SIRIUS S0 power contactor — 27 A AC-3, screw terminals, DIN-rail mount
The Siemens SIRIUS 3RT2027-1AP04 is a size S0 power contactor rated for 27 A at 480 V in AC-3 duty — the standard motor-switching category for squirrel-cage induction motors. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, and the mounting position is flexible: ±180° rotation on a vertical surface, plus ±22.5° tilt forward or backward. That helps when the panel layout is tight or the contactor sits at an odd angle in a swing frame. The magnet coil uses screw-type terminals — field-replaceable without special tools. Main contact wire range accepts 1 to 10 mm² solid or stranded, and auxiliary circuits can take 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²).
Switching frequency and thermal limits
Maximum mechanical switching rate is 10,000,000 operations typical. Electrical endurance varies by duty: 1,000 cycles/hour at AC-1, 750 cycles/hour at AC-2 and AC-3, and 250 cycles/hour at AC-4 (the harsher inching/jogging duty). The AC-3e rating also sits at 750 cycles/hour. That covers most indoor panel environments; if the panel sees direct sun or sits near a furnace, the 60 °C ceiling is the hard limit.
Auxiliary contact ratings and arcing clearance
This variant ships without an auxiliary switch block — the auxiliary contacts are a separate order. When added, the rated values at 24 V are 6 A, dropping to 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, and 3 A at 400 V. At 440 V it is 0.6 A. Arcing time is 10 to 10 ms (a tight window, meaning consistent arc extinction). That matters when you pack multiple contactors side-by-side on the DIN rail — keep 6 mm between units to avoid arc flashover.