Thermal Shutdown
The driver cutting off its output to protect the components when the measured temperature passes a critical threshold. Operation returns by itself after it has cooled by a certain amount of hysteresis. Repeated shutdowns are not a fault but a warning pointing to a sizing or mounting error.
Thermal shutdown is a last line of defence; it is expected never to be seen in normal operation. When it does engage, the source of the problem is almost always one of the following three headings:
- Excess current: The motor is working harder than expected. Bearing binding, dirt in the guide or an increased load raises the current, and the loss grows with the square of the current.
- Insufficient cooling: The module is in a closed, narrow space or surrounded by a cable bundle; it is mounted horizontally, or it has no contact with a metal surface.
- Ambient temperature: The temperature inside the panel is higher than assumed in the calculation.
The shutdown-cooldown-restart cycle is also harmful mechanically: the motion is left halfway and the load stops at an unexpected moment. Instead of ignoring this cycle and trying to raise the threshold, fix the current, the mounting and the ventilation.
If your continuous current requirement is close to the continuous rating of the module, moving up one capacity class (for example to the 30 A class instead of 15 A) is the most lasting solution.
Where this term is used: DC Motor Driver Selection Guide