Effect of unbalanced and inclined air-gap in double-stator inner-rotor axial flux permanent magnet machine

Abstract

Due to its novelty in structure, the appealing force between rotor and stator disks, axial flux (AF) permanent magnet (PM) machine are easily affected by air-gap asymmetries. In the inner-rotor double-stator AF machine, the rotor disk is assembled between two outer stators. It is usually assumed that the air-gap clearance is ideal condition in electromagnetic analysis. However, manufacturing imperfections in the machine or any perturbation to rotor disk during operation would results in an unbalanced and inclined air-gap clearance, which would generate unbalanced force acting on the structure and further increase the asymmetry extent. Cogging torque, which is imperative requirements for high performance applications, is directly related to modulating effect of the air-gap and slot opening permeance. In this paper, the cogging torque under un-normal air-gap condition of AF machines is first calculated using a combined analytical and numerical methods, followed by a structure analysis to study the effect to mechanical stress, deformation and bending force on bearings. Results and conclusions given in this paper are instructive for successful development of AFPM machines.Index Terms--Axial flux permanent magnet machine (AFPM), unbalanced air-gap, inclined air-gap, cogging torque, magnetic force, deformation 978-1-4799-4389-0/14/$31.00 ©2014 IEEE

Impact of Manufacturing Tolerances on Axial Flux Permanent Magnet Machines with Ironless Rotor Core: A Statistical Approach

“…The authors stated that the studied imperfections produce a bending torque of the stator structure and can increase the ripple torque. A similar analysis is presented in [17] for a double-stator one-rotor TCW-AFPM machine. Using quasi-3D FE simulations, it was found that the tilt of the rotor structure can increase the peak value and modify the wave-form period of cogging torque.…”

“…In this regard, AFPM machines have been also studied, but most of the research articles focus on analyzing the effect of rotor and stator misalignments, static and dynamic eccentricity, and magnet shape selection [16][17][18][19][20][21]. The analysis of a double-rotor one-stator TCW-AFPM machine for wind power generation was presented in [16].…”

Influence of Slot Openings and Tooth Profile on Cogging Torque in Axial-Flux PM Machines

“…This can be extended to other cogging torque mitigating methods such as pole-slot combinations, which affect NL, p and Qs. Furthermore, nonuniformities in the airgap [30] can be analysed by analytically incorporating them in (8), in addition to other methods described in [31] and [32]. This is the simplicity of the analytical quasi 3-D technique proposed in this paper.…”

Analytical Modeling of Static Eccentricities in Axial Flux Permanent-Magnet Machines with Concentrated Windings

“…The flux density in the slotless air gap with eccentricity (Becc) and without eccentricity (Bno-ecc) can be estimated by modifying the air gap length in Equation (9).…”