Design of a Dual DC-Bus Homopolar Generator Implementing a Direct-Cooled Excitation Coil

The drivetrains of large transportation systems, such as aircraft or ships, are evolving towards hybrid turbo-electric solutions with DC primary power distribution, aiming to reduce the related greenhouse gas emissions. Synchronous Homopolar Generators (SHGs) equipped with front-end diode rectifiers are a promising technology for on-board generation units. Following the work presented in previous publications, the design of a 2 kW@6000 rpm concept demonstrator is here refined by means of 3D-FE analysis, considering both no-load and load operation. A direct-cooled solenoid excitation coil provides the full voltage-control capability of two independent 400 V DC-buses supplied via the diode rectifiers. The electromagnetic design choices are focused on the minimisation of the DC-bus voltage ripple. The multi-physics design of the field winding considers both electromagnetic and thermal aspects, which are validated through CFD analysis.