The Siemens 3RB1026-1PB0 is a solid-state overload relay from the SIRIUS family, rated for a current range of 1.6 to 6 A with a Class 10 trip characteristic. It mounts directly onto a contactor of size S0, using screw terminals for the power and control connections. The manual-automatic reset selector gives the commissioning engineer a choice: manual reset for a fault that needs a visual check before restart, or automatic reset for remote or unattended installations where a self-recovering trip is acceptable.
The 1.6 to 6 A adjustable range covers standard small-to-medium motor loads — think fractional-horsepower pumps, small conveyors, or fan drives on 400 V three-phase. If your motor has a longer acceleration time (high-inertia loads like centrifuges), you would need a Class 20 or Class 30 relay instead; this one is sized for the common case.
Size S0 is the standard Siemens contactor footprint for this current class. The relay clips onto the contactor without additional DIN-rail space, keeping the panel layout compact. Screw terminals accept 0.5 to 4 mm² conductors; strip length is 8 to 10 mm. The manual-automatic reset selector is on the front face, accessible with the panel door closed if a clear cover is used.