Analytical-based iron loss assessment in the SPM slotless machine stator core

The use of slotless machines has acquired growing interest when features such as low vibrations and noise, along with low losses at high speed, are required. However, a careful assessment of the iron losses in the stator core will be relevant already in the design or pre-design phase. Standard methodologies for the iron losses estimation are typically FE analysis with constant loss coefficients, which can lead to weak extrapolations with huge errors. In this paper, an analytical method for iron losses prediction is derived. It is based on the extension of the field solution in the stator iron core, where an accurate 2-D field solution of the slotless machine topology is found. The analytical solution is combined with a variable loss coefficients model, which can be efficiently computed by vectorized post-processing. The case study proves that the approach can predict all of the loss phenomena over a wide operating range with improved precision.