The symbol for a fuse is one of the most widely used elements in electrical and electronic diagrams. Fuses are used in electronics with low voltages (a few volts), low-voltage systems (120/220V), and even in medium (over 13,000 V) and high-voltage (over 60,000 V) applications.
In this article, we’ll show some of the most common symbols used to represent a fuse.
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For this reason, the fuse symbol can vary depending on the voltage used, the intended application, and the internal function of the fuse. Therefore, there are various symbols representing different types of fuses.
The essential thing in fuse symbology is to indicate the fuse’s primary characteristics, such as amperage, operating voltage, and fuse type.
A fuse is an electrical and electronic component designed to protect various devices. If the nominal amperage of the fuse is exceeded, the fuse “blows” or “opens,” cutting off the power supply.
Example of a Fuse Symbol
The following image shows a fuse, which opens the circuit when there is a current exceeding 20 A.
The fuse will open the circuit if the nominal amperage is exceeded, thus preventing excessive current from flowing to the protected component.
The fuse is rated specifically for the device it protects, making proper selection important.
For example, if a device is rated for 20 amps, a 30 A fuse would not adequately protect it. However, in cases where a device has high inrush currents—where it briefly exceeds 20 A upon startup but then stabilizes at 20 A—a higher rating might be necessary.
Sometimes, circuit breakers are preferable to fuses since a breaker can open the circuit and be reused, while a fuse must be replaced once blown.
How to Select a Fuse
Fuse selection is based on the amperage of the device it will protect, typically with a margin allowed for startup or minor variations.
For electrical transformers, the Mexican standard NOM 001 SEDE 2012 specifies that the maximum fuse size should be up to 300% of the transformer’s nominal capacity.
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