Search

This paper proposes a novel hybrid excitation vernier permanent magnet machine (HE-VPM). The characteristics of the proposed machine are: 1) the PMs are embedded in the stator teeth, which is helpful for the heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high-speed operation; 3) the nonoverlapping concentrated winding shortens the end-connection, and improves the torque density, 4) only half of the stator teeth possess PMs, and the total amount of PMs are decreased; and 5) the dc current are injected to the armature coils, therefore, the exciting field can be adjusted flexibly. In this paper, the electromagnetic performance, including back electromotive force, torque, etc. are analyzed with finite element analysis. The results show that the proposed machine exhibits flexible field adjustment capability, which may be suitable for applications requiring wide speed range operation. Besides, it is found that, compared with the existing pure sinusoidal phase current, higher torque density can be obtained with dc-biased phase current under constant stator copper loss. [ABSTRACT FROM AUTHOR]

Compared with dc magnetic bearings, an ac magnetic bearing has obvious advantages in cost savings and reducing power consumption. For more precise control of the ac magnetic bearing, it is particularly important to build a correct mathematical model of radial suspension forces. Due to the working principle of the ac magnetic bearing, it has similarities to the suspension subsystem of a bearingless motor, thus the modeling method for radial suspension forces of the bearingless motor could be referenced for modeling the radial suspension forces of the ac magnetic bearing. This paper presents a new modeling method based on the Maxwell tensor method for radial suspension forces of the ac magnetic bearing. Compared with existing methods, the invention method designed specially for the ac magnetic bearing overcomes inaccuracy and possesses advantages of directness and universality. Taking the ac hybrid magnetic bearing (ac HMB), for example, this paper presents the mathematical modeling process of radial suspension forces with the proposed method. The comparison result between the models established by the equivalent magnetic circuit method (the most classical modeling method for magnetic bearings currently) and by the proposed method shows the high uniformity in their forms of expression (the only difference is the coefficient between them). Being different from the traditional modeling method, we do not need the detailed derivation and complex theoretical computation based on the particular magnetic circuit analysis for this particular case but simply modify several key expressions representing magnetic circuit features in the modeling process with this method. Therefore, the proposed method invented especially for the ac magnetic bearing has the greater advantage of directness and universality than previous modeling method. To illustrate the precision of the proposed modeling approach, the verification experiment is designed and the encouraging experimental results show that the model based on the Maxwell tensor method is more close to the test results comparing with equivalent magnetic circuit method. Thus, the proposed modeling method makes the modeling results on radial suspension forces of the ac magnetic bearing more accurate, universal, and direct. [ABSTRACT FROM PUBLISHER]

This paper compares the performance of three different topologies of spoke-type permanent-magnet vernier machines (PMVM): 1) dual airgap dual stator winding (DSW); 2) dual airgap single stator winding (SSW); and 3) single airgap (SA). These topologies were compared in terms of torque/machine volume, cogging torque, and torque ripples. The 2-D finite element method was utilized to compare the performance of the three models. The dual airgap PMVM with a SSW showed similar performance with the same machine outer diameter and similar power in terms of torque/machine volume and torque ripples compared with the DSW model. The performance of the SSW model was better than that of the SA model for the same outer diameter and rotor. Furthermore, stator slot optimization was performed to improve torque/machine volume and reduce torque ripples in the SSW model. [ABSTRACT FROM AUTHOR]

In this paper, an exact analytical solution based on Fourier analysis is proposed to compute the cogging torque in a surface-mounted permanent magnet synchronous machine. The analytical solutions are derived by solving the field-governing equations in each simple and regular subdomain, i.e., permanent magnet (PM), air, slot opening, and slot, and then by applying the boundary conditions to the interfaces between these subdomains. Based on these solutions, the cogging torque is also determined analytically. In order to verify the analytical results of the proposed method, an experimental system was implemented on a servomotor and a torque sensor. All analytical results were extensively validated using nonlinear 2-D finite-element analysis and experimental results. Using the proposed method, we investigated the influence on the cogging torque, according to the machine parameters. Therefore, the proposed method should be very useful in the initial design and cogging torque optimization of PM machines. [ABSTRACT FROM AUTHOR]

This paper investigates the vibration and noise characteristics of the coaxial magnetic gear (CMG) by the electromagnetic forces. In the CMG, the vibration and noise can be generated by the exciting forces acting on three parts, namely, low-speed rotor, high-speed rotor, and modulating pieces, respectively. The electromagnetic forces acting on three parts of the CMG and their force frequencies are calculated by using the Maxwell stress tensor method. Also, the mode shapes of the CMG full model and their resonance frequencies are obtained by the modal analysis. Through the electromagnetic forces and the result of the modal analysis, the vibration calculation is performed by using the 3-D-finite element method. Then, the effect of displacement on noise is confirmed by comparing the vibration calculation data and experiment data. The result shows the most affected part among the three parts of the CMG due to the noise is the low-speed rotor. [ABSTRACT FROM AUTHOR]

Electrodynamic bearings can guide rotating objects without contact and active control means. Consequently, their performance relies on passive phenomena that require specific models to be predicted. In the case of electrodynamic thrust bearings, early models involved assumptions on the rotor axial kinematics. This precludes their use for predicting the bearing behavior in dynamic conditions, which is critical when studying stability aspects. Other models require numerically solving of Faraday’s current law and the rotor equation of motion to obtain the dynamics of the bearing, thereby excluding a fast identification of its stability properties. Recently, a parametric model without these kinematic assumptions was derived. It consists in a linear state-space representation that allows studying the dynamic performance of electrodynamic thrust bearings using conventional system analysis tools. However, this model links up the rotor displacement to the currents in a winding with only two phases. This paper introduces a model free of this limitation, allowing to consider bearings with a higher number of phases, an improved copper usage, and potentially increased performance. Furthermore, the proposed model directly links up the rotor displacement to the force and torque exerted by the thrust bearing without requiring to solve for the currents. This also minimizes the number of state-space equations and model parameters. Finally, in addition to the modeling aspects, a set of bearing topologies that have not been explored yet and can be studied using the proposed model is introduced. [ABSTRACT FROM PUBLISHER]

This paper describes a new method aiming at the multi-objective optimization of a transverse flux machine with a claw-pole and flux-concentrating structure (CPTFM). Considering the 3-D main magnetic flux in the CPTFM, the time-consuming 3-D finite-element method (FEM) should be used to accurately analyze the performance of the machine. In order to reduce the calculation time for the optimization of the complex CPTFM, the Taguchi method is first applied to evaluate the importance of all the design parameters in the consideration of the predefined five objectives. Subsequently, a mathematical model is developed to replace the 3-D FEM, so that the objectives depending on the selected four critical parameters can be analytically calculated. With its help, the four parameters are further optimized with the multi-objective particle swarm optimization method and nondominated sorting genetic algorithm 2. Finally, the optimal design of the CPTFM is selected from all the searched Pareto solutions with the help of fuzzy logic. It can be concluded that the developed method is effective and efficient, which can make an appropriate compromise between the calculation time and the improvement of the machine performance. [ABSTRACT FROM PUBLISHER]

The split ratio is one of the most important design parameters for permanent-magnet (PM) brushless machines. It has been optimized for maximum torque density with both internal rotor and tubular PM brushless machines in existing papers. This paper proposes an analytical model to determine the optimal split ratio for external rotor PM brushless machine having nonoverlapping winding. The influence of winding factor, tooth tip, and end winding on the split ratio is considered. The theoretical analyses are verified by finite element analysis and validated with experimental measurement. [ABSTRACT FROM AUTHOR]

Magnetic actuators are successfully used in the control of rotating machinery using feedback to eliminate the undesired vibration. Control algorithms can be implemented through the magnetic forces applied using the magnetic actuator, which are controlled through the current induced in the coils. Throughout this paper, we suggest the elimination of the excessive oil whip vibration excited due to the rotation of flexible rotor supported on fluid film bearings using the magnetic forces. The fluid film bearings and magnetic actuators are integrated into one unit. An \textH\infty controller is designed considering the robustness issues to suit a flexible rotor. The controller performance is successfully tested. [ABSTRACT FROM AUTHOR]

An exact analytical model of a surface-mounted bearingless permanent-magnet synchronous motor (BPMSM) with rotor eccentricity by a perturbation method is proposed in this paper and its computational accuracy is verified by the finite-element method. Considering the rotor eccentricity, a compensation control system is implemented based on the mathematical model of levitation force by applying a coefficient of the rotor eccentricity calculated by the exact analytical method (EAM). The experimental results suggest the improvements of the dynamic and the static performances of the stable suspension state for the surface-mounted BPMSM and the feasibility and effectiveness of the EAM. [ABSTRACT FROM AUTHOR]

Flux-modulated permanent-magnet synchronous machine (FM-PMSM) is characterized as a high-torque direct-drive electrical machine, but may suffer from the low power factor. This paper aims to investigate the issue of the low power factor in theory and explore the possibilities for improvement. An analytical model for the FM-PMSM is developed to obtain the magnetic field distribution, and its accuracy is verified by the finite-element method. On the basis of the developed analytical model, a fast approach is developed to predict the power factor of the FM-PMSM. The analytical results indicate that the low flux density in the inner air gap excited by the PMs is responsible for the low power factor. Finally, the influences of several key design parameters on the power factor are studied, and the FM-PMSM is optimized afterward. The results show that the power factor of the FM-PMSM could be improved by 20% in comparison with the initial design. [ABSTRACT FROM AUTHOR]

High-frequency current in the bearings of variable-frequency motors coupled with their shafts is a common issue that will shorten the bearings lifetime ultimately. A new method, which could be used to suppress high-frequency discharge bearing current, was proposed in this paper. In this method, an electromagnetic shielding slot wedge (ESLW) was used to reduce the capacitive coupling between the stator windings and the rotor. The electromagnetic coupling resulted from the common-mode voltage could be blocked by this electromagnetic shield layer. In addition, the mathematical model of the suppression method was given and the high-frequency electromagnetism performance of the motor was analyzed. Finally, an experimental platform was setup and a motor was modified to evaluate the suppressing effectiveness. The shaft voltage, bearing currents, and the general features of the modified motors, with and without ESLW, were measured and compared. [ABSTRACT FROM AUTHOR]

In this paper, a new stator-permanent magnet (PM) bearingless machine (SPMBM) is proposed. Its suspending windings, armature windings, and PMs are in the stator, while no PMs or windings are in the rotor. However, it is the focus in establishing an accurate mathematical model of radial suspension force to levitate the rotor stably by directly and effectively controlling the rotor eccentric displacement. First, operating principle and air-gap flux density distributions of the SPMBM are analyzed in detail. Then, an accurate mathematical model of radial suspension force is deduced by the Maxwell stress tensor method, and it is verified by the 2-D finite-element method (FEM). Results are consistent both by the radial suspension force mathematical models of the SPMBM and FEM. [ABSTRACT FROM AUTHOR]

Dual rotor motors (DRMs) for the electric vehicle application are a competitive alternative to the multi-motor drivetrain configuration to meet the high-power density and better vehicle drive performance. In this paper, a steady-state model of a hybrid DRM is developed using electromechanical energy conversion principles. The developed model comprises electrical equivalent circuit and torque equation. The model helps in understanding the motor operation and can be used for quick performance evaluation. The finite element method has been used to validate the developed model and a good agreement has been achieved for the results obtained. [ABSTRACT FROM AUTHOR]

This paper proposes an axial permanent magnet-biased hybrid magnetic bearing, which possesses the advantages of low power consumption, simple structure, and easy control. The structure and operation principle are introduced. Then, the mathematical models, including the suspension force expression, are built based on traditional equivalent magnetic circuit. In addition, the basic principle of structure parameter design is presented, based on which the key parameters are given. Due to the inaccuracy of the traditional equivalent magnetic circuit, an improved method for magnetic circuit is introduced. Last, the accuracy of the analytical method is validated by finite element analysis and it also has an important reference value for other types of magnetic bearings design. [ABSTRACT FROM AUTHOR]

This paper proposes an improved analytical model to calculate the inductances of interior permanent magnet (IPM) machines, equipped with either fractional slot concentrated windings or distributed windings. A modified stator magnetic motive force expression is also presented firstly. It has been proven that the normal method for inductance calculation by airgap permeance function and winding function is not accurate enough for IPM machines. The improved analytical model is competent to predict the distribution of the armature-reaction magnetic field and inductances accurately. Several finite element analysis (FEA) models have been built, and a prototype has been designed and tested. Results by the improved analytical model are verified by both FEA and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a study on iron loss estimation for a solid rotor induction motor fed by pulsewidth modulated supply. The iron losses are often determined using an a posteriori method that can lead to more or less important deviations, compared with measurements, depending on the used models and implementation techniques. The methodology proposed here consists of computing the iron losses with an analytical method implemented in a post-processing of a 2-D finite-element analysis. Different implementation techniques are used to investigate the impact of the model on the iron loss. [ABSTRACT FROM AUTHOR]

Analytical models have been demonstrated to be effective tools in the analysis of electromagnetic devices by providing fast, yet accurate solutions. In this paper, a comprehensive analytical framework for double-rotor radial-flux air-cored permanent-magnet (PM) machines is developed whereby the average as well as the torque ripples, back-electromotive force (EMF) waveforms, air-gap flux density distribution, and a number of other characteristics regarding the design of the machine are predicted. Also, closed-form expressions for inductances of the stator coils are analytically derived. All machine parameters and material properties including iron saturation are considered in the model. Moreover, an algorithm in order to optimally design the thicknesses of the rotor yokes based on the utilized steel is presented. Finally, genetic optimizations regarding the enhancement of the produced torque and back-EMF are performed. It is also shown that the results obtained from the proposed model match well with those issued from finite element method. [ABSTRACT FROM PUBLISHER]

In this paper, an analytical model to calculate a canned switched reluctance machine (SRM) is presented. Such a model is characterized by a multilayer structure in a cylindrical coordinate. Maxwell's equations are used to derive the magnetomotive force (MMF) distribution of the stator armature and determine the arrangement of wires within a coil. The large rotor and stator slots of double saliency are taken using the magnetic equivalent circuit (MEC) method with adjustable elements. Based on Poynting's theorem, the loss from each part of the machine is obtained, including the can loss and iron loss. Finally, torque is deduced by a Maxwell stress tensor. [ABSTRACT FROM PUBLISHER]

In this paper, the configuration of a 2-axis radial hybrid magnetic bearing (RHMB) and its working principle of passive tilting stability are introduced. When the rotor of an RHMB is disturbed to tilt about a radial axis, a restoring moment is passively generated and draws the rotor back to its equilibrium position. The mathematical model of the passive restoring moment is established by using the equivalent magnetic circuit method. The calculated results of the passive restoring moment for a prototype of RHMB are compared to those calculated by using the finite element method. The results of the two methods are in agreement with each other when the tilting angle is less than 1.5^\circ, which verifies the feasibility of the mathematical model. The influence of some structural parameters such as air-gap length, stator diameter, and air-gap section shape on the passive restoring moment and the tilting stiffness is investigated. The results show that the passive restoring moment and the tilting stiffness can be increased by increasing the air-gap length and the stator diameter. However, the air-gap section shape has little influence on the passive tilting stability. [ABSTRACT FROM PUBLISHER]

This paper reports the work on a six-pole heteropolar radial hybrid magnetic bearing (HMB). Its configuration and working principle are introduced. The mathematical model is built based on equivalent magnetic circuit and coordinate transformation method. The model shows that the coupling in x and y directions is very low and can be ignored when the rotor is around the central position. A decoupling controller for this six-pole HMB is obtained. A design principle for bias flux density is presented based on maximization of load capacity in different directions, through which a prototype six-pole HMB for a five-degrees-of-freedom magnetic bearing system is designed and assembled. Both the simulation and experimental results show that the rotor can be suspended steadily and the whole control system has good dynamic and static performance. Finally, tests were done to determine power losses. As a result, the total power consumption of this six-pole HMB is just 12.77 W for a 2.2 kg rotor, which is only 13.35% of a traditional eight-pole active magnetic bearing with the same load capacity. [ABSTRACT FROM PUBLISHER]

Understanding the importance of saturation of parameters in line-start permanent magnet synchronous machine (LSPMSM) and the scanty available research literature on simplistic methods of determining the magnetizing characteristics of LSPMSM, this paper proposes a novel and yet simplistic approach towards its determination. Experimental investigations have been performed on a laboratory LSPMSM based on the proposed dq axis (two-axis)-based methodology and the measured magnetization characteristics of the machine has been incorporated into the machine model. The measured characteristics have hence been validated through dynamic and steady state performance analyses of the machine under direct online (DOL) starting. Furthermore, performance analysis of the machine has also been performed through the developed machine model with and without incorporating the magnetization characteristics of the machine to elicit the effects of parameter saturation during startup and synchronization of the machine. [ABSTRACT FROM PUBLISHER]

This paper presents challenges in an ongoing project related to the design of a premium efficiency three-phase line start permanent magnet synchronous motor (LSPMSM) and proposes an exclusive solution through development of a novel magnetic circuit model. Since the LSPMSM is rapidly replacing the conventional induction motors in industrial applications such as pumps, fans and conveyors which require the machine to operate under both frequent start-stop and steady-state conditions for a wide range of time, a trade-off has to be reached between their starting performance and efficiency post-synchronization. Until now this has only been possible with time consuming FEA based design methodology. Hence, understanding the need and scanty availability of literature on simplistic and yet precise magnetic circuit based design of three-phase LSPMSM, this manuscript proposes exclusively a novel magnetic circuit model to design LSPMSM with improved starting performance. Firstly, the aforementioned design issues have been illustrated using different machine configurations developed. Further, a detailed procedure to deal with the design issues with the help of the developed magnetic circuit model is discussed and validated by developing a machine where the trade-off has been reached. [ABSTRACT FROM AUTHOR]

This paper discusses non-conforming sliding interfaces for motion in combination with a magnetic scalar potential formulation. Lagrange multiplier are used to implement the relative motion of stator and rotor. The utilization of the specific Lagrange multiplier approach implies the application of a magnetic scalar potential formulation in 3D Finite Element (FE) modeling of electrical machines because up to the present a canonical definition of biorthogonal basis functions for the magnetic vector potential is not available. [ABSTRACT FROM AUTHOR]

The present paper presents a new modeling approach for null flux axial electrodynamic bearings. Such approach allows defining stability bounds for rotors supported with this type of passive magnetic suspension. The linearized models are developed using the bond graph methodology to better understand the multiphysics nature of the magnetic suspension. The adoption of complex variables together with the bond graph formalism is introduced in order to reduce the complexity of the system's equations. Rules for the use of this approach are established and demonstrated. [ABSTRACT FROM AUTHOR]

This paper performs a shape optimization of a grid-connected-to-the-rotor type doubly fed induction generator (DFIG) in which the rotor winding is connected to the grid instead of the stator winding. To analyze the characteristics of a DFIG accurately, a time step 2D-FEA is carried out, which is coupled with Simplorer. To maximize the torque per weight as well as to maintain the efficiency, the Kriging model based on latin hypercube sampling and genetic algorithm are utilized. As an optimal design result, the torque per weight on the optimal model has been increased. Finally, the analysis and the optimal design results are confirmed by the experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents the results of an experimental verification and electromagnetic field analysis for an axial flux permanent magnet (PM) synchronous generator (AFPMSG) with a double-sided PM rotor and slotless stator windings based on analytical field computation to offer improved analytical modeling method. An analytical approach to analyze the magnetic field distribution and estimate the equivalent circuit parameters is presented that dramatically reduces analysis time while maintaining high reliability. Since the flux leakage phenomenon is dominant in the inner and outer radii of this type of AFPMSG, it is specifically considered. In addition, an actual device was fabricated on the basis of one of the analysis models, and used to experimentally verify all of the analysis results. [ABSTRACT FROM PUBLISHER]

This paper deals with the temperature estimation of interior permanent magnet synchronous motor (IPMSM). A thermal equivalent circuit of IPMSM is proposed with considering eddy current loss of PM as well as core losses of rotor. Heat sources, which are core loss of stator/rotor core and eddy current loss of PM, are calculated by numerical method to enhance the accuracy of thermal estimation. The thermal equivalent model is represented by the thermal resistances and thermal capacitances, which are determined by motor configuration. Meanwhile, a temperature test is performed using prototype to determine the heat transfer. Finally, this thermal equivalent model is verified by a temperature test in a 25 kW 12-pole/18-slot IPMSM. [ABSTRACT FROM PUBLISHER]

An objective in the design of high performance machinery is to minimize weight so magnetic bearings are often designed to operate slightly lower than their magnetic material saturation. Further weight reduction in the bearings requires operation in the nonlinear portion of the B\-H curve. This necessitates a more sophisticated analysis at the bearing and rotordynamic system levels during the design stage. This paper addresses this problem in a unique manner by developing a fully nonlinear homopolar magnetic bearing model. The nonlinear dynamics of a permanent magnet-biased homopolar magnetic bearing (PMB HoMB) system with a flexible rotor is analyzed. Nonlinear effects due to power amplifier voltage and current saturation and position dependent reluctances are also included in the model. A new curve fit model of the B\-H curve is shown to have significantly better agreement with the measured counterpart than conventional piecewise linear. The modified Langmuir method, with a novel correction terms for the weak flux region, is used to form an analytical model of the experimental magnetization curve of Hiperco 50. High static and dynamic loads applied to the rotor force the magnetic bearing to operate in a flux saturated state. The response of the heavily loaded 4-DOF rotor-bearing system shows that limit cycle stability can be achieved due to the magnetic flux saturation or current saturation in the amplifier. The stable limit cycle prevents the linear model instability, creating what is experimentally observed as a “virtual catcher bearing.” To the authors' knowledge this is the first explanation of this commonly observed phenomenon. [ABSTRACT FROM PUBLISHER]

Magnetic gears are able to transmit torque without mechanical contact. Therefore, these have attractive features, such as low acoustic noise and maintenance-free operation in comparison with conventional mechanical gears. Planetary-type magnetic gears, especially, have higher transmission torque than the other types, and are expected to be put into practical use. This paper presents a method for calculating dynamic characteristics of the magnetic gear based on reluctance network analysis (RNA). The RNA has several features, including a simple analytical model, high calculation accuracy, and ease of coupled analysis with rotational motion of rotors. [ABSTRACT FROM AUTHOR]

This paper studies different iterative solution methods for nonlinear permeance network based machine models. A new transmission line modeling (TLM) algorithm for efficient solution of permeance network models (PNM) of induction machines is proposed. In this method, the TLM algorithm is used to decouple the nonlinear magnetic equations. The decoupled nonlinear equations are then solved by a look-up table method owing to the repetitive nature of equations across the geometry of the machine. It is shown that the proposed method offers significant speed-up compared to the conventional Newton-Raphson method. Simulation results for dynamic and steady-state conditions of a closed rotor slot induction motor are compared with experimental test results as well as finite element analysis to evaluate the performance of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

The effects of saturation on torque production for non-salient, single-phase, permanent-magnet machines are studied in this paper. An analytical torque equation is proposed to predict the instantaneous torque with saturation effects. Compared to the existing methods, it is computationally faster and easier to calculate the torque using the analytical equation proposed. It can also handle arbitrary armature current waveforms and arbitrary flux linkage waveforms produced by the rotor permanent magnets. The results obtained by using the proposed torque equation are validated using finite-element results, and experimental results obtained on a prototype single-phase permanent-magnet machine. [ABSTRACT FROM AUTHOR]

In this paper, a new detailed analytical model of a salient-pole synchronous generator (SPSG) under dynamic eccentricity (DE) is presented which is capable of accounting for the effects of magnetic saturation, rotor pole shoe saliency, and space distribution of stator phases and rotor winding. A real form of rotor pole shoes is taken into account in the proposed SPSG air-gap function distribution. Saturation effects incorporate into the air-gap function of SPSG as a simple proposed analytic equation that varies by the generator load and operating condition. Furthermore, variation of the resulted air-gap distribution of SPSG in the presence of DE fault is then computed precisely and the inverse air-gap function calculated using Fourier series in order to compute time varying self- and mutual-inductances of stator phases and rotor winding via the modified winding function approach (MWFA). The computed inductances are used for simulation of SPSG and studying the frequency spectrum of stator line current in the presence of DE fault. It is shown that the results of proposed model are closer to the finite-element (FE) computation results compared to the available analytic models. [ABSTRACT FROM PUBLISHER]

This paper presents copper and iron loss models of a classical switched reluctance motor (SRM) and a mutually coupled switched reluctance motor (MCSRM). The iron losses in different parts of machines are then detailed. Based on the power losses model, a lumped parameter (LP) transient thermal model during driving cycles is performed, the analytical results are validated by the finite-element (FE) transient thermal model. Special attention has been paid to model the salient rotor and a method to transform the salient rotor into a nonsalient one has been proposed. A comparison between the maximum temperatures obtained by using different heat source (average power losses or instantaneous power losses during driving cycles) is given. The experimental tests are also realized to verify the analytical and numerical results. [ABSTRACT FROM PUBLISHER]

The capabilities of proper start-up and synchronization are important issues in the design of line-start permanent magnet synchronous motors. Failing in early start-up or in synchronization under certain conditions prevents the widespread use of these motors. In order to draw useful guidelines for the design of line-start permanent magnet synchronous motors, the contradictory effects of a large value of magnetizing inductance in improving early start-up and deteriorating synchronization of line-start permanent magnet synchronous motors are analyzed in this paper. The analysis is done through three different methods. First, the effect of magnetizing inductance on average and pulsating torques of the motors during asynchronous operation is investigated and the role of these torques in start-up and synchronization performances of the motors is discussed. A critical load is then determined in terms of motors parameters as a torque limit above which the motors cannot start. The effect of magnetizing inductance, magnet flux, and saliency on the critical load is also investigated. A dynamic d\-q model of the motors is then implemented to support the discussions by analyzing two line start motors with different magnetizing inductances. Finite-element-based analyses are then carried out for both motors to consider motors parameters variation, skin effect, saturation, rotor asymmetry, and cross magnetization. A good agreement between the finite-element method and dynamic simulation results is evident. Finally, some design guidelines are proposed for the proper selection of the magnetizing inductance in motor designs for different applications. [ABSTRACT FROM PUBLISHER]