Soft starter for motor starting duty
The thyristor-based output stage provides adjustable current limitation, so you set the start current profile to match the load, and the built-in motor overload protection eliminates the need for a separate overload relay on the line side. Derating is linear with ambient: 385 A at 50 °C, 335 A at 60 °C. Minimum load is 20 % of the rated current, so it won't regulate properly on a fractional-horsepower motor; match the frame to the motor FLA. Mounting is screw-fixed to a vertical surface. With an additional fan, the unit can be rotated ±90° or tilted ±22.5° front/back; without the fan, rotation is limited to ±10° and tilt to ±10°. Side clearance is only 5 mm, but upwards needs 100 mm and downwards 75 mm for airflow — plan the gland plate and busbar routing accordingly.
Wiring and connection
Main current circuit connects via busbar or cable lugs. The front clamping point accepts 3/0 to 600 kcmil; the back clamping point takes 250 to 500 kcmil. Using both clamping points together, the range is 2/0 to 500 kcmil minimum. For stranded cable, the range is 70 to 240 mm²; finely stranded accepts 50 to 240 mm². Solid wire for auxiliary contacts is 2x (0.5 to 2.5 mm²). Maximum wire length from the soft starter to the motor is 300 m — beyond that, voltage drop and reflected-wave effects on the thyristors need evaluation. The external reset input allows remote fault recovery without opening the panel door.