What this SIRIUS S0 contactor delivers
The Siemens SIRIUS 3RT1025-1AK64 is a size S0 power contactor rated for motor switching at 7.5 kW in AC-2 duty at 400 V, and 11 kW at 690 V. That AC-2 rating covers wound-rotor motors and moderate inrush loads — the contactor handles the higher switching frequency without excessive contact wear. At AC-4 (plugging, inching, reversing), it carries 15.5 A at 400 V, so it's not just a general-purpose box; it's sized for applications where the motor sees frequent reversals or jogging. The 45 mm width allows three units per standard section. Screw-type terminals accept up to 2x 10 mm² stranded or 1x 8 AWG.
Ratings that matter for motor control
Auxiliary contacts handle 10 A at 24 V, 6 A at 230 V, and 0.3 A at 220 V DC — enough for PLC-level control signals and small relay coils. The 10 million mechanical operations typical life means this contactor outlasts most machines it's installed in; the electrical life depends on the load curve. Coil operates at 50/60 Hz with a tolerance band of 0.8 to 1.1 times rated voltage. Type 2 coordination (the standard for minimal contactor damage under fault) requires a 25 A gL/gG fuse upstream. Type 1 coordination (allow contactor replacement after fault) uses a 63 A fuse. That gives the panel designer flexibility: if the line can tolerate a swap-out, the 63 A fuse saves on upstream breaker sizing.
The 140 mm depth fits standard enclosures. Wire termination: solid conductors from 0.5 to 4 mm² (2x per clamp), stranded from 1 to 6 mm² (2x per clamp), with a max of 2x 10 mm² stranded or 1x 8 AWG. Strip length and torque values follow standard Siemens terminal specs — no special tooling needed beyond a common screwdriver.