Modeling and Analysis of a High-Speed Solid-Rotor Induction Machine
Di, Chong (2020-04-28)
Väitöskirja
28.04.2020
Lappeenranta-Lahti University of Technology
Acta Universitatis Lappeenrantaensis
School of Energy Systems
School of Energy Systems, Sähkötekniikka
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In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of Lappeenranta-Lahti University of Technology LUT's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_ standards/publications/rights/rights_ link.html to learn how to obtain a License from RightsLink.
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-507-1
https://urn.fi/URN:ISBN:978-952-335-507-1
Tiivistelmä
Over the last few decades, high-speed electrical machines have become more popular than ever before because of the rapid development of power electronics, magnetic materials, and control engineering. Among all the machine types, the solid-rotor induction machine (IM) has the greatest potential to rotate with the highest rotor peripheral speed. Therefore, this doctoral dissertation focuses on the high-speed solid-rotor IM, contributing to modeling of the solid-rotor IM, extraction of solid-rotor eddy-current harmonic losses, and mitigation of current unbalance caused by the asymmetric winding arrangement.
Because of its high accuracy, the Finite Element Analysis (FEA) is well appreciated in the electrical machine design. Nevertheless, the FEA transient magnetic (TM) solution is sometimes too time consuming, especially for the IM analysis. The situation is even worse when it comes to the solid-rotor IM. The doctoral dissertation introduces a potential approach to accelerate the TM analysis of IMs, implemented by reducing the stator and rotor electromagnetic time constants and shown to be more efficient than the traditional direct transient method.
The rotor eddy-current losses are a significant factor in the solid-rotor IM design. To efficiently mitigate the losses, it is of paramount importance to first fully understand the generation of losses and extract the harmonic losses from the total rotor losses. In this doctoral dissertation, the 2D fast Fourier transform was employed to extract the harmonics of the air-gap flux density. Then, all the important harmonics were rebuilt by a special setting in the air gap with the FEA to excite the solid rotor alone, which finally extracted the solid-rotor eddy-current harmonic losses successfully.
To achieve the stator winding installation with prefabricated coils, it was decided to apply an asymmetric winding arrangement in the electromagnetic design stage. Nevertheless, this solution produced some inherent stator leakage inductance unbalance. A novel winding coil arrangement was introduced to mitigate the current unbalance. The stator inductance was adjusted by placing coils in a different position in each slot. The final coil arrangement yielded a much more balanced three-phase stator current after the optimization.
Because of its high accuracy, the Finite Element Analysis (FEA) is well appreciated in the electrical machine design. Nevertheless, the FEA transient magnetic (TM) solution is sometimes too time consuming, especially for the IM analysis. The situation is even worse when it comes to the solid-rotor IM. The doctoral dissertation introduces a potential approach to accelerate the TM analysis of IMs, implemented by reducing the stator and rotor electromagnetic time constants and shown to be more efficient than the traditional direct transient method.
The rotor eddy-current losses are a significant factor in the solid-rotor IM design. To efficiently mitigate the losses, it is of paramount importance to first fully understand the generation of losses and extract the harmonic losses from the total rotor losses. In this doctoral dissertation, the 2D fast Fourier transform was employed to extract the harmonics of the air-gap flux density. Then, all the important harmonics were rebuilt by a special setting in the air gap with the FEA to excite the solid rotor alone, which finally extracted the solid-rotor eddy-current harmonic losses successfully.
To achieve the stator winding installation with prefabricated coils, it was decided to apply an asymmetric winding arrangement in the electromagnetic design stage. Nevertheless, this solution produced some inherent stator leakage inductance unbalance. A novel winding coil arrangement was introduced to mitigate the current unbalance. The stator inductance was adjusted by placing coils in a different position in each slot. The final coil arrangement yielded a much more balanced three-phase stator current after the optimization.
Kokoelmat
- Väitöskirjat [1091]