Dynamic study of electromechanical interaction in marine propulsion

Electrical propulsion is gaining popularity in the marine industry, because of its good energy management and better dynamic performance. An azimuth thruster driven by an electric motor is a common configuration found in modern electric propulsion systems. In recent years failures relating to bevel gears and bearings in azimuth thruster drive train failures were reported in the marine industry. The failures are believed to be attributed to the ship operation in extreme sea state conditions, resulting in dynamic mismatch between the motor drive and the mechanical drive train systems. Hence, an analysis of the mechanical drive train system behaviour under different control modes will be an asset to the industry. The azimuth thruster is simplified as a generalised six mass system and the induction motor dynamics are both modelled in MATLAB Simulink; under extreme condition in the sea, i.e. propeller ventilation, there are torsional stresses between masses that can affect the life expectancy of drive line components.