors to keep cost down, presenting customers with superficial security.

However, is a fuse resistor able to substitute a fuse to have the same function? The answer is obviously no.

As we know, a good fuse must possess three essential functions: protection, load bearing and safety, while a fuse resistor may not be able to work well in all three aspects.

The protection function covers overload protection and short circuit protection. Specifically, a fuse must operate within the specified time when an unexpected overcurrent, even an extremely short overcurrent, occurs in the circuit, so as to protect the circuit and parts. A fuse resistor may not be as accurate as the fuse in terms of technical parameters like starting time and operation duration, and thus cannot ensure overcurrent protection. It only works to some extent for short current.

The load bearing function of a fuse is ensured by the I2t value, which enables a fuse to withstand pulse shocks of a certain energy from switching operations. We should calculate and evaluate this value before fuse selection. Nevertheless, a fuse resistor has no similar technical indexes, so it may be blown by a pulse if the value is small or fail to protect the circuit if it is large.

As for safety, a fuse can be assured through rated voltage, interrupting capacity and other indexes, especially safety compliance certification by an authorized third party. A fuse resistor is not a safety component, so it does not need certification. Its safety is therefore questionable. Furthermore, it has insufficient protection, and it's hard to ensure no hazards occur during the breaking process.

In conclusion, a fuse resistor may blow upon overcurrent, but it cannot work the same as a fuse. In most applications, it will not be appropriate to replace a fuse with a fuse resistor to cut cost.