Do I need to fit a heatsink to the motor driver?
No heatsink requirement is stated in the product data for the ST42, KS250 and PT500, so it cannot be said that a heatsink is or is not required for these modules. The general principle applies: since the loss grows with the square of the current, running the module at 70-80% of its continuous current rating and leaving air circulation at the mounting location keeps the heating under control.
The logic of thermal management is simple: if the heat produced exceeds the heat that can be removed, the temperature rises. The heat produced grows with P = I² x R; the heat removed depends on surface area, air circulation and ambient temperature.
The right order before fitting a heatsink is this:
- Reduce the current. This is the most effective step, because the loss varies with the square of the current. Run the module at 70-80% of its continuous rating.
- Fix the mounting location. Squeezing the module into an airless cavity, or resting it against the motor body or a sheet-metal surface in the sun, is the most common cause of heating.
- Raise the voltage. Using 24V for the same power halves the current and cuts the loss to a quarter.
- Thin out the duty cycle. Leave cooling time between back-to-back starts.
These steps usually solve the heating problem. If the module still overheats in your application, that shows the selection is marginal; moving from the 15 A KS250 to the 30 A PT500 is the more correct solution. If you are considering any mechanical modification or fitting an external heatsink, consult the support team first so that the IP protection (KS250 IP45, PT500 IP67) is not compromised.
Full topic: DC Motor Driver Selection Guide