Affiliations: [a] School of Electrical and Computer Engineering, RMIT
University, Melbourne VIC, Australia | [b] School of Electrical and Electronic Engineering,
University of Nottingham, Nottingham, UK
Correspondence:
[*]
Corresponding author: W.U. Nuwantha Fernando, School of
Electrical and Computer Engineering, RMIT University, Melbourne VIC 3000,
Australia. E-mail: nuwantha.fernando@rmit.edu.au
Abstract: Certain aircraft and military applications require high speed
machines with low stack-length and the lowest possible weight. Hence, the
accommodation of the highest bore diameter may seem the natural option.
However, a rotor design with high diameter results in significant increase in
mechanical stresses in the employed magnet retention. In a sleeved magnet
retention mechanism, the sleeve thickness can be increased in order to
accommodate the stresses. However, this will result in significant drop in
air-gap flux-density and will not yield the high power density expected by the
machine. This paper presents an analytical technique that combines the sleeve
stress model and the air-gap flux density model to calculate the optimal rotor
diameter to achieve the maximum power of the machine design for a minimum
stack-length. The technique is applied to both a Carbon Fibre sleeve version
and a metallic sleeve version. The analytical calculation of the stresses is
validated with mechanical finite-element simulations. The machine design with
the analytical calculations is validated with electromagnetic finite element
simulations. The results confirm the rotor design strategy and the design
technique.
