The Siemens 3RT7017-1AB01 is a Size S00 contactor with three normally-open main poles, rated for AC-3 switching up to 690 V. The 24 V AC coil draws 0.27 W holding power and 0.8 W closing power, so the control transformer sizing is straightforward — no surprise inrush on a shared 24 V AC bus. The auxiliary contact block is field-addable (product extension auxiliary switch is supported), which matters when you need a feedback signal back to the PLC. Contact reliability is rated for PLC-level signals (17 V, 5 mA), meaning the N.O. auxiliary won't bounce or fail to wet a digital input at low voltage.
The 45 mm width and 72 mm depth leave room for adjacent devices in a crowded enclosure — side-by-side mounting is permitted. That covers most panel layouts without derating.
The AC-3 operating voltage maximum of 690 V means this contactor can switch three-phase motor loads on a 400 V or 480 V system with headroom — it's not limited to the common 400 V rail. The operating temperature range of -10 to +55 °C covers most non-conditioned enclosures; storage range of -25 to +70 °C covers shipping and warehouse extremes.
Screw-type terminals on both the main and auxiliary circuits accept 2 x (0.5 to 1.5 mm²) solid or stranded, or 2 x (0.75 to 2.5 mm²) finely stranded with ferrules. That covers standard control wiring up to 2.5 mm² without needing special crimp tools. The short-circuit coordination tables specify a 20 A gL/gG fuse for type 2 coordination and 35 A for type 1 — useful when you're filling out the panel schedule and need to match the upstream protection.