Overload relays:Dual Element Fuses

Dual Element Fuses

There are some fuses that are intended to provide both short circuit protection and overload protection. These fuses are called dual element time delay fuses. They contain two sections (Figure 4 – 2). The first contains a fuse link that is designed to open quickly under a large amount of excessive current. This protects the circuit against direct grounds and short circuits. The second section acts more slowly; it contains a solder link that is connected to a spring. The solder is a highly con- trolled alloy designed to melt at a particular temperature. If motor current becomes excessive, the solder will melt and the spring will pull the link apart. The de- sired time delay is achieved because of the time it takes for the solder to melt even under a large amount of current. If motor current returns to normal after starting, the solder will not get hot enough to melt.


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