Danfoss shaft generators drive down emissions on board Korean research vessel

The South Korean National Institute of Fishery Science is benefitting from 20-30% less emissions as well as savings on fuel on its latest research vessel. Danfoss Drives designed an innovative drive solution in conjunction with STX Engine, the South Korean ship engine experts which optimised the performance of the generator and engine on board the vessel. The Danfoss Drives solution contributed to helping the shipbuilder comply with the IMO environmental regulations which came into force in 2020.

Overcoming design problems

The customer requested that Danfoss Korea be involved the project, following initial problems with the design challenge of using the European synchronous generator, as determined in the project specification. Danfoss was able to offer its variable speed drives expertise and reputation for high-level design support and was the only supplier with the ability to meet the customer requirements.

Space saved by optimum drive dimensioning

On ships, shaft generators are classified as generators. The challenge of this design was to double the capacity of the standard shaft generator, to make sure that it met the current short circuit requirements.

The parties finally agreed on optimal AFE dimensioning and capacity, with standard over loadability after local on-site technical consultation between Danfoss Korea, Danfoss Center of Excellence team, and STX Engine.

Danfoss was able to deliver a less complex, more high performance shaft generator design for the project and installing a shaft generator onboard helped with meeting emission targets. This was a result of improved operational efficiency and enabling designers to downsize the engine.

Electric propulsion for reduced emissions

There are many benefits to using a Danfoss Drives shaft generator on ocean-going vessels:

  1. Use of asynchronous generators. Specifications needed to be converted from synchronous to asynchronous mode. This was made possible by site trials and local engineering.
  2. A lesser degree of noise, low vibration, lower energy consumption and lower CO2 and NOx emissions compared to ships without the Danfoss Drives shaft generator. This is a result of the generator and engine being powered up via the Danfoss drive to provide power to navigation and ship.
  3. Vessels can run in electric propulsion mode without firing up the engine during low-speed or part load operation.
  4. When operating the winch on board ship, the generator is protected from overload when in electric propulsion mode. Therefore, the stability of the vessel is maintained and the prevention of overload will also help to prolong the life of components.


Through local engineering, project management and local engineering commissioning, Danfoss conducted and ran a shaft generator demo system made by Danfoss Korea which showed how to create an end-to-end system, and how to adapt the hybrid solution to this specific installation.

The conditions required for the general generator were applied, as the shaft generator is classified as a generator on board the ship.

The Shaft Generator Components

The 500 kW shaft generator system is built up of these products:

  • VACON® NXP Grid Converter with LC sine filter
  • VACON® NXP generator converter with dU/dt filter
  • Liquid-cooling station HXM-M-120-N-S
  • Engineering cabinet
  • Transformer
  • Motor/generator Application: 500 kW shaft generator system

What makes the shaft generator work?

Conventional shaft generators used for controllable pitch propellers operate by generating an electromagnetic field between stator and rotor using automatic voltage regulation (AVR) and an excitation unit.

When running at low speed however, the output voltage and regularity can get to such reduced levels that rated output voltage and frequency cannot be generated. Therefore, an excitation unit with an additional drive is required to boost the excitation voltage – and ensure the correct frequency. This will drive the generator at rated speed.

An extra requirement of this job was power take-in (PTI) functionality for the electric propulsion in order to regulate the speed of the propeller, which required an AC drive.

Making use of an induction motor as a generator combined with a Danfoss AC drive, the complexity of the synchronous generator with excitation system was eliminated, which resulted in considerable savings in cost for maintenance and commissioning.