Investigation of the design, manufacture and testing of additively manufactured coils for electric motor applications

Silbernagel, Cassidy (2019) Investigation of the design, manufacture and testing of additively manufactured coils for electric motor applications. PhD thesis, University of Nottingham.

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Electric motor design has been relatively unchanged for nearly a century. However, there is a movement in our world to replace inefficient combustion technology with electricity. While current electric motor technology is being used in numerous areas, manufacturing has been limited to traditional techniques which result in inefficient and unreliable machines for achieving those electrification goals. As a result, there needs to be a shift in how these motors are manufactured and designed. Additive manufacturing (AM) can provide this shift, however, there has been both a lack of information on how to use AM to design for these applications and of electrical properties for AM materials processed by Laser Powder Bed Fusion (LPBF). This work helps to fill in some of this missing information.

The first part of this work used DfAM and first principles to design coils which help achieve the goals of efficient, powerful and robust electric motors. It was demonstrated that AM can greatly increase the fill factor of a motor which increases its power density and efficiency. It can minimise the amount of support material required which aids in creating coils with AM. AM can also modify the end-turns of a coil to aid in thermal dissipation which further improves efficiency and reliability.

Copper is a common material for electrical applications but has been very difficult to process with LPBF due to its high reflectivity and high thermal conductivity. Despite this, some have attempted to process copper but failed to provide any electrical properties such as resistivity. Despite a wide range of parameter optimisation, copper was not able to be processed in this work to a high density. Despite this, resistivity measurements with respect to initial build orientation and heat treatments were taken and found to be lower than fully dense AlSi10Mg. Artificial intelligence was also used to perform a secondary quality assessment of individual thin walls to aid in parameter optimisation. With the challenges of processing a high purity material to a high density, an aluminium alloy which can be processed to a high density was then studied.

AlSi10Mg is an alloy commonly used by LPBF, however, there has been an incomplete body of knowledge surrounding its electrical properties. Previous research has neglected initial build orientations, variations that heat treatment can cause, and used techniques that assumed isotropic properties. In this work, experiments were performed to characterise these effects to electrical resistivity and microstructure. In addition, a geometric accuracy study was performed in order to understand the differences between model and as-built dimensions.

The results from this work can be used as a guide to aid motor designers in using AM for electric motor manufacture. Through these improvements, electric motors can potentially become more powerful and reliable. They can then aid in global electrification and help reduce greenhouse gas emissions.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Ashcroft, Ian
Dickens, Phill
Galea, Michael
Keywords: Additive manufacturing; 3D printing; Copper; AlSi10Mg; Electric motor coil windings
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Faculties/Schools: UK Campuses > Faculty of Engineering
UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
Item ID: 57090
Depositing User: Silbernagel, Cassidy
Date Deposited: 30 Oct 2019 08:40
Last Modified: 06 May 2020 13:33

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