Melting Current of a Fuse

The melting current of a fuse is the current at which it will rupture (melt) and break the circuit. It is determined by the design and construction of the fuse.

Nominal Current

The nominal current of a fuse is the maximum current that it is designed to carry continuously without melting.

Overload Tolerance

Fuses have an overload tolerance, which is the amount by which the nominal current can be exceeded before the fuse will melt. This tolerance varies depending on the fuse type and is typically expressed as a percentage or multiplier.

Operating Current

The operating current of a fuse is the current that it will carry without melting. It is usually slightly higher than the nominal current to account for normal variations in current and to provide a safety margin.

Rule for Operating Current

There is no fixed rule for determining the operating current of a fuse. However, a common rule of thumb is to multiply the nominal current by the overload tolerance.

Example

For a 10 A gM fuse with an overload tolerance of 20%, the operating current would be:

Operating current = Nominal current x (1 + Overload tolerance)Operating current = 10 A x (1 + 0.2)Operating current = 12 A

Therefore, this fuse would melt at 12 A or higher, but not at 10 A.

Note:

It is important to note that fuses are designed to protect electrical circuits from overcurrents. If the operating current of a fuse is exceeded for an extended period, it may still melt, even if it does not melt immediately. Flag for review