The Siemens 3RB1025-2PB0 is an electronic overload relay from the SIRIUS 3RB family, rated for motor protection in the 1.5...6 A adjustment range. It mounts directly on a contactor in size S0, using screw terminals for the power and control wiring. The trip class is class 20, meaning it allows a 20-second thermal memory before tripping — a standard fit for standard-start induction motors driving pumps, fans, and conveyors where the starting transient is moderate.
The 1.5...6 A current range covers a common band of small to medium motor FLC values. Class 20 trip characteristic means the relay tolerates the inrush of a direct-on-line motor start without nuisance tripping, but still protects against sustained overloads. The manual reset only configuration — no auto-reset — is deliberate: after a trip, someone must physically press the reset button, which is standard practice for unattended or safety-monitored machinery where automatic restart could be hazardous. Size S0 is the physical footprint for contactor mounting. This relay clips onto the matching S0 contactor without additional wiring between the contactor and the overload block — the power pass-through is internal. Screw connections are the termination method.