Product Description:

The 178B9339 soft starter is produced by Danfoss as part of the MCD Soft Starters series. Installed between the mains supply and a three-phase induction motor, the device ramps voltage and current smoothly, limiting torque shocks on mechanical loads and preventing excessive inrush that can trip upstream breakers. Its micro-controlled firing angle gradually transfers the motor to full line voltage through an internal bypass, so conveyors, pumps, and fan drives reach operating speed without added heat or wear.

The unit draws a control supply of 24 VDC and requires 150 mA to energize logic, relays, and diagnostic LEDs. Main power terminals accept line voltages from 380 to 480 VAC, and the design tolerates variations of ±10% without nuisance shutdown. The internal insulation system withstands transient events up to 2.0 kV (1.2/50 µs), safeguarding low-level circuits. Across all three phases, the thyristor stack controls motor current during acceleration and deceleration, while an auxiliary run output supplies 24 VDC PNP at 20 mA for status feedback to PLC inputs. The three-phase topology aligns with standard industrial feeders, and a rated insulation voltage of 500 VAC separates power structures from grounded enclosures.

The polyester-coated housing carries an IP66 rating, allowing direct mounting in washdown or dusty zones without a separate panel. Continuous service is permitted from -10 °C to 60 °C, and conformal coating allows operation at ambient humidity up to 90% non-condensing. The starter handles motors up to 3.0 kW at 400 VAC and provides a 180 VDC, 1.0 A brake supply for DC-brake machines, eliminating extra brake rectifiers. Thermal design permits full load across the stated temperature range, and impulse ratings align with over-voltage category III installation practices.