The Siemens SIRIUS 3RA2125-1CD23-0AK6 is a non-fused motor starter in size S0, designed as a direct starter for three-phase induction motors. It combines a contactor and a thermal bimetallic overload relay in a single, coordinated package, rated for AC-3 switching duty up to 690 V. At 400 V it handles 750 W motor loads; at 480 V the full-load current is 2.15 A, and at 600 V it is 2.24 A.
This starter snaps onto 60 mm busbar systems using the included busbar adapter (8US1251-5NT10). Mounting position is vertical only. The unit occupies a 45 mm width on the busbar — two standard 22.5 mm module slots. Dimensions are 260 mm height, 45 mm width, 155 mm depth. Forwards clearance of 10 mm and sideways clearance of 9 mm are needed for air circulation and wiring access; no space is required behind the unit. The supplied link module (3RA2921-1AA00) connects the contactor coil circuit to the overload relay, so no additional control wiring between the two devices is needed.
Wiring and connection
Main contact terminals accept stranded wire from 1 to 10 mm², or two conductors of 2.5 to 6 mm² each — useful for looping through to a downstream device. The supplied contactor is a 3RT2023-1AK60; the circuit-breaker frame size is S00. Coil operating range is 88–121 V at 50 Hz and 96–132 V at 60 Hz, covering common control voltages in both 50 Hz and 60 Hz installations.