Power Balance in the Finite Element Analysis of Electrical Machines

Bishal Silwal

Research output: ThesisDoctoral ThesisCollection of Articles


This dissertation deals with the study of the power balance in the numerical simulations of electrical machines. In the numerical analysis of electrical machines using the finite element method, several methods and techniques to compute torque and force exist, but the existing methods are not free from accuracy issues. In this dissertation, approaches based on the power balance of the machine to obtain torque and force are presented, and the possibility to use the power balance approach to validate the existing methods is shown. Both healthy machines and machines with an eccentric rotor have been considered. The applicability of the power balance approach to study the electromagnetic damping of the mechanical vibrations during eccentricity is also assessed. This dissertation carefully compares a conventional torque and force computation method and the power balance approach, based on the finite element mesh used in the air gap of the machine during simulations. Variations in the air gap mesh is brought by changing the number of layers of elements and the layer used for the rotation of the rotor and for the torque and force computation. Results show that the conventional method suffers from an accuracy issue mainly related to the finite element discretization of the air gap of the machine. Variations in the air gap mesh do not affect torque from the power balance. However, force computation from the power balance is not yet robust. The influence of the rotor eccentricity on the torque of the machine was also studied. Results show that an eccentric machine does not exhibit the same torque as a healthy machine. The harmonic components around the principal slot harmonic are most affected. In this thesis, a measurement set-up to measure the torque harmonics of a machine was designed. The measured results were compared with the simulated results.
Translated title of the contributionTehotasapaino sähkökoneiden elementtimenetelmäanalyysissä
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Arkkio, Antero, Supervising Professor
  • Belahcen, Anouar, Thesis Advisor
  • Rasilo, Paavo, Thesis Advisor
Print ISBNs978-952-60-7433-7
Electronic ISBNs978-952-60-7432-0
Publication statusPublished - 2017
MoE publication typeG5 Doctoral dissertation (article)


  • eccentricity
  • electromagnetic torque
  • finite element method
  • forces
  • harmonics
  • induction machine
  • mesh
  • power balance
  • rotor dynamics

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