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A direct-on-line synchronous reluctance motor (DOLSynRM) with a rotor topology defined by the natural flux line curve approach is studied as an alternative to an induction motor (IM) using a 1.5 kW, 50 Hz synchronous reluctance motor as an example. If an IM stator is used, a direct squirrel cage rotor replacement by a synchronous reluctance rotor equipped with a damper winding might not guarantee a sufficient starting performance. To ensure the strong enough starting capability, the natural flux line curve approach was modified in the motor design. The proposed approach was applied in the optimization of the DOLSynRM using a genetic algorithm. The optimization results show a clear tendency in the rotor design when trying to achieve a reliable starting capability and to maximize the steady-state performance of the DOLSynRM. Both the stator design and the rotor diameter of the optimized DOLSynRM are different from those of a corresponding squirrel cage IM. A DOLSynRM prototype was built and tested. It showed about a 5.4%-unit higher efficiency than the original prototype IM and acceptable starting performance under the rated load condition. The starting capabilities of the motors under study are considered with different loads. The locked rotor apparent power and current stay below permissible limits in both the IM and the DOLSynRM. [ABSTRACT FROM AUTHOR]

This paper introduces a new nonlinear multidisciplinary design approach (NMDA) for axial-flux (AF) eddy current brakes (ECBs). The proposed NMDA is developed by nonlinear magnetic–thermal–structural coupled modeling. The nonlinear behaviors of the AF-ECB covering the BH curve, resistivity, heat capacity, thermal conductivity, and the temperature are jointly analyzed in time domain to investigate the actual brake properties and to determine brake operating range. In this paper, the nonlinear magnetic modeling based on two-dimensional (2-D) reluctance network is studied by a modified Newton–Raphson method. Furthermore, the nonlinear thermal modeling is carried out by lumped-parameters considering the change of heat capacity, thermal conductivity, and the temperature and updating the data in the evaluation process. Finally, the nonlinear structural modeling is performed to obtain the deflection and the mechanical safety factor of the brake. The nonlinear modeling methods in the proposed NMDA are validated by independent 3-D electromagnetic, thermal, and structural finite element analyses (FEAs), and the proposed NMDA is tested with two different AF-ECB prototypes. The experimental results confirm that the proposed NMDA has high accuracy, and compared to 3-D-FEA approaches, it provides a fast solution to predict the AF-ECB performance. [ABSTRACT FROM AUTHOR]

Direct liquid cooling (DLC) of electrical machine windings is a clearly effectual cooling method for high-torque and high-power-density applications needed, especially, in heavy vehicles. Usually, in electric vehicles, the stator copper winding losses are the most dominating losses during the accelerating or decelerating (recuperation) modes, and therefore, traditional windings may heat up significantly during high-torque periods. Removing the heat directly from the winding in which most of the heat is generated allows the most straightforward and effective way of cooling. This paper investigates the feasibility of the DLC in a radial-flux permanent-magnet traction motor. This case provides experimental information of the behavior of the DLC of the windings. The prototype motor equipped with DLC windings is installed in an electric bus so that typical bus load cycles can be tested. [ABSTRACT FROM AUTHOR]

Fast methods to estimate iron losses of the permanent magnet traction motor during the drive cycle of the electrical vehicle are compared. The methods use the iron loss information calculated by a finite-element analysis as a function of rotational speed both at no load and with a short-circuited stator to take into account the variable frequency and field weakening of the traction motor. The effect of iron losses on the optimal current components, providing the maximum efficiency, is studied. Several methods yield a good accuracy even based on the no-load iron loss only, but the accuracy can be improved especially in deep field weakening by including the short-circuit iron loss information in the analysis. [ABSTRACT FROM PUBLISHER]

An electrical and mechanical design process for a traction motor in a hybrid bus application is studied. Usually, the design process of an electric machine calls for close cooperation between various engineering disciplines. Compromises may be required to satisfy the boundary conditions of electrical, thermal, and mechanical performances. From the mechanical point of view, the stress values and the safety factors should be at a reasonable level and the construction lifetime predicted by a fatigue analysis. In a vehicle application, the motor has to be capable of generating high torque when accelerating, and in normal operation, the losses of the machine should be low to be able to cool the machine. Minimization of the no-load iron losses becomes a very important electrical design requirement if the traction motor and the generator are mechanically connected with an internal combustion engine when it is operating as the only source of torque. The manufacturing costs of the motor are also taken into account in this paper. [ABSTRACT FROM PUBLISHER]

This paper proposes an extended set of variables for numerical optimizations of tooth-coil permanent magnet synchronous machines (TC-PMSMs). The design variables for the extended set are chosen based on the magnetic asymmetries introduced by the saturated core under the loading conditions. The extended set allows to reach considerably higher values of torque density and significant reduction of torque ripple in comparison with a conventional set of optimization variables. The conventional and extended sets are compared on an example of an finite element method simulation of a double-layer winding surface permanent magnet-rotor TC-PMSM. A considerably better optimal machine is obtained when the extended set of variables is utilized. The paper showcases the design and the optimization of electrical machines using only free and open-source software. [ABSTRACT FROM PUBLISHER]

To compete with other types of electrical machines as well as other manufacturers, the performance characteristics of axial-flux permanent-magnet (AFPM) machines should be improved. Reduction of the higher harmonic components from the induced back electromotive force is preferred during design process of an electrical machine. To achieve an almost sinusoidal induced phase voltage, a sinusoidal air-gap flux density distribution should be produced. Furthermore, in order to easy startup and also less noisy performance of electrical machines, the cogging torque of the machine should be reduced. In this paper, the surface-mounted AFPM machines equipped with magnets with different outlines are investigated and the machine performances are computed via 3-D finite-element analysis. According to the obtained results, magnets with sinusoidal outline offer better performance characteristics compared with cylindrical and sector-like magnets. [ABSTRACT FROM PUBLISHER]

This paper introduces a method for the drive cycle performance analysis of a permanent-magnet traction motor based on a fast magnetostatic finite-element analysis (FEA). The flux linkage and torque behavior of the permanent-magnet synchronous machine is studied by a nonlinear magnetostatic FEA as a function of direct- and quadrature-axis stator current components. In the analytical machine performance analysis, the current combinations producing the desired torque and minimizing the losses are determined. The iron loss is calculated with the time-transient FEA at no load. The maximum stator flux linkage, limited by the battery voltage, is taken into account. The drive cycle analysis, based on optimal current component surfaces, is carried out for a traction motor of an electric sports car. The results are compared with values measured for the drive cycle on a racetrack. [ABSTRACT FROM PUBLISHER]

Permanent magnet synchronous machines (PMSMs) with fractional-slot non-overlapping windings, also known as tooth-coil winding PMSMs (TCW PMSM), have been under intensive research during the latest decade. There are many optimization routines explained and implemented in the literature to improve the characteristics of this machine type. This paper introduces a new technique for torque ripple minimization in TCW PMSM. The source of torque harmonics is also described. The low-order torque harmonics can be harmful for a variety of applications, such as direct drive wind generators, direct drive light vehicle electrical motors, and for some high-precision servo applications. The reduction of the torque ripple harmonics with the lowest orders (6th and 12th) is realized by machine geometry optimization technique using finite element analysis. The presented optimization technique includes the stator geometry adjustment in TCW PMSMs with rotor surface permanent magnets and with rotor embedded permanent magnets. Influence of the permanent magnet skewing on the torque ripple reduction and cogging torque elimination was also investigated. It was implemented separately and together with the stator optimization technique. As a result, the reduction of some torque ripple harmonics was attained. [ABSTRACT FROM PUBLISHER]

Traction motor design significantly differs from industrial machine design. The starting point is the load cycle instead of the steady-state rated operation point. The speed of the motor varies from zero to very high speeds. At low speeds, heavy overloading is used for starting, and the field-weakening region also plays an important role. Finding a suitable field-weakening point is one of the important design targets. At the lowest speeds, a high torque output is desired, and all current reserves of the supplying converter unit are used to achieve the torque. In this paper, a 110-kW 2.5-p.u. starting torque and a maximum 2.5-p.u. speed permanent-magnet traction motor will be studied. The field-weakening point is altered by varying the number of winding turns of machine. One design is selected for prototyping. Theoretical results are verified by measurements. [ABSTRACT FROM PUBLISHER]

The design process of direct-driven permanent-magnet (PM) synchronous machines (PMSMs) for a full electric 4 \times 4 sports car is presented. The rotor structure of the machine consists of two PM layers embedded inside the rotor laminations, thus resulting in some inverse saliency, where the q-axis inductance is larger than the d-axis one. An integer slot stator winding was selected to fully take advantage of the additional reluctance torque. The performance characteristics of the designed PMSMs were calculated by applying a 2-D finite-element method. Cross saturation between the d- and q-axes was taken into account in the calculation of the synchronous inductances. The calculation results are validated by measurements. [ABSTRACT FROM PUBLISHER]

This paper introduces an important source of torque ripple in permanent-magnet synchronous machines with tooth-coil windings (TC-PMSMs). It is theoretically proven that saturation and cross-saturation phenomena caused by the nonsynchronous harmonics of the stator current linkage cause a synchronous inductance variation with a particular periodicity. This, in turn, determines the magnitude of the torque ripple and can also deteriorate the performance of signal-injection-based rotor position estimation algorithms. An improved dq-inductance model is proposed. It can be used in torque ripple reduction control schemes and can enhance the self-sensing capabilities of TC-PMSMs. [ABSTRACT FROM PUBLISHER]

Hybrid and full electric technologies are fast emerging in vehicles and mobile working machines, where electric machines and internal combustion engines are used together to power the systems. Permanent magnet (PM) technology plays an important role here despite the high magnet prices. This paper theoretically and empirically studies the design principles of PM synchronous machines (PMSMs) for hybrid applications, where a high starting torque and a wide field weakening range are needed. Several embedded-magnet PMSM magnetic circuit topologies are considered as possible candidates. A 10-kW PMSM prototype was built and tested. Experimental results verify the theoretical considerations well. [ABSTRACT FROM PUBLISHER]

Permanent magnet synchronous machines (PMSM) are considered a viable option in various types of applications. However, particularly in consumer and low-power industrial applications, the price may be a factor that limits the use of PMSMs. In addition to a different technology, the main reason for the high price of PMSMs is the use of expensive neodymium or samarium-cobalt magnets. Their use is necessary only if a high motor torque T to linear current density A ratio (T/A) is required. Ferrite permanent magnets are low cost, abundant, and have negligible eddy current losses in low-frequency applications such as motor drives. They have a much lower energy product (BH\max) than the most modern magnets. Because of the high prices of rare earth magnets, many parties are seeking for opportunities to use ferrites instead. In the case of rotor surface ferrite magnets, the air gap flux density remains low. The air gap torque producing tangential Maxwell stress is proportional to the product of the air gap flux density B\delta[ \Vs/m^2] and the linear current density A [A/m]. If the flux density is low and A cannot be increased, the rotor has to be made larger than in machines having a high air gap flux density. In the case of multiple pole machines, the outer rotor approach, with its low rotor yoke height, offers an interesting alternative. The air gap diameter of these machines can be made larger than in conventional inner rotor type motors without increasing the machine outer dimensions. In this paper, an outer rotor PMSM with ferrite magnets is analyzed and tested. The machine characteristics in a fan drive are compared with an induction machine of the same power. [ABSTRACT FROM PUBLISHER]

High power machine has become a large market for wind power and ship propulsion electric, among other applications. Since the size of these machines is much larger than conventional industrial ones, optimum design must be considered in order to reduce the material cost and increase profitability. In this paper, a simple analytic optimization algorithm is used to maximize the apparent airgap power transferred under tangential stress constraint. In this approach, close related expressions between the main design variables, operational restrictions, and external dimensions are derived to build the mathematical structure of the optimization process. To improve the torque capacity estimation of the designed machine, a correction procedure, based on the previous result, is used to remove the idealizations considered for the initial design. Close agreement with the finite element analysis results are found with this approach, which is based on analytical method. [ABSTRACT FROM AUTHOR]

Optimal design for an axial-flux permanent magnet synchronous generator (AFPMSG) using genetic algorithm (GA) is presented, and the condition for minimum active material cost is deduced. A computer-aided design procedure based on the results of the GA is proposed. In the design procedure the practical and performance characteristics are taken into account as some restrictions for the object function used in the optimization algorithm. A 30-kW AFPMSG with two parallel connected stators and rotor-surface PMs is designed using the developed program, and then 3-D finite-element analyses are carried out to validate the design procedure. [ABSTRACT FROM AUTHOR]

Energy efficient pulse-width modulation inverters are widely used to control electrical machines accurately for process needs. The pulse-width modulation, however, has also adverse effects and produces additional losses in the motor. These losses increase the motor temperature and result in derating of the machine power in converter use. A reliable and reasonably accurate loss model of an induction motor drive system is important for the performance prediction of a variable-speed drive. A two-level frequency converter main circuit model is coupled to a finite-element method motor model. The drive model is controlled by closed-loop direct torque control. The frequency converter losses are calculated analytically, and the finite-element method motor model provides an analysis of the motor losses. The simulation results are compared with measurement results. [ABSTRACT FROM PUBLISHER]

Mechanical interactions between a wind turbine and a direct-driven permanent-magnet synchronous generator (PMSG) are studied, and a model to analyze the system behavior is suggested. The proposed model can be applied to analyze the mechanical vibrations of direct-driven wind turbine installations both in steady state and in dynamic cases. The cogging torque and torque ripple of the PMSG are used as excitation sources in the mechanical model. Four different permanent-magnet rotor constructions are analyzed. It is shown that the maximum allowable value of the cogging torque of the direct-driven permanent-magnet wind generator in this case is 1.5%–2% of the rated torque even when the corresponding resonance frequency does not occur in the operational speed range of the wind turbine. Furthermore, it was noticed that the resonance caused by the excitation torque should occur at the lowest possible speed. [ABSTRACT FROM AUTHOR]

This paper investigates the suitability of solid-rotor induction-motor technology for a natural-gas-compression application with a high power output. To this end, a new solid-rotor design for an 8-MW 6.6-ky 12 000-min-1 motor without any copper parts in the rotor was developed, and the motor performance was tested. In this paper, solid-rotor material selection, rotor slitting, and the end effects of the purely solid rotor are discussed. A frequency-dependent end-effect correction factor is introduced, and a method for the rotor-end-leakage correction is presented. The performance of the proposed end-effect correction factor is verified by comparing the calculated torque and power factor with the measured values. [ABSTRACT FROM AUTHOR]

Provides information on a study which deals with the numerical analysis of rotor losses in a medium speed direct torque controlled permanent-magnet synchronous motor. Methods; Results; Discussion.