It is a sealed, small size thermostat, mounted directly on the electric windings of the motor or compressor.
Operation: Silver contacts are normally closed. The bimetal is driven by the current passing through it and also by the temperature it receives from the windings. When the temperature in the bimetal reaches the predetermined calibration value, which corresponds to the maximum allowable temperature in the coil, the bimetal instantly changes the curvature interrupts the circuit.
This allows the protected motor to provide maximum power and, at the same time, is limited by the temperature of the coils.
When the temperature in the windings returns to the lower limit of the maximum permissible, the protector automatically drives the assembly.
The thermal protector has a fixed temperature differential. The result of this is an average temperature in the windings, being lower than the opening temperature of the protector, when an overload prolongs the protector cycle.
