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Main >> Applications >> Sample problems >> Safety fuse

Safety fuse temperature

QuickField simulation example

This is an example of the safety fuse simulation, performed with QuickField software.

Problem Type
Plane-parallel problem of heat transfer.

Geometry
Safety fuse temperature Determine the operating time at short-circuit current of 40 A Conductor Porcelain Sand 40 mm Ø 32 mm 40 mm

Given
Conductor diameter is d = 0.5 mm, copper resistivity ρ = 0.018 Ohm*mm²/m;
Copper melting point T = 1050 °C;
Nominal current I = 10 A, ambient air temperature +20°C.

Task
Determine the operating time at short-circuit current of 100 A.

Solution
First we need to calculate the power loss in the conductor. Conductor resistance is R = ρ*Length / Cross-section area.
The losses in the conductor are defined by the Joule-Lentz law as Q = I²R.
In QuickField we should specify the value of losses per volume: Q / V = I²R / (Length*Cross-section area) = I²*(ρ*Length / Cross-section area) / (Length*Cross-section area) = ρ * (I/Cross-section area)².
Conductor cross-section area is πd²/4 = 0.196 mm².

Result
Fuse will terminate the current in less than 2 seconds.
Safety fuse temperature