This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,includin...This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,including frame forced air/liquid cooling,oil jet cooling for endwinding,and rotor shaft cooling.To address the temperature misestimation in the LP thermal modelling due to assumptions of concentrated loss input and uniform heat flows,the developed HF-LPTM introduces two compensation thermal resistances for the winding and PM components,which are analytically derived from the multi-dimensional heat transfer equations and are robust against different load/thermal conditions.As validated by the finite element analysis method and experiments,the conventional LPTMs exhibit significant winding temperature deviations,while the proposed HF-LPTM can accurately predict both the midpoint and average temperatures.The developed HFLPTM is further used to assess the effectiveness of various cooling techniques under different scenarios,i.e.,steady-state thermal states under the rated load condition,and transient temperature profiles under city,freeway,and hybrid(city+freeway)driving cycles.Results indicate that no single cooling technique can maintain both winding and PM temperatures within safety limits.The combination of frame liquid cooling and oil jet cooling for end winding can sufficiently mitigate PMSM thermal stress in EV applications.展开更多
Solar photovoltaic(PV)cells have emerged as the primary technology for producing green electricity.This innovation harnesses direct sunlight to generate power and its flexibility of installation has drawn significant ...Solar photovoltaic(PV)cells have emerged as the primary technology for producing green electricity.This innovation harnesses direct sunlight to generate power and its flexibility of installation has drawn significant investment in PV panels.Despite numerous benefits,these cells are hindered by a decline in efficiency caused by elevated cell temperature.As such,researchers have undertaken extensive investigations into possible solutions aimed at enhancing the performance of photovoltaic cells using diverse techniques.This review paper provides a thorough analysis of cooling techniques for photovoltaic panels.It encompasses both passive and active cooling methods,including water and air cooling,phase-change materials,and various diverse approaches.Within each category,it delves into detailed sub-categories,such as evaporative cooling,water immersion,floating systems,water pipes,cooling channels,water sprayers,jet impingement,geothermal cooling,and natural convection enhanced by PV designs.It also covers forced convection using cooling ducts,heat sinks,and air collectors,alongside the integration of Phase Change Materials(PCMs),nanofluids,radiative cooling,thermoelectric methods,heat pipes,heat pumps,and other innovative techniques.Each of these approaches is illustrated with specific schematics and thoroughly discussed and compared.Furthermore,this paper introduces an original classification system for these cooling methods applied to photovoltaic panels,offering valuable guidance for future research and insights into improving efficiency.展开更多
The free shrinkage of ceramic or metal is restricted due to solidification of the solder. Hence the shrinkage stress arises and the jointing strength is reduced during the brazing of high-voltage vacuum interrupters ...The free shrinkage of ceramic or metal is restricted due to solidification of the solder. Hence the shrinkage stress arises and the jointing strength is reduced during the brazing of high-voltage vacuum interrupters （HVVIs）. The solder bound contour was gained by solved energy bound equation. The finite element model of weld beads was established with Surface Evolver software. Then the stress in two different cooling techniques （ natural cooling and force cooling） was calculated with ANSYS. Comparing the stress, a better cooling technique was selected for HVVIs. Its cooling time is shortened by 3 hours while the jointing stress doesn＇ t increase and the tensile strength of ceramic to metal seal is not decreased. The stress-rupture tests have validated the calculated results. More important, a method is found, by which the brazing technique could be improved in advance instead of blind experiments.展开更多
文摘This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,including frame forced air/liquid cooling,oil jet cooling for endwinding,and rotor shaft cooling.To address the temperature misestimation in the LP thermal modelling due to assumptions of concentrated loss input and uniform heat flows,the developed HF-LPTM introduces two compensation thermal resistances for the winding and PM components,which are analytically derived from the multi-dimensional heat transfer equations and are robust against different load/thermal conditions.As validated by the finite element analysis method and experiments,the conventional LPTMs exhibit significant winding temperature deviations,while the proposed HF-LPTM can accurately predict both the midpoint and average temperatures.The developed HFLPTM is further used to assess the effectiveness of various cooling techniques under different scenarios,i.e.,steady-state thermal states under the rated load condition,and transient temperature profiles under city,freeway,and hybrid(city+freeway)driving cycles.Results indicate that no single cooling technique can maintain both winding and PM temperatures within safety limits.The combination of frame liquid cooling and oil jet cooling for end winding can sufficiently mitigate PMSM thermal stress in EV applications.
文摘Solar photovoltaic(PV)cells have emerged as the primary technology for producing green electricity.This innovation harnesses direct sunlight to generate power and its flexibility of installation has drawn significant investment in PV panels.Despite numerous benefits,these cells are hindered by a decline in efficiency caused by elevated cell temperature.As such,researchers have undertaken extensive investigations into possible solutions aimed at enhancing the performance of photovoltaic cells using diverse techniques.This review paper provides a thorough analysis of cooling techniques for photovoltaic panels.It encompasses both passive and active cooling methods,including water and air cooling,phase-change materials,and various diverse approaches.Within each category,it delves into detailed sub-categories,such as evaporative cooling,water immersion,floating systems,water pipes,cooling channels,water sprayers,jet impingement,geothermal cooling,and natural convection enhanced by PV designs.It also covers forced convection using cooling ducts,heat sinks,and air collectors,alongside the integration of Phase Change Materials(PCMs),nanofluids,radiative cooling,thermoelectric methods,heat pipes,heat pumps,and other innovative techniques.Each of these approaches is illustrated with specific schematics and thoroughly discussed and compared.Furthermore,this paper introduces an original classification system for these cooling methods applied to photovoltaic panels,offering valuable guidance for future research and insights into improving efficiency.
基金Sponsored by the National Natural Science Foundation of China(50377003).
文摘The free shrinkage of ceramic or metal is restricted due to solidification of the solder. Hence the shrinkage stress arises and the jointing strength is reduced during the brazing of high-voltage vacuum interrupters （HVVIs）. The solder bound contour was gained by solved energy bound equation. The finite element model of weld beads was established with Surface Evolver software. Then the stress in two different cooling techniques （ natural cooling and force cooling） was calculated with ANSYS. Comparing the stress, a better cooling technique was selected for HVVIs. Its cooling time is shortened by 3 hours while the jointing stress doesn＇ t increase and the tensile strength of ceramic to metal seal is not decreased. The stress-rupture tests have validated the calculated results. More important, a method is found, by which the brazing technique could be improved in advance instead of blind experiments.
