178B9339 by Danfoss

The 178B9339 is a solid-state soft starter manufactured by Danfoss for the MCD Soft Starters series. Positioned between a three-phase supply and an induction motor, it gradually increases line voltage so that current and mechanical shock are reduced during every start. The device also allows controlled stops, helping prevent pressure hammer or load transients in pumps, conveyors, and fan systems. Because starting conditions are managed electronically, the unit helps extend bearing life and reduces electrical stress during startup in automated installations.

The mains input may be as low as 380 VAC and as high as 480 VAC, and a voltage tolerance of ±10% keeps the starter active during moderate brownouts or overvoltage events. With a rated motor capacity of 3.0 kW, the unit matches fractional and small integral horsepower drives. A built-in brake supply delivers 180 VDC at 1 A so the motor shaft can be stopped quickly when 400 VAC is present. Control electronics are powered from an external 24 VDC source that draws 150 mA, and status signaling is provided through a 24 VDC PNP run output limited to 20 mA. The power section is insulated for 500 VAC, and the design supports three-phase networks without additional transformers.

The housing carries an IP66 rating, blocking dust ingress and high-pressure water jets for direct machine-side mounting. Safe operation is maintained from -10 °C to 60 °C, and internal components withstand relative humidity up to 90% without condensation. The unit also has an impulse capability of 2.0 kV (1.2/50 µs), which helps protect control paths against switching surges, while the permitted supply variation covers slower fluctuations. It is suitable for washdown areas, outdoor kiosks, or hot switch rooms where voltage quality and ambient conditions vary throughout the duty cycle.