Siemens 3RT2028-4BB40 SIRIUS Power Contactor — Size S0, 480V 34A
The Siemens SIRIUS 3RT2028-4BB40 is a Size S0 power contactor rated for 34 A at 480 V and 27 A at 600 V in AC-3 duty, meaning it handles motor switching loads up to those currents without welding the main contacts. The S0 frame takes 45 mm width on the rail, with 85 mm height and 107 mm depth — factor that into your gland-plate layout and enclosure fill.
Switching Frequency and Duty Cycles
This contactor is rated for 1 000 switching cycles per hour at AC-1 (resistive loads), 750 cycles/h at AC-2 and AC-3 (motor starting/running), and 250 cycles/h at AC-4 (plugging/inching). The AC-3e rating also sits at 750 cycles/h. If your application involves frequent jogging or reversing, the AC-4 limit is the one that governs contact life — don't exceed 250 cycles/h in that duty.
DC Switching Capability and Coil Details
The magnet coil uses a ring cable lug connection — plan for ring terminals, not fork or pin. DC switching ratings are provided across multiple voltages: 10 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, 3 A at 400 V, 0.6 A at 440 V, 2 A at 500 V. These are the DC-1 or DC-13 ratings (not explicitly stated, but typical for this class) — if you're switching DC motor or solenoid loads, use the voltage-specific value, not the AC rating.
Environmental and Mounting Clearances
Keep those clearances for airflow and arc flash containment — especially the 10 mm forward clearance for the arc chute.