What it is and what it does
The Siemens 3RT1024-1AP64 is a SIRIUS power contactor in the S0 frame size, rated 12.5 A in AC-4 duty at 400 V — that's the reversing and plugging current, not the steady motor run. For motor starting (AC-3), it handles 7.5 kW at 400 V. The screw-type main terminals accept up to 2x 10 mm² or 1x 8 AWG. It mounts on 35 mm DIN rail per EN 50022, either snap-on or screw-fixed.
Panel fit and integration
At 45 mm wide and 85 mm tall, the S0 footprint fits standard distribution board pitch. Side-by-side mounting is permitted — no derating gap required — which saves rail space on a multi-contactor motor starter group. Depth is 140 mm, so check gland plate clearance if the panel is shallow. The front face carries IP20 protection; the terminals themselves are IP00, meaning the wiring zone needs enclosure-level protection against accidental contact.
Coordination and protection
For Type 2 coordination (no damage to the contactor under short circuit), Siemens specifies a gL/gG fuse rated 25 A. For Type 1 coordination (contactor may need replacement after fault), the fuse can go up to 63 A. That gives the panel builder a clear selectivity boundary: stay at 25 A if you want the contactor to survive a downstream weld or short.