International Journal of Applied Electromagnetics and Mechanics

High-speed and high-power-density drives are receiving more and more attention in today's industry. This study presents a switched reluctance motor (SRM) with conical magnetic bearings (CMBs), which is very suitable to operate in high speed and harsh environment such as starter/generator in aircraft. The proposed motor consists of a SRM and two CMBs. There is electric relationship between the SRM and two CMBs, this novel motor's three-phase motoring windings are constructed by connecting each phase biased winding of two CMBs and each phase winding of the SRM in series, respectively, and the three-phase motoring windings are driven by the traditional switched reluctance mode. Thus the rotational torque in SRM and the biased flux used for suspending force generation in two CMBs can be produced by motoring winding currents simultaneously. Initially, the structure and working principle of the proposed SRM with CMBs are demonstrated. Then, the theoretical formulas for computing the suspending force of this novel CMB in the proposed structure are deduced by taking advantage of the magnetic equivalent circuit method and the virtual displacement principle. Furthermore, its suspending force control and basic design method are described. Finally, the characteristics of the proposed SRM with CMBs are deeply analyzed and verified by 3D finite element method.

In order to meet energy consumption of the electronics and reuse the structural vibration energy, this study investigates a novel electromagnetic energy harvesting (EEH) method by employing a step-up and step-down circuit. The principle of the EEH system is introduced, and the electrical governing equation of the harvesting circuit is analyzed. A cantilever beam structure with EEH system is built up. The theoretical model is established and the corresponding experiment is setup to verify the energy harvesting performance of the EEH circuit. The experimental results prove that the proposed EEH system is able to harvest the vibrational energy and effectively step-up and step-down the harvested signal by changing the duty circle of the control circuit. Finally, the self-powered ratio of the EEH system is proposed and analyzed, which reaches to 6.1% for an electric circuit with 0.1 W consumption. The EEH method provides an effective self-powered solution for the low power consumption electronics.

A design scheme of the vehicle magnetic particle clutch with permanent magnets (PM-MPC) is proposed based on the principle of two magnetic fields superposition generated by both of the permanent magnets and the exciting coils. According to the working characteristics of the clutch, working process of the vehicle PM-MPC is analyzed, and the design objectives of the clutch torque are proposed to meet the requirement of vehicle operation under different loads. Based on a domestic economical passenger vehicle as the matching type, the structure parameters of the permanent magnet which can satisfy the design requirement are determined, and the torque performance of the PM-MPC is gained by electromagnetic field computation. Furthermore, it compares and analyzes the torque transmission performance as well as the energy consumption characteristics of the PM-MPC and the electromagnetic magnetic particle clutch (EM-MPC) with the same structural size. Then, the results show that the vehicle PM-MPC in this paper has the advantages of high torque transmission and low energy consumption. Finally, the prototype of PM-MPC is produced which performance is tested. More importantly, the correctness of the design and calculation is verified as expected.

This paper proposes a maglev device for a vertical hydro-turbine to replace the thrust-bearing. The structure of the device is given. For the given mechanical structure, a design and optimization method is put forward and the process is provided. The dimension parameters are optimized to make the best use of material for bigger force density and better control performance. The ideal common linear model is built and the nonlinear programming method is used to decide the primary size parameters. The results are inaccurate tested by finite element analysis (FEA) because the model is rough. A more accurate reluctance network (RN) model is set up and the PSO method is applied to get the optimal point. The results from the two models are compared. The feasibility and validity of the latter method is verified.

An optimal design procedure based on the dynamic characteristics of a hybrid excited linear actuator (HELA) constrained in a specific volume has been developed. For achieving fast response and low power consumption, two electrical parameters including excitation duration and coil diameter were optimized. Three models, including a loss model, an electromagnetic model, and a mechanical model were constructed, and optimal design calculation was performed by using 3D finite element method (FEM). According to the results, a hot-gas valve directly driven by HELA was manufactured and dynamic experiments were performed. The results show the experimental dates agree well with simulating calculation. The open and the closed response time is 2.3 ms and 3.5 ms separately, when the total mass of the HELA is 100 g. Moreover, the prototype's cycle loss is 0.7 J independent of the operation frequency. The experiments show that the design procedure is sufficiently accurate, which validate that the prototype has characteristics of fast response and low power consumption. Besides, the eddy current loss is 44.9% of the total loss, and the eddy current increases the response time over 8.6 percent according to quantitative analysis, which validate the necessity of the coupling model.

An analysis has been carried out to study combined effects of internal heat generation and mass effects on Casson fluid with convective boundary conditions towards linear stretching sheet and this physical phenomena is widely used in many food processing engineering. Appropriate transformations are invoked to renovate the leading partial differential equations into the ordinary differential equations. Exact solution for velocity profile is used. Further numerical solution for heat and concentration is acquired by shooting method. The explanation and analysis of the constraints are allotted by means of graphical results used for dimensionless velocity, temperature, concentration, skin resistance coefficient, surface heat and mass transfer.

A magnetically levitated linear slider (MagLevLS) with a non-contact power transfer method is proposed. The levitated platform was designed as a four-point suspended rigid metal plate. Magnetic levitation and zero power control under forces introduced by the non-contact power transfer method was experimentally investigated and presented. The presented MagLevLS is expected to use as a short-range transport system in a clean operating environment. An open-end generator was purposed to achieve non-contact power transfer. The open-end generator design was analyzed using FEM and experimental data obtained from an experimental prototype was presented. The proposed MagLevLS platform uses four hybrid electromagnets (HEMs) as actuators for levitation. A PD controller with integral feedback was used to achieve quasi-zero power operation of the levitated platform. A single rigid platform was used to mount all four HEMs, and a 0.25 W steady state power consumption for per HEM was achieved under disturbances introduced by the open-end generator. According to the results, MagLevLS can achieve stable levitation under cogging forces and generate sufficient power for continuous operation.

The purpose of this paper is to solve the problem of coaxial line may suffer the invasion of lightning current during the process of transferring microwave signal, which would damage the electronic equipment and then deteriorate the quality of transmission. First, the theories of transmission line and quarter-wave short circuit are analyzed. Second, by utilizing the simulation tool and vector network analyzer, this paper evaluates the analytical and experimental S21 parameters of protective devices to ensure the normal signal transmission. Finally, the simulated lightning currents generated from combined wave generator (1.2/50 μs, 8/20 μs) are also applied to the impact experiment. The simulation results are summarized as follows: quarter-wave short circuit with wavelength of 1/4λ shows high resistance to the lightning and does not affect the signal transmission; the residual voltage and current positively correlate with the impulse voltage magnifying from 0.2 to 5 kV and are suppressed in low ranges. The proposed method provides effective lightning protection in the application of signal transmission.

A spherical electromagnetic energy harvester is designed to harvest omni-directional kinetic energy. A novel spherical Halbach array is proposed, which increases the magnetic field gradient in the coil compared with the traditional permanent magnet array, to increase the output performance. The parameter optimization of the spherical structure is carried out in accordance with the analytical results of the corresponding physical model. Finite element analysis and experimental performance test are carried out on the prototype. Experimental results demonstrate that the novel transducer can harvest kinetic energy in any direction, and then transfer to electric power. When the excitation direction is horizontal with frequency of 7.5 Hz, the load resistance is 3.2 Ω, the electric power reaches its maximum value. The maximum load power of a single coil is 0.18 mW. It can meet the needs of some microelectronic devices and has the potential to take the place of chemistry batteries and supply power to wildlife monitoring and positioning systems.

A general model for the calculation of current density in two parallel conductors is proposed. The solution of the model is based on the calculation of magnetic fluxes and on the application of Faraday's law of electromagnetic induction. Magnetic fluxes are determined via magnetic field integration. For this purpose, formulae are given in the Appendix Section for the calculation of the magnetic field produced by an infinitely long conductor the cross section of which is a sector of a ring. The proposed model is used to examine a pair of tubular conductors. The conductors are supplied from a source of sinusoidal voltage in steady state. It is assumed that the voltage frequency does not exceed 1 MHz, and the displacement current is neglected. Solutions to several problems are given. The effect of the resistivity of conductors, their distance and the source frequency on the current density and current in the conductors and on their series impedance is analysed. For the calculation of the inductance of distant tubular conductors very simple and exact formulae are derived, and the transient current in these conductors is described when the voltage source is connected and disconnected.

The mechanical gear, which is used in many fields of modern industry, is used primarily in power transmitting mechanical devices. Magnetic gears, which solve the physical contact problem of mechanical gears, have drawn much attention. The magnetic gear has many advantages such as no mechanical friction loss, very little noise and vibration, and no need for lubricant. Because of these unique noncontact characteristics, the magnetic gear has many advantages and allows for high efficiency operation. However, magnetic gears are expensive because they contain rare-earth permanent magnets, to generate magnetic fields and thereby transmit power by using a magnetic field generated by permanent magnet. Therefore, this paper applies the salient structure of the conventional magnetic gear and progress optimization of both magnet angle and novel pole pieces using central composite design, which is a response surface method. In addition, experimental data required for predicting the relationships among design variables are obtained using the finite element method based on 2-D numerical analysis.