Design and performance of an integrated thruster motor

Remotely operated vehicles (ROVs) are widely used in the oil industry for inspection, repair and maintenance of offshore installations as well as supporting exploration and production operations. These are invariably box-like vehicles driven by 6-7 ducted-propeller thruster units. This paper reports a detailed design optimization study of an integrated thruster PM motor which can be designed to fit satisfactorily within the volume of a modified standard duct. The thruster is shown to have good performance and efficiency. Coupled propeller motor design optimization is essential in order to achieve well-balanced, optimum thruster performance. In the integrated thruster friction losses can be high, but these can be traded-off with ohmic losses by optimizing the propeller pitch ratio and motor length. High pole number and low magnetic loading are the key to reducing motor dimensions to an acceptable level. There are still some uncertainties regarding the accurate calculation of friction loss and possible effects of the presence of the motor on propeller performance.