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Permanent-magnet (PM) magnetization state estimation is important both for torque control and monitoring in conventional permanent-magnet synchronous machines (PMSMs). Furthermore, this can be critical for variable flux machines (VFMs). Use of high-frequency signal injection methods for PM magnetization state estimation in NdFeB magnets has already been proposed. These methods make use of the variation of the PM high-frequency resistance with the PM magnetization state due to the magnetoresistive effect. This paper addresses the generalization of magnetization state estimation using high-frequency signal injection to other types of magnets like SmCo and ferrite, as well as to other magnet structures, e.g., isolated and nonisolated segmented magnets. Use of the magnetoresitive effect for the detection of irreversible/reversible PM demagnetization will also be shown to be viable. [ABSTRACT FROM PUBLISHER]

In this paper, a vernier motor with a spoke permanent-magnet (PM) structure instead of a surface PM is proposed in order to obtain higher power factor (PF) and flux density. However, upon investigating this structure with a single gap, unique effects that virtually eliminate the vernier effect are analytically identified. To avoid these effects and improve the PF, a spoke PM vernier motor with a double gap is then proposed. Analytic equations for back electromotive force and the PF are then derived for this motor in terms of various geometric factors such as the numbers of magnets and winding poles, the magnet thickness, etc. For a case study, the practical achievable maximum power and PF are calculated and verified with accurate simulations. [ABSTRACT FROM AUTHOR]

This paper presents a semicircular tubular linear machine model, which is called a circular shaft motor (CSM), with trapezoidal magnets. For a conventional CSM system, the stator is difficult to construct as designed, and the thrust characteristics are not high enough. The proposed CSM model includes trapezoidal magnets that are magnetized in the axial direction. This structure can facilitate the construction of the stator and decrease the thrust ripple. In addition, the magnetic flux characteristics are shown as new results of a CSM. Magnetic field is related to thrust characteristics closely. By investigating magnetic distribution characteristics, it is shown that the proposed model can improve magnetic field characteristics. In this paper, the structure of the proposed CSM model is described. The improvement in the thrust characteristics is verified by magnetic field analysis. The thrust characteristics of the proposed CSM system are verified in a thrust characteristics test. The magnetic flux characteristics of the proposed CSM system are compared with those of a conventional CSM system to evaluate the thrust characteristics. [ABSTRACT FROM PUBLISHER]

Linear machines are currently considered as viable candidates for direct-drive wave and free-piston energy converters. This paper is devoted to an approach based on a magnetic equivalent circuit (MEC), which is also called lumped circuit, dedicated to the modeling and sizing of a tubular linear permanent-magnet synchronous machine (T-LPMSM). The proposed approach considers, in a first step, the cancelation of the end-effect phenomenon. To do so, a dedicated design procedure, consisting in 1) achieving a $2\pi/3$-shift between the armature phase flux linkages by selecting a fractional ratio of the stator pole pitch to the mover one and 2) balancing the amplitudes of the phase flux linkages by extending the stator magnetic circuit with teeth of appropriate dimensions, is firmly applied on two basic T-LPMSM topologies using a dedicated MEC. Then, an investigation of the influent sizing parameters on the force production capability of the initial concept is carried out. The MEC-based prediction of the force requires the incorporation of the mover displacement, yielding the so-called “position varying MEC” on one hand and the armature magnetic reaction on the other hand. The finite-element analysis of the armature phase flux linkages and the developed force enable the validation of the results yielded by the established MECs. [ABSTRACT FROM AUTHOR]

This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low-speed high-force linear motion of a translator into a high-speed low-torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17-kN demonstrator and a simplified motor model showed an efficiency of only 80% at low load; however, it was expected that the efficiency should be above 95%. For understanding and future optimization, a detailed study of the loss in the MLS is presented with the aim of identifying and segregating various loss components that was not accounted for in previous results. This is done through theoretical loss calculations and various experiments. It is concluded that the linear guide is the dominating loss component in the MLS demonstrator, whereas the losses in the axial thrust bearing is not as dominant as expected; furthermore, an efficiency above 94% was measured. [ABSTRACT FROM PUBLISHER]