What it is and what it does
The Siemens 3RT1024-3BB40-ZX95 is a SIRIUS power contactor in frame size S0, with three normally open main contacts and a 24 V DC coil. It is designed for switching motor loads in control panels and industrial machinery, rated for 5.5 kW at 400 V in AC-3 duty and 12.5 A in AC-4 duty at the same voltage. The AC-3 rating of 5.5 kW at 400 V means it handles the starting and running of standard squirrel-cage induction motors up to that power level without exceeding thermal limits. The AC-4 rating of 12.5 A at 400 V covers reversing or inching duty where the contactor makes and breaks the motor at full load.
Mounting and integration
Mounts via screw or snap-on onto a 35 mm standard mounting rail per DIN EN 50022. The S0 frame footprint is 45 mm wide, 85 mm tall, and 100 mm deep — a compact envelope that fits standard panel layouts. Side-by-side mounting is permitted, so you can gang multiple contactors without spacing gaps. Front-side protection is IP20, meaning the contactor is touch-safe from the front once installed in an enclosure. The terminal area itself is rated IP00, so the wiring compartment requires the panel door or additional guarding to meet IP2X requirements.
Termination and wiring
Main current circuit terminals are screw-type, accepting solid or stranded conductors: 2x (0.25 to 2.5 mm²), 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), or a single conductor up to 10 mm². AWG equivalents are 2x (16 to 12), 2x (14 to 10), and 1x 8. This range covers most motor and feeder wiring in control panels. Coil consumption is 5.4 W for both closing and holding at DC, so the 24 V DC supply needs to deliver roughly 225 mA steady-state per contactor. The auxiliary contact block (not included) can be added on the side; the contactor has no built-in auxiliary contacts.
Environmental and lifecycle
Mechanical endurance is rated at 10 million operating cycles typical for the contactor size. For short-circuit protection, the required fuse size depends on coordination type: 25 A gL/gG for Type 2 coordination, 63 A gL/gG for Type 1.
Sourcing posture
This is a current-production Siemens SIRIUS contactor. For BOM-line commitment, the key fit parameters are the S0 frame size, 24 V DC coil, 3-pole NO main contacts, and screw terminals. The AC-3 motor rating at 400 V (5.5 kW) and AC-4 current (12.5 A) define the load it can switch. Sourced to order against an RFQ through our industrial automation desk.