The ABB AF09Z-40-10-21 is a 1-pole (single-module) miniature circuit breaker (MCB) from the System Pro M compact® AF series. It features a Z-characteristic (selective) tripping curve, specifically designed for the protection of highly sensitive circuits such as those containing semiconductors, transformers, or measurement loops. The "Z" curve provides a very fast response to both short-circuit and low-level overload faults, making it ideal for applications where even minor overcurrents must be quickly interrupted to prevent damage to delicate equipment.
