Partial Demagnetization of Permanent Magnets in Electrical Machines Caused by an Inclined Field

Ruoho, S.; Arkkio, Antero

doi:10.1109/tmag.2008.921951

Cited by 67 publications

(38 citation statements)

References 7 publications

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“…Checking demagnetization in the current time step should be more time consuming since it will affect the calculation of the current step in each iteration. When checking for demagnetization, only the magnetic flux density parallel to the magnetization direction (here denoted y) was considered, since this has proven to work well for multi-pole machines, and it is hard to quantify the angular dependence [19,29]. Another difference between the models is that the Jacobian (the system matrix) had to be manually defined in the external function.…”

Section: Simulation Modelsmentioning

confidence: 99%

“…Faults in electrical machines is a common research topic, and there are several studies on demagnetization during different kinds of overload conditions [7,18,19]. However, it is very hard to recognize all possible faults, not only from a technical but also from an economical point of view.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, a study has been made on working point ripple in permanent magnets when the generator is connected to an external electrical circuit [22]. Important previous work on demagnetization include work by Ruoho [19,[23][24][25].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Permanent Magnet Demagnetization in Synchronous Machines during Multiple Short-Circuit Fault Conditions

Sjökvist

Eriksson

2017

Energies

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Faults in electrical machines can vary in severity and affect different parts of the machine. This study focuses on various kinds of short-circuits on the terminal side of a generic 20 kW surface mounted permanent magnet synchronous generator and how successive faults affect the performance of the machine. The study was conducted with the commercially available finite element method software COMSOL Multiphysics R , and two time-dependent models for demagnetization of permanent magnets were compared, one using only internal models and the other using a proprietary external function. The study is simulation based and the two models were compared to a previously experimentally verified stationary model. Results showed that the power output decreased by more than 30% after five successive faults. In addition, the no-load voltage had become unsymmetrical, which was explained by the uneven demagnetization of the permanent magnets. The permanent magnet with the lowest reduction in average remanence was decreased by 0.8%, while the highest average reduction was 23.8% in another permanent magnet. The internal simulation model was about four times faster than the external model, but slightly overestimated the demagnetization.

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Section: Simulation Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigation of Permanent Magnet Demagnetization in Synchronous Machines during Multiple Short-Circuit Fault Conditions

Sjökvist

Eriksson

2017

Energies

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“…The 3D FE static analysis is carried out for two values of peak armature currents 20 A and 200 A, corresponding to the full load and ten times the full load respectively. In [10], the authors proved that both antiparallel and perpendicular field components to the direction of magnetization are necessary to accurately estimate the level of demagnetization. Therefore, |H| and not |B| field distribution is [24], [25], the authors concluded that the edges and area of permanent magnet exposed to air gap are more susceptible to demagnetization than the inner volume.…”

Section: Estimation Of Demagnetization Level Of Ferrite Magnet Inmentioning

confidence: 99%

Performance Variation of Ferrite Magnet PMBLDC Motor With Temperature

et al. 2015

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The price fluctuations of rare earth metals and the uncertainty in their availability has generated an increased interest in ferrite magnet machines. The influence of temperature on BH characteristics of the ferrite magnet differ considerably from that of the rare earth magnet and hence, requires a different approach when deciding their operating point. In this work, laboratory measured BH curves of a ferrite magnet are used for estimating the possibility of demagnetization in a segmented axial torus (SAT) permanent magnet brushless DC (PMBLDC) motor. The BH characteristics for different temperatures have been used to study the performance variation of the ferrite magnet SAT PMBLDC motor with temperature. A detailed analysis is carried out to ensure that, the designed ferrite magnet motor is capable of delivering the specified torque throughout the operating speed, without any irreversible demagnetization of magnets. It has been shown that the ferrite magnet PMBLDC motor operation is influenced by the magnet temperature and the maximum motor speed for a given load torque decreases as the magnet temperature drops.

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“…Although the recoil curve will experience a slight bend upwards the linear model used and presented here is considered to be good enough [9], [10].…”

Section: Development Of Fem Modelmentioning

confidence: 99%

Experimental Verification of a Simulation Model for Partial Demagnetization of Permanent Magnets

Sjökvist

Eriksson

2014

IEEE Trans. Magn.

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PostprintThis is the accepted version of a paper published in IEEE transactions on magnetics. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. This article aims to verify a FEM simulation model for demagnetization of permanent magnets. The model is designed to determine the remaining magnetization within the permanent magnet after it has been exposed to high demagnetizing fields and/or temperature. An experimental set-up was built and a permanent magnet of SmCo type was experimentally tested. Good agreement is shown between the simulation and experimental results. A maximal deviation of 3 % of the simulation results in relative to the experimental results were achieved for most part of the magnet. During the calibration of the simulation model it was found that the coercivity had to be significantly more negative compared to the permanent magnet's reference value to match simulation results to the experimental results.

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Partial Demagnetization of Permanent Magnets in Electrical Machines Caused by an Inclined Field

Cited by 67 publications

References 7 publications

Investigation of Permanent Magnet Demagnetization in Synchronous Machines during Multiple Short-Circuit Fault Conditions

Investigation of Permanent Magnet Demagnetization in Synchronous Machines during Multiple Short-Circuit Fault Conditions

Performance Variation of Ferrite Magnet PMBLDC Motor With Temperature

Experimental Verification of a Simulation Model for Partial Demagnetization of Permanent Magnets

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