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This article proposes an accurate harmonic current suppression strategy for direct current (dc)-biased VRMs based on adaptive notch filter (ANF) to reduce torque ripple and power loss. A new harmonic reference frame is proposed in dq-axis and combined with ANF, thus harmonic currents are accurately extracted and analyzed. Furthermore, a phase-shift strategy is proposed for dc-biased VRMs, realizing precise compensation of harmonic voltages. The proposed ANF-based harmonic currents suppression strategy has a better performance in harmonic suppression and dynamic response and is suitable for a wider speed range in comparison with traditional harmonic suppression control strategy. What is more, the parameter design of the proposed method is easier compared with traditional method. Finally, the conclusions are verified by experimental results. [ABSTRACT FROM AUTHOR]

High-speed machines with a solid rotor or a high-strength retaining sleeve could offer design and performance advantages. For a specific application, if the use of a high-strength nonmagnetic metallic retaining sleeve is more advantageous than a nonmetallic (e.g., carbon fiber) one, one needs to evaluate the eddy-current losses due to armature reaction space and time harmonics and/or tooth ripple, as they can be significant. This problem is aggravated furthermore in fractional-slot concentrated-winding machines due to their inherent sub- and super nonsynchronous MMF harmonic components. In this paper, the impact of the number of phases is quantified to help design a lower eddy loss rotor sleeve for a high-speed surface-mounted permanent-magnet rotor machine with fractional-slot concentrated armature winding, FSPCW-SPM. The goal of this paper is to provide a general method for laying out preferred FSPCW configurations. Also, a general method for screening and choosing the optimal slot/pole combinations is presented. Index Terms--Concentrated windings, conducting sleeve, flux weakening, fractional-slot windings, losses, number of phases, permanent-magnet (PM) synchronous machine, surface, surface PM (SPM) machine.

A novel machine family--the dual-rotor, radial-flux, toroidafiy wound, permanent-magnet (RFTPM) machine--has been proven in a previous paper to be able to improve the machine efficiency and boost the torque density. This paper will present the key design equations and design procedure of the RFTPM machines, analyze parameter effects on machine performance, and give design guidelines to achieve specific design objectives. In addition, finite-element analysis is employed to prove the effectiveness of the design equations and find the machine overload capability. Experimental measurements of a prototype, which match the design specifications well, verify the effectiveness of the design equations. Index Terms--Parameter effect analysis, permanent-magnet (PM) machine design, radial-flux, toroidally wound, permanent-magnet (RFTPM) machine.

In this paper the magnetic characteristics of surface-mounted permanent-magnet machines are analyzed and modeled. The air-gap and zigzag leakage fluxes are analytically expressed in terms of the magnetic material properties and the motor dimensions. Both factors are essential quantities for the accurate prediction of the flux distribution within the machine and of the machine torque. Therefore, they are desired for the purpose of machine design and optimization. In order to evaluate the validity of the proposed models, the finite-element method (FEM) analysis is used. The results show that the errors between the FEM results and analytical predictions are less than 7% for the nonsaturated tooth flux and less than 17% for the saturated case. Finally, the models are applied to a novel permanent-magnet machine design. Index Terms--Air-gap leakage flux, permanent-magnet (PM) machine, PM machine design, zigzag leakage flux.

A novel machine family--dual-rotor, radial-flux, toroidally wound, permanent-magnet (RFTPM) machines--is proposed in order to substantially improve machine torque density and efficiency. After the principles of operation, configurations, and features are discussed, the machine design and optimization guidelines are given. A prototype has been designed, built, and tested. The measured torque density of the prototype, which well matches the design value, is almost three times of that of the induction machine with the same power of 3 hp and speed. Meanwhile the efficiency is still kept high and the material cost is kept low by using ferrite magnets. Three novel approaches are proposed to reduce the cogging torque in the RFTPM machines, whose validity is verified by finite-element analysis results and experimental measurements. Index Terms--Cogging torque, electrical machine optimization, permanent-magnet (PM) machine design, radial-flux, toroidally wound, permanent-magnet (RFTPM) machines, toroidal windings.

Thrust force ripple, including no-load detent force and electromagnetic thrust ripple, worsens the precision of the linear permanent magnet machine (LPMM) control system. This article focuses on the elimination of electromagnetic thrust ripple caused by the finite length of the LPMM mover core. On the basis of the asymmetrical current controller for suppression of thrust ripple, the observation of asymmetry plays an important role. The extraction strategy, including the extraction of fundamental frequency current/voltage symmetrical components and an observer for positive- and negative-sequence back electromotive force (EMF), is derived. Compared with off-line data, the proposed control strategy has wider application. Experimental results based on an LVPMM are presented. It verifies that the asymmetrical current control strategy based on the back EMF observer reduces electromagnetic thrust ripple by more than 66%. [ABSTRACT FROM AUTHOR]

This article proposes a dual-inverter pulsewidth modulation (PWM) scheme for dc-biased vernier reluctance machines (dc-biased-VRMs) with reduced switching frequency capable of zero-sequence current regulation. The dc-biased-VRM utilizes the additional dc bias current in armature winding to construct the rotor flux. To regulate the dc bias current, two sets of three-phase inverters with common dc bus are used to provide dc current flow path. In each switching cycle, the number of switching actions is doubled compared with the conventional three-phase inverter. There is still a certain optimization space for adjusting the dc bias current and reducing the switching loss. The proposed scheme reconfigures the zero voltage vector based on the discontinuous PWM (DPWM) scheme, it effectively reduces the switching actions, thus reducing the switching frequency and ensuring the low switching loss of the inverter. In addition, an inserted zero voltage vector regulation method is associated with the proposed DPWM scheme, and it assures the zero-sequence current regulation ability. Besides, by adopting complementary zero voltage vector distribution in odd and even sectors, the balanced voltage stress of upper and lower switching devices in each bridge arm is realized. The proposed dual-inverter PWM scheme does not require any additional devices, and it provides an effective solution to improve the efficiency of the dc-biased-VRM drive system. Finally, the effectiveness of the proposed scheme is verified experimentally. [ABSTRACT FROM AUTHOR]