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

Sjökvist, Stefan; Eriksson, Sandra

doi:10.1109/tmag.2014.2339795

Cited by 25 publications

(18 citation statements)

References 10 publications

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“…The two models were verified against a stationary model based on the same principle, which, with good agreement, has been compared to experiments [20,21]. A three-legged iron core where the middle leg had an air gap, one leg had a permanent magnet and one leg had a coil of 100 turns was used for the comparison.…”

Section: Comparison To Verified Modelmentioning

confidence: 99%

“…Previous work on demagnetization within this project includes a study on single short-circuit events on a 12 kW generator using a stationary model [20] as well as experimental verification of the stationary demagnetization model [21]. Furthermore, a study has been made on working point ripple in permanent magnets when the generator is connected to an external electrical circuit [22].…”

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: Comparison To Verified Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Sjökvist

Eriksson

2017

Energies

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“…The demagnetization risk has been analysed for the 12 kW generator installed in the Marsta wind turbine, and has shown no risk of demagnetization [51]. A simulation model studying partial demagnetizing of permanent magnet has been developed and experimentally verified [52].…”

Section: Research On Generators For Vawtsmentioning

confidence: 99%

A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University

2016

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This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of the work done on the 12 kW prototype VAWT in Marsta, Sweden. Several key aspects have been tested and successfully demonstrated at our two experimental research sites. The effort of the VAWT research has been aimed at developing a robust large scale VAWT technology based on an electrical control system with a direct driven energy converter. This approach allows for a simplification where most or all of the control of the turbines can be managed by the electrical converter system, reducing investment cost and need for maintenance. The concept features an H-rotor that is omnidirectional in regards to wind direction, meaning that it can extract energy from all wind directions without the need for a yaw system. The turbine is connected to a direct driven permanent magnet synchronous generator (PMSG), located at ground level, that is specifically developed to control and extract power from the turbine. The research is ongoing and aims for a multi-megawatt VAWT in the near future.

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“…The demagnetisation simulations were performed using a static FEM model developed in Comsol Multiphysics [9,10]. The demagnetisation model is based on an exponent function model presented by Ruoho et al [14].…”

Section: Demagnetisation Simulationsmentioning

confidence: 99%

“…This article aims to evaluate the demagnetisation risk of both generators during different short-circuit events. A detailed description of the finite element method (FEM) simulation model used for the demagnetisation simulations as well as experimental verification can be found in [9,10].…”

Section: Introductionmentioning

confidence: 99%

Determining demagnetisation risk for two PM wind power generators with different PM material and identical stators

Sjökvist

Eklund

Eriksson

2016

IET Electric Power Applications

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Ways to utilise ferrite permanent magnets (PMs), in a better way has been in focus the last couple of years since the use of neodymium-iron-boron (NdFeB) PMs has been debated. While ferrite PMs offer a low-cost alternative to rareearth PMs, it is a trade-off for lower energy density. Depending on the type of PM and if the PMs are surface mounted or buried, the risk of demagnetisation during a fault condition can vary significantly between machines. In this study, the demagnetisation risk of two electrically similar generators with identical stators has been studied during several shortcircuit faults at different temperatures. The study is simulation-based, and the results show that the generator with the ferrite rotor will suffer from a small but not significant amount of demagnetisation in the worst, three-phase-neutral, short-circuit case at a temperature of 5°C, whereas the NdFeB PMs will suffer from partial demagnetisation if a fault occurs at 120°C. For operational temperatures between 20 and 60°C both generators will sustain a short-circuit event.

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

Cited by 25 publications

References 10 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

A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University

Determining demagnetisation risk for two PM wind power generators with different PM material and identical stators

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