Siemens 48BSF3M20 Overload Relay

Siemens 48BSF3M20 Overload Relay is a three-phase, solid-state motor protection device from Siemens (originating with Furnas Electric Co.) that guards induction motors in control panels by monitoring line current and tripping on overload. It is rated for 13–27 A and features manual reset, aligning with ESP100-series overload relays used in motor circuits. This model is designed to be used with Siemens contactors in motor control circuits to protect three-phase motors in industrial equipment. When current exceeds the selected threshold, the relay interrupts the motor supply to prevent overheating and damage, and requires a manual reset before power can be restored. As part of the ESP100-series family, it embodies the Furnas/SIEMENS protection lineage within a compact, solid-state protector for three-phase motors, and is commonly chosen in systems that prioritize compatibility with Siemens’ motor-control ecosystem.