The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By ...The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne （DSV）, the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.展开更多
Electromagnetic forming （EMF） is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils ...Electromagnetic forming （EMF） is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils are generally used for electromagnetic forming of sheet metals. However, with this type of coil the central portion of the workpiece experiences marginal magnetic force. This leads to in-sufficient deformation at this portion and other problems like air entrapment. In this study, a conceptual design of flat coil was proposed for better distribution of magnetic forces over the workpiece. Comparative analysis of distribution of magnetic force, magnetic field and current density using the proposed and the existing coil designs were carried out using FEM. The result indicates that the proposed coil design produces comparatively better magnetic force distribution over the workpiece. Calculation of self-inductance of such coils was also carried out and was compared with FE simulation.展开更多
Transient electromagnetic method (TEM),as a non-seismic geophysical exploration mainstream electromagnetic method,is widely used in oil,gas,mineral and other underground resources exploration areas. The coil sensor is...Transient electromagnetic method (TEM),as a non-seismic geophysical exploration mainstream electromagnetic method,is widely used in oil,gas,mineral and other underground resources exploration areas. The coil sensor is generally used to collect data. In view of the problems of incomplete information of the abnormal body and the data loss in the existing TEM single-component coil sensor,a three-component TEM coil sensor is designed. By analyzing the relationship between sensor sensitivity and coil structure parameters,the coil structure and turns are designed. By analyzing the frequency response characteristics of the TEM magnetic field sensor,the signal distortion is reduced by using the under-damped matching mode. By analyzing the distribution of various noise sources of the magnetic sensor,the appropriate amplifier is selected to reduce the background noise. Finally,a three-component TEM induction magnetic field sensor is designed. The weight of the sensor is controlled at 3.2 kg and the working frequency is 10 mHz-10 kHz. The background noises of X and Y components probably keep in 1.5×10^-8 V/ Hz and sensitivities are 8.4 and 9.8 nT/s,respectively,the background noise of vertical component is 2.1× 10^-7 V/ Hz and sensitivity is 18.5 nT/s. Compared with the existing single-component TEM receiving magnetic field sensor,the designed sensor realizes the signal acquisition of three components. Without too much increase in volume and total weight,it improves the sensitivity of the sensor and reduces the background noise,thus the signal-to-noise ratio (SNR) of the signal is improved.展开更多
In order to resolve the problean of the unbalanced threephase and unstable voltage, intellectual economized technique on elec- tricity based on electromagnetic regulation and control is proposed in this paper. We choo...In order to resolve the problean of the unbalanced threephase and unstable voltage, intellectual economized technique on elec- tricity based on electromagnetic regulation and control is proposed in this paper. We choose the TMS320LF2407A as the control chip and stepper motor as the executing agency. The equipment controls the movable contact reaching to the assigned position on the magnetic coil quickly and accurately, and outputs the sine-wave voltage steadily along with the network voltage variation though the fuzzy Porportional Integral Derivative（PID） control algorithm of integral separation and incremental mode with setting dead area. The principle of work and the key technique on the electromagnetic regulation and control are introduced in detail in this paper. The experiment result gives a proof for all the algorithm mentioned in this paper.展开更多
Aiming at the major failure mode of prestressed concrete cylinder pipes (PCCP),namely the fracture of prestressed steel wires,the broken wire detection technology based on orthogonal electromagnetic principle is studi...Aiming at the major failure mode of prestressed concrete cylinder pipes (PCCP),namely the fracture of prestressed steel wires,the broken wire detection technology based on orthogonal electromagnetic principle is studied. The detection system model is established and optimized by using COMSOL finite element simulation software. Furthermore,the theoretical analysis of the wire-breaking effect is carried out. The influence of factors on broken wire signal characteristics such as edge effect,circumferential relative position of the detector and broken wires,excitation frequency and relative permeability of steel wires is analyzed,which provides a theoretical guidance for the field detection. The influence of the steel cylinder structure on the simulation results is analyzed,which provides a reference for the improvement of calculation efficiency. The corresponding detection system is designed and implemented. Concretely,a high-voltage and high-power sinusoidal signal coil drive scheme based on sinusoidal pulse width modulation technology and an intelligent power module is innovatively proposed and the corresponding protection circuit is designed. The broken wire signal could be effectively extracted through a lock-in amplifier. The experimental results show that this system can effectively identify the broken wires with low cost.展开更多
This paper describes technology of the electromagnetic pump made in a hybrid polymer-ceramic technology. The pumping mechanism is realized with a mutual excitation between an electromagnetic coil and a neodymium magne...This paper describes technology of the electromagnetic pump made in a hybrid polymer-ceramic technology. The pumping mechanism is realized with a mutual excitation between an electromagnetic coil and a neodymium magnet bonded to a flexible membrane. A PDMS （poly（dimethylsiloxane）） material was used to manufacture a membrane sufficient for the presented micropump. A fish trap construction is adapted to the ceramic technology. The bonding process of ceramics and polymer, using plasma oxidation method, is described as well. Moreover, a membrane deflection depending on magnet dimensions and applied voltage was measured.展开更多
Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requiremen...Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requirements and high sensitivity requirement,a three-component MMR air-core coil sensor is designed.Through the analysis of sensor sensitivity and coil structure parameters,the coil structure and turn number are designed.By analyzing the noise source of the sensor,a suitable amplifier is selected to reduce the background noise of the system.Through the analysis of the three-component non-orthogonal angles,the parameters of the non-orthogonal angles of the coils are corrected.Finally,a three-component MMR induction magnetic field sensor is designed.The volume of the sensor is controlled at 0.027 m 3.The background noise of X、Y and Z are 5.030435 nV/Hz@380 Hz and magnetic field sensitivities are 0.18995 pT/Hz@380 Hz.The three channels have good consistency,and the three-component nonorthogonal angles correction error of three components is controlled within 0.2%.展开更多
The effects of geometrical characteristics of echelon coil on the magnetic pressure distribution and their contribution to the final shape of parts were focused and investigated through experiments and numerical simul...The effects of geometrical characteristics of echelon coil on the magnetic pressure distribution and their contribution to the final shape of parts were focused and investigated through experiments and numerical simulation using FEM software ANSYS. The results show that the geometrical characteristics of echelon coil play a key role in controlling the magnetic pressure acting on the tube. They show a hump-like distribution near the interface between bigger diameter region and transition region of echelon coil, and affect the final shape of tubular parts then. With the reduction of relative diameter, the magnetic pressure in smaller diameter region decreases and its distribution gradient in transition region increases. With the augment of relative length, the magnetic pressure increases in bigger diameter region, while it almost remains constant in smaller diameter region, and the gradient in transition region enhances sharply. The distribution of magnetic pressure in the axial direction of tube agrees well with the profile of specimen.展开更多
Three differential equations based on different definitions of current density are compared. Formulation I is based on an incomplete equation for total current density （TCD）. Formulations II and {I1 are based on inc...Three differential equations based on different definitions of current density are compared. Formulation I is based on an incomplete equation for total current density （TCD）. Formulations II and {I1 are based on incomplete and complete equations for source current density （SCD）, respectively. Using the weak form of finite element method （FEM）, three formulations were applied in a spiral coil electromagnetic acoustic transducer （EMAT） example to solve magnetic vector potential （MVP）. The input impedances calculated by Formulation III are in excellent agreement with the experimental measurements. Results show that the errors for Formulations I ＆ II vary with coil diameter, coil spacing, lift-off distance and external excitation frequency, for the existence of eddy-current and skin ＆ proximity effects. And the current distribution across the coil conductor also follows the same trend. It is better to choose Formulation I instead of Formulation Ili to solve MVP when the coil diameter is less than twice the skin depth for Formulation I is a low cost and high efficiency calculation method.展开更多
The characteristics of the novel switched reluctance motor with auxiliary winding and four big swallow-tailed-slots in the internal surface of stator is analysed with the stator cross section and winding photo given, ...The characteristics of the novel switched reluctance motor with auxiliary winding and four big swallow-tailed-slots in the internal surface of stator is analysed with the stator cross section and winding photo given, and the nlathematical model of the novel switched reluctance motor presented. To show that the auxiliary winding causes the electromotive force to improve current waveform and increase output power. The different effects of auxiliary winding on system performance under different speeds are analyzed and experimented. Simulation analyzing and experiments studying of the novel switched reluctance motor demonstrate validity of auxiliary winding improving current waveforms, increasing output power.展开更多
ELF （extremely low frequency） magnetic fields from power-line current influence the yield of CMOS foundry. The poor yield happens because of ELF magnetic fields inducing directly the measurement or process equipment...ELF （extremely low frequency） magnetic fields from power-line current influence the yield of CMOS foundry. The poor yield happens because of ELF magnetic fields inducing directly the measurement or process equipment for cutting-edge chips below 28 nm process. The equipments of electron microscopes, including SEM （scanning electron microscope）, TEM （transmission electron microscopy）, STEM （scanning transmission electron microscopy） and EBLS （electron beam lithography system） are very susceptible to ELF magnetic fields emanating from various electrical power sources outside of the building and within next generation CMOS foundry recommends a maximum of 0.3 mG. The active canceling method uses active coils with current sensing field via sensor and inducing man-made electromagnetic field to reduce the stray magnetic field. Unfortunately, the conventional system takes more time to products field because of parasitical capacitance and resistance in long coil. The longer canceling coil the system construct, the more time it takes. Besides, canceling system should spend more time on calibrating non-linear current amplifier through software design. This research designs simpler anti-electro-magnetic system instead of typical frame and develops one turn canceling coil structure to reduce delaying time. Several parallel cells generate field up to 23.81 mG controlled by MPU （micro processor unit）. This system decreases the power-line inducing filed below 0.3 mG.展开更多
基金supported by the National Natural Science Foundation of China(No.50577063)
文摘The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne （DSV）, the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.
文摘Electromagnetic forming （EMF） is a high velocity forming process that uses impulse magnetic force. Coil is an important component of EMF system which needs to be designed depending on application. Flat spiral coils are generally used for electromagnetic forming of sheet metals. However, with this type of coil the central portion of the workpiece experiences marginal magnetic force. This leads to in-sufficient deformation at this portion and other problems like air entrapment. In this study, a conceptual design of flat coil was proposed for better distribution of magnetic forces over the workpiece. Comparative analysis of distribution of magnetic force, magnetic field and current density using the proposed and the existing coil designs were carried out using FEM. The result indicates that the proposed coil design produces comparatively better magnetic force distribution over the workpiece. Calculation of self-inductance of such coils was also carried out and was compared with FE simulation.
文摘Transient electromagnetic method (TEM),as a non-seismic geophysical exploration mainstream electromagnetic method,is widely used in oil,gas,mineral and other underground resources exploration areas. The coil sensor is generally used to collect data. In view of the problems of incomplete information of the abnormal body and the data loss in the existing TEM single-component coil sensor,a three-component TEM coil sensor is designed. By analyzing the relationship between sensor sensitivity and coil structure parameters,the coil structure and turns are designed. By analyzing the frequency response characteristics of the TEM magnetic field sensor,the signal distortion is reduced by using the under-damped matching mode. By analyzing the distribution of various noise sources of the magnetic sensor,the appropriate amplifier is selected to reduce the background noise. Finally,a three-component TEM induction magnetic field sensor is designed. The weight of the sensor is controlled at 3.2 kg and the working frequency is 10 mHz-10 kHz. The background noises of X and Y components probably keep in 1.5×10^-8 V/ Hz and sensitivities are 8.4 and 9.8 nT/s,respectively,the background noise of vertical component is 2.1× 10^-7 V/ Hz and sensitivity is 18.5 nT/s. Compared with the existing single-component TEM receiving magnetic field sensor,the designed sensor realizes the signal acquisition of three components. Without too much increase in volume and total weight,it improves the sensitivity of the sensor and reduces the background noise,thus the signal-to-noise ratio (SNR) of the signal is improved.
基金supported by Natural Science Foundation of Shandong Province(No.Z2007F08)
文摘In order to resolve the problean of the unbalanced threephase and unstable voltage, intellectual economized technique on elec- tricity based on electromagnetic regulation and control is proposed in this paper. We choose the TMS320LF2407A as the control chip and stepper motor as the executing agency. The equipment controls the movable contact reaching to the assigned position on the magnetic coil quickly and accurately, and outputs the sine-wave voltage steadily along with the network voltage variation though the fuzzy Porportional Integral Derivative（PID） control algorithm of integral separation and incremental mode with setting dead area. The principle of work and the key technique on the electromagnetic regulation and control are introduced in detail in this paper. The experiment result gives a proof for all the algorithm mentioned in this paper.
基金National Natural Science Foundation of China(No.61304244)
文摘Aiming at the major failure mode of prestressed concrete cylinder pipes (PCCP),namely the fracture of prestressed steel wires,the broken wire detection technology based on orthogonal electromagnetic principle is studied. The detection system model is established and optimized by using COMSOL finite element simulation software. Furthermore,the theoretical analysis of the wire-breaking effect is carried out. The influence of factors on broken wire signal characteristics such as edge effect,circumferential relative position of the detector and broken wires,excitation frequency and relative permeability of steel wires is analyzed,which provides a theoretical guidance for the field detection. The influence of the steel cylinder structure on the simulation results is analyzed,which provides a reference for the improvement of calculation efficiency. The corresponding detection system is designed and implemented. Concretely,a high-voltage and high-power sinusoidal signal coil drive scheme based on sinusoidal pulse width modulation technology and an intelligent power module is innovatively proposed and the corresponding protection circuit is designed. The broken wire signal could be effectively extracted through a lock-in amplifier. The experimental results show that this system can effectively identify the broken wires with low cost.
文摘This paper describes technology of the electromagnetic pump made in a hybrid polymer-ceramic technology. The pumping mechanism is realized with a mutual excitation between an electromagnetic coil and a neodymium magnet bonded to a flexible membrane. A PDMS （poly（dimethylsiloxane）） material was used to manufacture a membrane sufficient for the presented micropump. A fish trap construction is adapted to the ceramic technology. The bonding process of ceramics and polymer, using plasma oxidation method, is described as well. Moreover, a membrane deflection depending on magnet dimensions and applied voltage was measured.
文摘Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requirements and high sensitivity requirement,a three-component MMR air-core coil sensor is designed.Through the analysis of sensor sensitivity and coil structure parameters,the coil structure and turn number are designed.By analyzing the noise source of the sensor,a suitable amplifier is selected to reduce the background noise of the system.Through the analysis of the three-component non-orthogonal angles,the parameters of the non-orthogonal angles of the coils are corrected.Finally,a three-component MMR induction magnetic field sensor is designed.The volume of the sensor is controlled at 0.027 m 3.The background noise of X、Y and Z are 5.030435 nV/Hz@380 Hz and magnetic field sensitivities are 0.18995 pT/Hz@380 Hz.The three channels have good consistency,and the three-component nonorthogonal angles correction error of three components is controlled within 0.2%.
基金Sponsored by the Scientific Research Foundation of Harbin Institute of Technology (Grant No. HIT.2003.10)
文摘The effects of geometrical characteristics of echelon coil on the magnetic pressure distribution and their contribution to the final shape of parts were focused and investigated through experiments and numerical simulation using FEM software ANSYS. The results show that the geometrical characteristics of echelon coil play a key role in controlling the magnetic pressure acting on the tube. They show a hump-like distribution near the interface between bigger diameter region and transition region of echelon coil, and affect the final shape of tubular parts then. With the reduction of relative diameter, the magnetic pressure in smaller diameter region decreases and its distribution gradient in transition region increases. With the augment of relative length, the magnetic pressure increases in bigger diameter region, while it almost remains constant in smaller diameter region, and the gradient in transition region enhances sharply. The distribution of magnetic pressure in the axial direction of tube agrees well with the profile of specimen.
基金Project(2014BAF12B01)supported by the Key Projects in the National Science&Technology Pillar Program during the Twelfth Five-year Plan Period,ChinaProject(51405520)supported by the National Natural Science Foundation of ChinaProject(2012CB619505)supported by National Basic Research Program of China
文摘Three differential equations based on different definitions of current density are compared. Formulation I is based on an incomplete equation for total current density （TCD）. Formulations II and {I1 are based on incomplete and complete equations for source current density （SCD）, respectively. Using the weak form of finite element method （FEM）, three formulations were applied in a spiral coil electromagnetic acoustic transducer （EMAT） example to solve magnetic vector potential （MVP）. The input impedances calculated by Formulation III are in excellent agreement with the experimental measurements. Results show that the errors for Formulations I ＆ II vary with coil diameter, coil spacing, lift-off distance and external excitation frequency, for the existence of eddy-current and skin ＆ proximity effects. And the current distribution across the coil conductor also follows the same trend. It is better to choose Formulation I instead of Formulation Ili to solve MVP when the coil diameter is less than twice the skin depth for Formulation I is a low cost and high efficiency calculation method.
文摘The characteristics of the novel switched reluctance motor with auxiliary winding and four big swallow-tailed-slots in the internal surface of stator is analysed with the stator cross section and winding photo given, and the nlathematical model of the novel switched reluctance motor presented. To show that the auxiliary winding causes the electromotive force to improve current waveform and increase output power. The different effects of auxiliary winding on system performance under different speeds are analyzed and experimented. Simulation analyzing and experiments studying of the novel switched reluctance motor demonstrate validity of auxiliary winding improving current waveforms, increasing output power.
文摘ELF （extremely low frequency） magnetic fields from power-line current influence the yield of CMOS foundry. The poor yield happens because of ELF magnetic fields inducing directly the measurement or process equipment for cutting-edge chips below 28 nm process. The equipments of electron microscopes, including SEM （scanning electron microscope）, TEM （transmission electron microscopy）, STEM （scanning transmission electron microscopy） and EBLS （electron beam lithography system） are very susceptible to ELF magnetic fields emanating from various electrical power sources outside of the building and within next generation CMOS foundry recommends a maximum of 0.3 mG. The active canceling method uses active coils with current sensing field via sensor and inducing man-made electromagnetic field to reduce the stray magnetic field. Unfortunately, the conventional system takes more time to products field because of parasitical capacitance and resistance in long coil. The longer canceling coil the system construct, the more time it takes. Besides, canceling system should spend more time on calibrating non-linear current amplifier through software design. This research designs simpler anti-electro-magnetic system instead of typical frame and develops one turn canceling coil structure to reduce delaying time. Several parallel cells generate field up to 23.81 mG controlled by MPU （micro processor unit）. This system decreases the power-line inducing filed below 0.3 mG.
