Naval electric motors form the basis of the propulsion systems for many modern surface warships and submarines. The industry continually seeks to combine power density, robustness, noise quietness and efficiency to deliver the ideal combination of features. These features inevitably interact with each other and ultimately any design is a compromise that is optimised for a specific application. The compromises can involve different combinations of motor elements and different combinations of technology. Experience on how to apply the elements has developed over the large number of electrically propelled naval vessels that have seen service over the last 20-30 years. Furthermore, the technology underlying these elements has also developed in this timeframe, leading to significant advances. Some advances, such as experimental superconducting machines, while holding great promise appear unlikely to be mature enough for the next generation of platforms, others appear to be likely to applicable in the near term.
This paper looks at how electric motor technology has been applied to a range of naval vessels past, present and options for the future. It will consider where single motor, tandem and twin arrangements have been applied and also cover application of bearingless and spline shaft arrangements in naval vessels. It will also look at key technologies within motors for naval application, such as rotor and stator skewing, advanced anti-vibration mounting, shock-proofing and multi-phase windings. Recent developments in rotor and cooling design will also be discussed, building on the solution described in the Salter and Lewis paper at INEC2018, with the power density, noise quietness and efficiency benefits of the latest techniques being considered. Consideration will be based on advanced modelling combined with full scale testing results. In many ways this paper represents a retrospective of the career of the late Clive Lewis, a highly respected, regular contributor to this conference over many years and this paper will pay tribute to the enormous contribution he has made in this field.