Date of Award

10-30-2020

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Aluminum wire, Copper wire, Electric motor, Formability, Hairpin winding, Windability

Supervisor

Afsaneh Edrisy

Supervisor

A. R. Riahi

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Environmental concerns driven by climate change have resulted in increased market demand for lightweight and inexpensive electric vehicles. This study examines the feasibility of replacing copper conductors with aluminum conductors in automotive scale electric motors to address this demand. A comprehensive review of the literature contrasting aluminum and copper conductors is included to create a unified source for future research. This study also contains a two-part formability and windability analysis of square cross section electrical conductor aluminum and rectangular electrolytic tough pitch copper. The first part of the analysis applies standardized testing from ASTM D1676 to characterize the formability and windability of both conductors. Aluminum saw formability and windability advantages over copper, especially regarding springback, accommodation of elongation during high speed winding, and repeated absorption of bends and twists during winding; however, insulation adhesion and delamination issues occurred for elongation beyond 10% due to incompatibility of properties between the polymer coating and aluminum wire. The second part of the analysis compares forming behaviour of aluminum to known results for copper using a novel wire bending simulator machine. The effects of normal load, wire travel speed, and forming angle on coefficient of friction (COF) are analyzed to determine the feasibility of using aluminum for hairpin windings. The analysis finds that COF increases with both wire travel speed and forming angle. COF versus normal load shows a spike in COF followed by a sharp decrease indicative of a deformation mechanism that copper did not experience. Macroscopic analysis reveals aluminum to be more susceptible to damage from the forming equipment when compared to copper. Microscopic analysis reveals shingles and a suspected near-surface deformed layer at the aluminum/insulation interface. Detachment of these imperfections was found to occur at peak COF loads and higher from crack propagation and insulation flow into said cracks. Overall, this study shows aluminum is a viable conductor that provides significant cost and weight savings in electric machines with similar performance to copper; however, further improvement to aluminum surface quality and insulation properties is required to effectively replace copper.

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