scholarly journals Limitations and Constraints of Eddy-Current Loss Models for IPM Motors with Fractional-Slot Concentrated Windings

2017 ◽  
Author(s):  
Hui Zhang ◽  
Oskar Wallmark
Keyword(s):  
Eddy Current ◽  
Permanent Magnets ◽  
Eddy Currents ◽  
Angular Frequency ◽  
Density Variation ◽  
Permanent Magnet Motors ◽  
Approximate Analytical Expression ◽  
Loss Models ◽  
Interior Permanent Magnets ◽  
Fractional Slot

This paper analyzes and compares models for predicting average magnet losses in interior permanent-magnet motors with fractional-slot concentrated windings due to harmonics in the armature reaction (assuming sinusoidal phase currents). Particularly, loss models adopting different formulations and solutions to the Helmholtz equation to solve for the eddy currents are compared to a simpler model relying on an assumed eddy-current distribution. Boundaries in terms of magnet dimensions and angular frequency are identified (numerically and using an identified approximate analytical expression) to aid the machine designer whether the more simple loss model is applicable or not. The assumption of a uniform flux-density variation (used in the loss models) is also investigated for the case of V-shaped and straight interior permanent magnets. Finally, predicted volumetric loss densities are exemplified for combinations of slot and pole numbers common in automotive applications.

scholarly journals Eddy Current Transducer with Rotating Permanent Magnets to Test Planar Conducting Plates

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1408 ◽  
Author(s):  
Tomasz Chady ◽  
Jacek Grochowalski
Keyword(s):  
Magnetic Fields ◽  
Eddy Current ◽  
Permanent Magnets ◽  
Eddy Currents ◽  
Nonuniform Distribution ◽  
Current Transducer ◽  
Different Depths ◽  
Hall Sensors ◽  
Eddy Current Transducer

In this paper, we present an eddy current transducer with rotating permanent magnets for the inspection of planar conducting plates. The transducer consists of a rotating head with permanent magnets, which is used to generate variable magnetic fields and thus induce eddy currents in the tested material. Two Hall sensors connected in a differential manner are used to detect a nonuniform distribution of eddy currents induced in a specimen containing a defect. To prove the usability of the transducer, a number of experiments were conducted on thick aluminum samples containing notches at different depths. Selected results of the achieved measurements are presented.

scholarly journals Finite Element Solutions for Magnetic Field Problems in Terfenol-D Transducers

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2808
Author(s):  
Duo Teng ◽  
Yatian Li
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Eddy Current ◽  
Permanent Magnets ◽  
Eddy Currents ◽  
Iron Alloy ◽  
Current Response ◽  
Bias Magnetic Field ◽  
Field Range ◽  
Eddy Current Losses

An appropriate magnetic design helps ensure that the Terfenol-D (Terbium- Dysprosium-Iron alloy) rods in giant magnetostrictive transducers have the perfect magnetostriction ability. To determine the optimum Terfenol-D rod state, a segmented stack configuration comprised by the Terfenol-D rods and NdFeB (neodymium-iron-boron) permanent magnets is presented. The bias magnetic field distributions simulated through the finite element method indicate that the segmented stack configuration is one effective way to produce the desired bias magnetic field. Particularly for long stacks, establishing a majority of domain to satisfy the desired bias magnetic field range is feasible. On the other hand, the eddy current losses of Terfenol-D rods are also the crucial to their magnetostriction ability. To reduce eddy current losses, the configuration with digital slots in the Terfenol-D rods is presented. The induced eddy currents and the losses are estimated. The simulations reveal that the digital slots configuration decreases the eddy current losses by 78.5% compared to the same size Terfenol-D rod with only a hole. A Terfenol-D transducer prototype has been manufactured using a Terfenol-D rod with a mechanical prestress of about 10 MPa and a bias magnetic field of about 42 kA/m. Its maximum transmitting current response of 185.4 dB at 3.75 kHz indicates its practicability for application as an underwater projector.

Performance prediction and analysis of disk-type eddy-current drivers

2017 ◽  
Vol 40 (5) ◽  
pp. 1568-1578 ◽  
Author(s):  
Zhao Li ◽  
Dazhi Wang ◽  
Tongyu Shi ◽  
Xue Bai
Keyword(s):  
Eddy Current ◽  
Performance Prediction ◽  
Permanent Magnets ◽  
Eddy Currents ◽  
Three Dimensional ◽  
Prediction Method ◽  
Maximum Error ◽  
Static Field ◽  
Average Error ◽  
Three Dimensional Finite Element

For the disk-type eddy-current drivers, an accurate and simple performance prediction method is developed. The static field produced by the permanent magnets and induction field by eddy currents are calculated using magnetic equivalent circuit method, and Faraday’s and Ampere’s law, respectively. In this model, many factors, such as the saturation effect of ferromagnetic materials, working temperature and the electromagnetic effects of back iron are taken into consideration. Compared with other methods, the model has a good agreement with three-dimensional finite-element method, and the average error is 4.9%. Finally, a prototype and corresponding test platform are made. Test results show that the proposed method is effective, and the maximum error is less than 8%. Besides, it is confirmed that eddy-current drivers can tolerate shaft misalignment and be used as speeders.

A new analytical approach to determine slotting based eddy current losses in permanent magnets of PMSM taking into account axial and circumferential segmentation

2015 ◽  
Vol 34 (2) ◽  
pp. 398-412 ◽  
Author(s):  
Cornelius Bode ◽  
Wolf-Rüdiger Canders ◽  
Markus Henke
Keyword(s):  
Eddy Current ◽  
Analytical Approach ◽  
Permanent Magnets ◽  
Eddy Currents ◽  
3D Fem ◽  
Eddy Current Losses ◽  
Content Type ◽  
High Frequencies ◽  
Reaction Field ◽  
3D Fea

Purpose – The purpose of this paper is to calculate slotting-based eddy currents in permanent magnet excited synchronous machine (PMSM) taking into account axial and circumferential segmentation of magnets. Design/methodology/approach – An analytical approach to calculate eddy current losses in PM caused by slotting harmonics of PMSM is presented. The eddy current reaction field is taken into account as well as axial and circumferential segmentation of the magnets. Findings – The analytical model provides results comparable to 3D-FEM calculations even at high frequencies at reduced computation costs. To generalize the results the magnetic Reynold’s number is introduced. Originality/value – Taking into account the axial and circumferential segmentation in the PDE; the approach is much more accurate compared to known approaches; accuracy is comparable to 3D-FEA.

The Influence of Pole-Slot Match on Magnetomotive Force with Concentrated Fractional-Slot Winding

2013 ◽  
Vol 397-400 ◽  
pp. 1209-1213 ◽  
Author(s):  
Meng Si ◽  
Ying Li Yang
Keyword(s):  
Magnetic Field ◽  
Basic Principle ◽  
Eddy Current ◽  
Permanent Magnets ◽  
Eddy Current Loss ◽  
Harmonic Waves ◽  
Magnetomotive Force ◽  
Current Loss ◽  
Fractional Slot

Magnetic field, produced by magnetomotive force (MMF) harmonic waves, is harmful to motors, by reducing efficiency of motors, resulting in demagnetization of permanent magnets and so on. It is also responsible for the increase of eddy current loss and the rise of temperature of rotors. Thus, research on the influence of pole-slot match on MMF with concentrated fractional-slot winding is necessary. This paper aims at researching unit motors with different cooperation of slots and poles. First, basic principle of MMF is described. Then, with different kinds of unit motors, MMF of harmonic waves is analyzed. Based on these analyses, distributive regularities are summarized.

Determination of eddy current losses and hysteresis losses in magnetic circuits of electrical machines

2020 ◽  
pp. 54-58
Author(s):  
S. M. Plotnikov
Keyword(s):  
Eddy Current ◽  
Magnetization Reversal ◽  
Eddy Currents ◽  
Technical Problem ◽  
Electrical Machines ◽  
Eddy Current Losses ◽  
Hysteresis Losses ◽  
Magnetic Circuits ◽  
Core Losses ◽  
Reversal Frequency

The division of the total core losses in the electrical steel of the magnetic circuit into two components – losses dueto hysteresis and eddy currents – is a serious technical problem, the solution of which will effectively design and construct electrical machines with magnetic circuits having low magnetic losses. In this regard, an important parameter is the exponent α, with which the frequency of magnetization reversal is included in the total losses in steel. Theoretically, this indicator can take values from 1 to 2. Most authors take α equal to 1.3, which corresponds to the special case when the eddy current losses are three times higher than the hysteresis losses. In fact, for modern electrical steels, the opposite is true. To refine the index α, an attempt was made to separate the total core losses on the basis that the hysteresis component is proportional to the first degree of the magnetization reversal frequency, and the eddy current component is proportional to the second degree. In the article, the calculation formulas of these components are obtained, containing the values of the total losses measured in idling experiments at two different frequencies, and the ratio of these frequencies. It is shown that the rational frequency ratio is within 1.2. Presented the graphs and expressions to determine the exponent α depending on the measured no-load losses and the frequency of magnetization reversal.

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