Rated current and thermal derating — what the numbers mean for your motor
The 3RW4436-2BC34: The soft starter is rated 281 A at 40 °C ambient. This is the full-load current it can handle continuously at that temperature. The derating temperature threshold is 40 °C — above that, you must reduce the load current or improve cabinet ventilation to stay within the device's thermal limits. The insulation voltage is rated 690 V, and the operating frequency covers 50 to 60 Hz. Inside-delta circuit configuration is supported, which reduces the current through the soft starter to 58% of the motor full-load current — useful for larger motors where the starter frame size can be downsized. Adjustable current limitation and motor overload protection are built in, along with intrinsic device protection (thyristor overtemperature, phase imbalance).
Mounting, wiring, and panel integration
Dimensions are 170 mm wide, 200 mm high, 270 mm deep. Fastening is by screw fixing to a vertical mounting surface, rotatable ±90° and tiltable ±22.5° front-to-back. This gives flexibility in cabinet layout — the unit can be mounted on a backplate or sidewall without special brackets. Main circuit connections accept stranded wire 25–120 mm² or busbar connection. Auxiliary control wiring uses solid wire 0.25–1.5 mm² (2x terminals). The main terminals also accept AWG 4–250 kcmil. Maximum motor cable length is 500 m — sufficient for most industrial installations without output reactors. Degree of pollution is 3 per IEC 60947-4-2, meaning the device is suitable for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation. Clearance distances: 100 mm upwards, 75 mm downwards, 5 mm at the sides.
Protection and diagnostics
The soft starter includes a display for fault signals, showing the fault type directly on the unit — no need for a separate HMI or software to read error codes. External reset input allows remote fault clearing from a PLC or pushbutton panel. Minimum load is 8% of the rated current — the device can start very lightly loaded motors without instability. Storage temperature range is -25 to +80 °C, operating ambient up to 60 °C.