What this part is
The ABB 1SAZ311201R1001 is an electromechanical thermal overload heater, listed under the ABB ASEA BROWN BOVERI line for contactors and starters, where it sits as a thermal element that pairs with a matching motor-starter contactor to give class-10 thermal overload protection. Its home in the protection stack is thermal overload heaters for starters, the third tier under circuit breakers, fuses and protection, so it bolts into a starter assembly rather than running as a standalone switching device.