The split ratio which is defined as the ratio between rotor and stator outer diameters is critical for permanent magnet(PM)machines.In this paper,the split ratio in small high speed PM machines is optimized analytical...The split ratio which is defined as the ratio between rotor and stator outer diameters is critical for permanent magnet(PM)machines.In this paper,the split ratio in small high speed PM machines is optimized analytically by considering both stator and rotor loss limitations.By this way,the thermal constrains in both stator and rotor parts can be taken into account.It shows that both losses can significantly affect the optimal split ratio and the machine performance.By considering the influence of rotor losses,especially the rotor eddy current loss,the optimal split ratio is increased significantly in certain scenarios.The output torque is calculated analytically and the influences of several key design parameters on the optimal split ratio,i.e.slot/pole combinations and magnet materials,are also investigated in details.Finally,finite element(FE)analyses are carried out for validating of the analytical model.展开更多
Split ratio,i.e.the ratio of stator inner diameter to outer diameter,has a closed relationship with electromagnetic performance of permanent magnet(PM)motors.In this paper,the toroidal windings with short end-winding ...Split ratio,i.e.the ratio of stator inner diameter to outer diameter,has a closed relationship with electromagnetic performance of permanent magnet(PM)motors.In this paper,the toroidal windings with short end-winding axial length are employed in the 6-slot/2-pole(6s/2p)PM motor for high speed applications.The split ratio is optimized together with the ratio of inner slot to outer slot area,i.e.slot ratio,considering stator total loss(stator iron loss and copper loss).In addition,the influence of maximum stator iron flux density and tooth-tip on the optimal split ratio,slot ratio,and average torque is investigated.The analytical predictions show that when the slot ratio is 0.5,the maximum torque can be achieved,and the optimal split ratio increases with the decrease of slot ratio,as confirmed by the finite element(FE)analyses.Finally,some of predicted results are verified by the measured results of 6s/2p prototype motor with 0.5 slot ratio.展开更多
Wound field switched flux(WFSF)machines exhibits characteristics of the simple robust rotor,flexible flux-adjustable capability,and no risk of demagnetization.However,they suffer from a poor torque density compared wi...Wound field switched flux(WFSF)machines exhibits characteristics of the simple robust rotor,flexible flux-adjustable capability,and no risk of demagnetization.However,they suffer from a poor torque density compared with permanent magnet machines due to the saturation.Therefore,in this paper,two WFSF machines with single-and double-layer DC windings,respectively,are optimized for the maximum torque.The end-winding(EW)lengths differ in these two machines,which can affect the optimal design.Design parameters including the DC to armature winding copper loss ratio,slot area ratio and split ratio are optimized when two machines have the same copper loss and overall sizes.In addition,the influence of the flux density ratio,total copper loss,air-gap length and aspect ratio on the optimal split ratio is investigated using the finite element method and results are explained through the analytical model accounting for the saturation.It is discovered that the EWs have no effect on the optimal copper loss ratio,which is unity.In terms of the slot area ratio,the machine with single-layer DC windings prefers smaller DC slot areas than armature slot areas.In the WFSF machine with longer EWs,the optimal split ratio becomes smaller.Moreover,compared with other parameters,the flux density ratio can significantly affect the optimal split ratio.展开更多
The intraoperative management of split liver transplantation(SLT) has some unique features as compared to routine whole liver transplantations. Only the liver has this special ability to regenerate that confers benefi...The intraoperative management of split liver transplantation(SLT) has some unique features as compared to routine whole liver transplantations. Only the liver has this special ability to regenerate that confers benefits in survival and quality of life for two instead of one by splitting livers. Primary graft dysfunction may result from small for size syndrome. Graft weight to recipient body weight ratio is significant for both trisegmental and hemiliver grafts. Intraoperative surgical techniques aim to reduce portal hyperperfusion and decrease venous portal pressure. Ischemic preconditioning can be instituted to protect against ischemic reperfusion injury which impacts graft regeneration. Advancement of the technique of SLT is essential as use of split cadaveric grafts expands the donor pool and potentially has an excellent future.展开更多
文摘The split ratio which is defined as the ratio between rotor and stator outer diameters is critical for permanent magnet(PM)machines.In this paper,the split ratio in small high speed PM machines is optimized analytically by considering both stator and rotor loss limitations.By this way,the thermal constrains in both stator and rotor parts can be taken into account.It shows that both losses can significantly affect the optimal split ratio and the machine performance.By considering the influence of rotor losses,especially the rotor eddy current loss,the optimal split ratio is increased significantly in certain scenarios.The output torque is calculated analytically and the influences of several key design parameters on the optimal split ratio,i.e.slot/pole combinations and magnet materials,are also investigated in details.Finally,finite element(FE)analyses are carried out for validating of the analytical model.
文摘Split ratio,i.e.the ratio of stator inner diameter to outer diameter,has a closed relationship with electromagnetic performance of permanent magnet(PM)motors.In this paper,the toroidal windings with short end-winding axial length are employed in the 6-slot/2-pole(6s/2p)PM motor for high speed applications.The split ratio is optimized together with the ratio of inner slot to outer slot area,i.e.slot ratio,considering stator total loss(stator iron loss and copper loss).In addition,the influence of maximum stator iron flux density and tooth-tip on the optimal split ratio,slot ratio,and average torque is investigated.The analytical predictions show that when the slot ratio is 0.5,the maximum torque can be achieved,and the optimal split ratio increases with the decrease of slot ratio,as confirmed by the finite element(FE)analyses.Finally,some of predicted results are verified by the measured results of 6s/2p prototype motor with 0.5 slot ratio.
基金supported in part by the National Key R&D Program of China under 2019YFB1503700by the National Natural Science Foundation of China under Grant 51677169。
文摘Wound field switched flux(WFSF)machines exhibits characteristics of the simple robust rotor,flexible flux-adjustable capability,and no risk of demagnetization.However,they suffer from a poor torque density compared with permanent magnet machines due to the saturation.Therefore,in this paper,two WFSF machines with single-and double-layer DC windings,respectively,are optimized for the maximum torque.The end-winding(EW)lengths differ in these two machines,which can affect the optimal design.Design parameters including the DC to armature winding copper loss ratio,slot area ratio and split ratio are optimized when two machines have the same copper loss and overall sizes.In addition,the influence of the flux density ratio,total copper loss,air-gap length and aspect ratio on the optimal split ratio is investigated using the finite element method and results are explained through the analytical model accounting for the saturation.It is discovered that the EWs have no effect on the optimal copper loss ratio,which is unity.In terms of the slot area ratio,the machine with single-layer DC windings prefers smaller DC slot areas than armature slot areas.In the WFSF machine with longer EWs,the optimal split ratio becomes smaller.Moreover,compared with other parameters,the flux density ratio can significantly affect the optimal split ratio.
文摘The intraoperative management of split liver transplantation(SLT) has some unique features as compared to routine whole liver transplantations. Only the liver has this special ability to regenerate that confers benefits in survival and quality of life for two instead of one by splitting livers. Primary graft dysfunction may result from small for size syndrome. Graft weight to recipient body weight ratio is significant for both trisegmental and hemiliver grafts. Intraoperative surgical techniques aim to reduce portal hyperperfusion and decrease venous portal pressure. Ischemic preconditioning can be instituted to protect against ischemic reperfusion injury which impacts graft regeneration. Advancement of the technique of SLT is essential as use of split cadaveric grafts expands the donor pool and potentially has an excellent future.
