Thermal Overload Relay : Thermal overload relays prevent an electric motor from drawing too much current and overheating.  Thermal overload conditions are the most likely faults to be encountered in industrial motor applications.

Thermal overload conditions are the most likely faults to be encountered in industrial motor applications. They result in a rise in the motor running current, which produces an increase in the motor's thermal dissipation and temperature. Overload protection prevents an electric motor from drawing too much current, overheating, and literally burning out.
 

Thermal overload relays can be bimetallic relays, eutectic alloy relays, temperature control or probe relays, and solid-state relays.