Simplified Diesel Electric Propulsion
Electric power has been used for marine propulsion since 1903 when the first multi engine diesel powered ship, the 800 ton M/V Vandal was launched in St Petersburg, Russia. Many electric power variations have been developed since then, from the steam turbo-electric liners of the 1930s to nuclear propulsion systems and with increasing popularity in the last decade with the introduction of hybrid systems - all using electric motors to turn the propeller.
Caption: M/F Eiksund, a RoRo car and passenger ferry of LOA 160 ft (49 m) uses the
ΦDRIVE direct diesel electric propulsion system.
Image credit: Wikipaedia
Controlling the generators and managing the power has produced a large variety of systems that claim to increase efficiency while simplifying their operation through automation. Each system has its pros and cons with some working better than others.
The Norwegian company Inpower A/S has produced a direct diesel electric propulsion system called ΦDRIVE (Phi drive) which they claim is as flexible as a conventional diesel-electric system, yet offering the same levels of efficiency, simplicity and robustness as a conventional diesel mechanical system. It can control single or multiple drives up to approximately 5MW.
The ΦDRIVE is based on directly coupled, permanent magnet machines thus reducing the use of power electronics with associated energy losses; consequently the drive achieves an improvement in efficiency. Compared to traditional diesel-electric machinery, the use of permanent magnet machines also has the benefit of a more compact installation freeing up valuable revenue producing space on board commercial vessels.
Last year a ΦDRIVE installation was completed in the M/F Eiksund, a RoRo car and passenger ferry of LOA 160 ft (49 m), beam 34.7 ft (10.6 m) and draft 10.2 ft (3.1 m). Power is produced by two Volvo Penta D12 gensets each of 370 kW at 1,800 rpm driving two steerable thrusters. Speed is controlled by varying the diesel engines between 600 to 1,800 rpm.
The drawing below demonstrates the relative simplicity in a twin engine installation of the ΦDRIVE direct diesel electric drive compared to a conventional mechanical drive and a representative diesel electric drive.
Caption: Simplified installation schematic comparing (l to r) conventional mechanical drive,
ΦDRIVE direct diesel electric drive, and diesel electric drive.
Image credit: Inpower A/S
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