Fuses can be either fast-acting or time-delay. Most fuses, such as Class CC, J, R, T, L and high-speed fuses are current-limiting. Class T fuses are fast-acting and are very current-limiting. High-speed fuses are fast-acting and extremely current-limiting (the most of any fuse). Class CC, J, R, and L have both fast-acting and time-delay versions and have good current-limiting abilities.
Fast-Acting fuses are typically used for heating and lighting circuits (Class CC and T) and have good current-limiting abilites.
A special type of fast-acting fuse is the high speed fuse. This is a very current-limiting type of fuse, specifically selected for the protection of drives and SCRs. Often drive manufacturers will recommend a specific type of high speed fuse for their drive. Replacement of this fuse, with another type or class is not recommended since it may sacrifice the needed protection. At Bussmann we have specialists for these applications and they can be contacted for assistance.
Time-delay fuses have the ability to pass temporary inrush currents from motors or transformers (primary), but can also be used for general applications. Time-delay fuses have the ability to be sized closer to the load than fast-acting fuses. Typically these fuses are applied in eletrical distribution systems (usually Class J, R, and L) and have good current-limiting abilitites.
The bottom line, for drives and SCRs, use the fuses recommended by the manufacturer, typically a high-speed fuse.