Safety switch to latch when power turns off till reset
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Latched thermal monitoring.

How it works:


The thermostat, T-STAT, has a normally closed contact. It opens when the drive goes over-temperature.
Pressing RESET energises RLY1 which latches itself on via RLY1-b.
Contact RLY1-a powers the drive. Using a separate contact for the drive power means that the RESET button doesn't have to carry the full drive current. The RESET button can be lightweight.
On over-temperature T-STAT's contact will open, the relay will unlatch. The drive will not be powered again until RESET is pressed.


Note that with this arrangement a reset is required on power-up.