CHAPTER ELEVEN - Electric Propulsion

Abstract

This chapter discusses electric propulsion system in ships. An electric propulsion arrangement for a ship is often simply described as a diesel electric or turbo-electric system. It is characterized only by the type of prime mover, with no reference to the type of electric propulsion motor, the generator, or the electrical power system. The electrical side of the system will be based on a direct current or an alternating current motor, coupled to the ship's propeller shaft, with speed and direction of propeller rotation being governed by electrical control of the motor itself or by alterations of the power supply. An electric motor used with a controllable-pitch propeller is arranged for either constant or variable speed operation. Electric propulsion has been used mainly for specialized vessels rather than for cargo ships in general. The main advantage lies with the flexibility and absence of physical constraints on machinery layout. Support ships for the offshore industry, particularly those with two submerged hulls, can use electric propulsion motors to give high propulsive power in the restricted pontoon space, while generators and their prime movers are housed in the large platform machinery space.