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dc.contributor.advisorVan Schoor, G.
dc.contributor.advisorBessinger, N.
dc.contributor.authorRanft, Cornelius Jacobus Gerhardusen_US
dc.date.accessioned2011-10-05T13:32:30Z
dc.date.available2011-10-05T13:32:30Z
dc.date.issued2010en_US
dc.identifier.urihttp://hdl.handle.net/10394/4940
dc.descriptionThesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.
dc.description.abstractThe McTronX research group at the North–West University designs and develops Active Magnetic Bearings (AMBs). The group’s focus shifted to the design and development of AMB supported drive systems. This includes the electromagnetic and mechanical design of the electric machine, AMBs, auxiliary bearings as well as the development of the control system. The research group is currently developing an AMB supported high speed Induction Machine (IM) drive system that will facilitate tests in order to verify the design capability of the group. The research presented in this thesis describes the mechanical design and manufacturing of a high speed IM rotor section. The design includes; selecting the IM rotor topology, material selection, detail stress analysis and selecting appropriate manufacturing and assembly procedures. A comprehensive literature study identifies six main design considerations during the mechanical design of a high speed IM rotor section. These considerations include; magnetic core selection, rotor cage design, shaft design, shaft/magnetic core connection, stress due to operation at elevated temperatures and design for manufacture and assemble (DFMA). A critical overview of the literature leads to some design decisions being made and is used as a starting point for the detail design. The design choices include using a laminated cage rotor with a shrink fit for the shaft/magnetic core connection. Throughout the detail design an iterative process was followed incorporating both electromagnetic and mechanical considerations to deliver a good design solution. The first step of the iterative design process was, roughly calculating the material strengths required for first iteration material selection followed by more detailed interference fit calculations. From the detail stress analysis it became apparent that the stress in the IM rotor section cannot be calculated accurately using analytical methods. Consequently, a systematically verified and validated Finite Element Analysis (FEA) model was used to calculate the interferences required for each component. The detail stress analysis of the assembly also determined the allowable manufacturing dimensional tolerances. From the detail stress analysis it was found that the available lamination and squirrel cage material strengths were inadequate for the design speed specification of 27,000 r/min. The analysis showed that a maximum operating speed of 19,000 r/min can be achieved while complying with the minimum factor of safety (FOS) of 2. Each component was manufactured to the prescribed dimensional tolerances and the IM rotor section was assembled. With the failure of the first assembly process, machine experts were consulted and a revised process was implemented. The revised process entailed manufacturing five small lamination stacks and assembling the stack and squirrel cage afterwards. The end ring/conductive bar connection utilises interference fits due to the fact that the materials could not be welded. The process was successful and the IM rotor section was shrink fitted onto the shaft. However, after final machining of the rotor’s outer diameter (OD), inspections revealed axial displacement of the end rings and a revised FEA was implemented to simulate the effect. The results indicated a minimum FOS 0.6 at very small sections and with further analytical investigation it was shown that the minimum FOS was reduced to only 1.34. Although the calculations indicated the FOS was below the minimum prescribed FOS ? 2, the rotor spin tests were scheduled to continue as planned. The main reasons being that the lowest FOS is at very small areas and is located at non critical structural positions. The fact that the rotor speed was incrementally increased and multiple parameters were monitored, which could detect early signs of failure, further supported the decision. In testing the rotor was successfully spun up to 19,000 r/min and 27 rotor delevitation test were conducted at speeds of up to 10,000 r/min. After continuous testing a secondary rotor inspection was conducted and no visible changes could be detected. The lessons learnt leads to mechanical design and manufacturing recommendations and the research required to realise a 27,000 r/min rotor design.en_US
dc.publisherNorth-West University
dc.subjectInduction machineen_US
dc.subjectRotor sectionen_US
dc.subjectLaminationsen_US
dc.subjectMagnetic coreen_US
dc.subjectSquirrel cageen_US
dc.subjectShrink fiten_US
dc.subjectMaterialen_US
dc.subjectFinite element analysisen_US
dc.subjectFactor of safetyen_US
dc.subjectContact pressureen_US
dc.subjectTangential stressen_US
dc.subjectVon Misesen_US
dc.subjectHigh speeden_US
dc.titleMechanical design and manufacturing of a high speed induction machine rotoren
dc.typeThesisen_US
dc.description.thesistypeMastersen_US


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