Finite Element Analysis of a Permanent Magnet Machine with Two Contra-rotating Rotors

Abstract

Electrical machines with contra-rotating rotors find applications in directdrive energy conversion systems and in ship propulsion systems that employ hydraulic machinery with two contra-rotating stages. In this article, the operating characteristics of permanent magnet machines with two contra-rotating rotors moving on opposite sides of a common stator core are studied via two-dimensional finite element analysis. Particular attention is devoted to the special flux distortion patterns that arise in contra-rotating machine topologies. The study suggests that the introduction of a screening iron core between the rotors provides for negligible flux distortion levels during contra-rotating synchronous operation of the two rotors.

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“…Where, m 1 is number of phases of each stator, m is number of phases of the machine, K p is termed the electrical power waveform factor, K e is the EMF factor which incorporates the winding distribution factor K w and the per unit portion of the total air gap area spanned by the salient poles of the machine (if any), K i is the current waveform factor, A is the electrical loading, ɳ is machine efficiency, N ph is the number of turn per phase, B g is the flux density in the air gap, f is the converter frequency, p is the machine pole pairs, λ is the diameter ratio for AFPG defined as D i /D o , D o is the diameter of the machine outer surface, D i is the diameter of the machine inner surface [1,[3][4][5][6].…”

“…Selecting double-sided AFPGs with high power density is an important parameter. So, comparison of power density between different topologies of double-sided AFPGs seems to be necessary [1,3,[6][7][8].…”

Evaluation of Power Density for Three Phase Double-Sided Axial Flux Slotted PM Generator

“…In conventional machines, the air gap flux density has normally radial direction; in AFPGs, the air gap flux density presents mainly axial direction. In general, AFPGs exhibit an axial length much smaller than the length of a conventional generator of the same rating [1][2][3][4].…”

Characteristics of an axial-flux permanent magnet synchronous machine with contra-rotating rotors under unbalanced load condition from 3-D finite element analysis

“…Hence, this paper presents an investigation into the characteristics of the back-EMF and torque production of the axial-flux PMSM with contra-rotating rotors under unbalanced load. Related research can only be found in [15]- [16], which investigated a radial-flux PMSM with contra-rotating rotors and analyzed the mutual effects of the two rotors through the common stator based on 2-D FEA (finite element analysis). The results suggested that the peak value of the back-EMF in the stator winding is related to the relative position of the two rotors.…”