Wärtsilä Low Loss Concept (LLC) - Electric propulsion system

The transformerless configuration of the LLC system results in a higher system efficiency of 2% – 3%. This in turn implies a 10% lower fundamental current supplied from the switchboard to the frequency converter. The lower electric losses in the system will result in improved fuel economy and a reduced need for auxiliary machinery systems. The introduction of the LLC transformer in the electric distribution system reduces the overall short circuit current level by 15% to 20%. This allows for a system design comprising Low Voltage (LV) components, and subsequently significant weight and volume reductions compared to traditional systems that include transformers. For certain applications, the weight reduction may be 35% to 40% compared to competing designs. The Total Harmonic Distortion (THD) of the voltage in a LLC system is slightly better than in a traditional 12 pulse system, and is always designed to be less than 5%. The dual supply to the frequency converters, and the four galvanic separated switchboards, increase the total system availability significantly. The converter supplying the propellers will continue to operate should a switchboard failure occur.