What is the PTC sensor and what are its benefits and where do we use it?

A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.

PTC-resistor temperature sensors (also called PTC-resistors or thermistors) are temperature dependent semiconductor resistors whose main function is to alter their electrical resistance drastically when their body temperature reaches the nominal trip temperature NAT (TNF).

PTC-resistors are used principally to protect windings in electromotors or transformers against excess temperature. They also find application in machines, tooling machines especially machine bearings and controlling the temperature of power semiconductors.

PTC thermistor act as thermal protection for electrical machines , it have a non linear resistance/temperature response , and at specified temperature the resistance changes rapidly to a very high value .

PTC ( positive temprature coeffiecient ) it used in many ways 

mainly in the motors to detect the winding tempature.

also in the TV. in order to limit the current .

PTC is a semiconductor used as an overload relay . PTC is adjacent to refrigeration compressors using the refrigerant gas R134a in fridges.