Experimental and simulated modal analyses of stator coils of electric generators

Jukka Junttila, Kalle Vehviläinen

Research output: Book/ReportReportProfessional

Abstract

The mechanical behavior of a stator has not been frequently simulated using finite element method (FEM). This may be due to unknown material parameters of the materials used in the stator windings or as well the complex geometry and composite structure of a stator that has made creating a reasonably sized finite element model (FE models) very hard if not impossible. The goal of this study was to find an effective way to simulate the dynamics of stator windings accurately using FEM. The unknown material parameters of the materials used in stator windings were defined as a part of this study. The goals of this study were reached by first measuring the natural frequencies and mode shapes of three different pieces of coil of a stator. Then FE models of the three measured pieces of coil were created and the material parameters in the FE models were adjusted so that the calculated natural frequencies and mode shapes corresponded with the measured. The comparison of the measured and simulated mode shapes was done visually and using MAC. Based on the results of this study it can be said that the goals were reached. An accurate and effective way of modelling stator windings was found and the material parameters of the materials used in the windings and the effect of temperature of the coil to its dynamics were defined. The MAC comparisons showed that the correlation between the experimental and simulated modal analyses was very good for the first two pieces of coil and adequate for the third piece of coil. The differences between the calculated and measured natural frequencies were small in general. However, the maximum absolute difference between the natural frequencies of a natural mode shape pair was 19.8 %. The FE models of the pieces of coil were updated to match the results of the experimental modal analyses by modifying only the value of modulus of elasticity of the materials used in the windings. Although the correlation between the experimental and simulated modal analyses was good, better results could be achieved by adding more variable parameters, such as Poisson's ratio and density or by using anisotropic material definition, in the model updating process. It would be recommended to use an existing routine in the model updating process if the number of the variable parameters is increased.
Original languageEnglish
PublisherCLEEN Cluster for Energy and Environment
Number of pages50
ISBN (Print)978-952-5947-37-3
Publication statusPublished - 2013
MoE publication typeD4 Published development or research report or study

Publication series

Name
PublisherCLEEN Cluster for Energy and Environment
No.D2.18

Fingerprint

Electric generators
Stators
Natural frequencies
Finite element method
Poisson ratio
Composite structures
Elastic moduli

Keywords

  • electric generator
  • stator
  • coil
  • winding
  • copper
  • experimental modal analysis
  • free vibration analysis
  • finite element method (FEM)
  • modal assurance criteria (MAC)

Cite this

Junttila, J., & Vehviläinen, K. (2013). Experimental and simulated modal analyses of stator coils of electric generators. CLEEN Cluster for Energy and Environment.
Junttila, Jukka ; Vehviläinen, Kalle. / Experimental and simulated modal analyses of stator coils of electric generators. CLEEN Cluster for Energy and Environment, 2013. 50 p.
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title = "Experimental and simulated modal analyses of stator coils of electric generators",
abstract = "The mechanical behavior of a stator has not been frequently simulated using finite element method (FEM). This may be due to unknown material parameters of the materials used in the stator windings or as well the complex geometry and composite structure of a stator that has made creating a reasonably sized finite element model (FE models) very hard if not impossible. The goal of this study was to find an effective way to simulate the dynamics of stator windings accurately using FEM. The unknown material parameters of the materials used in stator windings were defined as a part of this study. The goals of this study were reached by first measuring the natural frequencies and mode shapes of three different pieces of coil of a stator. Then FE models of the three measured pieces of coil were created and the material parameters in the FE models were adjusted so that the calculated natural frequencies and mode shapes corresponded with the measured. The comparison of the measured and simulated mode shapes was done visually and using MAC. Based on the results of this study it can be said that the goals were reached. An accurate and effective way of modelling stator windings was found and the material parameters of the materials used in the windings and the effect of temperature of the coil to its dynamics were defined. The MAC comparisons showed that the correlation between the experimental and simulated modal analyses was very good for the first two pieces of coil and adequate for the third piece of coil. The differences between the calculated and measured natural frequencies were small in general. However, the maximum absolute difference between the natural frequencies of a natural mode shape pair was 19.8 {\%}. The FE models of the pieces of coil were updated to match the results of the experimental modal analyses by modifying only the value of modulus of elasticity of the materials used in the windings. Although the correlation between the experimental and simulated modal analyses was good, better results could be achieved by adding more variable parameters, such as Poisson's ratio and density or by using anisotropic material definition, in the model updating process. It would be recommended to use an existing routine in the model updating process if the number of the variable parameters is increased.",
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Junttila, J & Vehviläinen, K 2013, Experimental and simulated modal analyses of stator coils of electric generators. CLEEN Cluster for Energy and Environment.

Experimental and simulated modal analyses of stator coils of electric generators. / Junttila, Jukka; Vehviläinen, Kalle.

CLEEN Cluster for Energy and Environment, 2013. 50 p.

Research output: Book/ReportReportProfessional

TY - BOOK

T1 - Experimental and simulated modal analyses of stator coils of electric generators

AU - Junttila, Jukka

AU - Vehviläinen, Kalle

N1 - Project code: 41976 Appendix 47 p.

PY - 2013

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N2 - The mechanical behavior of a stator has not been frequently simulated using finite element method (FEM). This may be due to unknown material parameters of the materials used in the stator windings or as well the complex geometry and composite structure of a stator that has made creating a reasonably sized finite element model (FE models) very hard if not impossible. The goal of this study was to find an effective way to simulate the dynamics of stator windings accurately using FEM. The unknown material parameters of the materials used in stator windings were defined as a part of this study. The goals of this study were reached by first measuring the natural frequencies and mode shapes of three different pieces of coil of a stator. Then FE models of the three measured pieces of coil were created and the material parameters in the FE models were adjusted so that the calculated natural frequencies and mode shapes corresponded with the measured. The comparison of the measured and simulated mode shapes was done visually and using MAC. Based on the results of this study it can be said that the goals were reached. An accurate and effective way of modelling stator windings was found and the material parameters of the materials used in the windings and the effect of temperature of the coil to its dynamics were defined. The MAC comparisons showed that the correlation between the experimental and simulated modal analyses was very good for the first two pieces of coil and adequate for the third piece of coil. The differences between the calculated and measured natural frequencies were small in general. However, the maximum absolute difference between the natural frequencies of a natural mode shape pair was 19.8 %. The FE models of the pieces of coil were updated to match the results of the experimental modal analyses by modifying only the value of modulus of elasticity of the materials used in the windings. Although the correlation between the experimental and simulated modal analyses was good, better results could be achieved by adding more variable parameters, such as Poisson's ratio and density or by using anisotropic material definition, in the model updating process. It would be recommended to use an existing routine in the model updating process if the number of the variable parameters is increased.

AB - The mechanical behavior of a stator has not been frequently simulated using finite element method (FEM). This may be due to unknown material parameters of the materials used in the stator windings or as well the complex geometry and composite structure of a stator that has made creating a reasonably sized finite element model (FE models) very hard if not impossible. The goal of this study was to find an effective way to simulate the dynamics of stator windings accurately using FEM. The unknown material parameters of the materials used in stator windings were defined as a part of this study. The goals of this study were reached by first measuring the natural frequencies and mode shapes of three different pieces of coil of a stator. Then FE models of the three measured pieces of coil were created and the material parameters in the FE models were adjusted so that the calculated natural frequencies and mode shapes corresponded with the measured. The comparison of the measured and simulated mode shapes was done visually and using MAC. Based on the results of this study it can be said that the goals were reached. An accurate and effective way of modelling stator windings was found and the material parameters of the materials used in the windings and the effect of temperature of the coil to its dynamics were defined. The MAC comparisons showed that the correlation between the experimental and simulated modal analyses was very good for the first two pieces of coil and adequate for the third piece of coil. The differences between the calculated and measured natural frequencies were small in general. However, the maximum absolute difference between the natural frequencies of a natural mode shape pair was 19.8 %. The FE models of the pieces of coil were updated to match the results of the experimental modal analyses by modifying only the value of modulus of elasticity of the materials used in the windings. Although the correlation between the experimental and simulated modal analyses was good, better results could be achieved by adding more variable parameters, such as Poisson's ratio and density or by using anisotropic material definition, in the model updating process. It would be recommended to use an existing routine in the model updating process if the number of the variable parameters is increased.

KW - electric generator

KW - stator

KW - coil

KW - winding

KW - copper

KW - experimental modal analysis

KW - free vibration analysis

KW - finite element method (FEM)

KW - modal assurance criteria (MAC)

M3 - Report

SN - 978-952-5947-37-3

BT - Experimental and simulated modal analyses of stator coils of electric generators

PB - CLEEN Cluster for Energy and Environment

ER -

Junttila J, Vehviläinen K. Experimental and simulated modal analyses of stator coils of electric generators. CLEEN Cluster for Energy and Environment, 2013. 50 p.