Natural Convection
It is the fanless form of cooling that occurs as heated air becomes lighter and rises while cold air comes in from below to replace it. It requires no moving parts and no maintenance, but gives a thermal resistance several times higher than forced-air cooling. For it to work correctly, vertical mounting and a free air path above and below the device are needed.
In natural convection the only force creating air movement is the temperature difference. For this reason the geometry of the arrangement is far more decisive than it is in fan-cooled systems.
- Vertical placement: The fins and the board must be vertical, and air must be able to enter from below and leave from above.
- Clearance: Leave free volume above and below the driver. A module wrapped in a cable loom or squeezed into a corner will re-breathe the air it has heated itself.
- Enclosure effect: Inside a closed enclosure the internal temperature is typically 10–20 °C above ambient; put this internal value into your calculations, not the outside air temperature.
In fully sealed housings such as IP67 there is no air exchange; heat is removed only from the housing surface. Mounting this type of module in contact with a metal surface gives the housing an additional heat path.
If the driver runs continuously hot, first check the mounting orientation and the clearance around it; most heating complaints are resolved here.
The context in which this term is used: DC Motor Driver Selection Guide