What It Is and Where It Fits
The Siemens 3RT7045-1AH00 is a Size S3 3-pole contactor from the SIRIUS family, built for switching motor loads and resistive loads in industrial control panels. Its AC-3 rated voltage goes up to 690 V, which covers 400 V and 480 V distribution systems common in European and North American plants. The three normally-open main contacts handle the power circuit; there are no NC main contacts on this variant. Mounting is flexible: screw-fix or snap onto a 35 mm or 75 mm standard mounting rail. The contactor can be rotated ±180° on a vertical surface and tilted forward or backward ±22.5°, which helps when fitting into a crowded panel where gland-plate access or busbar orientation is tight. Front protection is IP20 — safe against finger contact when installed in an enclosure. The terminal area is rated IP00, meaning the connection points are not touch-protected on their own; the panel enclosure provides the required safeguarding.
What the Ratings Mean for Your Panel
The AC-3 maximum switching frequency is 800 operations per hour; for AC-4 (plugging/inching) duty it drops to 250 operations per hour. That tells you this contactor is designed for normal motor starting cycles, not for high-speed jogging applications. If your application needs frequent reversing or inching, the AC-4 limit governs the real duty cycle. Auxiliary contacts are rated for PLC-level reliability — the spec calls out acceptability for PLC control at 17 V, 5 mA. That means the silver-alloy contacts are designed to switch low-energy signals without oxidation problems, so you can wire the auxiliary block directly to a 24 VDC digital input card without worrying about contact wetting current. The coil is AC-operated with a closing power of 0.61 W DC equivalent and a holding power of 0.26 W DC equivalent. These are low enough to keep control transformer sizing modest in a multi-contactor panel. The surge voltage resistance is rated at 6 kV, which aligns with IEC 60947-1 overvoltage category III for industrial environments. For type 1 coordination (no-weld-after-fault), the spec calls for a gL/gG NH 3NA fuse rated at 200 A upstream. That is the maximum fuse that still protects the contactor under short-circuit conditions — verify your existing branch-circuit protection does not exceed this if you are retrofitting into an existing panel.
Environmental and Installation Limits
Operating temperature range is -10 °C to +55 °C; storage range extends from -25 °C to +70 °C. The storage range matters if you are holding this as a critical spare in an unheated warehouse — it can sit through a winter without damage. Installation altitude is limited to 2000 m above sea level; above that, dielectric strength and air-gap clearance derate, so a different contactor or derating factor applies. Pollution degree 3 rating means the contactor is suitable for environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation — typical for most industrial control panels that are not sealed to cleanroom standards. Side-by-side mounting is permitted without derating, which saves DIN-rail space when grouping multiple contactors.