Transient thermal modelling of an Axial Flux Permanent Magnet (AFPM) machine with model parameter optimisation using a Monte Carlo method

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Thermal management of an axial flux permanent magnet machine considering heat pipes

Thesis (MScEng) -- Stellenbosch University, 2003.ENGLISH ABSTRACT: Axial Flux Permanent Magnet (AFPM) machines have become attractive because of significant improvements in permanent magnets over the past decade, improvements in power electronic devices, and the ever increasing need for more efficient machines in electric vehicle systems. In comparison with the cylindrical radial flux motor, the AFPM machine is better in a number of aspects: short frame; compact construction; high efficiency; brush less construction; good starting torque and high-power density. The common modes of failure and typical operating conditions of AFPM machines are discussed further. The focus of this research project is a prototype AFPM machine developed by the Electrical Engineering Department of The University of Stellenbosch. The machine considered has a power rating of 300 kW and an operating efficiency of 95 % at a speed of 2300 rpm. This specific machine is used as an example to illustrate the thermal characteristics of geometrically similar AFPM machines. The thermal characterization was achieved with the use of two numerical computer models. Firstly a fluid model was specially developed and experimentally verified. The objective of the fluid model was to calculate the mass flow rate of air through any geometrically similar AFPM machine. The fluid model was further used to investigate the effects of different magnet thickness and axial gaps between the stator and the rotor plates on the mass flow rate of air through the machine. The fluid model was verified with experimental testing that was done on a half-scale Perspex model. During the experimental testing the magnet thickness was varied between 2.5 mm, 5.0 mm, and 7.5 mm along with axial gaps of 6.5 mm, 7.5 mm, 8.5 mm, and 9.5 mm. The fluid model showed a correlation to within 10 % of the experimental mass flow rates. The results of these tests showed that the magnet thickness and axial gap between the stator and the rotor plates had no significant effect on the mass flow rate of air. The fluid model was based on one-dimensional, steady-state, and incompressible flow. The second numerical computer model was a thermal model. This model was used to calculate the transient temperature response of the AFPM machine. The model was based on a twodimensional transient finite difference solution technique. Experimental temperatures taken from the prototype AFPM machine were used to verify the thermal model. Correlations between the experimental and theoretical temperatures were within 5.8 % of each other. The thermal model was used to investigate the effect of geometrical changes on the temperatures in the AFPM machine. It was found that these geometrical changes had no significant effect on the temperatures in the AFPM machine. It was also established that increasing the air mass flow rate over about I kg/s had no further effect on lowering the temperatures. The stator was also identified as being the most critical component as it reached its maximum temperature limit before any other component. Heat pipes were considered as an alternative thermal management technique. The location of the heat pipe was limited to the stator. Further simulations were done to investigate the effect of the heat pipe properties on the amount of heat removed from the stator. Recommendations were made concerning the thermal management of the current and possible future prototype AFPM machines. It was recommended that a further more detailed investigation into the use of heat pipes be considered. This recommendation is substantiated by the fact that in this research project only one type of heat pipe was considered and its location was limited to within the stator.AFRIKAANSE OPSOMMING: AFPM masjiene het meer aantreklik geword weens betekenisvolle verbeteringe in permanente magnete gedurende die laaste dekade, verbeteringe in elektroniese toestelle en die vraag na meer effektiewe masjiene in elekriese voertuigstelsels. Die AFPM masjien is beter as die Silindriese Radiale Fluksie Motor wat die volgende aspekte betref: die kort raamwerk; kompakte konstruksie; hoe effektiwiteit; borsellose konstruksie; goeie aanvangsdraaimoment; en hoe-krag digtheid. Die algemene vorms van faling en ook die tipiese werkstoestande van die AFPM word verder bespreek. Hierdie navorsingsprojek fokus op die prototipe AFPM masjien wat ontwikkel is deur die Elektriese Ingenieurs Departement van die Universiteit van Stellenbosch. Die masjien onder bespreking wek 300 kW per uur op en is 95% effektief teen 'n spoed van 2300 rpm. Hierdie masjien word gebruik om die termiese kenmerke van geometries-gelyksoortige masjiene te illustreer. Die termiese eienskappe is bepaal deur die gebruik van twee numeriese rekenaarmodelle. Eerstens is 'n vloeistofmodel spesiaal ontwerp en eksperimenteel geverifieer. Die doel van die vloeistofmodel was om die massa vloeitempo van lug deur enige geometries-gelyksoortige AFPM masjien te bereken. Die vloeistofmodel is verder gebruik om die uitwerking van verskillende magneetdiktes en aksiale gapings tussen die stator en die rotorplate op die massa vloeitempo van lug deur die masjien te ondersoek. Die vloeistofmodel is geverifieer deur eksperimentele toetsing wat gedoen is op 'n halfskaal Perspex model. Tydens die toetsing het magneetdiktes gewissel tussen 2.5 mm, 5.0 mm en 7.5 mm en die aksiale gapings tussen 6.5 mm, 7.5 mm en 9.5 mm. Die vloeistof model het 'n korrelasie van binne 10 % van die eksperimentele massa vloeistempo getoon. Die resultate van hierdie toetse het getoon dat die magneetdiktes en die aksiale gapings tussen die stator en die rotorplate geen noemenswaardige uiterking op die massa vloeitempo van lug gehad het nie. Die vloeistofmodel is gebaseer op een-dimensionele, gestadigde, onsamedrukbare vloei. Die tweede numeriese model was 'n termiese model. Hierdie model is gebruik om die transiente temperatuur respons van die AFPM masjien te bereken. Die model is gebaseer op 'n tweedimensionele, transiente eindige-verskil oplossingstegniek. Eksperimentele temperature gemeet op die prototipe AFPM masjien is gebruik om die termiese model te verifeer. Die eksperimentele en teoretiese temperature het binne 5.8% met mekaar gekorrelleer. Die termiese model is gebruik om die uitwerking van geometriese veranderinge op die temperatuur in die AFPM masjien te ondersoek. Daar is gevind dat hierdie geometriese veranderinge geen noemenswaardige uitwerking op die temperature van die AFPM masjien gehad het nie. Daar is ook vasgestel dat 'n vermeerdering in die lug massa vloeitempo yerby I kg/s geen verdere uitwerking het op die verlaging van die temperatuur gehaad het nie. Die stator is ge-identifiseer as die mees kritiese komponent aangesien dit sy maksimum temperatuur limiet bereik het voor enige ander komponent, Hittepype is oorweeg as 'n alternatiewe termiese bestuurstegniek. Die plasing van die pype is tot die stator beperk. Verdere simulasies is uitgevoer om die uitwerking van die hittepyp eienskappe op die hoeveelheid hitte wat verwyder word van die stator te ondersoek. Aanbevelings is gemaak m.b.t die termiese bestuur van die huidige en moontlike toekomstige prototipes van AFPM masjiene. Daar is aanbeveel dat daar in meer besonderhede ondersoek ingestel word na die gebruik van hittepype. Die rede hiervoor is dat daar in hierdie studie net gebruik gemaak is van een tipe hittepyp en dat die plasing daarvan beperk is tot binne die stator

"Divine discontent" : women, identity, and the Western Producer

This thesis is a study of the construction of identity of farm women on the "Mainly For Women" pages of the Western Producer from 1930 to 1939. It is an examination of how farm women drew upon and challenged traditional concepts of women's work roles on the farm to create a collective identity more practical to the reality of their everyday experiences. During the Great Depression, women's work roles took on greater importance, and farm women sought greater recognition and appreciation of the value of their labour. They turned to the "Mainly For Women" pages, which were edited by fellow farm woman Violet McNaughton, to discuss and debate their reproductive, productive, and community work. Since the material published on the pages was largely written by farm women, the pages revealed the qualities that united them as a group as well as how they perceived themselves as a collective

Thermal modelling of an axial flux permanent magnet machine

IngenieursweseElektriese En Elektroniese IngeniePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Highly Sensitized Patients: Miami Transplant Institute Experience

BACKGROUNDTransplantation continues to be challenging in highly sensitized patients. Herein, we compared induction immunosuppression (IS) based on immunologic risk stratification and desensitization with intravenous immunoglobulin (IVIG).METHODSOf the 42 highly sensitized kidney and 3 kidney-pancreas transplant recipients who underwent IVIG for desensitization from 2008-2014, 10 (Control group) received standard induction IS with antithymocyte globulin, basiliximab, and methylprednisolone, and 35 (Rituximab group) received standard IS with rituximab ± IVIG ± plasmapheresis. Immunologic risk stratification was based on donor specific antibodies (DSA), flow crossmatch ratio, and calculated panel reactive antibody. All patients received tacrolimus, mycophenolate, and steroids for maintenance IS. Unacceptable antigen cut-offs for class I and II DSA were 6000 and 9000 mean fluorescence intensity and 2.0 and 4.4 channel shift ratios for T and B cell flow cytometry crossmatch, respectively. All complement dependent cytotoxicity T cell crossmatch negative patients were transplanted.RESULTSCharacteristics between groups, including high risk level, previous transplantation rate, number of human leukocyte antigen mismatches, delayed graft function rate, rejection rate, serum creatinine, and estimated glomerular filtration rate at 1 year (1.48 ± 0.6 and 50 ± 17 versus 1.1 ± 0.4 mg/dl and 66 25 ml/min) were not statistically significant between the Control and the Rituximab groups, respectively. Waiting time for the Control group was 6.4 years versus 4.1 years for the Rituximab group (p = 0.009). The cumulative proportion of patients who remain free of death or allograft failure was significantly higher in the Rituximab (87%) versus the Control group (60%) (p = 0.047).CONCLUSIONSIn highly sensitized patients who received desensitization with IVIG, the addition of Rituximab to our standard IS (and/or IVIG and plasmapheresis as per the immunologic risk stratification model) resulted in higher cumulative patient and graft survival