Motor thermal protection circuit controlled by 3UN2 (with two temperature sensors)

The 3UN2 motor thermal protection device produced by Siemens of Germany is used for motor overload protection and phase failure protection.
The device consists of a temperature sensor and a trip controller . The circuit is shown in Figure 4-43 and Figure 4-44 (the main circuit is not shown).
The part in the dashed box is the 3UN2 motor thermal protection device. In the figure, Rt is the thermistor, So is the stop button, and sl is
the start button. S2 is the power switch, Ki is the contactor, K is the output relay, and T/R is the reset button. S3 is the remote
reset button, and Hi~Hs are indicator lights.