A theoretical analysis is outlined to determine, for a specified direct current, the pre-arcing opening duration of miniature zinc-element electric fuses used extensively in the automotive industry. The effects of ohmic heating and natural convective cooling are treated using analytical methods. A closed-form solution for the opening duration, as a function of the applied current, is derived. Moreover, an approximation for the high overcurrent condition is determined. The results are compared with published data, derived from experimentation, to show that the model is an accurate representation of the devices under consideration.
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