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This article investigates novel fractional slot nonoverlapping winding hybrid excited (HE) machines with consequent-pole permanent magnet (PM) rotors. The proposed machines accommodate the rotor PM and stator field winding separately, which has solved the spatial confliction of double excitations. Different consequent-pole interior PM rotor configurations are extended to retain the PMs and utilize the flux-concentrating effect. Then, the relationship of field and armature current ratio with the PM and wound field fluxes is identified theoretically, which provides design and optimization guidelines for the HE machines. Furthermore, the HE machines are optimized and compared with conventional PM machines. It is revealed that the HE machines exhibit enhanced torque density with flux-enhancing field excitation, and extended operation range with flux-weakening field excitation. Besides, the HE machine utilizing flux-concentrating effect exhibits the highest PM torque but sacrificed flux regulation capability due to magnetic saturation. Finally, the HE prototypes with different rotor configurations are fabricated and tested to validate the analyses. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid excitation synchronous machine (HESM) with magnetic shunting rotor is designed for electric vehicle traction applications with consideration of electromagnetic performance and mechanical strength. The HESM with magnetic shunting rotor is a topology of brushless HESM with extended magnetic bridge to embed field windings. The rotor core extends along the axial direction and the increase of rotor length is inevitable, which reduces torque density. In order to improve torque density, the excitation structure is optimized by built-in field windings and the HESM with one-end built-in field windings is presented. To improve the flux regulation capability and decrease the magnet consumption further, the HESM with dual-end built-in field windings is proposed and investigated. The comparative study of the performances of the original HESM and the HESMs with one/dual-end built-in field windings is carried out by three-dimensional finite element method (FEM). An original HESM prototype and a permanent magnet synchronous machine prototype have been developed and the experimental results, which agree well with the FE-predicted results, confirm the advantages of HESM and the validity of FEM used in predictions in this paper. [ABSTRACT FROM PUBLISHER]

This paper suggests a possible design of variable flux motor for adjustable speed operation. A method to calculate electrical parameters to meet variable speed conditions is suggested, and the basic motor shape is decided using the relationships between the calculated electrical parameters and motor geometry. The difference between coercivity of two types of magnet is used to control the flux. To prevent irreversible demagnetization of low-coercivity magnet, the approximate shape of magnet is decided by calculating the operating point of the magnet using an equivalent magnetic circuit. The optimum shape of magnet considering the nonlinear characteristics is suggested using a finite-element method. To validate the design, magnetizing/demagnetizing, and load operation tests are conducted. [ABSTRACT FROM PUBLISHER]

The hybrid excitation synchronous machine (HESM) with magnetic shunting rotor is a new topology of brushless HESM. To optimize the excitation construction, improve the flux control capability, and decrease the magnet consumption as well, two types of HESMs with different air-gap features are further proposed and investigated in this paper. First, configuration of the HESM with axial auxiliary air-gaps is presented. The comparative study of axial auxiliary air-gap scheme with respect to radial one is carried out. Three-dimensional (3-D) finite-element analysis (FEA) of the HESM is performed to achieve the field distribution, air-gap flux density and flux control characteristic, which indicates the HESM with axial auxiliary air-gaps also has good flux control capability and moreover enlarged excitation housing. Afterwards, construction and flux control principle of the new HESM with axial non-uniform air-gaps are introduced. A prototype HESM is developed, and the experimental results of open-circuit characteristic and terminal characteristic, which agree with the 3-D FEA results, verify the satisfactory field control performance, desirable power output capability, and the improved flux control capability of the HESM at negative excitation current as well. [ABSTRACT FROM PUBLISHER]

Switched-flux permanent magnet (PM) (SFPM) machines have attracted considerable interest in recent years, since the flux focusing can be utilized, both armature windings and PM excitation sources are on the stator, while the salient pole rotor is very simple and robust. In SFPM machines, the high variable flux densities throughout the stator core result in iron loss being a significant proportion of the total losses. This paper presents a novel modular-rotor SFPM machine that facilitates a reduction in iron loss for a marginal reduction in output torque. The modular rotor also offers a reduction in rotor mass over the conventional-rotor topology. The electromagnetic performance of both conventional- and modular-rotor SFPM machines is analyzed by 2-D finite element analyses and is verified by measurements on small-scaled prototype SFPM machines. [ABSTRACT FROM AUTHOR]

This paper proposes a parametric optimization of a flux-switching electrical machine customized for a wind turbine application with a typical operating range for average and low-power wind energy sites. Statistics of wind resources are taken into consideration for the machine design for definition of the turbine power envelope. Both copper and iron losses for three different machine designs are evaluated. A very important consideration taken in this design is the elimination of gearbox requirements for coupling to the turbine. Although the developed approach makes the machine somewhat voluminous, the overall performance is highly improved because a direct-drive flux-switching electrical generator becomes very competitive for small-scale wind turbines. The design methodology presented in this paper will support widespread application of small-scale wind turbines for rural systems, farms, and villages. This paper concludes by demonstrating that a very cost-effective distributed wind system can be approached with this design. [ABSTRACT FROM AUTHOR]

This paper proposes a novel permanent-magnet (PM) flux switching (PMFS) machine with an outer-rotor configuration for in-wheel light traction applications. The geometric topology of the outer-rotor PMFS machine is introduced, and the analytical sizing equations are derived to determine the main design parameters of the machine. Two-dimensional finite-element analysis (FEA) models are developed to investigate and optimize the machine performance. Furthermore, the flux-weakening capability of the machine is analyzed and further improved by segmental PMs with iron bridges. The machine performance predictions by 2-D FEA models are validated by experimental tests on the prototype machine. The suitability of the proposed outer-rotor PMFS machine for in-wheel light traction application is demonstrated. [ABSTRACT FROM PUBLISHER]

This paper presents a comparative study of torque–speed characteristics and cogging torque of the fractional-slot interior permanent magnet brushless ac machines having different slot openings, viz. open slot, closed slot, and hybrid slot (sandwiched open and closed slots), and unskewed and step skewed rotors. The influence of such alternate slot openings on the magnetic cross-coupling and cogging torque is particularly emphasized. Furthermore, the repercussion of the manufacturing limitations and tolerances on the cogging torque of machines having these alternate slot openings is also investigated. The magnetic cross-coupling level and the sensitivity of cogging torque to manufacturing limitations and tolerances strongly depend on the slot opening materials. The finite-element analyses are experimentally validated. [ABSTRACT FROM PUBLISHER]

An author index for the 2011 issue of "IEEE Transactions on Industry Applications" is presented.

A novel E-core switched-flux permanent-magnet (SFPM) brushless machine is proposed, and its electromagnetic performance is compared with that of the conventional SFPM brushless machine. The operation principle of the E-core SFPM machine will be first described, and the influence of stator and rotor pole number combinations is investigated, while the electromagnetic performance of the optimized E-core SFPM machine is predicted by finite-element analyses and validated by experiment. It is shown that the number and volume of magnets in the E-core SFPM machine is significantly reduced, only half of that in the conventional machine, while the phase back electromotive force and torque of the E-core machine are \sim 15% larger than those of the conventional machine. [ABSTRACT FROM AUTHOR]

The influence of stator and rotor pole numbers, viz. 6/5, 6/7, 12/10, 12/11, 12/13, and 12/14 stator/rotor poles, etc., on the electromagnetic performance of three-phase flux-switching permanent-magnet (FSPM) machines with all and alternate poles wound is investigated in this paper. It shows that the back-EMF waveform, winding inductance, unbalanced magnetic force, and torque density in an FSPM machine are all significantly affected by the stator and rotor pole numbers and winding configurations, as confirmed by both finite-element analyses and measurements. [ABSTRACT FROM AUTHOR]

Flux-switching permanent-magnet (FSPM) brushless machines have attracted considerable interest as a candidate machine technology for applications requiring high torque density and robust rotors. To date, published findings have focused exclusively on single- and three-phase FSPM machines. This paper investigates FSPM brushless machines of higher phase numbers by means of a detailed comparison of the electromagnetic performances of three-, four-, five-, and six-phase variants within the specific context of aerospace machine. Machines having both all poles and alternate poles wound are investigated, with the latter offering scope to reduce mutual coupling between phases so as to achieve improved fault tolerance. The finite-element (FE)-predicted electromagnetic performances in both machines, such as electromotive force waveform, winding inductance, cogging torque, and static torque, are validated by the experiments made on a small-scale five-phase FSPM machine. The nature of the machine specification requires that consideration must be given to mechanical stress in the rotor and the tradeoff with electromagnetic design considerations, notably the degree of rotor saliency which can be incorporated. Therefore, a mechanical FE study of the rotor mechanical stresses of multiphase FSPM machines is also comparatively assessed. [ABSTRACT FROM AUTHOR]

An author index for the 2007 issue of the "IEEE Industry Applications Society Publications" is presented.