Rating and fit
The Siemens 3RT1035-1AN20 is a SIRIUS power contactor in the S2 frame size, rated for 22 kW at 500 V in AC-3 duty — that's the motor-switching rating that governs most conveyor, pump, and fan applications. At 400 V AC-2 it carries 18.5 kW, and at 690 V AC-4 it handles 11.4 kW, covering reversing or inching loads where the contactor makes and breaks under full current. The 55 mm width and 112 mm height fit a standard 35 mm DIN rail per EN 50022, with screw and snap-on mounting; side-by-side mounting is permitted, so you can pack multiple units without derating for heat buildup. The main circuit uses screw-type terminals, accepting solid conductors from 2x 0.5 to 1.5 mm² up to 2x 0.75 to 4 mm², and stranded up to 2x 25 mm². That covers most panel wiring from control to power feeds without needing lug adapters. Pollution degree 3 means it's rated for industrial environments with conductive contamination — no conformal coating required for typical panel conditions. Auxiliary contact ratings are specified: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, 6 A at 230 V, and 3 A at 400 V — all at 50/60 Hz. These cover PLC input sensing and relay interlocking in the same panel without a separate auxiliary block.
Switching frequency and thermal limits
Maximum switching frequency depends on duty class: 1 200 operations per hour at AC-1 (resistive), 600 at AC-2, 1 000 at AC-3, and 300 at AC-4. For a typical AC-3 motor start, that's one cycle every 3.6 seconds — fine for most process cycling but not for high-speed jogging. The mechanical life is rated at 10 000 000 operations typical, so the contactor outlasts the panel in most installations. Operating temperature range is -25 to +60 °C; storage from -55 to +80 °C. The IP20 front enclosure protects against finger contact, while the terminals themselves are IP00 — meaning the wiring zone is open and must be inside a panel or enclosure. Operating time at AC coil is 7 to 20 ms, arcing time 10 to 15 ms.