The Siemens 3RT2028-1AB04 is a SIRIUS S0 power contactor with screw-type terminals, sized for motor and resistive loads up to 34 A at 480 V in AC-3 duty. The contactor accepts solid or stranded wire from 1 to 10 mm², with dual-wire capability on the coil terminals (2x 0.5 to 2.5 mm²).
This contactor's switching frequency is duty-specific: up to 1 000 cycles/hour for AC-1 resistive loads, 750 cycles/hour for AC-2 and AC-3 motor duty, and 250 cycles/hour for AC-4 plugging or inching. The AC-3e rating also caps at 750 cycles/hour. Arcing time sits at 10 ms, and the main contact gap is 16 to 8 mm. The 34 A at 480 V figure is the AC-3 motor-switching rating — that's the number to size against your motor nameplate current, not the AC-1 resistive number.
The S0 frame measures 85 mm high by 45 mm wide by 141 mm deep, leaving clearance requirements: 10 mm upward, 10 mm downward, 10 mm forward, and 6 mm at the sides. Coil terminals are screw-type, accepting 2x 0.5 to 1.5 mm² or 2x 0.75 to 2.5 mm² solid or stranded. No auxiliary switch is built in; add a separate block if you need status feedback.