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This paper presents the thermal modelling and analysis of a hybrid excitation synchronous generator with alternated current linkages (HESG-ACL) for stand-alone power supply. The HESG-ACL belongs to a class of hybrid excitation synchronous machines (HESMs), which combine the merits of electrically excited synchronous machines (EESMs) and permanent magnet synchronous machines (PMSMs). To confirm the performance and thermal behaviour of the HESG-ACL, an experimental prototype (69 kVA apparent power) equipped with thermal sensors was built and tested. A description of the HESG-ACL is given. The thermal analysis of the HESG-ACL is carried out based on the thermal resistance network model. The results obtained from the thermal model are verified by the experimental results. [ABSTRACT FROM AUTHOR]

This paper provides design guidelines for the passive LC filters. Based on these guidelines, a method to design a new type of a passive filter, called hybrid LC filter, is proposed. A filter design example accompanies the considerations; simulation and test results of the proposed filter in time and frequency domains are shown. [ABSTRACT FROM PUBLISHER]

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]

This paper continues the design considerations of a novel type of passive filter called hybrid LC filter (HLCF). The filter is aimed at significant reduction in high-frequency differential mode (DM) and common mode (CM) currents in speed-controlled ac drives. A model of the HLCF is presented. Based on the model, a transfer function of the HLCF is found. The HLCF behavior is analyzed in frequency domain. A method for HLCF frequency-domain behavior estimation with asymptotes is proposed. A comparison of the measured, simulated, and calculated results in frequency domain is presented. [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]

A lumped-parameter-based thermal analysis applicable to radial-flux electrical machines with a high power density is presented. The modeling strategies using T-equivalent lumped-parameter blocks as well as conventionally defined thermal resistances are discussed. Special attention is paid to the modeling of the convective heat transfer in the air gap of radial-flux electrical machines at different rotational speeds. A brief overview of the evaluation of different loss components is given. The performance of the developed thermal model was verified by comparing the calculated temperature values with the measurements in three different applications. [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.

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]

A self-holding three-position electric tubular actuator (SHTPETA) is described in the article. The proposed linear actuator can be applied in a clutch system, where it is necessary to change certain mover positions over time. Other potential applications of such actuators can be shift of gears, coupling (decoupling) of various moving (rotating) mechanisms, or electromagnetic valves. The self-holding force of the proposed SHTPETA is achieved by the reluctance force between the armature and mover cores, where a magnetic flux is excited by a permanent magnet located in the armature and an excitation current is not needed, whereas the moving force is determined by the dc voltage (current) applied to two coils located in the stationary part of the SHTPETA. The article proposes a relatively fast and simple approach for the SHTPETA design process based on the required forces and moved distance. [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]

Being much more rugged than a rotor made of traditional steel sheets, a solid rotor is frequently used in high-power high-speed induction machines (IMs). Furthermore, by a solid-rotor machine, a higher rotating speed can be achieved. However, the solid rotor also has certain disadvantages, the relatively high solid-rotor eddy-current losses being the most serious one. Basically, solid-rotor eddy-current losses are mainly induced by time–spatial air-gap flux density high-order harmonics. The suppression of the high-order harmonics is the key means to mitigate the rotor eddy-current losses. In this paper, a novel computational model is proposed for evaluating the rotor harmonic eddy-current losses of a 2 MW, 12 000 r/min IM. The model was built on a special machine referred to as a virtual permanent magnet harmonic machine (VPMHM). The model was constructed by applying the finite-element method (FEM), and it is based on the time–spatial harmonics produced by a rotating magnet with sinusoidal magnetization. The VPMHM model links the air-gap flux density harmonics directly to the specific rotor eddy-current losses. Furthermore, according to the proposed model, three options, namely, the use of air-gap permeance modifying notches on the stator teeth, semimagnetic wedges, and their combination, were investigated in detail for mitigating the rotor eddy-current losses in the motor nominal operating point. The results and conclusions in this paper are based on the FEM analysis. [ABSTRACT FROM AUTHOR]

High-power high-speed induction machines (IMs) are gaining ground in various industrial applications, especially in replacing traditional motors and gearboxes driving compressors or high-pressure pumps, etc. However, the high-speed technology presents extra challenges for the mechanical structure of the machine including bearing systems. Therefore, it is often reasonable to use active magnetic bearings (AMBs) instead of traditional bearings as they provide much smaller friction and allow a not perfectly centered orbit of the rotor without affecting the lifetime of the bearings. Using AMBs in a machine, the nonuniformity of the rotor leads to an inevitable rotor eccentricity; the level of which depends on the control tolerance and dynamic characteristics of the AMB and the maximum force generated by the AMB. This rotor eccentricity results in an unbalanced magnetic pull (UMP) of the rotor, which has to be compensated by the AMB. This paper analyzes the UMPs of a 2 MW, 12 000 r/min IM in the static eccentricity, dynamic eccentricity, and mixed eccentricity conditions. The AMB system was designed and optimized with the consideration of gravity and UMP effects. Furthermore, the required current compensation for the forces in the horizontal and vertical directions was studied during the operation and verified by the finite-element method. [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]

Permanent-magnet synchronous machines (PMSM) are gaining a foothold in a growing number of applications. However, the high cost of these machines compared with the prices of induction motors, whose production process is mature and material costs are low, limits the use of PMSMs with rare-earth permanent magnets in many potential cases. A viable design solution for a PMSM cost reduction is to use low-cost ferrite magnets instead of rare-earth ones. Nevertheless, it is challenging to apply ferrite magnets to a high-power rotor surface magnet PMSM because of their weaker magnetic properties compared with the rare-earth magnets and the risk of irreversible demagnetization. This paper aims to investigate the boundaries and limiting factors for achieving the maximum tangential stress and linear current density at a certain air gap diameter by using rotor surface ferrite magnets. The computed results are validated by a prototype, which was designed within the described boundaries. [ABSTRACT FROM PUBLISHER]

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]