CURRENT LIMITING FUSE TIME CURRENT CHARACTERISTIC (TCC) CURVES BASIC INFORMATION AND TUTORIALS

Specifically, minimum-melting and tota lclearing TCCs of fuses, which are plotted on a log-log scale with time on the Y axis and current on the X axis.

The fuse operates within the area between the two curves. Minimum melting curves are used for selecting fuses to provide maximum protection without operating unnecessarily. The total-clearing curves are used when upstream device coordination is required.

Figure 1 and Figure 2 show typical minimum-melting and total-clearing characteristics for high-voltage fuses. The fuse characteristics are different for each fuse type and design and for each manufacturer.

Thus, in a coordinated protective scheme, fuses cannot be substituted without first matching their characteristics, conducting a coordination study, or consulting the fuse manufacturer.

Figure 1 — Typical TCC curves for a current-limiting fuse.

Figure 2 — Typical TCC curves for an expulsion fuse