A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/...A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.展开更多
Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high frequency.However,the nonmagnetic binder impairs the magnetostriction of t...Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high frequency.However,the nonmagnetic binder impairs the magnetostriction of the composites.To achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic field.After this,the aligned samples were recompressed by cold isostatic pressing(CIP).Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also studied.The results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80μm.The oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×10-6.The bonded Terfenol-D composites had good compact structure and high density(7.24 g/cm3).The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3 at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.展开更多
Due to the large rotor eddy current loss and low thermal conductivity of carbon fiber sleeve,the high temperature usually occurs in high speed permanent magnet machines(HSPMMs)at the rated operation condition,resultin...Due to the large rotor eddy current loss and low thermal conductivity of carbon fiber sleeve,the high temperature usually occurs in high speed permanent magnet machines(HSPMMs)at the rated operation condition,resulting in irreversible demagnetization of the permanent magnet(PM).To obtain low rotor temperature,two novel rotor structures with low rotor eddy current loss are proposed in this paper.With the output torque and air gap flux density unchanged,the performance of HSPMMs with the two proposed rotor structures are analyzed based on finite element algorithm(FEA),including eddy current loss and temperature.Finally,the appropriate parameters of the proposed rotor structures are selected,and the electromagnetic(EM)performance,rotor stress and temperature are compared with those of the conventional rotor structure.Index Terms-Eddy current loss,finite element algorithm(FEA),electromagnetic(EM)performance,high speed permanent magnet machines(HSPMMs).展开更多
This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applicati...This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applications for small vehicles.Compared with the conventional round wire inserter method,the space factor can be improved and the coil-end length can be shortened by applying a so-called hairpin windings using a pre-formed into hairpin shape of bar conductor,and as a result,DC current resistance of the armature winding can be reduced.However,since the conductor cross-sectional area tends to increases,the conductor eddy current loss generated by the space harmonics linkage becomes too large to ignore.In order to study the reduction of the conductor eddy current loss,it is important to visualize the spatial leakage flux distribution which causes loss and finely analyze how the magnetic path is formed.Therefore,analysis of the conductor eddy current loss distribution generated in the bar-wound conductor is performed using the CAE model that faithfully reproduces the coil-end shape of the actual machine.Furthermore,it was qualitatively clarified what ratio of conductor eddy current loss at various driving points.Finally,the results of preliminary study on reduction of conductor eddy current loss are reported.展开更多
The post-hole convolute(PHC),which is used to transport and combine the pulse power flux,is a key component in huge pulsed power generators.Current loss at the PHC is a challenging problem for researchers.To explore a...The post-hole convolute(PHC),which is used to transport and combine the pulse power flux,is a key component in huge pulsed power generators.Current loss at the PHC is a challenging problem for researchers.To explore a method of reducing the current loss,a single-hole PHC was designed for experiments on the current loss on the Qiang Guang I generator.The experimental results showed that the current loss at the single-hole PHC is related to the distance/between the vicinity of the cathode hole and the surface of the downstream side of the post.Meanwhile,a single-hole PHC with a blob cathode hole transmitted current more effectively than the PHC with a circle cathode hole.The relative current loss at the single-hole PHC with the cathode coaled w ith gold foil was about 30%-50% of that with the cathode coated with nickel and titanium foil.The gap closing speed was also obtained from the current waveforms in the experiments.The speed was 5.74-14.52 cmμs 1 which was different from the classical plasma expansion velocity of 3 cmμs 1.展开更多
Alternating-current losses in a two-layer superconducting cable, each layer being composed of 15 closely-spaced rectangular wires made up of second-generation superconductors when the ends of wires are coated by eithe...Alternating-current losses in a two-layer superconducting cable, each layer being composed of 15 closely-spaced rectangular wires made up of second-generation superconductors when the ends of wires are coated by either a non-magnetic or strong ferromagnetic material having a U profile is numerically investigated. Computations are carried out through the finite-element method. The alternating-current losses do not increase significantly if the relative permeability of the coating is increased three orders of magnitude, provided that the current amplitude is less than half of the critical current in a superconducting wire. However, the losses are much higher for ferromagnetic coating if the amplitude of the applied current oscillating at 50 Hz is close to the critical current. The ferromagnetic coating is seen to accumulate the magnetic field lines normally on its surfaces, while the field lines are parallel to the long axes of the wires, leading to more significant flux penetration in the coated regions. This facilitates a uniform low-loss current flow in the uncoated regions of the wires. In contrast, coating with a non-magnetic material gives rise to a considerably smaller current flow in the uncoated regions, whereas the low-loss flow is maintained in the coated regions. Moreover, the current flows in opposite directions in the coated and uncoated regions, where the direction in each region is converse for the two materials.展开更多
Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode （MICD） is studied through experiment and particle-in-cell （PIC） simulation when the guiding magnetic field is strong e...Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode （MICD） is studied through experiment and particle-in-cell （PIC） simulation when the guiding magnetic field is strong enough. Cathode nega- tive ions are clarified to be the predominant reason for it. Theoretical analysis and simulation both indicate that the velocity of the negative ion reaches up to 1 cm/ns due to the space potential between the anode and cathode gap （A-C gap）. Accord- ingly, instead of the reverse current loss and the parasitic current loss, the negative ion loss appears during the whole pulse. The negative ion current loss is determined by its ionization production rate. It increases with diode voltage increasing. The smaller space charge effect caused by the beam thickening and the weaker radial restriction both promote the negative ion production under a lower magnetic field. Therefore, as the magnetic field increases, the current loss gradually decreases until the beam thickening nearly stops.展开更多
Coaxial-disk transitions can generate non-uniform magnetic fields and abrupt impedance variations in magnetically insulated transmission lines(MITLs),resulting in disturbed electron flow and non-negligible current los...Coaxial-disk transitions can generate non-uniform magnetic fields and abrupt impedance variations in magnetically insulated transmission lines(MITLs),resulting in disturbed electron flow and non-negligible current loss.In this paper,3 D particle-in-cell simulations are conducted with UNPIC-3 d to investigate the current loss mechanism and the influence of the input parameters of the coaxial-disk transition on current loss in an MITL system.The results reveal that the magnetic field non-uniformity causes major current loss in the MITL after the coaxialdisk transition,and the non-uniformity decreases with the distance away from the transition.The uniformity of the magnetic field is improved when increasing the number of feed lines of a linear transformer driver-based accelerator with coaxial-disk transitions.The number of input feed lines should be no less than four in the azimuthal distribution to obtain acceptable uniformity of the magnetic field.To make the ratio of the current loss to the total current of the accelerator less than 2%at peak anode current,the ratio of the current in each feed line to the total current should be no less than 8%.展开更多
The paper is mainly concerned with the penalty incurred in finite element analysis of the eddy-current loss problem in a fully established multi-filamentary superconducting wire. A finite element model with 4-node qua...The paper is mainly concerned with the penalty incurred in finite element analysis of the eddy-current loss problem in a fully established multi-filamentary superconducting wire. A finite element model with 4-node quadrilateral isoparametric elements is formulated for the present problem. Unlike the conventional vector potential scheme in use for electromagnetic field problem, the present work features a direct computational approach to eddy current loss. Simplicity and remarkable enhancement in computational accuracy can be obtained with the proposed method.展开更多
Aiming at the problem of high temperature and even demagnetization failure of permanent magnet (PM) due to PM eddy current loss in PM synchronous high-speed motors, this paper proposes a technique to lessen PM eddy cu...Aiming at the problem of high temperature and even demagnetization failure of permanent magnet (PM) due to PM eddy current loss in PM synchronous high-speed motors, this paper proposes a technique to lessen PM eddy current loss by cutting the angle of PM poles to change the shape of PM structure. Firstly, an analysis is conducted on the mechanism of PM synchronous high-speed motor eddy current loss production, the theoretical analytical model of PM eddy current loss is deduced, and it is theoretically proved that the magnetic pole shaving angle can reduce PM eddy current loss. Then, a 25 KW surface-type PM synchronous high-speed motor as an object, using two-dimensional time-step finite element method (FEM) to model and analyze PM eddy current loss. The results show that the smaller the PM pole shaving angle, the less its eddy current loss will be, it is possible to minimize the pole shaving angle of eddy current loss by 9.8% compared to the unshaved angle. Finally, the temperature field of the PM is calculated using a finite element method, and the outcomes demonstrate that the maximum temperature of the PM with a magnetic pole shaving angle can be reduced by about 5% compared with the unshaved angle.展开更多
The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination o...The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.展开更多
This study examines the impact of circulating currents on copper loss in alternating current systems and introduces a method to reduce these losses.Initially,a circuit model for the winding is developed to analyze the...This study examines the impact of circulating currents on copper loss in alternating current systems and introduces a method to reduce these losses.Initially,a circuit model for the winding is developed to analyze the magnetic leakage field in the stator slot.Subsequently,an equivalent model based on this magnetic leakage field is constructed to assess the magnetic linkage of the strand as the conductor’s position within the slot varies.Comparisons of circulating currents in two different winding configurations are presented.Based on these analyses,a specific winding arrangement designed to reduce circulating current losses is proposed.The effectiveness of this design is then corroborated through experimental validation.展开更多
Inductive power transfer system can generate eddy current when operating in seawater medium. On the one hand, it can cause eddy current loss, and reduce operating efficiency of the system. On the other hand, it can ch...Inductive power transfer system can generate eddy current when operating in seawater medium. On the one hand, it can cause eddy current loss, and reduce operating efficiency of the system. On the other hand, it can change parameters of the system and increase difficulty of system design. To grasp the influence mechanism of seawater on the inductive power transfer system,firstly, an equivalent circuit model of double-sided inductor-capacitor-capacitor(LCC) inductive power transfer system in seawater environment was established based on loosely-coupled transformer model of eddy current. Then, based on Maxwell’s equations, the distribution function of the magnetic field and electric current density along radium direction of the coupling coils in seawater medium was obtained by analytical calculation. Besides, in combination with Biot-Savart law, expression of the eddy current loss in transfer direction was derived, and based on which expression of the equivalent of the eddy current loss on the coupling coils was got. Thus the equivalent resistance of the eddy current on the coupling coils in a seawater environment could be predicated, and the optimal operating frequency of the inductive power transfer system could be further optimized. Finally, a prototype of inductive power transfer system was established, which gave the experimental results, and verified the correctness of theoretical analysis, and the experiments showed that: in air medium, the transfer distance was 100 mm, the transfer power was 3.3 k W, and the transfer efficiency was 92.6%;while, in seawater medium, the transfer efficiency was 87%. Eddy current losses mainly caused the reduction in efficiency, and the experimental results of eddy current loss were consistent with the simulation results.展开更多
Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span&g...Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mec</span><span style="font-family:Verdana;">hanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour </span><span style="font-family:Verdana;">that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in </span><span style="font-family:Verdana;">the armour of the cables,</span><span style="font-family:""> </span><span style="font-family:Verdana;">besides providing the strategies and solutions used for armour loss reduction.展开更多
针对水下无线电能传输(underwater wireless power transfer,UWPT)系统中涡流损耗对系统传输效率的制约作用,文中提出一种利用接收端阻抗调控进行效率优化的控制策略。通过构建UWPT系统传输效率的数学模型,得到系统最大效率条件,发现UWP...针对水下无线电能传输(underwater wireless power transfer,UWPT)系统中涡流损耗对系统传输效率的制约作用,文中提出一种利用接收端阻抗调控进行效率优化的控制策略。通过构建UWPT系统传输效率的数学模型,得到系统最大效率条件,发现UWPT系统效率与负载电抗存在强耦合关系;基于“功率优先、效率次优”的原则,利用有源整流保持输出功率稳定为首要控制目标;通过引入辅助H桥并和有源整流器进行协同控制,以副边回路电流相位为调控变量,进行涡流抑制和效率提升。提出辅助H桥和有源整流器的协同控制方法,实现系统阻抗匹配与输出控制双重目标;搭建787 W的实验样机进行验证,实验结果表明:相较于传统LCC-S补偿,所提方法在额定工况下传输效率提升1.58%,对其进行损耗分布分析发现,涡流损耗占比由初始的82.8%降至71.1%,验证了所提协同控制策略在涡流损耗抑制方面的有效性。展开更多
基金supported by National Natural Science Foundation of China(No.10905047)
文摘A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.
基金supported by the National Natural Science Foundation of China(No.51004011 and 50874010)the Specialized Research Fund for the Doctoral Program of China Higher Education(No.20090006120012)
文摘Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high frequency.However,the nonmagnetic binder impairs the magnetostriction of the composites.To achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic field.After this,the aligned samples were recompressed by cold isostatic pressing(CIP).Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also studied.The results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80μm.The oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×10-6.The bonded Terfenol-D composites had good compact structure and high density(7.24 g/cm3).The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3 at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.
基金This work has been partly supported by the National Natural Science Foundation of China(NSFC 51877093,51807075)National Key Research and Development Program of China(Project ID:2018YFE0100200)+2 种基金Fundamental Research Funds for the Central Universities(2019kfyXMBZ031)Project funded by China Postdoctoral Science Foundation(2019M652640)Natural Science Basic Research Plan in Shaanxi Province of China under Grant 2018JQ5009 and Scientific Research Program Funded by Shaanxi Provincial Education Department of China under Grant No.18JK0398。
文摘Due to the large rotor eddy current loss and low thermal conductivity of carbon fiber sleeve,the high temperature usually occurs in high speed permanent magnet machines(HSPMMs)at the rated operation condition,resulting in irreversible demagnetization of the permanent magnet(PM).To obtain low rotor temperature,two novel rotor structures with low rotor eddy current loss are proposed in this paper.With the output torque and air gap flux density unchanged,the performance of HSPMMs with the two proposed rotor structures are analyzed based on finite element algorithm(FEA),including eddy current loss and temperature.Finally,the appropriate parameters of the proposed rotor structures are selected,and the electromagnetic(EM)performance,rotor stress and temperature are compared with those of the conventional rotor structure.Index Terms-Eddy current loss,finite element algorithm(FEA),electromagnetic(EM)performance,high speed permanent magnet machines(HSPMMs).
文摘This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applications for small vehicles.Compared with the conventional round wire inserter method,the space factor can be improved and the coil-end length can be shortened by applying a so-called hairpin windings using a pre-formed into hairpin shape of bar conductor,and as a result,DC current resistance of the armature winding can be reduced.However,since the conductor cross-sectional area tends to increases,the conductor eddy current loss generated by the space harmonics linkage becomes too large to ignore.In order to study the reduction of the conductor eddy current loss,it is important to visualize the spatial leakage flux distribution which causes loss and finely analyze how the magnetic path is formed.Therefore,analysis of the conductor eddy current loss distribution generated in the bar-wound conductor is performed using the CAE model that faithfully reproduces the coil-end shape of the actual machine.Furthermore,it was qualitatively clarified what ratio of conductor eddy current loss at various driving points.Finally,the results of preliminary study on reduction of conductor eddy current loss are reported.
文摘The post-hole convolute(PHC),which is used to transport and combine the pulse power flux,is a key component in huge pulsed power generators.Current loss at the PHC is a challenging problem for researchers.To explore a method of reducing the current loss,a single-hole PHC was designed for experiments on the current loss on the Qiang Guang I generator.The experimental results showed that the current loss at the single-hole PHC is related to the distance/between the vicinity of the cathode hole and the surface of the downstream side of the post.Meanwhile,a single-hole PHC with a blob cathode hole transmitted current more effectively than the PHC with a circle cathode hole.The relative current loss at the single-hole PHC with the cathode coaled w ith gold foil was about 30%-50% of that with the cathode coated with nickel and titanium foil.The gap closing speed was also obtained from the current waveforms in the experiments.The speed was 5.74-14.52 cmμs 1 which was different from the classical plasma expansion velocity of 3 cmμs 1.
基金Project supported by the Fund from the Scientific and Technological Research Council of Turkey(TüB˙ITAK)(Grant No.110T876)
文摘Alternating-current losses in a two-layer superconducting cable, each layer being composed of 15 closely-spaced rectangular wires made up of second-generation superconductors when the ends of wires are coated by either a non-magnetic or strong ferromagnetic material having a U profile is numerically investigated. Computations are carried out through the finite-element method. The alternating-current losses do not increase significantly if the relative permeability of the coating is increased three orders of magnitude, provided that the current amplitude is less than half of the critical current in a superconducting wire. However, the losses are much higher for ferromagnetic coating if the amplitude of the applied current oscillating at 50 Hz is close to the critical current. The ferromagnetic coating is seen to accumulate the magnetic field lines normally on its surfaces, while the field lines are parallel to the long axes of the wires, leading to more significant flux penetration in the coated regions. This facilitates a uniform low-loss current flow in the uncoated regions of the wires. In contrast, coating with a non-magnetic material gives rise to a considerably smaller current flow in the uncoated regions, whereas the low-loss flow is maintained in the coated regions. Moreover, the current flows in opposite directions in the coated and uncoated regions, where the direction in each region is converse for the two materials.
文摘Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode （MICD） is studied through experiment and particle-in-cell （PIC） simulation when the guiding magnetic field is strong enough. Cathode nega- tive ions are clarified to be the predominant reason for it. Theoretical analysis and simulation both indicate that the velocity of the negative ion reaches up to 1 cm/ns due to the space potential between the anode and cathode gap （A-C gap）. Accord- ingly, instead of the reverse current loss and the parasitic current loss, the negative ion loss appears during the whole pulse. The negative ion current loss is determined by its ionization production rate. It increases with diode voltage increasing. The smaller space charge effect caused by the beam thickening and the weaker radial restriction both promote the negative ion production under a lower magnetic field. Therefore, as the magnetic field increases, the current loss gradually decreases until the beam thickening nearly stops.
基金supported by National Natural Science Foundation of China(Nos.U1530133 and 52007152)the Special Foundation of State Key Laboratory of Intense Pulsed Radiation Simulation and Effect(No.SKLIPR2005)the Youth Innovation Team of Shaanxi Universities。
文摘Coaxial-disk transitions can generate non-uniform magnetic fields and abrupt impedance variations in magnetically insulated transmission lines(MITLs),resulting in disturbed electron flow and non-negligible current loss.In this paper,3 D particle-in-cell simulations are conducted with UNPIC-3 d to investigate the current loss mechanism and the influence of the input parameters of the coaxial-disk transition on current loss in an MITL system.The results reveal that the magnetic field non-uniformity causes major current loss in the MITL after the coaxialdisk transition,and the non-uniformity decreases with the distance away from the transition.The uniformity of the magnetic field is improved when increasing the number of feed lines of a linear transformer driver-based accelerator with coaxial-disk transitions.The number of input feed lines should be no less than four in the azimuthal distribution to obtain acceptable uniformity of the magnetic field.To make the ratio of the current loss to the total current of the accelerator less than 2%at peak anode current,the ratio of the current in each feed line to the total current should be no less than 8%.
文摘The paper is mainly concerned with the penalty incurred in finite element analysis of the eddy-current loss problem in a fully established multi-filamentary superconducting wire. A finite element model with 4-node quadrilateral isoparametric elements is formulated for the present problem. Unlike the conventional vector potential scheme in use for electromagnetic field problem, the present work features a direct computational approach to eddy current loss. Simplicity and remarkable enhancement in computational accuracy can be obtained with the proposed method.
文摘Aiming at the problem of high temperature and even demagnetization failure of permanent magnet (PM) due to PM eddy current loss in PM synchronous high-speed motors, this paper proposes a technique to lessen PM eddy current loss by cutting the angle of PM poles to change the shape of PM structure. Firstly, an analysis is conducted on the mechanism of PM synchronous high-speed motor eddy current loss production, the theoretical analytical model of PM eddy current loss is deduced, and it is theoretically proved that the magnetic pole shaving angle can reduce PM eddy current loss. Then, a 25 KW surface-type PM synchronous high-speed motor as an object, using two-dimensional time-step finite element method (FEM) to model and analyze PM eddy current loss. The results show that the smaller the PM pole shaving angle, the less its eddy current loss will be, it is possible to minimize the pole shaving angle of eddy current loss by 9.8% compared to the unshaved angle. Finally, the temperature field of the PM is calculated using a finite element method, and the outcomes demonstrate that the maximum temperature of the PM with a magnetic pole shaving angle can be reduced by about 5% compared with the unshaved angle.
文摘The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.
基金Supported by the National Natural Science Foundation of China(52377055).
文摘This study examines the impact of circulating currents on copper loss in alternating current systems and introduces a method to reduce these losses.Initially,a circuit model for the winding is developed to analyze the magnetic leakage field in the stator slot.Subsequently,an equivalent model based on this magnetic leakage field is constructed to assess the magnetic linkage of the strand as the conductor’s position within the slot varies.Comparisons of circulating currents in two different winding configurations are presented.Based on these analyses,a specific winding arrangement designed to reduce circulating current losses is proposed.The effectiveness of this design is then corroborated through experimental validation.
基金supported by the Youth Program of National Natural Science Foundation of China(Grant No.52007195)Group Project in Hubei Province Natural Science Foundation of Innovation(Grant No.2018CFA008)+1 种基金General Program in Hubei Province Natural Science Foundation(Grant No.2019CFB608)the Major Projects of Military Logistics Research(Grant No.BHJ18C007)。
文摘Inductive power transfer system can generate eddy current when operating in seawater medium. On the one hand, it can cause eddy current loss, and reduce operating efficiency of the system. On the other hand, it can change parameters of the system and increase difficulty of system design. To grasp the influence mechanism of seawater on the inductive power transfer system,firstly, an equivalent circuit model of double-sided inductor-capacitor-capacitor(LCC) inductive power transfer system in seawater environment was established based on loosely-coupled transformer model of eddy current. Then, based on Maxwell’s equations, the distribution function of the magnetic field and electric current density along radium direction of the coupling coils in seawater medium was obtained by analytical calculation. Besides, in combination with Biot-Savart law, expression of the eddy current loss in transfer direction was derived, and based on which expression of the equivalent of the eddy current loss on the coupling coils was got. Thus the equivalent resistance of the eddy current on the coupling coils in a seawater environment could be predicated, and the optimal operating frequency of the inductive power transfer system could be further optimized. Finally, a prototype of inductive power transfer system was established, which gave the experimental results, and verified the correctness of theoretical analysis, and the experiments showed that: in air medium, the transfer distance was 100 mm, the transfer power was 3.3 k W, and the transfer efficiency was 92.6%;while, in seawater medium, the transfer efficiency was 87%. Eddy current losses mainly caused the reduction in efficiency, and the experimental results of eddy current loss were consistent with the simulation results.
文摘Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mec</span><span style="font-family:Verdana;">hanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour </span><span style="font-family:Verdana;">that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in </span><span style="font-family:Verdana;">the armour of the cables,</span><span style="font-family:""> </span><span style="font-family:Verdana;">besides providing the strategies and solutions used for armour loss reduction.
文摘针对水下无线电能传输(underwater wireless power transfer,UWPT)系统中涡流损耗对系统传输效率的制约作用,文中提出一种利用接收端阻抗调控进行效率优化的控制策略。通过构建UWPT系统传输效率的数学模型,得到系统最大效率条件,发现UWPT系统效率与负载电抗存在强耦合关系;基于“功率优先、效率次优”的原则,利用有源整流保持输出功率稳定为首要控制目标;通过引入辅助H桥并和有源整流器进行协同控制,以副边回路电流相位为调控变量,进行涡流抑制和效率提升。提出辅助H桥和有源整流器的协同控制方法,实现系统阻抗匹配与输出控制双重目标;搭建787 W的实验样机进行验证,实验结果表明:相较于传统LCC-S补偿,所提方法在额定工况下传输效率提升1.58%,对其进行损耗分布分析发现,涡流损耗占比由初始的82.8%降至71.1%,验证了所提协同控制策略在涡流损耗抑制方面的有效性。
