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Early magnetic-geared motors have a high transmission torque density. However, the torque due to the coil is low because the permanent magnets in the stator become a large magnetic resistance when the current is applied to the coil. The purpose of this paper is to propose magnetic-geared motors which have a high transmission torque density and torque due to the coil. In addition, the proposed magnetic-geared motors are compared with past magnetic-geared motors and the effectiveness is verified by using finite element analysis.

A new magnetic-geared motor which has permanent magnets in the stator slot are proposed. The torque due to the coil increases by removing permanent magnets at the tip of the stator of past magnetic-geared motors. The permanent magnets placed in the stator slots are all magnetized to the outward direction and then the stator teeth are all magnetized to the inward direction. The maximum transmission torque and torque constant are compared.

The proposed magnetic-geared motor has a slightly smaller maximum transmission torque than the early magnetic-geared motors. However, the maximum transmission torque of the proposed magnetic-geared motor is high enough for practical uses. The torque due to the coils is higher than the early magnetic-geared motors.

The proposed magnetic-geared motor has originalities in its structure, especially in the permanent magnets in the stator slots.

The purpose of this paper is to propose a magnetic‐geared motor with permanent magnets only on the high‐speed rotor as a solution to the problems of magnetic gears. Magnetic gears have some advantages such as no mechanical loss and maintenance‐free operation that are not observed in conventional mechanical gears. Furthermore, they have inherent overload protection. A novel structure which the magnetic gear is integrated with the brushless motor (magnetic‐geared motor) was proposed by Atallah et al. This magnetic‐geared motor is based on the magnetic gear which consists of a high‐ and low‐speed rotor, and a stator. Although this magnetic‐geared motor has a high‐torque density, problems with manufacturing and cost exist because multi‐pole permanent magnets are mounted on the high‐speed rotor and stator.

A magnetic‐geared motor with permanent magnets only on the high‐speed rotor was proposed and its operational principle was described. The cogging torque characteristics were mathematically formulated and the authors ascertained that the cogging torque contains components of multiples of 60th order. In order to verify the order of the cogging torque, the 3‐D finite element method analysis was conducted and measurements on a prototype were carried out.

The 60th component and its multiples were observed in the computed and measured cogging torque waveform. However, the cogging torque characteristics, especially the order of the cogging torque on the low‐speed rotor, have not been clarified.

In the near future, cogging torque reduction methods will be proposed, and verified by conducting 3‐D FEM analyses and carrying out measurements on a prototype. Furthermore, the torque characteristics when an electrical current is applied to the coils and the eddy‐current loss characteristics will be verified.

This paper aims to introduce a new structure for coaxial magnetic gears.

The study discusses the design and electromagnetic modeling of a triple-speed coaxial magnetic gear (TSCMG) for three different levels of torques in special applications such as wind energy conversion and electrical vehicles. The proposed TSCMG consists of inner, middle and outer rotor, which has one rotor more than its conventional counterpart. The suggested TSCMG’s related equations such as transform ratio and torque are calculated, then TSCMG is simulated in a finite element environment. A comprehensive study has been done on TSCMG, and results are compared with two other magnetic gears with the same volume but two speeds.

The obtained results show that the proposed structure for TSCMGs is significantly practical and applicable in higher ranges of torques. Finally, an experimental TSCMG is prototyped to verify the results.

The achievements are excellent and confirm that TSCMG can be used as powerful equipment in a wide range of application like permanent wind turbines to generate electricity in 24 h per every single day.

This paper aims to propose a new magnetic-geared motor (MGM) which can easily increase the gear ratio up to approximately several hundred. The operational principle is described, and the relationship between the maximum transmission torques of each layer of the differential harmonic magnetic gear is investigated using a mathematical model and finite element method (FEM).

The operational principle and maximum transmission torque are described using a mathematical model. The FEM is used to investigate the operational principle and torque characteristics.

As the proposed model can realize a larger gear ratio than the conventional model, the torque constant can be approximately 100 times as large as that of the conventional model.

The proposed and conventional models have the same shape stator, and it is not optimized.

The relationship between the maximum transmission torques of each layer is described, and this helps the design of a differential type MGM.

Aims to show that efficiency and accuracy of integral equation methods (IEMs) in combination with the fast multipole method for the design of a novel magnetic gear.

A novel magnetic gear was developed. Magnetic fields and torque of the gear were simulated based on IEMs. The fast multipole method was applied to compress the matrix of the belonging linear system of equations. A computer cluster was used to achieve numerical results within an acceptable time. A three‐dimensional post‐processing and visualization of magnetic fields enables a deep understanding of the gear.

IEMs are very well suited for the numerical analysis of a magnetic gear. Especially, the treatment of the air gap between the rotating components, which move with significant varying velocities, is relatively easy. Furthermore, a correct computation and visualization of flux lines is possible. A magnetic gear is advantageous for high rotational velocities.

A quasi static numerical simulation has sufficed for an understanding of the principle of the magnetic gear and for the development of a prototype.

IEMs are very suitable for the analysis of complex problems with moving parts. Nowadays, the efficiency is very good even for large problems, since matrix compression techniques are well‐engineered.

The design of a novel magnetic gear is discussed. Well‐known techniques like IEMs, fast multipole method and parallel computing are combined to solve a very large and complex problem.

The purpose of this paper is to investigate the transient performance of an induction machine coupled with a magnetic gear for industrial applications with low speed and high torque requirements. This new solution increases mechanical reliability and does not require maintenance and lubrication. The main objective is to study the direct-on-line starting ability of the electrical machine and its stability regarding a sudden change for the load torque.

A nonlinear analytical model for the induction machine and the magnetic gear is first developed. The model is then linearized around an operating point to obtain the transfer function between the load angle and the electromagnetic torque from which an analytical expression for the mechanical resonant frequency is obtained.

It is shown that the direct on-line starting is possible, if the moment of inertia of the load is not greater than a maximum value. Moreover, it is demonstrated that this new system present inherent overload protection.

A new high-performance direct-on-line starting electrical machine is proposed to achieve high torque at low speed without mechanical gear to improve reliability and reduce maintenance.

In this paper, a computational model of a coaxial magnetic gear (MG) design with viscose ferrofluid between rotors is proposed. Viscose ferrofluid is used to decrease the magnetic reluctance and therefore creates higher magnetic torque. However, viscose friction of ferrofluid is undesirable and must be minimised in this particular application. MG is supposed to operate under low rotational speeds, where the dynamic viscose friction is very low, and the effects of the viscose ferrofluid over the MG’s efficiency must be estimated. The paper aims to analyze the performance of MG with viscose ferrofluid and to estimate the MG efficiency by computational model using finite element method (FEM).

An MG design with viscose ferrofluid between the outer low-speed rotor and modulating steel segments was modelled as a coupled transient magnetic field problem and a kinematic model with viscous friction coefficients derived from a previously computed fluid dynamics model.

The proposed computational implementation is suitable for homogeneous magnetic fluid modelling in electromagnetic actuators and rotational machines. The results regarding power and torque transmission of MG were obtained by coupled finite element modelling. The efficiency of MG significantly decreased due to ferrofluid friction.

The described MG design with viscose ferrofluid is a novel device with new operational characteristics, and new results for the effects of viscose ferrofluid friction in the outer magnetic field over the MG efficiency are estimated.

The purpose of this research is to achieve a novel magnetic nutation drive for an industry robotic wrist reducer.

A novel magnetic nutation drive is proposed, and the structure and principle of the designed magnetic nutation drive are described in this study. Three-dimensional finite element analysis is used to compute the magnetic and torque of the magnetic nutation drive. Furthermore, a prototype of this novel magnetic nutation drive device is developed with 3D printing technology and tested to verify the feasibility of the proposed structure and principle.

The simulation and experimental results indicated that the proposed magnetic nutation drive device could meet the desired specifications, and that this novel magnetic nutation drive device successfully realized the non-contact transmission ratio of 105:1 required for a robotic wrist reducer.

This novel magnetic nutation drive is low-cost and easy to make and use, and which provides the non-contact transmission ratio of 105:1 required for a robotic wrist reducer.

For the first time, this research applies the permanent magnet drive technology to nutation drive and puts forward a new non-contact nutation drive mode. The novel drive mode can solve some problems of the traditional mechanical contact nutation drive, such as vibration, friction loss, mechanical fatigue and necessity of lubrication. The proposed non-contact nutation drive device can achieve a high reduction ratio with compact structure and can be suitable for industry application.

Wind energy has matured to a level of development at which it is ready to become a generally accepted power generation technology. The aim of this paper is to provide a brief review of the state of the art in the area of electrical machines and power‐electronic systems for high‐power wind energy generation applications. As the first part of this paper, latest market penetration, current technology and advanced electrical machines are addressed.

After a short description of the latest market penetration of wind turbines with various topologies globally by the end of 2010 is provided, current wind power technology, including a variety of fixed‐ and variable‐speed (in particular with doubly‐fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) supplied with partial‐ and full‐power converters, respectively) wind power generation systems, and modern grid codes, is presented. Finally, four advanced electrical‐machine systems, viz., brushless DFIG, open winding PMSG, dual/multi 3‐phase stator‐winding PMSG and magnetic‐gear outer‐rotor PMSG, are identified with their respective merits and challenges for future high‐power wind energy applications.

For the time being, the gear‐drive DFIG‐based wind turbine is significantly dominating the markets despite its defect caused by mechanical gears, slip rings and brush sets. Meanwhile, direct‐drive synchronous generator, especially utilizing permanent magnets on its rotor, supplied with a full‐capacity power converter has become a more effective solution, particularly in high‐power offshore wind farm applications.

This first part of the paper reviews the latest market penetration of wind turbines with a variety of mature topologies, by summarizing their advantages and disadvantages. Four advanced electrical‐machine systems are selected and identified by distinguishing their respective merits and challenges for future high‐power wind energy applications.

This paper aims to show a complete optimization tool that can be used for the design of coaxial magnetic gears. In the first part, the paper deals with the semi-analytic modelling of these machines and also discusses how to reduce the computational efforts. In the second part, an optimization algorithm is adopted for finding the Pareto optimal geometries.

The machine is subdivided into a set of domains according to their physical and geometrical properties, and the potential distribution is found semi-analytically in them under some simplifying hypothesis. A loss estimation is performed for both ferromagnetic and permanent magnet regions. A stochastic differential evolution (DE) algorithm for multi-objective constrained problems is then applied.

It is shown that the presented design tool gives results in accordance to finite element method (FEM)-based analysis keeping the advantages of robustness and simplicity of the analytical methods. The DE-based strategy performs well on the magnetic gear optimization problem.

The proposed tool appears to be a good starting point when designing coaxial magnetic gears. The optimal Pareto points can be used as initial seeds of FEM-based optimizations, resulting in a cheaper computational method with respect to a full FEM optimization.

This paper takes inspiration from recent works on magnetic gear modelling and completes the design procedure with a suitable efficiency estimation. The paper also shows how to use mature optimization strategies to solve the constrained multi-objective magnetic gear design problem.