Application note
AN0013Continuous Current Carry Ratings
What sets the continuous current carry rating, and how installation conditions change it for the same contactor.
Summary
The continuous current carry rating defines how much current a contactor can conduct indefinitely while staying within acceptable temperature limits, and in most cases it is set by thermal performance rather than by the switching capability of the contacts. This application note explains why published values can vary significantly with test conditions and why the same contactor can achieve different continuous current levels depending on how it is installed. It details the key factors that influence current carry, including load duration, conductor cross-sectional area and material, ambient temperature, active cooling, and adjacent heat sources. The guidance helps engineers interpret ratings correctly and derate them for practical, real-world designs.
