The 3RT1023-3AG20 is a SIRIUS power contactor in frame size S0, delivering 5.5 kW at 690 V in AC-3 duty — that's the motor-switching rating that governs real panel fit, not the higher resistive-load figure. For a 400 V motor circuit, the AC-3 rating drops to 4.5 kW, so size the contactor to the load's nameplate kW, not the line voltage. The 45 mm width and snap-on DIN rail mount (DIN EN 50022) mean it occupies one standard 45 mm module slot in a panel. Rated operational current at AC-4 (the most demanding duty — plugging and inching) is 8.5 A at 400 V. That's the number to check if the application involves frequent reversing or jogging; AC-3 is for normal start-run-stop cycles. The coil operates on 50/60 Hz with a voltage tolerance of 0.8 to 1.1 times rated at 50 Hz and 0.85 to 1.1 at 60 Hz. That 0.8 lower bound at 50 Hz means it holds in during a brownout down to 80% of nominal coil voltage, which matters for ride-through on marginal utility feeds.
Main circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), or up to 2x 10 mm² stranded. For AWG, that's 2x (16 to 12), 2x (14 to 10), or 1x 8.
For a panel originally specified around the 3RT1023-1AL20 variant, the 3RT1023-3AG20 shares the same S0 frame, 45 mm width, and DIN-rail mounting footprint. The difference is in the coil voltage range and terminal type; verify coil compatibility before drop-in substitution.