TABLE OF CONTENTS Fuses (fusible wire links) are one of the oldest and most universally used overload protection methods. However, because the function of the fuse is thought to be elementary, it tends not to get the close attention it deserves for a thorough understanding of its characteristics.
Modern fuse technology is an advanced science; new and better fuses are continually being developed to meet the more demanding requirements for protection of semiconductor circuitry. To obtain the most reliable long-term performance and best protection, a fuse must be knowledgeably chosen to suit the application.
From an electrical standpoint, fuses are categorized by three major parameters: current rating, voltage rating, and, most important, let-through current, or I 2 t rating.
Current Rating
It is common knowledge that a fuse has a current rating and that this must exceed the maximum DC or rms current demanded by the protected circuit. However, there are two other ratings that are equally important for the selection of the correct fuse.
Voltage Rating
The voltage rating of a fuse is not necessarily linked to the supply voltage. Rather, the fuse voltage rating is an indication of the fuse s ability to extinguish the arc that is generated as the fuse element melts under fault conditions. The voltage across the fuse element under these conditions depends on the supply voltage and the type of circuit. For example, a fuse in series with an inductive circuit may see voltages several times greater than the supply voltage...
