Inter-laminar Contacts and Losses in Cores of Electrical Machine
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School of Electrical Engineering |
Doctoral thesis (article-based)
| Defence date: 2018-01-17
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Authors
Date
2017
Major/Subject
Mcode
Degree programme
Language
en
Pages
95 + app. 51
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 202/2017
Abstract
This dissertation deals with the modeling of inter-laminar contacts in the cores of electrical machines. A series of punching and pressing processes forms random burrs at the edges of electrical sheets. These burrs form random inter-laminar galvanic contacts when pressed. Several numerical formulations based on finite element method were developed. A surface boundary layer model is implemented in a 2D finite element analysis of the electrical machine. An efficient stochastic model to account for random inter-laminar contacts is proposed and validated. Eddy current loss due to inter-laminar contacts in a laminated core was obtained experimentally, and the effect on eddy current loss coefficient was studied. Based on 3D FE simulations, and obtained eddy current loss, an iterative method was developed to estimate the equivalent conductivity of the laminated core. Finally, a measurement setup was designed to perform a short-circuit and thermal test on the inter-laminar contacts. A statistical study of random inter-laminar galvanic contacts at the edges of the stator of an induction machine showed a 7.7 % increase in mean electromagnetic losses. An efficient stochastic method was implemented to account for random inter-laminar contact that reduced computation time by 76 %. The eddy current loss coefficient due to inter-laminar contacts was increased by 2 % in the case of one limb fault of the EI core and 2.7 % in the case of two limb fault. Finally, the measurements from thermography test were used to estimate the size of the inter-laminar contacts and the finite element method validated the results.Description
Supervising professor
Arkkio, Antero, Prof., Aalto University, Department of Electrical Engineering and Automation, FinlandThesis advisor
Rasilo, Paavo, Asst. Prof., Tampere University of Technology, FinlandKeywords
Finite element analysis, inter-laminar contacts, stochastic finite element methods, thermography measurement
Other note
Parts
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[Publication 1]: Sahas Bikram Shah, Paavo Rasilo, Anouar Belahcen, and Antero Arkkio. Modeling of Losses Due to Inter-laminar Short Circuit Currents in Lamination Stacks. RTU Electrical, Control and Communication Engineering, Vol. 3, No. 1, pp 31–36, September 2013.
DOI: 10.2478/ecce-2013-0012 View at publisher
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[Publication 2]: Sahas Bikram Shah, Paavo Rasilo, Anouar Belahcen, and Antero Arkkio. Estimation of Additional Losses Due to Random Contacts at the Edges of an Electrical Machine. COMPEL-The international journal for computation and mathematics in electrical and electronic engineering, Vol. 34, No. 5, pp 1501–1510, November 2015.
DOI: 10.1108/COMPEL-02-2015-0083 View at publisher
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[Publication 3]: Sahas Bikram Shah, Paavo Rasilo, Harri Hakula, and Antero Arkkio. Efficient Finite Element Method to Estimate Eddy Current Loss due to Random Interlaminar Contacts in Electrical Sheets. Accepted for publication in International Journal of Numerical Modeling, May 2017.
DOI: 10.1002/jnm.2254 View at publisher
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[Publication 4]: Sahas Bikram Shah, Paavo Rasilo, Anouar Belahcen and Antero Arkkio. Experimental and Theoretical Study of Interlaminar Eddy Current Losses in Laminated Cores. In The 20th International Conference on Electrical Machines and Systems (ICEMS 2017), pp 1-6, Sydney, Australia, August 2017.
DOI: 10.1109/ICEMS.2017.8056356 View at publisher
- [Publication 5]: Sahas Bikram Shah, Osaruyi Osemwinyen, Paavo Rasilo, Anouar Belahcen and Antero Arkkio. A Thermographic Measurement of Inter-laminar Contact Sizes and Losses in Electrical Sheets. IEEE Transactions on Instrumentation and Measurement, Submitted, pp1–6, 2017.