Review of marine a.c. installations

Electrical power has been used in ships since about 1870, and until comparatively recently all marine systems have employed direct current. The past 15 years have seen a change in practice by all the leading maritime nations and a.c. systems are now becoming more popular. The paper describes the extent of this change and reviews the reasons for it. The special operating conditions applicable to a marine system are described, and also the necessary features which must be built into the electrical installation in consequence. The basic problem of voltage, frequency, size and type of generating plant, voltage regulation and protection are described. The general approach to the solution of these problems is outlined, together with some noteworthy exceptions as practised in certain shipbuilding countries. The effect of increased size of generating plant on system layout is described and current trends in various countries are noted. Mention is made of the present trend towards centralisation of control and/or automatic control for main plant items.