Evaluation of open-source FEM software performance in analysing converter-fed induction machine losses
Zaheer, Minhaj (2022-01-28)
Väitöskirja
28.01.2022
Lappeenranta-Lahti University of Technology LUT
Acta Universitatis Lappeenrantaensis
School of Energy Systems
School of Energy Systems, Sähkötekniikka
Kaikki oikeudet pidätetään.
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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:978-952-335-782-2
https://urn.fi/URN:ISBN:978-952-335-782-2
Tiivistelmä
Converter-fed induction machines are widely used in variable speed applications. They are renowned for their good controllability, low manufacturing cost, and robustness. These machines are used in various applications both on an industrial and a commercial scale, for instance in pumps, cranes, lifters, conveyor belts, automation systems and drives, packaging machines, and in various other industrial equipment. Manufacturers are investing in their design and production systems to make their machines more cost-effective and efficient. Nowadays, the computational capabilities of the finite element analysis (FEA) make it possible to optimize machines in a successful way, and comparison of FEA results with laboratory experiments provides a further means to improve machines reliability. However, there is still a long and hard path to make the FEA more efficient. One step forward in the realm of FEA is the development of open-source FEA platforms, which make it possible to analyse machines more efficiently and faster, without the need to pay licence fees to any organization. In this doctoral dissertation, IE3-rated 5-kW converter-fed induction machine models are analysed using an open-source FEA considering different operating situations.
In this study, losses in a 2D model of the open-source FEA are compared with commercial FEA results and laboratory measurement results. Furthermore, a 2.5D model is analysed in the open-source FEA to achieve more accurate results than what can be obtained with the 2D analysis. The benefit of the open-source FEA is that the simulation time is efficiently reduced by increasing the number of cores and by parallel computing. Moreover, during the laboratory experiment, the PWM-recorded voltage has a 1 μs sample time. For the FEA, the recorded data are down-sampled to three different time steps for faster calculations. In the FEA analysis, the length of each time step is analysed against the accuracy of the results and the computational speed.
Computing additional losses and stray losses in the FEA is extremely challenging, and therefore, these losses are estimated analytically. In this dissertation, measured loss components obtained by the IEC loss segregation method are compared with two FEAbased methods, post-processing, and an emulating test procedure. The latter one employs the loss segregation procedure by using FEA values to obtain fixed and variable losses. Laboratory measurement results confirm that the FEA-based methods are valid to be used.
Furthermore, laboratory experiments and a FEA analysis are performed using different switching frequencies at the operating fundamental frequencies of 25 and 40 Hz. The results confirm that the losses in the 5-kW induction machine decrease as the switching frequency is increased. However, the distribution of the losses varies. The results, however, support the general concept of reducing the overall losses with an increasing switching frequency.
Overall, the open-source FEA shows fast, acceptable, and as reliable results as the commercial FEA and laboratory measurements. Therefore, in future research, it can be used more efficiently to obtain accurate results.
In this study, losses in a 2D model of the open-source FEA are compared with commercial FEA results and laboratory measurement results. Furthermore, a 2.5D model is analysed in the open-source FEA to achieve more accurate results than what can be obtained with the 2D analysis. The benefit of the open-source FEA is that the simulation time is efficiently reduced by increasing the number of cores and by parallel computing. Moreover, during the laboratory experiment, the PWM-recorded voltage has a 1 μs sample time. For the FEA, the recorded data are down-sampled to three different time steps for faster calculations. In the FEA analysis, the length of each time step is analysed against the accuracy of the results and the computational speed.
Computing additional losses and stray losses in the FEA is extremely challenging, and therefore, these losses are estimated analytically. In this dissertation, measured loss components obtained by the IEC loss segregation method are compared with two FEAbased methods, post-processing, and an emulating test procedure. The latter one employs the loss segregation procedure by using FEA values to obtain fixed and variable losses. Laboratory measurement results confirm that the FEA-based methods are valid to be used.
Furthermore, laboratory experiments and a FEA analysis are performed using different switching frequencies at the operating fundamental frequencies of 25 and 40 Hz. The results confirm that the losses in the 5-kW induction machine decrease as the switching frequency is increased. However, the distribution of the losses varies. The results, however, support the general concept of reducing the overall losses with an increasing switching frequency.
Overall, the open-source FEA shows fast, acceptable, and as reliable results as the commercial FEA and laboratory measurements. Therefore, in future research, it can be used more efficiently to obtain accurate results.
Kokoelmat
- Väitöskirjat [1099]