A New Approach to the Rating of Fuses for Electronic Circuits

The traditional approach to the design of fuses has been primarily empirical in nature. With the more sensitive electronic devices and finer gauge wiring in use in modern electronic circuits, it is desirable to have a more complete knowledge of fuse performance. This paper will describe a method of fuse element selection and rating based on two characteristics of the materials being used, the voltage drop as a function of current and the time to blow as a function of current. Specifying a maximum for each at given current levels determines the minimum and maximum element diameters, respectively. The characteristics will be derived theoretically and shown to agree with experiment. It will also be shown that fuse performance may be dependent upon the characteristics of the fuse holder. Examples will be taken from a high-speed fuse being developed in the Bell System for use in electronic switching systems.