Stator core material selection for kinetic energy storage
Grönlund, Mikko (2018)
Grönlund, Mikko
2018
Materiaalitekniikka
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
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Hyväksymispäivämäärä
2018-05-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201804241541
https://urn.fi/URN:NBN:fi:tty-201804241541
Tiivistelmä
The goal of this thesis was to study a novel electric machine stator configuration. The main target was to screen possible material groups for the fabrication of such stator and to provide a design process for further evaluation and quick assessment method for new materials and material groups.
The main differentiating point in comparison to traditional machinery in the discussed energy storage design is the large radius of the rotor combined to a hubless flywheel. The question that lead to the work was: ”Does the large radius enable the use of high drive frequency low loss stator materials?”. The purpose of stator in a motor/generator is to transform electrical energy to kinetic form and back to electric with high efficiency. In high speed rotating machines this involves a trade off between high operation frequency, which causes increased eddy-current losses, and lower pole number which causes increase in stator unit size thus increasing the fabrication costs or makes the manufacturing of the core units difficult or impossible. On the other hand a large rotor radius helps in torque production by increasing the lever of the tangential force by many times when compared to typical machine design which usually aims to create as much torque in small space as possible.
The main material groups discussed in this work are traditional laminated electric steels, that are widely used in electric machinery, powder compacted ferrites that are typically used in transformers but ignored in traditional machine design for their poor magnetic permeability and soft magnetic materials that are in the middle ground of aforementioned materials. The main results of this work are analytically derived dimensions of E-cores of these materials for three different machine sizes in two different use cases. The resulting configurations are then evaluated from manufacturing and efficiency standpoints.
The main differentiating point in comparison to traditional machinery in the discussed energy storage design is the large radius of the rotor combined to a hubless flywheel. The question that lead to the work was: ”Does the large radius enable the use of high drive frequency low loss stator materials?”. The purpose of stator in a motor/generator is to transform electrical energy to kinetic form and back to electric with high efficiency. In high speed rotating machines this involves a trade off between high operation frequency, which causes increased eddy-current losses, and lower pole number which causes increase in stator unit size thus increasing the fabrication costs or makes the manufacturing of the core units difficult or impossible. On the other hand a large rotor radius helps in torque production by increasing the lever of the tangential force by many times when compared to typical machine design which usually aims to create as much torque in small space as possible.
The main material groups discussed in this work are traditional laminated electric steels, that are widely used in electric machinery, powder compacted ferrites that are typically used in transformers but ignored in traditional machine design for their poor magnetic permeability and soft magnetic materials that are in the middle ground of aforementioned materials. The main results of this work are analytically derived dimensions of E-cores of these materials for three different machine sizes in two different use cases. The resulting configurations are then evaluated from manufacturing and efficiency standpoints.