Iconsys was asked to design, supply and commission the variable speed drives for dpplv audacia – a pipe laying vessel converted from a bulk carrier. The superstructure was removed and rebuilt in the form of a machinery tunnel from stern to bow, fitting thruster drives to allow for gps positioning, together with a stringer assembly at the bow. Iconsys supplied of the following:
19 associated drive panels were designed using ‘vacon’ nxp series converters, to be used as standard for all variable speed drives on the vessel. They were also selected as they operate in a marine environment with a ‘non-earthed’ 440v 60hz supply from the ship’s generator system.
All were designed and constructed with an ip54 rating, utilising panel mounted air-water heat exchangers. Apart from the hard-wired emergency stop system, the drives are totally controlled from the siemens plc via an optical profibus® network, with a siemens ‘olm’ unit fitted in each drive panel to convert the optical profibus® signal to electrical for the drives. During operation and due to the motion of the waves, the pipe can move back and forth along the ‘s lay tunnel’, so each drive may alternately drive and regenerate. Excess energy from the motors is dissipated from the converter dc bus into stainless steel dynamic brake resistors in stainless steel cases and located remotely from the panels in the ‘s lay tunnel’.
The drives have now been operating successfully for several years, with increased performance and high utilisation in both the north sea and the coastal waters of equatorial africa.
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