What this contactor is and what it handles
The Siemens 3RT1025-3EG24-0KS0-ZX95 is a SIRIUS power contactor in frame size S0, designed for switching motor loads and resistive loads in control panels. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, so it fits standard panel layouts without adapters. The headline motor rating is 11 kW at 690 V, with a 7.5 kW rating at 400 V AC-2 duty. For high-stress reversing or inching applications, the AC-4 rating at 400 V is 15.5 A — that is the number to watch if the load cycles frequently under full current. The contactor carries an integral RC surge suppressor across the coil, which reduces EMI on the control wiring — useful when the coil shares a 24 VDC supply with PLC outputs or sensors.
Mounting and wiring constraints
At 45 mm wide, 88 mm tall, and 140 mm deep, the S0 frame fits a standard 8-module DIN-rail pitch. Side-by-side mounting is permitted with no derating gap, so you can pack contactors tightly in a motor control center row. Main circuit terminals are screw-type, accepting solid conductors from 2x (0.25 to 2.5 mm²) up to 2x 10 mm² stranded. AWG equivalents run from 2x 16–12 up to 1x 8. The front face is rated IP20 — finger-safe once wired; the terminal area itself is IP00, so live parts are exposed until the enclosure cover is on. For type 2 coordination (no weld after a short circuit), the required upstream fuse is gL/gG 25 A. Pollution degree 3 means it is rated for the conductive environment typical of industrial panels — no conformal coating needed for normal factory atmospheres.
Environmental limits and lifecycle
Operating temperature range is -25 to +60 °C, which covers most indoor industrial environments including non-conditioned enclosures near process heat. Maximum operating altitude is 2 000 m — above that, derate for air density. Mechanical endurance is typical at 10 million operations — that is the no-load switching life. Electrical life will be shorter and depends on the switched current and duty cycle; for a tire-curing press cycling once per cure, the mechanical life alone covers years of shifts.
Coil and auxiliary contact ratings
The coil operates on 50/60 Hz control voltage, with a rated value of 110 V at both frequencies. The operating range is 0.8 to 1.1 times rated at 50 Hz, and 0.85 to 1.1 at 60 Hz — so the coil pulls in reliably down to about 88 V at 50 Hz. The contactor carries 2 instantaneous auxiliary contacts. Their switching capacity varies with voltage: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 0.3 A at 220 V DC. For DC switching, the lower current limit reflects arc extinction limits — use the DC rating for valve or relay loads.