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. 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.
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.
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.