Function:
They function as safety devices to disconnect the current to the heating element in case of a malfunction (such as a defective thermostat) that would otherwise allow the temperature to rise to dangerous levels, possibly starting a fire. They contain a fusible, temperature-sensitive alloy which holds a spring contact mechanism normally closed. When the surrounding temperature gets too high, the alloy melts and allows the spring contact mechanism to break the circuit. Unlike electrical fuses or circuit breakers, thermal fuses only react to excessive temperature, not excessive current, unless the excessive current is sufficient to cause the thermal fuse itself to heat up to the trigger temperature.
Important properties and why:
The fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. The metal strip or wire melts at a lower temperature than the wire and other components in the rest of the circuit.
Fuse elements may be supported by steel or nichrome wires, so that no strain is placed on the element, but a spring may be included to increase the speed of parting of the element fragments.
The fuse element may be surrounded by air, or by materials intended to speed the quenching of the arc.
The material that the part is made from:
A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. One mechanism is a small melt able pellet that holds down a spring. When the pellet melts, the spring is released, separating the contacts and breaking the circuit.
The manufacturing method:
A machine cuts notches in a long silver strip that will
