Current derating drives the real-world rating
The 3RW4426-3BC34: For a panel with a 50°C internal ambient — common in enclosed drives — the usable continuous current is 118 A, not the headline figure. The 690 V rated insulation voltage and 50/60 Hz operating frequency cover standard global supply voltages without a voltage derating step.
Inside-delta wiring cuts line current by 42%
This soft starter supports inside-delta circuit configuration, which reduces the current through the thyristors to 58% of the motor full-load current. For a 133 A motor, the line-side contactor and cabling see only about 77 A — allowing smaller upstream components. The integrated bypass contactor then closes at full speed, removing the thyristors from the circuit and eliminating their heat dissipation during run.
Pollution degree 3 and clearance planning
Rated pollution degree 3 per IEC 60947-4-2, this soft starter is designed for industrial environments where conductive dust or occasional condensation occurs. The required clearances are 100 mm above, 75 mm below, and 5 mm at the sides — the vertical clearance is the binding constraint in a shallow enclosure.
Integrated protection eliminates external overload relay
Motor overload protection is built in, removing the need for a separate thermal or electronic overload relay in the motor circuit. Intrinsic device protection monitors thyristor temperature and overcurrent — a fault display on the unit gives local diagnostics without a connected HMI. The adjustable current limitation lets you set the start current between 8% and 100% of the soft starter rating, which also serves as a torque limiter for delicate loads.
Termination: spring-loaded control, box-terminal power
The main current circuit uses box terminals accepting 2x (4 to 50 mm²) stranded, with front and back clamping points both rated for 10 AWG to 2/0 AWG. Maximum motor cable length is 500 m, sufficient for remote motor installations without a drive-end reactor.