Search

Most permanent magnet (PM) loss studies consider only eddy current loss and neglect hysteresis. In this article, the hysteresis behavior of two NdFeB PM grades with different magnetic properties is assessed when applied in a PMSM. Data from vibrating sample magnetometer measurements and hysteresis modeling are used as a base. In addition to the main magnetic phase, the samples contained magnetic phases with reduced coercivity. Such phases may contribute to hysteresis losses in a PM material. A new model is introduced to simulate the hysteresis of rare-earth magnets of any geometric shape in the second and first quadrants of the intrinsic BH-plane. The magnetic field strength distribution in the PM material of an electrical motor is analyzed by two-dimensional finite-element method. The results are used as the input data for an analytical hysteresis model. The results indicate that the hysteresis loss resulting from the structural imperfections and geometry of the magnet may introduce a considerable loss in NdFeB PMs applied in rotating electrical machines. [ABSTRACT FROM AUTHOR]

This article proposes an analytic coupled magneto-thermal analysis of an axial-flux (AF) permanent-magnet-assisted (PMA) eddy-current brake (ECB) at high-temperature working conditions. In the topology investigated, permanent magnets (PMs) are placed into stator slot openings to increase the braking torque production capability. This modification enables to control the magnet flux by altering the dc excitation current. However, the utilization of PMs will make the construction vulnerable at high operating temperatures simply because the magnet properties and the brake capability are strongly dependent on temperature. Such problems require complex coupled multiphysics finite-element analyses to obtain the actual brake performance. The proposed approach offers a simple and effective solution that consists of magnetic and thermal models, which are coupled to each other in the time domain. The nonlinear electrical, magnetic, and thermal properties are influenced by the temperature variation in time. An AF-PMA-ECB prototype is manufactured to validate the proposed coupled models and the experimental studies confirm that the proposed approach provides very practical results to determine the working conditions of the AF-PMA-ECB at high-temperature operations. [ABSTRACT FROM AUTHOR]

A high demand for electrification of the transport sector has resulted in a need to provide compact and reliable electric power trains where the electric machine is a key element. The cooling system has a strong impact on the specific torque and power capability of the machine. The selection of the cooling solution should not be based on the steady-state cooling performance only but also on the transient characteristics owing to the typical operational load nature of the propulsion system, where the load is not continuous (as it usually is in industrial applications), but it frequently varies in time depending on the vehicle type and the driving style. This article investigates in detail the cooling capabilities of a direct winding liquid cooling solution and compares it with a traditional frame liquid cooling arrangement in the transient condition. As a result of the comparison, it was found that the location of heat removal close to the heat source makes the temperature transient time faster, which allows to apply overload operating points more frequently. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for the analytical computation of the slot leakage inductance of tooth-coil winding permanent magnet synchronous machines. Generalized equations for the slot leakage inductance of the whole phase are derived, suitable for several slot-pole combinations, and meant to be used during the machine design stage. For simplicity, self- and mutual-inductance components are formulated using the classical method with detailed permeance determination for both horizontal and vertical distribution of coil sides in the slots, considering a straight-line path for the flux leakage. Several slot-pole combinations were simulated by means of the finite element (FE) method in order to validate the analytical equations in both approaches, FE and analytical, showing adequate concordance. [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]

In this paper, hysteresis loss in magnetic poles of electrical machines with ferrite permanent magnets is studied. A vibrating sample magnetometer is used to observe the hysteresis behavior of three distinct commercial ferrite magnet grades. The measurement results indicate the presence of additional magnetic phases with reduced coercivity in the samples under study. These phases can act as an additional source of loss in ferrite magnets. A new modeling concept is introduced to simulate the hysteresis behavior of the ferrite magnet grades in the second and first quadrants of the intrinsic BH plane. Finite-element-calculated magnetic field distribution is used as an input for the analytical model to determine the hysteresis loss in the magnets of two distinct permanent magnet machine designs. The results indicate that some hysteresis loss in the ferrite permanent magnet magnetic poles of electrical machines may occur, but it plays a minor role in practice. [ABSTRACT FROM AUTHOR]

Traditional industrial electrical machines are designed avoiding strong iron saturation in the magnetic circuit. Flux-switching permanent magnet synchronous machines (FSPMSMs), however, differ significantly by their construction and magnetic circuit from the traditional PMSMs. In PMSMs, local saturation in the stator at no load can be avoided by a proper stator tooth and yoke design, but in FSPMSMs, the flux accumulates in the teeth toward the air gap, and the armature steel often becomes heavily saturated in the region close to the air gap. Therefore, it is difficult to avoid local saturation in an FSPMSM, and proper design tools are required to take this saturation into account when the machine is designed. This paper demonstrates the importance of accurate knowledge of steel properties in regions with heavy magnetic saturation. It is shown that especially the design process of an FSPMSM should be supported by an accurate $B - H$ curve of the steel up to 2.2 T and beyond (or at the point where the steel is completely saturated), because it has a significant influence on the overall performance of the machine. [ABSTRACT FROM PUBLISHER]

Hysteresis losses in ferrite permanent magnets (PMs) of a rotor-surface-magnet (RSM) PM synchronous machine (PMSM) were studied by means of vibrating sample magnetometer (VSM) measurements, updated static history dependent hysteresis model (HDHM) and finite element analysis (FEA). Open magnetic circuit VSM measurement results were applied to determine the magnet intrinsic properties. The HDHM developed originally for electrical steel hysteresis modeling is adopted for ferrite PM material. FEA-based results for magnetic field strength in PMs of a tooth coil winding RSM PMSM under ideal sinusoidal and frequency converter supplies were used as input data for the HDHM and the hysteresis losses were calculated in the machine's magnets. Differently from NdFeB and SmCo PMs ferrite PMs do not seem to demonstrate significant hysteresis behavior. It was found that the hysteresis loss could be neglected in ferrite PMs in most PMSM designs if the magnet is fully polarized. [ABSTRACT FROM PUBLISHER]

This paper presents an analysis of three different electrical machine topologies for a turbo circulator application. The electrical machines are designed to operate with 6 kW output power at 120 000 r/min. This paper demonstrates the design aspects of one solid rotor squirrel cage induction motor and two permanent magnet synchronous machines. The machines are compared using electromagnetic, thermal, and mechanical analyses. The benefits and disadvantages of each topology under study are discussed. For other high-speed applications presented, a comparative approach helps in selecting the suitable electrical machine topology by analyzing the performance criteria discussed. The prototype construction of one of the topologies is analyzed. [ABSTRACT FROM AUTHOR]

In permanent magnet synchronous machines (PMSM), depending on the machine application, different types of permanent magnets (PM) can be used. The most common PMs are ferrite magnets, neodymium iron boron magnets (NdFeB), and samarium cobalt magnets (SmCo). The selection of a suitable magnet for a particular machine design depends on the magnet properties: remanence, conductivity, mechanical rigidity, losses, and demagnetization characteristics. Usually, the possibility of hysteresis losses in PM materials is neglected. In this paper, however, it is demonstrated that possible hysteresis losses have to be evaluated in the machine design. It is shown by measurements and simulations that in some machine designs, hysteresis losses in NdFeB, SmCo, and ferrite magnets can be a source of significant additional ac losses that may lead to too high PM operating temperatures and a reduction in the machine efficiency. [ABSTRACT FROM PUBLISHER]

A novel rotor structure for a tooth-coil-winding (concentrated winding) open-slot axial-flux permanent-magnet (PM) machine that reduces the eddy currents and increases the main flux linkage is proposed in this paper. A composite-body-based rotor assembly and a steel-laminated layer inserted on top of the magnets are used to reduce eddy-current losses in the PMs. A prototype of an axial flux generator for a heavy-duty vehicle following this structure is optimized, analyzed and measured. The tooth coil windings produce high-amplitude harmonics in the air gap and the large slot openings reduce the rotor flux. Consequently, a rotor structure that decreases the amount of harmonics travelling through the magnets is required. Steel laminations covering the magnets have positive effects on both phenomena. Two-dimensional and three-dimensional finite-element analysis is used to verify and optimize the geometry of the laminations. Computations are verified by experimental measurements of a 100 kW test machine prototype. [ABSTRACT FROM PUBLISHER]

High-speed permanent-magnet synchronous machines (HS PMSMs) are a popular topology among modern electrical machines. Suitable applications for such machines are low-power vacuum pumps, compressors, and chillers. This paper describes a systematic design methodology for an HS PMSM using two case studies. The design process for such high-speed (HS) machines is multidisciplinary and highly iterative due to the complex interaction of the many design variables involved. Consequently, no single optimum solution exists, and multiple possible solutions can meet the customer requirements. Practical solutions should be within acceptable thermal limits, should be energy-efficient, and should be rigid enough to withstand the forces exerted during operation. The proposed design flow is divided into steps that are presented in this paper in the form of a flowchart with emphasis on mechanical aspects. Each step represents a task for a thermal, mechanical, or electrical engineer. The features of each step and the prerequisites for moving to the next step are discussed. The described methodology was implemented in the design of two HS PMSMs. The output performance results of the design flow are compared with measured results of the prototypes. The design process described in this paper provides a straightforward procedure for the multidisciplinary design of HS permanent magnet electrical machines. [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]

Permanent magnet (PM) materials are nowadays widely used in the electrical machine manufacturing industry. The eddy-current loss models of PMs used in electrical machines are frequently discussed in research papers. In magnetic steel materials we have, in addition to eddy-current losses, there are hysteresis losses when alternating current or a rotating flux travels through the material. Should a similar phenomenon be also taken into account in calculating the losses of PMs? Every now and then, authors seem to assume that some significant hysteresis losses are present in rotating machine PMs. This paper studies the mechanisms of possible hysteresis losses in PMs and their role in PMs when used in rotating electrical machines. [ABSTRACT FROM PUBLISHER]

Analytical calculation methods for all the major components of the synchronous inductance of tooth-coil permanent-magnet synchronous machines are reevaluated in this paper. The inductance estimation is different in the tooth-coil machine compared with the one in the traditional rotating field winding machine. The accuracy of the analytical torque calculation highly depends on the estimated synchronous inductance. Despite powerful finite element method (FEM) tools, an accurate and fast analytical method is required at an early design stage to find an initial machine design structure with the desired performance. The results of the analytical inductance calculation are verified and assessed in terms of accuracy with the FEM simulation results and with the prototype measurement results. [ABSTRACT FROM PUBLISHER]

Armature-reaction-compensated permanent-magnet synchronous generators are a particular type of hybrid excitation synchronous generators, where the main flux is created by the permanent magnets and the field winding is needed only to compensate the armature reaction. This paper studies the feasibility of an armature-reaction-compensated permanent magnet synchronous generator in island operation by comparison with a conventional electrically excited synchronous generator and permanent magnet synchronous generator. The aim of this paper is to demonstrate the performance of an armature-reaction-compensated permanent magnet synchronous generator and its operation principle in island operation. As part of the study, a 55 kW prototype was built and tested. The experimental results of the prototype are presented. [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 excitation synchronous generators are a special class of electrical machines in which the total rotor current linkage is produced by the simultaneous action of two different excitation sources: permanent-magnet (PM) excitation and field winding excitation. In the island operation, there is a need to compensate the armature reaction to keep the generator terminal voltage constant. The permanent magnet excitation is used to create the no-load excitation to the generator and the rotor winding is used as an armature reaction compensating winding. This paper studies the applicability of an armature-reaction-compensated PM synchronous generator to a marine diesel genset. This paper presents an analytical approach for the electromagnetic design of the proposed topology. Finite-element analysis and experimental measurements are performed to verify the results of the analytical approach. [ABSTRACT FROM PUBLISHER]

Heat transfer is a limiting factor in the performance of electrical machines. Measuring the heat flux in an electrical machine is traditionally carried out indirectly with temperature measurements as there are only a few sensors for heat flux measurements. This paper describes a new experimental method to measure the local heat flux inside an electrical machine. The measurement was proven successful in the air gap of the permanent magnet machine, 37 kW 2400 \min^-1, under an influence of the air gap magnetic flux. The heat flux was measured by using sensors based on the transverse Seebeck effect. The test machine was an axial flux permanent magnet machine with two stator stacks and one internal, ironless rotor disc. A gradient heat flux sensor was installed in the air gap on the stator side. Local Nusselt and Reynolds numbers were calculated according to the measured heat flux results and compared with the results given by traditional methods to verify the new measurement method. [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]

Most of the high-power, low-speed, direct-driven permanent magnet synchronous generators for wind energy applications apply a cooling solution where the stator core is divided into a number of substacks. Cooling air is blown through the stator through radial cooling channels formed between the adjacent stator substacks. The use of the stator substacks has an effect on the equivalent length of the generator, and thus, if neglected, leads to an incorrect no-load voltage and synchronous inductance calculation. In this paper, the design issues related to the thermal and electromagnetic design of permanent magnet synchronous machines are highlighted. The analysis starts with a preliminary electromagnetic design. Then, the allowable number and width of cooling ducts are calculated based on the maximum allowable temperatures and fluid flow speed with a thermal resistance network model. The effect of cooling ducts on the no-load voltage and synchronous inductances of the machine are discussed in detail. The calculated no-load voltage and synchronous inductances are used in the analytical performance evaluation. It is shown that the cross-saturation of the synchronous inductances must be taken into account in order to get realistic results. [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]

The energy efficiency of an electro-hydraulic forklift is significantly improved by using a permanent-magnet-synchronous-motor-servo-drive-based direct pump control to control the position of the fork without control valves. This paper provides a short evaluation of the hydraulic system and a more detailed analysis of the losses of the electric machine drive system. A theoretical approach is taken and the results are verified by practical measurements. Finally, possible improvements of the energy efficiency in the suggested system are discussed. [ABSTRACT FROM PUBLISHER]

The effect of lamination stack ends and radial cooling channels on the effective stator stack length, no-load voltage, and synchronous inductances of a permanent-magnet synchronous machine are studied using three-dimensional finite element analysis. The stack ends and the radial cooling channels decrease the equivalent electrical length of the machine, thus leading to the fact that a two-dimensional (2-D) approach overestimates the no-load voltage. The effect of stack ends and radial cooling channels on the electrical length of the machine can be compensated by making the rotor stack and permanent magnets longer than the corresponding stator stack. It is shown that in case of no radial cooling channels, synchronous inductances are typically overestimated with the 2-D approach. However, in the case of stator structure having several radial cooling channels, inductances are underestimated using the 2-D approach. [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]

Permanent-magnet synchronous machines (PMSMs) are gaining popularity in the industry and, especially, in distributed generation, for instance in windmill applications. Some of the traditional analytical design principles seem not to be valid for permanent magnets in machine excitation. We report on the effects of the permanent-magnet length in machine design. [ABSTRACT FROM PUBLISHER]

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.