SIRIUS Size S0 power contactor — 3RT1023-1BM40-ZW97
The Siemens 3RT1023-1BM40-ZW97 is a SIRIUS Size S0 power contactor rated 4.5 kW at 500 V in AC-3 duty and 8.5 A at 400 V in AC-4 duty. The AC-4 rating is the one that matters for reversing or plugging applications where the contactor makes and breaks motor current at full load — that 8.5 A figure governs real switching life in those cycles. For standard motor starting (AC-3), the 4.5 kW at 500 V and 5.5 kW at 690 V tell you the load it can handle across common industrial voltages. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 50022, fitting the standard panel footprint. The front face carries an IP20 rating, meaning finger-safe when installed in an enclosure; the terminal area is IP00, so live parts are exposed during wiring — standard for this class. Operating temperature spans -25 to +60 °C, which covers most indoor panel environments without derating until the upper end.
Termination and wiring
Main circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²) stranded, 2x (2.5 to 6 mm²), or max 2x 10 mm². Solid wire range is 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). AWG equivalents for main contacts: 2x (16 to 12), 2x (14 to 10), 1x 8. The 45 mm width leaves room for side-by-side mounting without derating, with a 6 mm side clearance specified.
Coil and control circuit
The magnet coil draws 5.4 W on both closing and holding at DC, so the control transformer or DC supply must sustain that continuous draw. Rated control supply voltage is 220 V. Auxiliary contact ratings: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V — these are the make/break capacities for the built-in auxiliary, not the main poles.
Short-circuit coordination
For Type 1 coordination, the maximum fuse rating is gL/gG 63 A; for Type 2, it's gL/gG 25 A. Type 2 coordination (25 A fuse) keeps the contactor usable after a fault — the contacts may weld but the device remains functional. Type 1 (63 A) allows the contactor to be destroyed but clears the fault. The degree of pollution is 3, meaning the contactor is rated for conductive pollution environments typical in industrial panels, and the maximum operating altitude is 2 000 m without derating.