Search results

In the present paper the influence of the magnetization patterns of rotor magnets on the performance characteristics of a surface permanent magnet (SPM) motor has been investigated. The purpose of this paper is to show how the electromagnetic and electromechanical characteristics of this type of motor can be significantly changed by applying various magnetization patterns of permanent magnets (PM) on the rotor surface.

First, a survey of possible and most frequently used magnetization patterns for PM motors is presented. The research is focussed on the comparison of performance characteristics and is developed at three levels. The study starts with investigation of a conventional SPM motor having segmented PM, and two magnetization patterns are considered: parallel and radial. As there was no significant difference in motor performance at parallel and radial magnetization, for further investigation only radial magnetization, being more conventional, was considered. In the second step, the counterparts of SPM with two Halbach array configurations, under the constraint of fixed magnet volume, are studied. Finally, detailed comparative analyses of SPM at radial, Halbach 1, and Halbach 2 magnetic patterns are presented. The advantages and drawbacks of the suggested magnetic configurations are then discussed.

The authors have shown how the magnetization pattern of rotor PM can have a substantial impact on the SPM motor performance characteristics. From the analysis of magnetic field properties at various types of magnetization, it is observed that both the shape and the rates of the characteristics, for radial magnetization and Halbach 2 configuration, exhibit similar features. This is because the Halbach 2 array cancels the magnetic flux above the PM – that is, it strengthens the magnetic field in the rotor, and enhances the coupling between the rotor and stator magnetic field. It is worth emphasizing that, because of less saturation of the magnetic core and lower iron loss at Halbach 1 and Halbach 2 magnetization, it is possible to increase the armature current and consequently increase the electromagnetic torque. This finding could be an interesting for further research.

The paper presents an original comparative analysis of the performance characteristics of a surface permanent motor at various magnetization patterns. The novelty of the paper is seen in the introduction of two Halbach magnetization arrays for PM and improvement of the performance characteristics of the analysed motor.

The purpose of this paper is to present a semi‐analytical modeling technique to describe magnetic fields due to PMs in 3D cylindrical structures. The model is based on 2D Fourier series and is applied to model the magnetic field of checkerboard magnetization patterns for rotary‐linear actuators.

The modeling technique based on Fourier series provides a direct solution of the Poisson and Laplace equation by means of separation of variables and is widely used to describe magnetic fields in electromagnetic devices in 2D coordinate systems. In this paper the magnetic scalar potential is used in the Poisson and Laplace equations.

The magnetic field calculated by the semi‐analytical model is compared with that obtained by Finite Element Modeling and shows excellent agreement. The calculation time of the semi‐analytical model is approximately 60 times shorter than that of finite element analysis.

The method as presented in the paper assumes linear material properties, e.g. the non‐linear B‐H characteristics of iron cannot be taken into account. Furthermore, the structure is assumed to be slotless, that is, stator slots or end‐effects cannot be taken into account.

The semi‐analytical modeling technique is applied to checkerboard magnetization patterns for 2‐DoF actuators in this paper. However, it can be applied to a wide range of slotless cylindrical electromagnetic devices.

As an addition to the common 2D modeling by means of Fourier series, this paper extends the applicability to 3D cylindrical structures. Furthermore, a new checkerboard magnetization is presented which can be used in 2‐DoF rotary linear actuators.

The purpose of the paper is to evaluate theoretically and experimentally the static and dynamic characteristics of a single‐phase claw‐pole motor using soft magnetic composite (SMC) for the stator core.

On the basis of the static characteristics, which are measured and obtained from a series of 3D FE magnetostatic solutions, the dynamic characteristics are simulated according to a proposed control strategy. The same strategy is tested in dSpace control environment. Apart from the evaluation of the prototype SMC motor, some study has been made in order to improve the existing motor design.

The static characteristics of the single‐phase claw‐pole motor have been modelled in 3D FE magnetostatic solver, where the rotor position and stator current have been changed. The characteristics compare well with the measurements, while the discrepancy with the cogging torque waveform needs further analyses and experiments to explain the real magnetization pattern of the plastic bounded ferrite magnet‐ring and the influence of magnetic hysteresis. The 3D FE magnetostatic optimization routine shows the maximum quantities for magnetic coupling and static core loss. Furthermore it is used to obtain the improved pole distribution so that the resting position of the unexcited motor co‐aligns at the position of the maximum electromagnetical torque. This is achieved by changing the angular width of claw‐poles. The specific output of the maximum coupling torque from the single‐phase claw‐pole motor can be increased from the recent 0.1 to 0.6 Nm/kg at a temperature rise of 60°. The simulations of dynamical characteristics show a good correlation with the experiments where the same control system in Simulink is applied to the prototype via dSpace. It is practically easier to implement a simple control strategy for the direct current controlled voltage source inverter. A more advantageous control system needs to be applied for the sampled current controller.

The influence of the magnetization of a multi‐pole magnet ring is not considered while computing the static characteristics in 3D FE magnetostatic solver.

The evaluation of the realistic magnetization pattern in the magnet aggravates the proper theoretical evaluation of static characteristics.

The design of a small size powder core motor is faced with the complexity of evaluating properly the static characteristics, while the magnetization pattern is not exactly known. The broad search here is for an efficient tool to visualize the output of the 3D FE optimization for an improved design.

In semi-analytical modeling of spoke-type permanent-magnet (PM) machines (STPMM), the saturation effect is usually neglected (i.e. iron parts are considered to be infinitely permeable) and the PM magnetization is assumed tangential (i.e. magnetization pattern is considered to be tangential-parallel). This paper aims to present an improved two-dimensional (2D) subdomain technique for STPMM with the PM magnetization orientation in quasi-Cartesian coordinates by using hyperbolic functions considering non-homogeneous Neumann boundary conditions (BCs) in non-periodic regions and by applying the interfaces conditions (ICs) in both directions (i.e. t- and θ edges ICs).

The polar coordinate system is transformed into a quasi-Cartesian coordinate system. The rotor and stator regions are divided into primary subdomains, and a partial differential equation (PDE) is assigned to each subdomain. In the PM region, the magnetization orientation is considered in the equations. By applying BCs, the general solution of the equations is determined, and by applying the ICs, the corresponding coefficients are determined.

Using the proposed coordinate system, the general solution of PDEs and their coefficients can mathematically be simplified. The magnetic field and non-intrinsic unbalanced magnetic forces (UMF) calculations have been performed for three different values of iron core relative permeability (200, 800 and ∞), as well as different magnetization orientation values (135 and 80 degrees). The semi-analytical model based on the subdomain technique is compared with those obtained by the 2D finite-element analysis (FEA). Results disclose that the PM magnetization angle can affect directly the performance characteristics of the STPMM.

A new model for prediction of electromagnetic performances in the STPMM takes into account magnetization direction, and soft magnetic material relative permeability in a pseudo-Cartesian coordinate system by using subdomain technique is presented.

This paper deals with the numerical modelling of electromagnetic losses in electrical machines, using electromagnetic field computations, combined with advanced material characterisations. The paper gradually proceeds to the actual reasons why the building factor, defined as the ratio of the measured iron losses in the machine and the losses obtained under standard conditions, exceeds the value of 1.

This paper aims to investigate the magnetostrictive phenomenon in a single electrical steel sheet, which may cause vibration and noise in the cores of transformers and induction motors. A measurement system of magnetostriction is created and the principal strain of magnetostriction is modeled. Furthermore, the magnetostriction property along arbitrary alternating magnetization directions is modeled.

A measurement system with a triaxial strain gauge is developed to obtain the magnetostrictive waveform, and the principal strain is computed in terms of the in-plane strain formula. A three-layer feed-forward neural network model is proposed to model the measured magnetostriction property of the electrical steel sheet.

The principal strain of magnetostriction of the non-oriented electrical steel has strong anisotropy. The proposed estimation model can be effectively used to model the anisotropic magnetostriction with an acceptable prediction time.

This paper develops the neural network combined with fast Fourier transform (FFT) to model the principal strain property of magnetostriction under alternating magnetizations, and its validation has been verified.

Manufacturing processes, such as laminations, may introduce uncertainties in the magnetic properties of materials used in electrical machines. This issue, together with magnetization errors, can cause serious deterioration in the performance of the machines. Hence, stochastic material models are required for the study of the influences of the material uncertainties. The purpose of this paper is to present a methodology to study the impact of magnetization pattern uncertainties in permanent magnet electric machines.

The impacts of material uncertainties on the performances of an interior permanent magnet (IPM) machine were analyzed using two different robustness metrics (worst-case analysis and statistical study). In addition, two different robust design formulations were applied to robust multi-objective machine design problems.

The computational analyses show that material uncertainties may result in deviations of the machine performances and cause nominal solutions to become non-robust.

In this paper, the authors present stochastic models for the quantification of uncertainties in both ferromagnetic and permanent magnet materials. A robust multi-objective evolutionary algorithm is demonstrated and successfully applied to the robust design optimization of an IPM machine considering manufacturing errors and operational condition changes.

The aim of the paper is to provide a simple and reliable hysteresis model for prediction of magnetization curves of a resistance spot welding transformer (RSWT) core, operating in a wide range of flux densities and excitation frequencies.

The hysteresis model considered in the paper is the T(x) description advanced by J. Takács. Three options to extend the model to the dynamic magnetization conditions are considered. The excitation conditions differ from those prescribed by international standards.

The quasi‐static Takács model combined with a fractional viscosity equation similar to that proposed by S.E. Zirka outperforms other considered options. The effect of eddy currents may be considered as a disturbance factor to the frequency‐independent quasi‐static hysteresis loop.

The combined approach yields in most cases a satisfactory agreement between theory and experiment. For highest frequency considered in the paper (1 kHz) excessive “heels” were observed in the modelled loops. This artifact may be reduced by the introduction of a more complicated relationship for the viscous term. Future work shall be devoted to this issue.

The combined Takács‐Zirka model is a useful tool for prediction of magnetization curves of a RSWT core in a wide range of flux densities and excitation frequencies.

The usefulness of the Takács description has been verified in a practical application. The model is able to predict magnetization curves under non‐standard excitation conditions.

Force output is extremely important for electromagnetic linear machines. The purpose of this study is to explore new permanent magnet (PM) array and winding patterns to increase the magnetic flux density and thus to improve the force output of electromagnetic tubular linear machines.

Based on investigations on various PM patterns, a novel dual Halbach PM array is proposed in this paper to increase the radial component of flux density in three-dimensional machine space, which in turn can increase the force output of tubular linear machine significantly. The force outputs and force ripples for different winding patterns are formulated and analyzed, to select optimized structure parameters.

The proposed dual Halbach array can increase the radial component of flux density and force output of tubular linear machines effectively. It also helps to decrease the axial component of flux density and thus to reduce the deformation and vibration of machines. By using analytical force models, the influence of winding patterns and structure parameters on the machine force output and force ripples can be analyzed. As a result, one set of optimized structure parameters are selected for the design of electromagnetic tubular linear machines.

The proposed dual Halbach array and winding patterns are effective ways to improve the linear machine performance. It can also be implemented into rotary machines. The analyzing and design methods could be extended into the development of other electromagnetic machines.

This paper deals with magnetic field calculations and model‐based prediction of electromagnetic torque pulsations in a brushless DC (BLDC) motor.

The impact of a Halbach‐like magnetization and a multipolar excitation of permanent magnets are analysed. The measurement results from the prototype motors are well‐compared with those obtained from the model calculations. It is shown that the cogging torque in the motor with the multipolar excitation of permanent magnets is reduced six times as compared with the conventional BLDC motor.

The proposed method provides high accuracy of the analysis of coupled electromagnetic phenomena. The comparison between measured and calculated values of electromagnetic torque, cogging torque and EMF shows a very good agreement.

Reduction of the machine cogging torque is essential for practical applications of DC motors, in particular in the robotics industry.

This paper shows that multipolar excitation contributes to essential reduction of the cogging torque in a BLDC motor. This is confirmed by high‐quality numerical models of the motor, positively verified in experiments with motor prototypes.