The motor driver is overheating, what are the possible causes?
The primary cause of heating is current: since the loss follows P = I² × RDS(on) and depends on the square of the current, doubling the current quadruples the heat. The second group of causes comes from the installation: being trapped without air inside a closed enclosure, a loose terminal, insufficient cable cross-section and high ambient temperature.
Checklist:
- Measure the real current. If you are approaching the driver's continuous current rating, heating is to be expected. The KS250 is defined for 15 A and the PT500 for 30 A continuous current; values above the continuous rating are only for a limited time (45 A peak for 5 s on the KS250, 40 A maximum for 15 s on the PT500).
- Duty cycle: Frequently repeated starts produce a high current pulse every time. A ramp (soft start/stop on the KS250, RMP on the PT500) softens the pulse.
- Mechanical resistance: An unlubricated bearing, misalignment and a binding guide raise the current needlessly; the heat you see at the driver is really the result of a mechanical problem.
- Mounting: A module trapped without air in a closed plastic enclosure runs significantly hotter because there is no convection. Mount the module on a metal surface and in a position with air circulation.
- Terminal and cable: A loose connection creates contact resistance, and insufficient cross-section heats both the cable and the terminal.
- Ambient temperature: As the ambient rises, the component temperature rises at the same loss; since RDS(on) also increases with temperature, the process feeds itself.
Note: no heatsink requirement or operating temperature range defined by the manufacturer is stated in the product data for these models; the above are general engineering principles.
Full topic: Locked rotor and thermal protection