I see this on the website:
If this is a concern, put a thermister on the router and monitor it with the microprocessorWarning! The closed-loop nature of this motor speed controller means
that it is capable of delivering significant power to the motor during low RPM
use. At low RPMs the cooling ability of universal motors is reduced and we recommend
monitoring of the motor power and heat during low RPM use. We will not be held
responsible for damage to the router or to the Super-PID device caused by abuse.