Modeling and analysis of proximity losses in high-speed surface permanent magnet machines with concentrated windings

Abstract

Surface permanent magnet (SPM) machines can be designed with fractional slot-concentrated windings (FSCW) to achieve extended speed ranges. High-speed operation can lead to significant levels of proximity losses in the stator windings due to substantial spatial harmonic magnetic fields in the air-gap as well as the high-frequency currents themselves. An integrated analysis tool is presented in this paper to calculate the strandand bundle-level proximity losses in slotted stator conductors without requiring finite element analysis. A combination of analysis techniques, including Laplace equation solutions and conformal mapping, is used to estimate the magnetic field in each stator slot, providing the basis for proximity loss estimation. The match between losses estimated using the analytical model and finite element analysis is very promising.

AC losses in high frequency electrical machine windings formed from large section conductors

“…In general the AC loss factor is a function of a characteristic height, , pertaining to a dimension D of the conductor arrangement normalised to the skin depth δ. (2) AC Losses in High Frequency Electrical Machine Windings formed from Large Section Conductors In (2) σ is the electrical conductivity of the conductor material, ω is the electrical frequency and μ0 is the permeability of free space. The frequency and temperature dependence of the AC loss factor is exclusively defined through the change in skin depth.…”

“…The eddy current behaviour of a winding formed from bundles of parallel conductors is complex [2] and without proper transposition AC losses similar to that of a single large conductor can be observed. Consequently the most effective Litz wire will have a large strand number and be woven to maximise the degree of transposition.…”

A computationally efficient method for calculation of strand eddy current losses in electric machines

“…In addition to the value of the ac loss, the distribution of the overall copper losses in the stator winding is of interest particularly if coupled-thermal electromagnetic design optimization is desired. 2,3 In a broad categorization, the popular methods for analysis of eddy current losses in PM machines rely on analytical models as in, [4][5]6,7,8,9,10,11,12 numerical finite element/difference analysis as in, [13][14]15,16 or rely on combined analytical-FE-experimental procedures as in. [17][18]19 The analytical models lack the desired accuracy under magnetic core saturation and are not applicable to complex geometry without compromising further the accuracy.…”

Modeling and analysis of eddy current losses in permanent magnet machines with multi-stranded bundle conductors

“…Alternative analytical methods [1,3,5,7] are also proposed to predict proximity losses within acceptable accuracy and less computation time. But, the influence of the number of strands and the strand cross-sectional area of the Litz/ multi-stranded conductor is not reported.…”