The Siemens 3RT1025-3VB40 is a SIRIUS power contactor in Size S0, designed for switching three-phase motor loads in control panels. It carries a 24 VDC coil with integrated diode suppression, and its screw-type main terminals accept up to 2x 10 mm² conductors. The contactor is rated for 10 kW at 500 V and 11 kW at 690 V, with an AC-4 switching current of 15.5 A at 400 V — the rating that governs reversing or inching duty cycles.
Mounting and panel fit
Mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022. The 45 mm width and 88 mm height fit a standard S0 footprint, and side-by-side mounting is allowed with 6 mm spacing to adjacent devices. Depth is 100 mm — account for that when routing wiring behind the panel door.
Coil and control circuit
The 24 VDC coil draws 4.2 W during both pick-up and hold, so the control transformer or DC supply must sustain that continuously. The built-in diode surge suppressor handles the inductive kickback — no external flyback diode needed across the coil terminals.