81 A at 40 °C — the derating curve sets your panel budget
The 3RW4424-3BC46: That 21 % drop from 40 to 60 °C means the panel ventilation and adjacent heat sources directly govern whether this starter holds its full current rating in your enclosure. Inside-delta wiring reduces the current through each thyristor leg to 58 % of the line current — so this 81 A unit can start a motor with a nominal FLA well above 81 A when wired inside-delta. Confirm the motor winding configuration before specifying; the starter supports both standard and inside-delta connections. Integrated bypass contact system eliminates the need for an external bypass contactor — the bypass closes after the start ramp, shunting the thyristors and dropping the heat load to near zero during run. This saves panel space and wiring compared to a starter-plus-bypass combination.
Mounting, wiring, and clearance — what fits in the panel
Dimensions are 270 mm deep, 170 mm wide, 192 mm high — a compact footprint for the 81 A rating. Screw fixing to the mounting plate; the unit can be rotated ±90° on a vertical surface and tilted ±22.5° front-to-back, giving flexibility in tight enclosures. Clearance requirements: 100 mm above, 75 mm below, 5 mm at the sides. The top clearance is the critical one — it allows hot air from the thyristor heatsink to rise without recirculating. Skimping on the 100 mm overhead will force derating beyond the published curve. Main current circuit uses box terminals accepting 2x (4 … 50 mm²) stranded or 2x (10 … 1/0) AWG.
Protection and diagnostics — built-in, no add-ons
Motor overload protection and intrinsic device protection (thyristor overtemperature, phase imbalance, stalled rotor) are integrated. No external overload relay or motor protection circuit breaker is required for the starter itself — the 3RW44 series handles it internally. Adjustable current limitation lets you set the start current anywhere from 0 to the rated value — useful for soft-starting conveyors or pumps where a hard limit on inrush protects downstream mechanicals. Minimum load is 8 % of rated current, so it can start lightly loaded motors without dropping out. Fault signal is displayed on the unit itself — a local display shows the fault code, which speeds troubleshooting on the floor without needing a laptop. External reset input allows remote clearing from a PLC or pushbutton station.
Environmental and electrical ratings — industrial duty
Pollution degree 3 per IEC 60947-4-2 — the standard for industrial environments where conductive dust or condensation can occur. Insulation voltage rated 690 V, giving headroom on 400/480 V systems. Operating frequency 50 … 60 Hz — one unit covers both line frequencies. Storage temperature range -25 … +80 °C, operation up to 60 °C ambient. Maximum motor cable length 500 m — long enough for most pump and conveyor runs without output reactors.