In electronics and electrical engineering, fuses are electrical safety devices that are designed to provide overcurrent protection of an electrical circuit. The most essential component is a metal strip or wire that melts when too much current flows through it, and therefore interrupts the current. Fuses are sacrificial devices, meaning that once a fuse has operated, it must be replaced or rewired.

Fuses have been used since the early days of electrical engineering, with the first examples of expendable wiring being used to protect electrical devices dating back to 1864 and Thomas Edison patented the first true fuse in 1890. There are now thousands of fuse designs, each with their own specific current and voltage ratings, breaking capacity, and response times. Time and current operating characteristics are especially important for providing adequate protection without needless interruption. Properly wired, fuses can prevent short circuits, overloads, mismatched loads, and device failure.

Fuses consist of the aforementioned metal strip or wire fuse, mounted between a pair of electrical terminals, and are usually enclosed by a non-combustible housing. The fuse is arranged in a series to carry all of the current passing through the protected circuit. The resistance of the element generates heat due to the current flow and influences the size and construction of the element; however, the heat produced cannot cause the element to reach an unsafely high temperature. The fuse element is made from aluminum, copper, silver, zinc, or alloys to provide stable and predictable characteristics. Ideally, a fuse can carry its rated current indefinitely, and melt quickly with little to no excess. A fuse element cannot be damaged by minor current surges and cannot oxidize or change its behavior after years of service.

Fuses have several parameters they must operate under. The rated current is the maximum current that the fuse can continuously conduct without interrupting the circuit. The speed at which a fuse blows depends on how much current flows through it, and the material the fuse is made of; it is not a fixed interval but decreases as the current increases. The breaking capacity is the maximum current that can be safely interrupted by the fuse. This should be higher than the prospective short-circuit current. For example, fuses for small, low-voltage residential wiring systems are commonly rated to interrupt 10,000 amps, while fuses for commercial or industrial power systems are rated for 300,000 amps.

At ASAP Components, owned and operated by ASAP Semiconductor, we can help you find all the fuse systems and parts for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asap-components.com or call us at 1-919-348-4040.


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The electrical systems within an aircraft are extensive. Steps need to be taken to ensure that the system doesn’t overload causing a power outage on an aircraft. Resistors are electrical components that oppose the flow of electrical current. They are by nature, passive components that only reduce voltage rather than increase them. Wirewound resistors are cylindrical components with resistive wire wrapped around them. The rod is typically made of ceramic or fiberglass and the wire is usually made out of an alloy such as nichrome. An exterior casing insulates the wirewound resistors to help block any heat coming from the circuit interruption.

The key to wire wound resistors is in the winding and the material of the wire. The level of resistance can be changed by adjusting the wire resistivity and wire length. A metal wire with high resistance opposes large amounts of electric current, while, a metal wire with low resistance blocks a small amount of electric current. The longer the wire, the more space the free electrons have to travel and collide with atoms, therefore the higher the resistance. During collision, energy is lost in the form of heat and only a small amount of electric current flows through the wire resistor. In comparison, electrons only have to travel a short distance, thus do not collide with atoms as frequently. The result is that a larger amount of electricity passes through the resistor. In a similar principle to the length of the wire, the size of the wire coil spiral directly affects the level of resistance. If the cross section of the coil is small, the electrons are more compact, so collide with the atoms, thus losing energy. If the coil is larger, the resistance is lower as more electrons escape collision and carry on through the resistor.

Two types of wire resistors are commonly used with aircraft equipment. Precision wire resistors are used for low temperature applications that require a high level of accuracy for example calibration equipment. Power wire resistors are used in instances of high temperature. In an aircraft, a power resistor can be found in the main electrical system as a current sensor. Due to their adaptability, wire resistors are a popular hardware component to use in aircraft. They can be manufactured in all different sizes and materials to suit the desired task. Compared to other resistors, wire resistors are low cost, have high accuracy and stability rates, and offer wide variances in resistance. The downfall of wire resistors is that, under high frequencies, the wire acts as an inductor.

At ASAP Components, owned and operated by ASAP Semiconductor, we can help you find all the wire resistors for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asap-components.com or call us at +1 919-348-4040.


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