81 A at 40 °C, integrated bypass, inside-delta ready
The 3RW4424-1BC35: It carries an integrated bypass contact system that eliminates the power dissipation of the thyristors once the motor is at full speed, so the enclosure heat load drops to the bypass contact resistance rather than the semiconductor forward drop. The unit supports inside-delta circuit wiring, which lets the starter control a motor wound for delta connection using a lower current rating than a standard in-line configuration — useful when the motor terminals are accessible and the panel space is tight.
Current derating and thermal budget
Rated current drops from 81 A at 40 °C to 73 A at 50 °C and 64 A at 60 °C. The derating temperature is 40 °C, meaning the full 81 A is available only up to that ambient; above it the output must be reduced per the curve. Maximum operating temperature is 60 °C, with storage from -25 to +80 °C. Minimum load is 8 % of the rated current — below that the soft starter may not reliably detect the motor current zero-crossing for thyristor gating. The maximum motor cable length is 500 m, which limits the cable charging current that can interfere with the current measurement.
Mounting, clearances, and terminal wiring
Dimensions are 170 mm wide, 192 mm high, 270 mm deep. Fastening is by screw fixing, not DIN rail snap-on — plan for four mounting holes in the back panel. Mounting position allows vertical surface with +/-90° rotation and +/-22.5° tilt front-to-back, giving flexibility in tight cabinets. Required clearances: 100 mm above, 75 mm below, 5 mm at the sides. Main current circuit uses box terminals accepting 2x (4... 50 mm²) stranded or 2x (10... 1/0) AWG using both clamping points. The back and front clamping points each accept 10... 2/0 AWG.
Protection and control features
Motor overload protection is built in, along with intrinsic device protection that monitors the thyristor junction temperature and adjusts the start profile to prevent overtemperature. Adjustable current limitation lets the user set the start current between the minimum load and the rated current. Fault indication is via a display (not just LEDs), showing the fault code directly. External reset input allows remote clearing of a tripped condition without opening the panel door.