What the 25 A rating means on a hot mill floor
The 3RW4026-2BB04: Derate to 23 A at 50 °C and 21 A at 60 °C. In a steel mill cabinet pulling radiant heat from the rolls, that 60 °C ceiling is where the part survives; the 21 A limit is the one to budget for the motor nameplate. Insulation voltage is rated 600 V, matching IEC 60947-4-2 pollution degree 3 — meaning it holds up in the conductive dust and humidity of a rolling mill electrical room without tracking.
Integrated bypass and spring terminals — panel wiring reality
The integrated bypass contact system pulls the thyristors out of the circuit after start, so the 25 A rating is for the start duty only — no continuous heat sink burden on the semiconductors. Motor overload protection is built in, with adjustable current limitation to dial in the start ramp. Main and auxiliary/control circuits both terminate on spring-loaded terminals — no screw torque to verify, no loosening under vibration. Frame size S0 — 45 mm wide, 150 mm tall, 155 mm deep. Screw and snap-on mounting to DIN rail; the 45 mm width leaves room for a contactor and overload alongside in a standard 600 mm enclosure.
Active production — sourcing posture
Lifecycle stage is current — Siemens still produces this order code.
Mounting position and clearance for heat
With the additional fan, the unit mounts on a vertical surface rotatable +/-90° and tiltable +/-22.5° front/back. Without the fan, rotation is limited to +/-10°. Clearance: 60 mm upward, 40 mm downward, 15 mm at the sides — respect these for natural convection cooling, especially at the 60 °C ambient limit.