Analysis Of Electrical Machines Research Articles

Lumped parameter magnetic equivalent circuit model for design of segmented PM consequent pole flux switching machine

PurposeThe purpose of this paper is to investigate an alternative simplified analytical approach for the design of electric machines. Numerical-based finite element method (FEM) is a powerful tool for accurate modelling and electromagnetic performance analysis of electric machines. However, computational complexity, magnetic saturation, complex stator structure and time consumption compel researchers to adopt alternate analytical model for initial design of electric machine especially flux switching machines (FSMs).Design/methodology/approachIn this paper, simplified lumped parameter magnetic equivalent circuit (LPMEC) model is presented for newly developed segmented PM consequent pole flux switching machine (SPMCPFSM). LPMEC model accounts influence of all machine parts for quarter of machine which helps to reduce computational complexity, computational time and drive storage without affecting overall accuracy. Furthermore, inductance calculation is performed in the rotor and stator frame of reference for accurate estimation of the self-inductance, mutual inductance and dq-axis inductance profile using park transformation.FindingsThe developed LPMEC model is validated with corresponding FEA using JMAG Commercial FEA Package v. 18.1 which shows good agreement with accuracy of ∼98.23%, and park transformation precisely estimates the inductance profile in rotor and stator frame of reference.Practical implicationsThe model is developed for high-speed brushless AC applications.Originality/valueThe proposed SPMCPFSM enhance electromagnetic performance owing to partitioned PMs configuration which make it different than conventional designs. Moreover, the developed LPMEC model reduces computational time by solving quarter of machine.

Generalized and Reduced Analytical Formulation for Ultra-Fast 3-D Field and Vector Potential Calculation From Arch-Shaped Axially Magnetized Bodies in Electrical Machines

Arch-shaped axially magnetized bodies tend to appear frequently in electrical machine analysis such as in the overhang parts of the classical radial-flux machines as well as in the main parts of the axial-flux machines. The calculation of the 3-D fields originating from these bodies is demanding. The 3-D FEA suffers from high computational burden as well as no knowledge of the field origin. Analytic techniques involve the use of elliptic integrals and complex numbers for numerical evaluation, which makes them significantly slower than the 3-D FEA. In this article, a new analytical technique is proposed to speed up the computation by a factor of 20 for the global magnetic field created by a generic magnetized body by removing complex numbers and reducing the analytic equations significantly without any loss of precision. As a result, it can compete with the conventional 3-D FEA. In addition, integral methods may contribute to the wider use of parallel processing techniques. The original expressions for the vector potential are also provided, which has its own benefits and applications. Finally, the showcased magnetized body is assessed against 3-D FEA and discussed in terms of practical applications.

Influence of Asymmetrical Stator Axes on the Performance and Multi-Physical Field of Canned Permanent Magnet Machine for Vacuum Dry Pump With Vector Converter Supply

Limitation in manufacturing tolerances and assembly imperfections are the source of asymmetrical stator axes (ASA) defect, in particular, in a vacuum dry pumps (VDP) where the canned permanent magnet machines (CPMMs) are with fractional slot concentrated winding (FSCW). The performance and multi-physical field of CPMM in the vacuum environment is vulnerable to ASA. This work provides comprehensive research on the influence of ASA on the performance and multi-physical field of CPMM for VDP. This article establishes a mathematical model and Park transformation of a 1.6kW 6-pole/9-slot CPMM under the ASA condition. With the universality of ASA and not so strictly symmetrical stator axes as commonly expected, the experimental results demonstrated the significant impacts of ASA on the drive performance and multi-physical field, especially the inductance characteristics, the symmetry degree of stator current and flux linkage, rotor electromagnetic force and stator electromagnetic vibration of CPMM. The obtained conclusions can act as a significant reference for robust design and analysis of electric machines and drives.

Analysis of air‐gap permeance functions in flux‐modulation double‐stator electrical excitation synchronous machine

The air-gap magnetic field analysis of the field-modulation double-stator electrical excitation synchronous machine (FM-DSEESM) is complicated due to its double stator and modulation-ring rotor configuration. Aimed to investigate the influence of the each part of the machine on the magnetic fields in the air-gaps, this study focuses on the permeance function analysis of FM-DSEESM to reveal its air-gap magnetic field distribution. Due to the limited physical space, the non-ferromagnetic segments of modulation-ring rotor in FM-DSEESM cannot be regarded as infinitely deep slots. Therefore, by adding a new flux line in the non-ferromagnetic segments, a new permeance function is proposed based on the calculation of the equivalent air-gaps. Then, analytical results of flux densities in the air-gaps are calculated and verified by finite element analysis. Finally, a FM-DSEESM prototype is fabricated to prove the feasibility of the permeance functions.

Improved air gap permeance model to characterise the transient behaviour of electrical machines using magnetic equivalent circuit method

AbstractTransient analysis of electrical machines with mixed eccentricity requires dedicated, fast and accurate solvers. This article proposes an improved air gap permeance expression which (a) is physically interpretable and (b) can be easily derived based on the rotor position. This expression is very suitable for inclusion in a solver based on the magnetic equivalent circuit (MEC) method. This allows to for example, calculate the torque and forces when vibrations act on the rotor. The results of the MEC solver agree very well with those obtained with a finite element method (FEM) solver, but are obtained with a fraction of the simulation time of the FEM solver.

Rapid 3-D Magnetic Integral Field Computation of Current-Carrying Finite Arc Segments With Rectangular Cross Section

The computation of 3-D magnetic fields is a demanding task in the analysis of electrical machines and other electromagnetic devices. In this context, integral field calculation provides a smooth solution, high precision and resolution, “on-demand”-calculation, and an origin-based formulation of the magnetic field and the magnetic vector potential. However, conventional elliptic methods lead to huge parallelizable computing efforts and significant errors. In this article, a 3-D generic current-carrying arc segment with rectangular cross section is studied. A new analytic formulation is proposed to speed up the computation of magnetic fields and reduce the error by more than three orders of magnitude. In addition, the proposed magnetic vector potential expression has a similar accuracy as numerical integration. In fact, a significant reduction of the error level has been showcased clearly with respect to the existing approaches. This article is promising for improving the design methodology and optimization of large superconducting dipole magnets or arched end-winding geometries of large electrical machines.

An Efficient Parallel Computing Method for the Steady-State Analysis of Electric Machines Using the Woodbury Formula

This article describes a parallel computing method for the steady-state analysis of electric machines. In this method, due to the low rank of the coupling sub-matrix, the Woodbury formula is exploited to develop a highly efficient parallel algorithm to solve the formulated linearized block matrix. The algorithm and the analysis of the computational complexity are worked out in detail. The performance of the algorithm is demonstrated by an application example.

An Overview of Modern Thermo-Conductive Materials for Heat Extraction in Electrical Machines

This article presents a comprehensive review of the modern thermo-conductive materials that have potential to improve the heat extraction in electrical machines by conduction. Currently, there is a significant interest in thermal design and analysis of electrical machines as the demand for high power/torque density is substantially raised in applications such as marine, aerospace, e-mobility and rail. Thermal design engineering has become very important to develop smaller and more efficient electric motors, therefore electrical machine designers need to be more informed with the recent development in novel thermo-conductive (insulation) materials. Such developments can provide enhanced thermal characteristics for high power dense electrical machines. It is reported that high voltage electrical insulations can have more sophisticated thermal properties with the recent advancements in materials science. This study aims to inform electrical machine designers with and without a thermal background about recent thermo-conductive materials. Thus, a profound understanding can be gained in thermally conductive materials for the use of numerous applications in electrical machines for which thermal management is a crucial aspect of the overall multi-physics design and optimization process.

Coupled Electromagnetic and Thermal Analysis of Electric Machines

This paper deals with the design process of electric machines, proposing a design flowchart which couples the electromagnetic and thermal models of the machine, assisted by finite element techniques. The optimization of an electrical machine, in terms of the energy efficiency and cost reduction requirements, benefits from the coupling design of the electromagnetic and thermal models. It allows the maximization of the current density and, consequently, the torque/power density within thermal limits of the active materials. The proposed coupled electromagneticthermal analysis is demonstrated using a single-phase transformer of 1 kVA. Finite element analysis is carried out via ANSYS Workbench, using Maxwell 3D for the electromagnetic design, with resistive and iron losses directly coupled to a steady-state thermal simulation, in order to determine the temperature rise which, in turn, returns to electromagnetic model for material properties update.

Fault Analysis of Electrical Machine Drives Employing Novel Model Predictive Control

Electrical machine drives play a crucial role in various industrial applications. Therefore, its control system design became more significant in the last decades. Numerous high powers and high-efficiency machine drives require faultless continuous operation. Fault-tolerant control is a productive solution for the improvement of the reliability of the machine drives. Model Predictive Control (MPC) is an optimal control algorithm developed for constrained control of Multi-Input-Multi-Output (MIMO) systems. MPC can handle MIMO systems and can incorporate several constraints in the form of equalities and inequalities. A Novel Model Predictive Control(NMPC) method for a Synchronous Servo Motor Drive (SSMD) integrating a real-time fault diagnostic method for Insulated Gate Bipolar Transistor ((IGBT) faults in an inverter has been presented in this paper. NMPC ensures the system's better performance and minimal fault clearance time.

Rotor/Stator Internal Phase to Phase Fault Detection in Three-Phase Wound Rotor Induction Machines

This paper presents a novel method based on Magnetic Equivalent Circuit (MEC) to model the wound rotor three-phase induction machine under healthy and faulty conditions. Different parameters of machine such as the number of poles, number of slots, winding configuration and dimension can be selected based on designed properties of a given machine. Internal phase to phase fault is also detected by stator current signature analysis in dq frame. Saturation effect is modeled by a tunable function as well as the core nonlinearity characteristic is considered. Finally, Finite Element Method (FEM) is used to evaluate the accuracy of the proposed MEC model. Short computational time of MEC method shows that this model is suitable for electrical machine modeling and analysis.

A New Hysteresis Loss Estimation in the Induction Motor Core Considering Rotating Magnetic Fields

A rotating machine such as inductor motor has highly distorted elliptical magnetic flux densities in its stator core. The iron loss estimation taking into account the rotating magnetic field is significant not only for the design but also for the performance analysis of electrical machines. A rotational hysteresis loss formula is also proposed to improve the computation accuracy especially when the magnetic flux density is high or the axis ration of a rotational magnetic flux density is big. For an induction motor core model, iron losses are experimentally measured on the top sheet of the core by using a self-developed B–H vector sensor. The proposed iron loss model is validated through comparisons of the calculated iron losses with experimentally measured ones.

Performance Analysis of Single-Phase Electrical Machine for Military Applications

A permanent magnet assisted synchronous reluctance generator (PMA-SynRG) and an induction generator (IG) were compared for portable generator applications. PMA-SynRG with two rotor configurations, namely rotors with ferrite magnet and NdFeB, were designed. Furthermore, a design strategy for both PMA-SynRG and IG is presented with their geometrical dimensions. The machine was designed and results were analyzed using finite element analysis. Results such as flux density, open circuit and full load voltages, torque in generating mode, weight comparison and detailed cost analysis were investigated. In addition, thermal analysis for various ambient conditions (−40 °C, +30 °C, +65 °C) was evaluated for both PMA-SynRG and IG. Furthermore, acoustic versus frequency plot and acoustic pressure level were investigated for both the generators. Finally, the results confirmed that the machine with a higher power-to-weight ratio was the right choice for military applications.

Core-Loss Analysis of High-Speed Doubly Salient Electromagnetic Machine for Aeronautic Starter/Generator Application

Core-loss calculation is an important issue in the design and analysis of electric machines, especially in high-speed applications. However, because of the severe uneven distribution and local supersaturation of the flux density, in combination with the evident dc magnetic bias and the skin effect of the eddy current at a high frequency, it is difficult to estimate the core loss in a high-speed doubly salient electromagnetic machine. In this paper, two improved core-loss calculation methods are proposed. Additionally, an approach is established to determine the core-loss coefficients, which considers the influence of the frequency and amplitude of the flux density by adopting the function-fitting method. The change pattern of the core-loss coefficients is also investigated, together with the influence of the dc magnetic bias on the eddy-current loss. Finally, rotor-lock experiments and high-speed rotating experiments are both conducted. Additionally, two improved methods are used and compared for core-loss calculation.

Transient thermal regime trough the constitutive matrix applied to asynchronous electrical machine using the cell method

Abstract In this paper, a new constitutive matrix for thermal conduction in transient thermal regime is developed and tested. We use cell method as a numerical method that is included in finite formulation methodology. The constitutive matrix defines through the cell method the behavior of solids when they are under a thermal potential. We have demonstrated that this matrix is equivalent to the electrical conduction constitutive matrix in steady state. We have applied this constitutive matrix to thermal analysis of asynchronous electric machines in transient regime. This constitutive matrix has been validated with comparisons based on finite element method. In finite formulation, the physical laws governing the electromagnetic fields and the physical thermal phenomena are expressed in integral formulation. The final algebraic equation system is tailored directly without discretizing of the differential equations. This is an important advantage because we omit a complex differential formulation and the discretization of the respective equations.

An Improved Core-Loss Calculation Method With Variable Coefficients Based on Equivalent Frequency

Core-loss calculation is an important issue in design and analysis of electric machine, especially in high-speed applications. However, because of the diverse structure, flux distribution, and rotational variation of flux density, it is difficult to predict core loss in electric machines exactly. In this paper, a concept of equivalent frequency is proposed for arbitrary waveforms. An improved core-loss calculation method with variable coefficients based on equivalent frequency is established for electric machines. Finally, the improved core-loss calculation method is verified by experiments on doubly salient electromagnetic motor. The conclusions are also applicable to many other kinds of electric machines.

An isoparametric approach to model ferromagnetic hysteresis including anisotropy and symmetric minor loops

Abstract Modelling hysteresis behaviour is an essential task in transient analysis of electrical machines. A curve fitting approach based on isoparametric elements is proposed in this work. A hysteresis loop is split into sub-curves and each sub-curve has been modelled in terms of a second degree polynomial using three data points. Thus the model requires few data points to model a complete loop. The model equations can be easily derived using predefined shape functions of an isoparametric element without using any curve fitting algorithms. The proposed approach has been applied to model hysteresis data of two different materials, namely, grain-oriented (GO) laminations and soft magnetic composites (SMC). Symmetrical minor loops of GO materials with magnetization along any arbitrary direction are modelled for the first time. The calculated results are in close agreement with measured values. Compared to existing methods, the proposed technique in this paper is simple to understand and computationally efficient.

Performance Analysis of Three-Phase Induction Motor with AC Direct and VFD

The electrical machine analysis and performance calculation is a very important aspect of efficient drive system design. The development of power electronics devices and power converters provide smooth speed control of Induction Motors by changing the frequency of input supply. These converters, on one hand are providing a more flexible speed control that also leads to problems of harmonics and their associated ailments like pulsating torque, distorted current and voltage waveforms, increasing losses etc. This paper includes the performance analysis of three phase induction motor with three-phase AC direct and variable frequency drives (VFD). The comparison has been concluded with respect to various parameters. MATLAB-SIMULINKTM is used for the analysis.

Input and Output Power in Finite-Element Analysis of Electric Machines Taking Account of Hysteretic Property

This paper used a finite-element magnetic field analysis (FEA) to investigate the instantaneous and average power in a single phase transformer and a three-phase rotating machine. We examined the influence of the hysteretic properties of the magnetic materials on the instantaneous power in FEA using the isotropic vector play model. We applied post-correction to estimate the accuracy of the average power from their equivalent circuits.

The Study of Permanent Magnets Synchronous Machine (PMSM) of the Autonomous Electric Power Supply System (ASE), compatible with the Concept of a More Electric Aircraft (MEA)

Based on the analysis and mathematical models of synchronous electric machines (motor/generator), basing on permanent magnets, presented in this paper, the main importance of alternator AC power sources in the form of starter/generator (for conventional aircraft) and in the form of integrated unit starter (motor)/AC synchronous generator S/G AC (with respect to advanced aircraft concept in terms of more electric aircraft) was highlighted. Additionally, through the analysis and selected simulations of the on-board autonomous power supply system of the modern aircrafts, sources of electrical energy (synchronous motor/generator, integrated unit starter/AC generator) were located in board autonomic power system ASE (EPS, PES). Main components of this system are the electro-energetic power system EPS and the energo-electronic power system PES. In addition, the analysis and exemplary simulations of main electricity sources based on mathematical models have contributed to highlighting the main practical applications in accordance with the concept of MEA.