Eddy Current Loss Analysis Research Articles

Iron loss and eddy-current loss analysis in a low-power BLDC motor with magnet segmentation

Iron loss and eddy-current loss analysis in a low-power BLDC motor with magnet segmentation This paper considers a Brushless Direct Current (BLDC) machine prototype with six poles and 36 stator slots including a three phase double-layered distributed winding. Presented modifications of rotor construction are identified in order to achieve the best possible compromise of eddy-current losses and cogging torque characteristics. The permanent magnet (PM) eddy-current loss is relatively low compared with the iron loss; it may cause significant heating of the PMs due to the relatively poor heat dissipation from the rotor and it results in partial irreversible demagnetization. A reduction in both losses is achieved by magnet segmentation mounted on the rotor. Various numbers of magnet segmentation is analysed. The presented work concerns the computation of the no-load iron loss in the stator, rotor yoke and eddy-current loss in the magnets. It is shown that the construction of the rotor with segmented magnets can significantly reduce the PM loss (eddy-current loss). The eddy-current loss in PMs is caused by several machine features; the winding structure and large stator slot openings cause flux density variations that induce eddy-currents in the PMs. The effect of these changes on the BLDC motor design is examined in order to improve the machine performance. 3-D finite-element analysis (FEA) is used to investigate the electromagnetic behaviour of the BLDC motor.

Literature survey of eddy-current loss analysis in rotating electrical machines

Eddy current is a very important and intriguing phenomenon. A direct result of Lenz's law, it has been an integral part of research on electrical machines. The applications and associated research field of eddy currents are very widespread and virtually impossible to include in a singlestudy. Therefore this study tends to capture research trends in eddy-current loss analysis pertaining to the field of rotating electrical machines only. The research period taken up is from 1892 to 2010. The trends in research and application have been brought out. This study aims to serve as a reference guide to all those interested in the field of eddy-current loss analysis in electrical machines.

MODELING OF EDDY CURRENT LOSS AND TEMPERATURE OF THE MAGNETS IN PERMANENT MAGNET MACHINES

The eddy current loss in the magnets of permanent magnet (PM) motors in a hybrid electric vehicle (HEV) and plug-in HEV is usually not taken into consideration in traditional motor design and analysis. However, due to the high conductivity of the rare-earth magnet, neodymium-iron-boron (NdFeB), and slot/tooth harmonics, there is eddy current loss generated inside the magnets. This loss may not attribute very much to the efficiency of the motor, but the temperature-rise inside the magnets caused by this loss can lead to the unpredictable deterioration of the magnets, such as the degradation of performance and potential demagnetization. In addition, the output voltage of pulse-width-modulated (PWM) inverter contains abundant high frequency harmonics, which induce excessive loss in the magnets. The excessive heat in PM motor induced by the eddy current loss combined with other losses can degrade the performance of the machine. This paper presents the modeling and analysis of eddy current loss in surface-mounted-magnets PM synchronous motors (SPMSM) and interior-magnets PM synchronous motors (IPMSM), operated by PWM inverter supply. Analytical methods are implemented, in conjunction with time-stepped finite-element analysis (FEA) for the calculation of eddy current loss in the magnet. Based on the calculated losses in the machines, simplified analytical models are developed as thermal circuits with network of interconnected nodes, thermal resistances and heat sources representing the heat processes within the SPMSM and IPMSM, to predict the temperature of the magnets. The predicted machine temperatures are found to be consistent with the experimental measurement.

Eddy-Current Analysis of Double-Stator Inset-Type Permanent Magnet Brushless Machines

In this paper, a new multi-pole double-stator inset-type permanent magnet (PM) machine is proposed for low-speed direct-drive applications. In the outer stator, a fractional-slot concentrated winding is adopted to reduce the slot number and stator yoke height, hence saving the space and improving the torque density. In the inner stator, a vernier structure is used to reduce the winding slots and enlarge the slot area to accommodate more conductors, hence fully utilizing the inner stator space. Consequently, the torque density is improved, and the cogging torque is reduced. Since the machine structure is so unique while its operating principle is so distinct, a nodal method based network-field coupled time-stepping finite element method (NF-TS-FEM) is newly developed. The corresponding modeling and analysis are simpler and more convenient than its loop method based counterpart. The analysis of eddy-current loss in both of the PMs is conducted. The performance of the proposed machine is verified by the proposed NF-TS-FEM.

Analysis of Eddy-Current Loss in End Shield and Frame of a Large Induction Machine

This paper proposes an effective method of analyzing the eddy-current loss within the end shield and frame of an electric machine. The standard impedance boundary condition is applied to the conducting surfaces of complete 3-D models, and the models are solved by time-harmonic finite-element analyses. Measurement of the temperature rise is completed as a validation of the proposed method. The effect of the distances between the conducting surfaces and coil ends is studied by computing the eddy-current loss for a series of 3-D models having different distances. In addition, simplified 2-D models are used to study the influence of material nonlinearity. In brief, the proposed method is feasible in computing the eddy-current loss. The eddy-current loss within the regions close to the coil ends is larger than the other regions in the end shield and frame, but the total loss is quite small, compared, for instance, with the copper loss within the stator winding. Furthermore, the farther the end shield and frame are from the coil ends, the smaller the eddy-current loss is. Finally, it is found that the eddy-current loss is larger in the nonlinear case than in the linear case.

Analysis of Eddy-Current Loss in a Double-Stator Cup-Rotor PM Machine

In this paper, a new double-stator cup-rotor permanent-magnet brushless DC (PMBDC) machine is proposed and analyzed. Since the machine structure is so unique while its operating principle is so distinct, a numerical field approach, namely the circuit-field-torque grid-model time-stepping finite-element method (CFT-GM-TS-FEM), is newly developed to analyze the steady-state and dynamic characteristics of the machine. Particularly, the analysis of eddy-current loss in both the PMs and iron core of the machine is conducted. Experimental results are given for verification.

Iron Loss and Magnet Eddy Current Loss Analysis of IPM Motors with Concentrated Windings

In this paper, we investigate losses of interior permanent magnet motors with concentrated windings using the 3-D finite element method considering carrier harmonics of PWM inverters. The calculated results are compared with the measurement to verify the validity of the calculation. The motor with the distributed windings is also calculated to clarify the difference of the main loss factors. The measured and calculated results agree well. It is clarified that the losses generated at the rotor core and magnets especially increase, whereas the harmonic iron losses generated at the stator decrease, in the case of the motor with concentrated windings.

3D finite element analysis of eddy current loss of HTS tapes – External field analysis

The eddy current losses in the matrix of two twisted filaments Bi-2223 HTS tapes in applied external AC magnetic field was calculated using 3D FEM software. The highest eddy current loss in the matrix was experienced when magnetic field is applied perpendicular to the wide side of the rectangular model. Numerically calculated eddy current losses are plotted as the function of frequency, filament twist pitch, matrix conductivity and magnetic field amplitude. Longer filament twist pitch models have higher eddy current losses in transverse magnetic field. In longitudinal magnetic field shorter filament twist pitch have higher eddy current losses. Increases in the applied external field amplitude, frequency and matrix conductivity contributes to higher eddy current losses. Numerical calculation results shows that the contribution of eddy current loss at commercial frequency is not minimal. The numerical results presented are for uncoupled filaments HTS tapes.

Eddy Current and Loss Analysis of Multisteel Configuration and Validation

Three-dimensional nonlinear eddy current and stray-field loss analysis of multisteel configurations based on TEAM Problem 21 family and the related validation are presented. Some extended investigations to Problem 21, referred to as postbenchmarking, are outlined. The newly measured and calculated results of both the magnetic field and the stray-field loss illustrate the electromagnetic behavior of the prototype model. It is indicated that the power loss distribution in the multisteel parts closely depends on the material configuration and the applied fields

Analysis of Eddy-Current Loss for Design of Small Active Magnetic Bearings With Solid Core and Rotor

As the size of rotors levitated by active magnetic bearings (AMBs) gets smaller, it becomes increasingly difficult to make laminated cores and rotors that have low eddy-current loss, and solid cores and rotors have to be substituted. Thus, accurate modeling of eddy-current loss is important for small-size AMB systems with solid cores and rotor. In this paper, we propose a new eddy-current loss model for AMB systems, based on the eddy-current brake concept. We show that the eddy-current loss in AMBs strongly depends on the arrangement and size of poles. We compare test results for hetero- and homopolar AMBs having nonlaminated cores and rotor to analytical findings based on the eddy-current loss model. The experimental results confirm that the eddy-current loss in small homopolar AMBs with nonlaminated cores and rotor can be greatly reduced by optimizing the arrangement and size of poles.

Analysis of eddy current AC loss for untwisted, multifilamentary superconducting composites with various aspect ratios

AC loss was measured for several types of untwisted multifilamentary superconducting tapes using a VSM (vibrating sample magnetometer) at 4.2 K in fields both face-on (FO) and edge-on (EO) to the wide sides of aspected samples. The strand types investigated were NbTi/Cu-Mn (5000 filaments), NbTi/Cu (5000 filaments), and Bi2223/Ag. The samples were typically 1-1.5 cm long, untwisted, with a wide variety of outer aspect ratios, a/b. The measured losses were compared to those predicted by an expression linear in a/b. From this expression, the transverse resistivity of the matrix, /spl rho//spl perp/, was extracted and compared to that determined from directly measured RRR values, where /sub /spl rho//spl perp//=((1+/spl lambda/)/(1-/spl lambda/))/sup /spl plusmn/1/ /sub /spl rho/bulk/=G/sub /spl rho/bulk/. While the measured losses were generally in agreement with the calculations for strand types with larger numbers of filaments, significant deviations were found for strand types with smaller numbers of filaments. Strands with lower numbers of filaments always had lower than expected losses, leading to a/spl rho//sub /spl perp/,eff/ /spl Gt/G/spl rho//sub bulk/, which was interpreted in terms of a reduced or effective eddy current volume, V/sub f/. This effect, while quite strong for these untwisted samples, is expected to be less pronounced in twisted samples, with some exceptions as noted.

Eddy-current loss analysis in PM of surface-mounted-PM SM for electric vehicles

Recently the rare-earth magnet NdFeB has been applied to electric vehicles. The rise of temperature due to eddy current loss in the permanent magnet (PM) leads to serious deterioration of the PM, especially in high speed operation. This paper describes an original analysis of the eddy current loss in the PM of a surface-mounted-PM SM for electric vehicles. The finite element analysis makes clear the effect of eddy current loss in the PM of the PM synchronous motor (SM) in the high speed range of operation including field weakening.

Analysis of eddy current loss and magnetization process in Mn-Zn ferrites for power supplies

Analysis of eddy current loss and magnetization process in Mn-Zn ferrites for power supplies

Analysis of eddy current loss in Mn–Zn ferrites for power supplies

From the investigation regarding the dependence of power loss and electrical resistivity at a temperature at which crystalline anisotropic energy becomes zero, eddy current loss and residual loss could be obtained separately. The increase in residual loss as exciting magnetic flux density, Bm, follows Bm2 at 1 MHz and Bm3–4 at 100 kHz. This result shows that the residual loss arises from spin rotation inside the magnetic domain wall. The domain size was estimated to be in the region of 1–2 μm by applying the barlike domain-wall model to the eddy current loss obtained experimentally. The frequency of the spin rotation is estimated using the domain size, the thickness of the domain wall, and the exciting condition. The spin rotation inside the domain wall can reach the magnetic resonant frequency of Mn–Zn ferrites under the exciting condition of f>500 kHz and Bm>70 mT. This magnetic resonance occurring inside the domain wall is considered to generate the large residual loss.

Nonuniform domain magnetization in CoFeSiB amorphous ribbons

The low field ac susceptibility, χ=χ′−jχ′′, and domain structures of as-cast, stress relieved, and field annealed CoFeSiB amorphous ribbons are studied in the remanence state. An eddy current loss analysis is made based on a model which combines the contributions of domain wall displacements (DWD) and domain magnetization rotations (DMR). It is found that although having similar longitudinal bar domain structures, χ of the field annealed ribbon is due to DWD, but it is dominated by DMR for the first two, which indicates a nonuniform magnetization in the domains.

Analysis of eddy current loss in Mn-Zn ferrites for power supplies

An attempt was made to divide power loss in Mn-Zn ferrites into hysteresis loss, eddy current loss and residual loss factors experimentally. We noticed the correspondence between the temperature, Tmin at which hysteresis loss exhibits minimum value, and secondary peak temperature of initial permeability. Analyzing the power loss and electrical resistivity measured at Tmin, it was found that the powerless can be divided into hysteresis loss, resistivity dependent loss component (eddy current loss) and resistivity independent loss component. Consequently, the residual loss was identified to be a loss component independent of resistivity.

High-field effective linewidth and eddy current losses in moderate conductivity single-crystal M-type barium hexagonal ferrite disks at 10–60 GHz

The losses associated with the high-field tail region of the ferromagnetic resonance (FMR) absorption curve were investigated at 10, 19, 35, and 60 GHz for 0.10–1.75-mm-thick c-plane circular disks of flux-grown single-crystal M-type barium ferrite materials. A conventional high-field effective linewidth analysis of the data yielded an effective linewidth which increased with the square of the disk thickness and linearly with frequency, dependencies which indicate a predominant eddy current loss process. Based on these results, an eddy current loss analysis of the tail region was done, based on the insulator FMR response and eddy current losses driven by the FMR response. This analysis leads to a new noninvasive technique for the determination of the microwave conductivity in moderate conductivity ferrites. One obtains the conductivity from an appropriate analysis of the FMR absorption tail in the same way that analysis of the magnetic loss tail yields a high-field effective linewidth. Based on this technique, the microwave conductivity of these flux-grown barium ferrite single-crystal materials was determined as a function of frequency and found to increase linearly from 0.033±0.004 Ω−1 cm−1 at 10 GHz to 0.10±0.02 Ω−1 cm−1 at 60 GHz. These results are consistent with a measured dc conductivity of 0.03–0.05 Ω−1 cm−1.

Hybrid method for analysis of eddy-current loss in electrical machine winding caused by the main flux

A hybrid method for the analysis of eddy-current loss caused by the given main flux in rectangular bars of an electrical machine winding is described. Different bar structures are considered. With the help of a hybrid field analyzer, the effective damping coefficient of the magnetic field is calculated. Using this coefficient an analytical formula for computing the eddy-current loss is proposed. The accuracy of the method is investigated numerically. The influence of the magnetic saturation in the teeth on the eddy-current loss caused by the main flux is also analyzed. >