Frequency Converter

When the generators of the fishing vessel were found to be too small, a VLT AutomationDrive frequency converter solved the problem. VLT earns its keep aboard Denmark’s largest fishing vessel, when it sets off on a typical 14-day jaunt at sea. The “S 349 Gitte Henning #8” is designed for ocean (pelagic) fishing, with rights to no less than 10% of the national ocean fishing quota.

The trawler was built as a turnkey project by Western Baltija Shipbuilding, Lithauania and delivered in April 2014. The ship belongs to Henning Kjeldsen in Skagen, Denmark.

As the sizing of the generators was optimized for best energy efficiency – without a large power reserve - the shipyard discovered that the ship’s generators were too small to start the 1.47MW variable pitch azimuth thruster with a soft starter or star/delta starter. But it was out of the question to rebuild the ship and install larger generators.

Danfoss and the electrical contractor, SEMCO Maritime A/S helped to find a practical solution. Using a VLT frequency converter to limit the starting current, whilst starting the thruster with the propeller blades in neutral position, it was possible to retain the specified generators.

The solution required a 560kW VLT AutomationDrive frequency converter with a DEIF synchronizing controller and bypass contactors. Both could be installed in the thruster switchboard with no requirement for additional space. Additional Danfoss products installed included two 400kW VLT drives for the refrigeration compressors, and an active harmonic filter to meet the class requirements.