Search results

The purpose of this paper is to minimize the torque pulsation in Halbach array permanent magnet synchronous machines (PMSMs).

Because of its specific structure, the cogging torque influences the main part of the torque pulsation in a Halbach array PMSM. In this paper, first it is shown that the conventional magnet skewing method does not have a significant effect on the torque pulsation in this motor, and then an improved skewing method with fewer skewing steps is proposed. In this method permanent magnet segments are placed sinusoidally, with two‐step skewing along the rotor. Generalization with different combinations of slots and poles is considered for a Halbach array PMSM.

Using a detailed finite element method (FEM) it was found that with the proposed technique the cogging torque factor is reduced to as low as 8 percent, while the average value of the torque is maintained near the machine nominal average torque.

Halbach array PMSMs are very good candidates for high dynamic performance applications such as aerospace applications due to their high acceleration and deceleration features. This technique also resolves the mechanical vibration and acoustic noise issues, which are caused by torque pulsation and significantly affect machine performance.

The originality of this paper lies in the FEM results. Since Halbach array PMSMs have a special structure it was shown that the conventional skewing method does not work well for this machine. The new proposed technique has a significant effect on the torque pulsation.

The purpose of this paper is to investigate the impact of the stator core design for a surface permanent magnet motor (SPMM) on the cogging torque profile. The objective is to show how the cogging torque of this type of motor can be significantly reduced by implementing an original compound technique by skewing stator slots and inserting wedges in the slot openings.

At the beginning generic model of a SPMM is studied. By using FEA, for this idealised assembly, characteristics of cogging and electromagnetic torque are simulated and determined for one period of their change. Afterwards, actual stator design of the original SPMM is described. It is thoroughly investigated and the torque characteristics are compared with the generic ones. While the static torque is slightly decreased, the peak cogging torque is almost doubled and the curve exhibits an uneven profile. The first method for cogging torque reduction is skewing the stator stack. The second technique is to insert wedges of SMC in the slot openings. By using 2D and 2 1/2D numerical experiment cogging curves are calculated and compared. The best results are achieved by combining the two techniques. The comparative analyses of the motor models show the advantages of the proposed novel stator topology.

It is presented how the peak cogging torque can be substantially decreased due to changes in the stator topology. The constraint is to keep the same stator lamination. By skewing stator stack for one slot pitch 10° the peak cogging torque is threefold reduced. The SMC wedges in slot opening decrease the peak cogging almost four times. The novel stator topology, a combination of the former ones, leads to peak cogging of respectable 0.182 Nm, which is reduced for 7.45 times.

The paper presents an original compound technique for cogging torque reduction, by combining the stator stack skewing and inserting SMC wedges in the slot openings.

To provide a general framework for the electromagnetic analysis of axial flux motors and generators.

The procedure is based on the solution of Maxwell's equation in a cylindrical frame. All field sources (permanent magnets, windings) are subdivided into filamentary windings. The expansion of the 2D air‐gap magnetic field into a Fourier series is computed at every radius. The contributions of the harmonics are then added to achieve the expressions of the stator and rotor flux densities, back emf and developed torque. Slotting and skewing are taken into account also.

The model can be written in a compact form by introducing a generalisation of the space vectors theory. The analysis is proved to be in accordance both with the finite element analysis and with experimental data.

The model does not take into account eddy‐currents and non‐linearities. It does not take into account also specifically 3D phenomena, as the radial components of the flux densities.

The analysis is of practical interest from the standpoint both of control and of machine design. In this latter occurrence, it represents a valid alternative over computationally heavier 3D finite elements models.

Although the procedure is partly based on previous analyses, it is original in the way it exploits the basic theory in order to introduce skewing, slotting, and finite length of the iron. With respect to other models introduced so far, the present one is more compact in the end, its parameters can be easily computed and their physical meaning is easily understood.

Evaluating the multiphysics performance of an electric motor can be a computationally intensive process, especially where several complex subsystems of the motor are coupled together. For example, evaluating acoustic noise requires the coupling of the electromagnetic, structural and acoustic models of the electric motor. Where skewed poles are considered in the design, the problem becomes a purely three-dimensional (3D) multiphysics problem, which could increase the computational burden astronomically. This study, therefore, aims to introduce surrogate models in the design process to reduce the computational cost associated with solving such 3D-coupled multiphysics problems.

The procedure involves using the finite element (FE) method to generate a database of several skewed rotor pole surface-mounted permanent magnet synchronous motors and their corresponding electromagnetic, structural and acoustic performances. Then, a surrogate model is fitted to the data to generate mapping functions that could be used in place of the time-consuming FE simulations.

It was established that the surrogate models showed promising results in predicting the multiphysics performance of skewed pole surface-mounted permanent magnet motors. As such, such models could be used to handle the skewing aspects, which has always been a major design challenge due to the scarcity of simulation tools with stepwise skewing capability.

The main contribution involves the use of surrogate models to replace FE simulations during the design cycle of skewed pole surface-mounted permanent magnet motors without compromising the integrity of the electromagnetic, structural, and acoustic results of the motor.

The purpose of this paper is to present novel analytical expressions which describe the 3D magnetic field of arbitrarily magnetized triangular‐shaped charged surfaces. These versatile expressions model that the field of triangular‐shaped permanent magnets (PMs) are very suitable to model skewed slotless machines.

The analytical 3D surface charge method is normally used to provide field expressions for PMs in free space. In this paper, the analytical surface charge integrals are analytically solved for charged right‐triangular surfaces. The resulting field is compared with that obtained by finite element modeling (FEM) and subsequently applied in two examples.

The comparison with FEM shows that the 3D analytical expressions are very accurate and exhibit very low‐numerical noise. These fast‐solving versatile expressions are therefore considered suitable to model triangular‐shaped or polyhedral‐shaped PMs.

The surface charge method assumes that the relative permeability is equal to 1 and therefore soft‐magnetic materials need to be modeled using the method of images. The PMs are assumed to be ideal in terms of homogeneity, magnetization vector, permeability, demagnetization, and geometrical tolerances.

Many applications, such as the subclass of slotless synchronous linear actuators with a skewed PM structure and planar magnetic bearings, are very suitable to incorporate this modeling technique, since it enables the analysis of a variety of performance data.

As an addition to the common 3D analytical field expressions for cuboidal or cylindrical PMs, this paper presents novel expressions for magnets having triangular surfaces.

This paper demonstrates how the 3D edge element method can be applied to the analysis of permanent magnet motors. The edge element method using the vector magnetic potential has been used. Special attention has been paid to the analysis of systems with inhomogeneously magnetized permanent magnets. The magnets are not skewed and are mounted on a cylindrical laminated rotor. Calculations have been performed for different magnet widths and different distribution of the magnetization vector. Brushless motors with radially and inhomogeneously magnetized magnets have been compared.

A fundamental disadvantage of three‐dimensional finite element (FE) simulations is high computational cost when compared to two‐dimensional models. The purpose of this paper is to present an approach to minimize the computation time by achieving the same simulation accuracy.

The applied approach for avoiding high computational cost is the multi‐slice method. This paper presents the adoption of this method to a tubular linear motor.

It is demonstrated that the multi‐slice method is applicable for tubular linear motors. Furthermore, the number of slices and thereby computation time is minimized at the same accuracy of the simulation results.

The results of this paper offer a faster computation of skewed linear motors. At this juncture, the results are independent from the deployed FE solver.

The methods developed and proved permit a faster and more accurate design of tubular linear motors.

This paper gives an overview of the design, manufacturing and testing of a high‐speed (16,000 rpm and 30 kW) AFPM synchronous machine, which is mounted inside, and as an integral part of, a flywheel. This system will subsequently be used for transient energy storage and ICE operating point optimization in an HEV. The paper focuses on the major design issues, particularly with regard to the high rotational speed, and investigates the loss mechanisms which are apparent therein, e.g. iron losses, rotor losses, and friction losses. The paper describes the high‐speed testing facility and includes measured results, which will be compared to calculated values.

The paper aims to present the hybrid excited claw pole generator design, simulation and experimental results. The prototype has claw poles on two rotor sections, between which an excitation coil is located. The innovation of this machine is permanent magnets location on claws of one part of the rotor. The paper presents construction of the machine and analysis of the current in the excitation control coil influence on the electromagnetic torque, cogging torque and back-emf values. Presented studies enabled the determination of the torque and the back-emf for both: the strengthening and the weakening of magnetic field.

In the study, finite element analysis was used to perform simulation research. Then, based on the simulation studies, an experimental model was built. The paper also presents selected experimental results.

Achieved results show that the proposed machine topology allows to eliminate the disadvantages mentioned in paper, i.e. necessary to introduce special areas inside the machine to limit magnetic flux leakage or its complicated construction.

The obtained cogging torque values and back-emf pulsation are still relatively high. In the near future, some of known techniques for reducing these pulsations can be applied, including the use of magnetic wedges, changing shapes of rotor’s poles and/or skewing of permanent magnets.

The proposed solution can be used in wind turbines as a generator.

The paper presents an original design of a new construction of a hybrid-excited claw pole machine and also an excitation current influence on cogging torque and back-emf values.

This paper aims to the improvement of permanent magnet shape in the popular permanent magnet synchronous machine (PMSM) is proposed in this paper in view to mitigate cogging torque magnitude and torque ripple.

A two-dimensional exact analytical approach of magnetic field distribution is established for the PMSM considering magnet shape and slot opening. The optimal magnet shape is constituted of small number of layers stacked radially. The thickness of each magnet layer is considered equal to about one mm or more; however, a parametric study was performed to determine pole pitch ratio value. The finite element method is used to validate the analytical results.

Cogging torque peaks and torque ripples can be mitigated significantly more than 90 per cent compared to results issued from machine having classical magnet shape. Raising the number of magnet layers can give better results. The results of this paper are compared also with those issued from the machine having sinusoidal magnet shape and give a good solution.

A new technique for cogging torque and torque ripple mitigation is proposed in this paper by changing permanent magnet shape. The proposed final magnet shape is constituted of a set of stacked and well-dimensioned layers relative to the opening angle.