Continuous Current
The current value a driver can carry without a time limit, determined by thermal equilibrium. Operating at this value, the temperature of the power stage settles; above it, the temperature climbs continuously. In the product data it is stated as 15 A for the KS250 and 30 A for the PT500.
Continuous current capacity and peak capacity describe different physics: the continuous value is limited by how well the heat can be removed, the peak value by how much heat can be stored temporarily. That is why the mounting conditions directly affect the continuous value.
- Ambient temperature: Catalogue values are usually given for a 25 °C ambient. In a hot panel or under a bonnet, the junction temperature rises at the same current and the safety margin shrinks.
- Airflow: Squeezing the module into a narrow box or burying it under a bundle of cables lowers the continuous current it can carry.
- Placement: Modules cooled by natural convection are mounted vertically, with clearance above and below.
When selecting, aim to keep the measured continuous current within 70–80 percent of the module capacity. A system running very close to the limit will start tripping into protection shutdowns in summer heat or as the current rises with a dirty commutator.
Where this term is used: DC Motor Driver Selection Guide