The 3RW4424-1BC46: At 60 °C during operation, that is the hard ceiling — the unit must not see ambient above that while running, which matters in a hot mill panel or near a furnace wall where radiant heat pushes enclosure internals past 50 °C. The insulation voltage is rated 690 V, and the pollution degree is 3 per IEC 60947-4-2, meaning the creepage distances are designed for conductive dust and humidity — a common condition in cement plants, foundries, and steel mills where the soft starter sits in a non-climate-controlled MCC.
Integrated bypass and inside-delta wiring
This unit includes an integrated bypass contact system, so after the start ramp the thyristors are shorted out — no continuous heat dissipation from the silicon, which is what lets it hold 81 A in a 40 °C enclosure without forced air. The inside-delta circuit capability means the soft starter can be wired in the delta leg of a six-lead motor, reducing the current through the thyristors to 58% of line current — useful for larger motors where the starter frame would otherwise jump a size. Minimum load is 8 % of the rated current — below that the motor current may be too low for the thyristor firing to regulate reliably. If the connected load draws less than about 6.5 A at 40 °C, the starter may not commutate cleanly.
Termination and panel fit
Main power circuit termination is box terminals accepting 2x (4 … 50 mm²) stranded, or 2x (10 … 1/0 AWG) using both clamping points. That is a generous lug range — no need for reducers on 35 mm² motor cables. Dimensions are 170 mm wide, 192 mm high, 270 mm deep — a standard SIRIUS 3RW44 frame size. Mounting is screw fixing with the unit oriented vertically, rotatable ±90° and tiltable ±22.5° front-to-back. Clearance: 100 mm above, 75 mm below, 5 mm at the sides.