How does a PTCR electrical self-hold thermal protector work?
A PTCR thermal protector has a tiny PTC (positive temperature coefficient) ceramic heater imbedded into its body, it is connected in parallel with the contacts of the switch and as long as the switch is closed it does not heat. When the contacts of the protector open due to an external heat source the PTC heater begins to heat the bimetal disc which prevents it from reaching its reset temperature. As long as electrical power is available, the contacts will remain open in dead air down to -25°C. The contacts will reset a short time after the electrical power is removed from the product. Therefore the PTCR protector acts like a manual resetting device by permanently removing the power from a potentially dangerous appliance without the inconveniences of having to push a button to reset it.
