Siemens 3RB1257-0KM11 Overload Relay, 125-500A, Discontinued

The 3RB1257-0KM11: This relay mounts in size S10/S12 frames — either continuous (ganged) or individually. The main circuit uses busbar connection, typical for high-current panel builds where bolted bus links replace cable lugs. Auxiliary wiring lands on screw terminals. The control voltage is AC 220-240 V, so verify the panel's control transformer taps before wiring. Bistable outputs mean the relay holds its last state on power loss — useful for applications that must remember a trip condition after a control power cycle.