Semiconductor fuses run hotter than most fuses. In order to achieve a very accurate melting temperature, these fuses have been engineered with a high proportion of pure silver in their element and their body filling is high quality silica, which helps to draw heat away from the fuse element. Due to this fact, it is generally accepted that they should not be enclosed so as to ensure sufficient cooling of the fuses so they can operate as specified. Fuse cooling is very challenging if the fuse holder doesn’t allow sufficient airflow around the fuse.
The ‘power loss’ value of a fuse is a measure of the heat emanating from the fuse under full load. It is used to determine how quickly the fuse dissipates its heat. This is also known as the ‘heat loss’, ‘watts loss’ or ‘heat dissipation value’. Power loss is measured in Watts. If any fuse is to be used in a fully enclosed holder, then the power loss rating of the fuse holder used must be greater than that of the fuse to ensure that there is sufficient dissipation of the heat around the fuse. In other words, the fuse holder’s ability to tolerate heat must be higher than the heat the fuse produces. If this is not followed, the fuse holder may warp, melt or explode. Due to the fact that semiconductor fuses run much hotter than type gG or type aM fuses, extra care must be taken when choosing fuse holders for them.