Search results

Non‐linear characteristics, as relations between linked fluxes and currents of individual machine coils, are sought for in the so called circuit models of saturated electrical machines. Their determination can be based on the co‐energy of the magnetic field only, which is a multivariable function of all coil currents and rotor position angle. The author proposes the calculation of co‐energy values at necessary points by the FEM and the interpolation of the results by a suitable multivariable spline function. The functions of linked fluxes are generated as the first derivatives of the spline. This way could be used to separate the circuit calculation from the field calculation when saturated machines are modelled. An example of a wound rotor induction machine is used to show the elementary problems of the calculation of the non‐linear characteristics.

The aim of the paper is to present the approximation methods of the magnetizing characteristics of the salient pole synchronous machines with the fundamental MMF harmonics.

The energy based approach is used to formulate a set of the functions approximating the magnetic flux linkages versus an equivalent magnetizing current in the circuit model of the synchronous machine. The estimation of the approximation functions parameters is based on the results of the field calculations.

The identification of the approximation functions is effective and significantly simpler on the basis of the magnetic field co‐energy function, than on the basis of the magnetic flux linkages.

The magnetic field co‐energy function determined by FEM is sufficient for simplified calculations of the magnetic parameters occurring in the circuit models of the electrical machines with nonlinear core.

The paper provides guidance for the circuit modelling of the multi‐pole generators and motors under conditions of magnetic saturation.

A paper has succeeded in determining the internal magnetic characteristics of the synchronous machine with a salient pole rotor.

This paper aims to reviewed analytical methodologies, i.e. lumped parameter magnetic equivalent circuit (LPMEC), magnetic co-energy (MCE), Laplace equations (LE), Maxwell stress tensor (MST) method and sub-domain modelling for design of segmented PM(SPM) consequent pole flux switching machine (SPMCPFSM). Electric machines, especially flux switching machines (FSMs), are accurately modeled using numerical-based finite element analysis (FEA) tools; however, despite of expensive hardware setup, repeated iterative process, complex stator design and permanent magnet (PM) non-linear behavior increases computational time and complexity.

This paper reviews various alternate analytical methodologies for electromagnetic performance calculation. In above-mentioned analytical methodologies, no-load phase flux linkage is performed using LPMEC, magnetic co-energy for cogging torque, LE for magnetic flux density (MFD) components, i.e. radial and tangential and MST for instantaneous torque. Sub-domain model solves electromagnetic performance, i.e. MFD and torque behaviour.

The reviewed analytical methodologies are validated with globally accepted FEA using JMAG Commercial FEA Package v. 18.1 which shows good agreement with accuracy. In comparison of analytical methodologies, analysis reveals that sub-domain model not only get rid of multiples techniques for validation purpose but also provide better results by accounting influence of all machine parts which helps to reduce computational complexity, computational time and drive storage with overall accuracy of ∼99%. Furthermore, authors are confident to recommend sub-domain model for initial design stage of SPMCPFSM when higher accuracy and low computational cost are primal requirements.

The model is developed for high-speed brushless AC applications.

The SPMCPFSM enhances electromagnetic performance owing to segmented PMs configuration which makes it different than conventional designs. Moreover, developed analytical methodologies for SPMCPFSM reduce computational time compared with that of FEA.

To study effects in the Fourier spectra of cage motor phase currents due to saturation of the main magnetic circuit by the fundamental MMF harmonic.

An idea of an equivalent magnetizing current is applied, which allows to consider an influence of all currents of stator and rotor windings on the main magnetic circuit permeability. The energy base approach is used to write machine equations and the harmonic balance method is used to determine the Fourier spectra of currents.

It has been shown that the saturation generate additional harmonics in phase currents, which are shifted by 100 Hz from the so called slot harmonics.

A model and a solving method allows to predict all slot harmonics quantitatively, but qualitative difference of the Fourier spectra to measurement still exist.

More precise prediction of the Fourier spectra of stator phase currents for on‐line diagnostic systems.

A circuit model of a cage motor accounting for saturation by slot harmonics and an algorithm for determination of additional components in the phase current Fourier spectra.

The application of the equivalent source methods for the numerical calculation of the total magnetic force acting upon a permanent magnet is proposed. These methods are formulated in terms of the external field, which allows the complete avoidance of the numerical inaccuracies affecting force computation due to the singularity of the self‐field of the magnet on its edges. It is shown, with the help of some 2D and 3D test cases, that the proposed formulae provide reliable and stable results, even when the FEM mesh is not refined. Such results have also been compared with those derived from more traditional methods, such as the surface integration of the Maxwell’s stress tensor and the virtual work method, exhibiting better precision and lower computational costs.

Grain‐oriented steel has a distinctly anisotropic and nonlinear behaviour. Only in rare cases is the magnetisation curve known for directions other than the principal ones. The paper aims at providing a model to obtain these curves for any direction if those in the easy and hard directions are only given.

The well‐known elliptic model is modified in order to correctly mimic the typical behaviour of grain‐oriented steel which is not described correctly by the original elliptic model. An additional condition is introduced to fix the angle between the flux density and magnetic field intensity.

The model is found to yield good agreement with measurements in case of a special material for which measured curves for intermediate angles are available.

Further research is necessary to establish whether the model is applicable to other materials.

The new model can be used in numerical analyses of devices comprising saturated grain‐oriented steel material if the magnetisation curves are given in the principal directions.

The S-MCSRM is a two-phase excited switched reluctance motor (SRM), with the short flux path and mutual inductance coupling, which is suitable for the oil submersible pump application owing to large torque and three-wire connection with the standard full-bridge power converter. However, there is not literature to disclose its model due to the complicated mutual inductance coupling. The FEM model is a time-consuming method to analyze this motor. For the first time, this paper aims to propose an S-MCSRM model for performance analysis and control method developing. The proposed model would save simulation time and be a theoretical fundamental for further implementing control algorithm.

The S-MCSRM's operating principle is analyzed, and the voltage equation and the generated torque are deduced. The FEM is utilized to obtain the five typical magnetization curves that describe the S-MCSRM's magnetic path characteristic. The magnetic co-energy equation, phase torque and total torque equations are obtained. From the basic voltage equation, the S-MCSRM's state space model is built for the dynamic analysis and control purpose. The S-MCSRM is widely analyzed in detail by using the proposed model and comparison with the conventional SRM. JMAG finite element package is used to verify the proposed model.

The proposed modeling method is validated by the identical results to those from FEM-based JMAG software. The proposed model just takes second-level time, which is far less than minute-level time consuming of FEM method. The S-MCSRM generates larger torque than the conventional SRM, with three-wire and standard full bridge power converter, and it is confirmed that the S-MCSRM is suitable for the oil submersible pump applications.

This paper proposes a new modeling method for the S-MCSRM to exactly analyze the motor's operating performances, and also it is a theoretical fundamental for developing control algorithm. The proposed model saves much time in analysis, calculation, and simulation, when compared to the FEM method. The completed analysis including flux linkages, torque, torque-ripple, and torque-speed characteristic discloses the S-MCSRM's steady-state operating performances, which provides the deep insight for this kind of motor's applications.

The purpose of this paper is to compare torque calculation methods when a non‐conforming movement interface is implemented by means of Lagrange multipliers.

The following methods are here used for computing the torque in a synchronous machine and in a switched reluctance motor: Arkkio's method (AM), local Jacobian matrix derivative (LJD) method, Maxwell stress tensor method (MST) and co‐energy variation method.

This paper shows that, the numerical stability produced by Lagrange multipliers yields a stable torque result, even in thin airgap machines if AM, LJD method or MST method are used.

This work presents a comparative study to indicate the performance of the most commonly used torque calculation methods, when a non‐conforming technique is used, considering a small displacement of the rotor, which is necessary for dynamic cases or coupling with circuit.

The purpose of this paper is to achieve the multi-objective optimization design of novel tubular switched reluctance motor (TSRM).

First, the structure and initial dimensions of TSRM are obtained based on design criteria and requirements. Second, the sensitivity analysis rules, process and results of TSRM are performed. Third, three optimization objectives are determined by the average electromagnetic force, smoothing coefficient and copper loss ratio. The analytic hierarchy process-entropy method-a technique for order preference by similarity to an ideal solution-grey relation analysis comprehensive evaluation algorithm is used to optimize TSRM. Finally, a prototype is manufactured, a hardware platform is built and static and dynamic experimental validations are carried out.

The sensitivity analysis reveals that parameters significantly impact the performance of TSRM. The results of multi-objective optimization show that the average electromagnetic force and smoothing coefficient after optimization are better than before, and the copper loss ratio reduces slightly. The experimental and simulated results of TSRM are consistent, which verifies the accuracy of TSRM.

In this paper, only three optimization objectives are selected in the multi-objective optimization process. To improve the performance of TSRM, the heating characteristics, such as iron loss, can be considered as the optimization objective for a more comprehensive analysis of TSRM performance.

A novel motor structure is designed, combining the advantages of the TSRM and the linear motor. The established sensitivity analysis rules are scientific and suitable for the effects of various parameters on motor performance. The proposed multi-objective optimization algorithm is a comprehensive evaluation algorithm. It considers subjective weight and objective weight and fully uses the original data and the relational degree between the optimization objectives.

The purpose of this paper is to calculate forces created by the magnetic leakage field, which are directly applied to tank walls via magnetic shield.

Electromagnetic and mechanical calculations use 3D finite element technology, both applied to materials having constant orthotropic properties. The magnetic solver uses harmonic excitation; the analysis of mechanical deflection is carried out in static conditions. Two types of forces are considered: magnetostatic surface forces and magnetostriction volumetric ones. In measurements, the laser scanning vibrometer was applied.

Electromagnetic calculations must use an FE mesh much denser than that for typical power loss analysis. The magnetic orthotropy of the shield material does not create any important effects and it may be omitted. Magnetostriction forces are similar in value to magnetostatic ones, but their influence on the shield deformation is negligible.

The results obtained for the analysis of the displacement of elements of the tank wall are exemplary – they show the difference between magnetostatic and magnetostriction excitation only. The analysis of the vibration of the transformer tank must include the presence of the oil inside the tank.

The asymmetrical placement of magnetic shields against the transformer core creates the visible differences in the magnitudes of magnetostatic forces applied to particular shields. Therefore, the design of magnetic shielding should also include the vibrational point of view.