S00 coupling contactor for signal-level switching
The Siemens 3RT2017-1KB41 is a SIRIUS coupling contactor in size S00 — a compact 45 mm wide, 73 mm deep, 58 mm high frame built for switching control signals and light loads rather than motor power. The contactor carries no built-in auxiliary switch block, so any auxiliary signalling needs a separate add-on block mounted to the front.
Switching performance and ratings
The 24 VDC coil has a pickup threshold of 0.7 times rated voltage and a dropout threshold of 1.25 times rated voltage — meaning the coil picks up reliably at about 16.8 V and drops out when voltage rises above 30 V, which is a wide hysteresis band for noise immunity. At 400 V AC the contactor switches 3 A, and at 230 V it is rated for 2 hp motor load — this confirms it is sized for small motors or transformer loads, not main motor contactor duty.
Operating frequency and mechanical life
Maximum switching frequency: 1,000 cycles/hour in AC-1 (resistive), 750 cycles/hour in AC-2 and AC-3, and 250 cycles/hour in AC-4 — the AC-4 limit reflects the harsher inrush of motor starting under full load.