Reduction of non-circulating bearing currents by electrical machine design
Vostrov, Konstantin (2023-09-22)
Väitöskirja
22.09.2023
Lappeenranta-Lahti University of Technology LUT
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:978-952-335-961-1
https://urn.fi/URN:ISBN:978-952-335-961-1
Kuvaus
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Tiivistelmä
Electrical machines and drive systems play a crucial role in industrial processes and everyday life. Electrical drive systems that are capable of operating in the variable speed mode allow applying electric motors for the widest range of tasks. Nowadays, drive systems based on the induction motor fed by a frequency converter have become the common setup and universal solution in various fields.
Nevertheless, the specific parasitic phenomenon of non-circulating bearing currents always accompanies modern electrical drive systems and is a common reason for bearing failures. Parasitic current passing the bearings can damage the raceways of the bearing and cause accelerated wear of its components, grease degradation, and early failure of the bearing unit, which leads to the failure of the entire system.
This doctoral dissertation focuses on inverter-induced non-circulating bearing currents and proposes countermeasures against the phenomenon. Other types of parasitic currents present in electrical machines are outside the scope of this work.
In the study, two approaches aimed to mitigate non-circulating bearing currents are introduced and verified. The approaches are numerically investigated by using FEA and verified in practice with 15 kW industrial induction machines. Analytical and experimental results show that non-circulating bearing currents can be mitigated if special countermeasures are applied to the electrical machine. For instance, placing the stator winding further from the rotor surface is a simple and effective countermeasure. Another mitigation technique is to employ partial electrostatic shields to break the capacitive coupling between the stator winding and the rotor.
The role of end windings in the generation of parasitic capacitances is also studied. An analysis carried out using the FEM showed that a notable part of parasitic capacitance between the rotor and the winding is generated in the end-winding area. An option to apply the electrostatic shielding principle to mitigate parasitic capacitances produced by end windings is studied, and several structural designs of special shields are shown.
Nevertheless, the specific parasitic phenomenon of non-circulating bearing currents always accompanies modern electrical drive systems and is a common reason for bearing failures. Parasitic current passing the bearings can damage the raceways of the bearing and cause accelerated wear of its components, grease degradation, and early failure of the bearing unit, which leads to the failure of the entire system.
This doctoral dissertation focuses on inverter-induced non-circulating bearing currents and proposes countermeasures against the phenomenon. Other types of parasitic currents present in electrical machines are outside the scope of this work.
In the study, two approaches aimed to mitigate non-circulating bearing currents are introduced and verified. The approaches are numerically investigated by using FEA and verified in practice with 15 kW industrial induction machines. Analytical and experimental results show that non-circulating bearing currents can be mitigated if special countermeasures are applied to the electrical machine. For instance, placing the stator winding further from the rotor surface is a simple and effective countermeasure. Another mitigation technique is to employ partial electrostatic shields to break the capacitive coupling between the stator winding and the rotor.
The role of end windings in the generation of parasitic capacitances is also studied. An analysis carried out using the FEM showed that a notable part of parasitic capacitance between the rotor and the winding is generated in the end-winding area. An option to apply the electrostatic shielding principle to mitigate parasitic capacitances produced by end windings is studied, and several structural designs of special shields are shown.
Kokoelmat
- Väitöskirjat [1179]