S0 contactor for 3-phase motor switching — what the ratings mean
The Siemens 3RT7027-1AG00 is a 3-pole S0-frame contactor rated for AC-3 and AC-3e switching up to 690 V. The insulation voltage is 690 V, matching the maximum rated operating voltage. At 45 mm wide, three units fit a 145 mm DIN section — typical for a group of motor starters. The screw-type terminals on both main and auxiliary/control circuits accept 2x 0.5…1.5 mm² solid or stranded, or 2x 0.75…2.5 mm² — common panel wire sizes. The IP20 finger-safe enclosures on the front and terminals allow safe handling inside a closed panel.
Switching frequency and contact reliability — real-world limits
Rated for 800 operations per hour under AC-3 duty (motor starting), but only 250 ops/h under AC-4 (plugging/reversing) — the difference matters if the contactor sees frequent inching or reversing cycles.
Mounting flexibility and environmental limits
Side-by-side mounting is permitted, so no derating for heat buildup when ganged. Operating temperature range -10…+55 °C; storage -25…+70 °C.
Auxiliary contact extension and coil data
The product extension for auxiliary switches is available, so you can add up to four auxiliary contact blocks on the front without removing the contactor from the rail. Coil holding power is only 0.24 W DC — negligible heat in a crowded panel. Closing power peaks at 0.82 W DC.