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Spoke structure can increase the torque density of coaxial magnetic gear (CMG). However, the outer rotor can produce a large number of magnetic leakages. To improve the utility of PMs, a novel magnetic gear was proposed in this paper. The structure of the auxiliary flux modulator is a slotted iron yoke, and the slot angle is same as the stationary ring. Among, the permanent magnets (PMs) of inner rotor are adopted uneven block structure to improve air gap flux density. At the same time, the stationary ring adopts high-temperature superconducting (HTS) bulks, replacing the epoxy resin. In addition, Genetic algorithm (GA) is applied to calculate the optimal parameters of the proposed CMG. Finally, the air gap flux density and output torque of the magnetic gear a compared by the finite element method. The results show that the output torque of the proposed magnetic gear is effectively improved. [ABSTRACT FROM AUTHOR]

This article focuses on a novel design of rotor topology for an interior permanent magnet superconductive radial flux magnetic gear to achieve sinusoidal air-gap flux density and lower cogging torque. The method is based on optimization of buried magnet's pole shape in a radial flux structure, modified by using a pulsewidth modulation technique and variable air-gap length applying the supershape formula on the iron core of the inner rotor. The unsatisfied harmonic contents of the air-gap flux density can be reduced with this technique while the main harmonic component and average torque can be maintained or enhanced. The key idea is to set the distribution of the air-gap flux density by segmenting the pole shoe into several elementary blocks and predetermined grooves based on a special curve. Superconductor bulks are placed between pole pieces of modulator ring to improve the flux-modulation effect and decrease cogging torque percentage. The computation of the block sizes and effects of variation of supershape formula parameters are performed by solving a constrained optimization problem. Results show that the radial air-gap flux density harmonics are eliminated, leading to almost sinusoidal air-gap flux density and lower level of cogging torque. [ABSTRACT FROM AUTHOR]

The novel linear flux switching permanent magnet machine with a three-dimensional magnetic circuit is proposed in this paper, which is suitable for aerospace, missile launch, and other fields, benefiting from high thrust force and low cost. First, the basic structure and working principle of the machine are introduced. Second, the equivalent magnetic circuit model considering the variable reluctance is established and the equations are put forward for magnetic analysis. Third, the simplified finite element model is performed to calculate the field distribution, the air-gap flux density, the flux linkage of winding, and the back electromotive force. Finally, a prototype is constructed and experiments show a good agreement with analysis. [ABSTRACT FROM AUTHOR]

This study considers the reduction of the force ripple of a permanent magnet linear synchronous machine (PMLSM). The PMLSM has a relatively large magnetic air gap. Therefore, a slotted type of stator structure is generally employed. Furthermore, the detent force, which is caused by the energy imbalances owing to the interaction between the teeth-slot structures and the permanent magnets, must be minimized for better start-up performance. Therefore, in this study, the addition of the auxiliary teeth and teeth notching are employed to reduce the detent force. In particular, the influence of the auxiliary teeth and notching on the detent force is analyzed, and an experiment is performed to verify the proposed design. [ABSTRACT FROM AUTHOR]

A vernier permanent magnet (VPM) machine using high-temperature superconducting (HTS) winding for dual excitation is proposed for wind power generation. The proposed VPM machine adopts the parallel hybrid excitation configuration, the stator consists of an identical tooth pair connected together by the stator yoke and the rotor contains two sets of consequent-pole permanent magnets joined together by the rotor yoke. The armature winding is located at the stator main slots while the field winding using HTS coils is wound on the stator yoke. With the benefit of the HTS field winding, the air-gap flux can be flexibly adjusted by controlling the magnitude of the dc current. Therefore, the machine performance is improved to cope with different operating conditions. [ABSTRACT FROM PUBLISHER]

The dual-memory machine utilizes two kinds of permanent magnets (PMs), namely the aluminum-nickel-cobalt (Al-Ni-Co) and neodymium-iron-boron (Nd-Fe-B) materials, to provide effective flux-mnemonic feature. Namely, the Al-Ni-Co PM can be forward or backward magnetized in such a way that it can coordinate with the Nd-Fe-B PM to online tune the air-gap flux density. Based on the proposed DC-excited memory machine structure, the magnet proportioning between the Al-Ni-Co PM and the Nd-Fe-B PM is analysed. Both simulation and experimentation are carried out to verify the validity of the proposed dual-memory machine design. [ABSTRACT FROM PUBLISHER]

The quantitative interaction body force density was calculated in soft magnetic materials by using a freezing procedure of magnetization and virtual air-gap scheme, which were implemented by using the Finite Element Method. Until now, the virtual air-gap concept has been successfully applied to evaluating contact force and body force density in soft magnetic materials. When the generalized methods, methodologies with virtual air-gap scheme, are introduced, one can have an irregular force field, which seems to be random distribution of body force density. Even though this irregular pattern generates a correct global force and reasonable trend of mechanical deformation, it is quite difficult to predict the resultant deformation by the irregular force field. This irregular force field pattern is originated from the field direction to the finite element edge where the virtual air gap is inserted and an additional strong force arises with the outward normal direction. To remove this irregular pattern and evaluate an interaction body force density, the self-force density by the frozen magnetization should be withdrawn from the total body force density. To verify the proposed method, first, a critical magnetic system, which cannot be solved by the equivalent magnetizing source methods, were tested for evaluating the interaction body force density corresponding to the resultant mechanical deformations. After confirming the interaction force, two additional specific models were tested with the resultant mechanical deformations due to the different local force densities. [ABSTRACT FROM PUBLISHER]

Torque density of a novel dual-rotor, radial-flux multiphase permanent magnet (PM) machine is enhanced by injecting stator current harmonics without increasing stator yoke thickness. In order to enhance a regular PM machine torque capability by injecting harmonic currents, the no-load air-gap flux density should be designed to be trapezoidal, which increases the flux per pole, and results in a thicker stator yoke. However, this drawback can be avoided in a dual-rotor, radial-flux PM machine. In such a dual-rotor PM machine, the main flux can be designed to go directly from the inner rotor poles, to stator inner and outer teeth, then to the outer rotor poles, or reverse, without through the stator yoke. Therefore, the stator yoke thickness is not affected by air-gap flux at all and can actually be reduced to minimum for mechanical reasons . [ABSTRACT FROM PUBLISHER]

This paper introduces a design methodology for a multi-tesla permanent magnet. Normally the permanent magnet is designed to provide the magnetic fields below 2 T. By employing high performance materials and the 3D magnetic circuit design method, a prototype magnet has been built and generates maximum 2.987 T field strength in 0.008 m air gap with less than 20 kg total weight. It is expected a practical, compact and light-weight high field source for NMR, MRI or other instruments. [ABSTRACT FROM PUBLISHER]