Siemens 3RT2028-1AK60-ZX95 — SIRIUS Size S0 Power Contactor
It includes a factory-installed auxiliary switch, which saves a panel slot versus adding a separate auxiliary contact block.
Duty Ratings and Switching Rates
Maximum mechanical switching rate varies by duty class: 1 000 cycles/hour for AC-1 resistive loads, 750 cycles/hour for AC-2 and AC-3 motor starting, and 250 cycles/hour for AC-4 inching/plugging. The AC-3e rating also caps at 750 cycles/hour. These limits govern the contactor's thermal rise and wear — exceeding them shortens life regardless of current. Arcing time is specified at 4 to 16 ms at AC, with a narrower 10 to 10 ms window for the main contacts. The holding power draw is 0.25 VA at 50 Hz and 0.28 VA at 60 Hz — low enough for a standard 24 VDC control transformer without derating.
Wiring and Clearance
For fine-stranded wire, the terminal also accepts 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²). Minimum clearance to adjacent metalwork: 10 mm upwards, downwards, and forwards; 6 mm at the side. These are the bare-minimum air gaps — in a real panel, allow more for heat dissipation and tool access. The auxiliary contact ratings span from 10 A at 24 V down to 0.3 A at 220 V, with a 5 hp rating at 230 V. For motor control, the auxiliary contact can switch a small pilot relay or PLC input directly at 24 VDC. Main contact spring force is listed as 16 to 8 (likely Newtons, per Siemens convention), which ensures positive break under low-current conditions.