0034.4221

Fuses

When it comes to protecting circuits, nothing beats a fuse. Fuses are a type of protective device used to protect circuits from overcurrent, overvoltage, and other electrical hazards. The term “fuse” is derived from Latin fusare, which roughly translates to “to melt.” This is because fuses contain a thin metal element, usually copper or brass, that melts when current is too high for the circuit. The melted element breaks the circuit and thus preventing the overcurrent from damaging the circuit.

From a strictly technical perspective, fuses can be characterized by their application field and working principle. The application field of a given fuse is the application it is designed for, such as motor control, power distribution, lighting, etc. Fuses operate by sensing the amount of current going through the protected circuit, and then breaking the circuit at a pre-defined level of current, known as the trip current. This voltage is usually conservative, allowing enough current to pass for the system to work well, but no more.

A prime example of a particular fuse type and its application is number 0034.4221. This particular fuse type is used for motor control applications, and comprises a thermal-magnetic fuse with a NEMA rating of F-8. It operates by having two separate, independent, overcurrent sensing elements: one element is thermal, and will become hotter the more current is flowing through, while the other is magnetic, detecting the increase in the magnetic field created by a large current flow. When either, or both, elements detect an overload, the fuse trips and breaks the circuit.

The advantage fuses have over other protective devices, such as circuit breakers, is that they can guarantee protection. This is because once the element melts, the circuit is irreparably broken, thus preventing further current from damaging the circuit. Additionally, fuses are relatively inexpensive, and easy to replace. But this is counteracted by their sometimes slow response time and one-time use.

The use of fuses to protect circuits is applicable to nearly any electrical system, ranging from automotive and industrial applications to household appliances and equipment. Due to this wide usage, there are a variety of international standards put in place to assure proper design, operation, and safety. On the other hand, when using fuses it is important to note that the maxim “the right tool for the job” applies. Only use the fuse type specified for the application, and be sure to size the fuse correctly for the circuit. This will ensure the optimal performance and protection the fuse is designed to provide.