Abstract
Double rotor machine, an electronic continuously variable transmission, has great potential in application of hybrid electric vehicles (HEVs), wind power and marine propulsion. In this paper, an axial magnetic-field-modulated brushless double rotor machine (MFM-BDRM), which can realize the speed decoupling between the shaft of the modulating ring rotor and that of the permanent magnet rotor is proposed. Without brushes and slip rings, the axial MFM-BDRM offers significant advantages such as excellent reliability and high efficiency. Since the number of pole pairs of the stator is not equal to that of the permanent magnet rotor, which differs from the traditional permanent magnet synchronous machine, the operating principle of the MFM-BDRM is deduced. The relations of corresponding speed and toque transmission are analytically discussed. The cogging toque characteristics, especially the order of the cogging torque are mathematically formulated. Matching principle of the number of pole pairs of the stator, that of the permanent magnet rotor and the number of ferromagnetic pole pieces is inferred since it affects MFM-BDRM’s performance greatly, especially in the respect of the cogging torque and electromagnetic torque ripple. The above analyses are assessed with the three-dimensional (3D) finite-element method (FEM).
Highlights
In recent years, double rotor machine has attracted great attention due to its wide application prospects in hybrid electric vehicles (HEVs) [1,2,3,4,5,6], wind power [7,8] and marine propulsion [9].Consisting of a stator and two rotors, a double rotor machine can realize flexible energy transformation as an electronic continuously variable transmission
To achieve stable torque transmission in the air gap adjacent to the stator, the pole-pair number of the comparatively large modulated space harmonic produced by the permanent magnet rotor pp(1, −1) (h = 1, k = −1) should be equal to that of the stator ps, which can be expressed by Equation (10): p p − pm = p s
To achieve stable torque transmission in the air gap adjacent to the permanent magnet rotor, the pole-pair number of the comparatively large modulated space harmonic produced by the stator winding ps(1, −1) (v = 1, l = −1) should be equal to the pole-pair number of the permanent magnet rotor pp, which can be expressed by Equation (21): p s − pm = p p
Summary
Double rotor machine has attracted great attention due to its wide application prospects in hybrid electric vehicles (HEVs) [1,2,3,4,5,6], wind power [7,8] and marine propulsion [9]. There have been several proposals for double rotor machines in the past, such as compound-structure permanent-magnetic synchronous machines (CS-PMSM) [10,11], induction machines based electrical variable transmission [12,13], switched reluctance double-rotor machines [14] and dual mechanical port machines [15]. Though these double rotor machines meet the demand of power-split characteristics, they have two major disadvantages. The axial magnetic-field-modulated brushless double rotor machine (MFM-BDRM) comprizes three parts: a stator, a modulating ring rotor and a permanent magnet rotor [18,19]. The above analyses are examined by three-dimensional (3D) finite-element method (FEM)
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