Magnetic bearing: structure, model, and control strategy

In this article, polypropylene (PP), polyimide (PI), polyvinylidene difluoride (PVDF), and polyethylene (PE) dielectric materials are applied to analyze the performance degradation mechanism under magnetic field. The properties of the dielectrics are investigated under different magnetic fields. With the increase of magnetic field, the dielectric constant of materials is reduced and that of PVDF decreases the most. The conductivity of dielectric materials is all on the rise due to the magnetic field. Compared with under normal environment, the conductivity of the PVDF under 12-T magnetic field climbs to 574%, which is the largest increase in all dielectrics. The breakdown strength of PP and PE decreases by 17.2% and that of PVDF decreases by 22%. On the one hand, the magnetic field deflects the electric dipole in the opposite direction through Lorentz force, so as to limit the dipole steering and reduce the dielectric constant. On the other hand, the magnetic field increases the quantity of carriers by exciting electrons, which is the main reason for the decrease of breakdown strength. This article is of significance to the application of dielectric capacitors under harsh magnetic environment. 

Dielectric Properties of Polymer Films in Strong Electromagnetic Field for Energy Storage Capacitor

To solve the key problems of strong infrared radiation, poor continuous combat capability of the system, serious ablation of the launching device, and environmental pollution during missile launch, the electromagnetic launch system (EMLS) has been studied for missile launching tasks. However, most of the current research studies are aimed at specific technical points and lack the overall design and evaluation of the system. Therefore, the designed system may have problems such as excessive cost, lack of economy, or low overall efficiency. In order to complete the overall evaluation of the missile electromagnetic launch system (MEMLS), this article established an ADC model improved by entropy weight method-fuzzy analytic hierarchy process-improved combination weighting model of game theory (EWM-FAHP-ICWGT). The established model integrates subjective and objective weights, eliminating the problem of negative combination coefficients that traditional CWGT may bring, and the average difference in combination weights is the smallest. Difference analysis and differential analysis are also used here to discuss the requirements for the reliability indicator which is mean time between failure (MTBF) and maintainability indicator which is mean time to repair (MTTR) to further improve the effectiveness of the system. Finally, the indicators that have a significant impact on the performance of MEMLS are analyzed, which provides a direction for further research on the system.

/pdf/effectiveness-evaluation-of-missile-electromagnetic-launch-zmoa2dj3xo.pdf

Effectiveness Evaluation of Missile Electromagnetic Launch System Based on ADC Model Improved by EWM-FAHP-ICWGT

This paper presents a novel structure of the permanent magnet linear synchronous motors (PMLSMs). Using oriented silicon steel sheet (OSSS) instead of traditional non-oriented silicon steel sheet (NOSSS) as the mover of the proposed PMLSM. The OSSS possess better magnetic permeability and anti-saturation ability than NOSSS in the rolling direction, so setting the rolling direction is consistent with the magnetic circuit directions of the tooth. By the analysis thrust and saturation effect and employed the finite element software, the results display that the use of OSSS as the mover core material can increase the electromagnetic thrust and overload capacity.

Analysis of Permanent Magnet Linear Synchronous Motor made by Oriented Silicon Steel Sheet

In this article, polypropylene (PP), polyimide (PI), polyvinylidene difluoride (PVDF), and polyethylene (PE) dielectric materials are applied to analyze the performance degradation mechanism under magnetic field. The properties of the dielectrics are investigated under different magnetic fields. With the increase of magnetic field, the dielectric constant of materials is reduced and that of PVDF decreases the most. The conductivity of dielectric materials is all on the rise due to the magnetic field. Compared with under normal environment, the conductivity of the PVDF under 12-T magnetic field climbs to 574%, which is the largest increase in all dielectrics. The breakdown strength of PP and PE decreases by 17.2% and that of PVDF decreases by 22%. On the one hand, the magnetic field deflects the electric dipole in the opposite direction through Lorentz force, so as to limit the dipole steering and reduce the dielectric constant. On the other hand, the magnetic field increases the quantity of carriers by exciting electrons, which is the main reason for the decrease of breakdown strength. This article is of significance to the application of dielectric capacitors under harsh magnetic environment.

The surface-mounted permanent magnet linear synchronous motor (PMLSM) is a good candidate for the Electromagnetic Launch System due to its merits of high-power density, power factor and efficiency. However, this kind of machine needs a lot of permanent magnets (PMs) on the long stator, which is costly. To solve this problem, a novel PMLSM is proposed in this paper. The stator of novel PMLSM has the consequent poles structure and the mover of novel PMLSM has two iron cores, which sandwiches a mover PM. Firstly, the structure and operation principle of the proposed PMLSM have been investigated. Then, the analytical calculation of thrust and detent force is analyzed and the structural parameters of the motor are optimized for larger thrust and less detent force. Finally, for a fair comparison, the proposed motor is designed and built based on an existing PMLSM with similar electromagnetic and geometrical parameters. The thrust performance indexes of the novel PMLSM are estimated and compared with the conventional surface-mounted PMLSM, which indicates that the proposed PMLSM can keep similar performances with the exciting PMLSM. Moreover, it has a simple structure, less thrust ripple and can save many PMs, which can help reduce costs.

A Novel Permanent Magnet Linear Motor for the Application of Electromagnetic Launch System

A typical flywheel energy storage system (FESS) includes an electrical machine, a flywheel, and magnetic bearings, which are independent of each other. Therefore, the structure of FESS is complicated, which leads to the problems of high cost and low integration. This article presents a novel stator PM excitation solid rotor machine (SPE-SRM) for FESS, which integrates an electrical machine, flywheels, and a magnetic bearing. The design method of the SPE-SRM is presented specifically. First, the structure and operation principle of the SPE-SRM are illustrated. Second, the design and optimization of the flywheel-rotor are presented with considering of power, energy storage, and mechanical strength. Third, the magnetic equivalent circuit of the SPE-SRM is established to simplify the design. Besides, the armature reaction and leakage flux factor are investigated. Fourth, the performance indexes, including torque, suspension force, no-load back electromotive force (back-EMF), losses, and temperature rise are fully analyzed by the finite element analysis. Finally, a 22 kW prototype is manufactured and tested. The rationality of the concept and design is validated by experiments. The SPE-SRM has the merits of high integration, robust structure, and low cost, so it has the potential for wide application in FESS.

Research of a Stator PM Excitation Solid Rotor Machine for Flywheel Energy Storage System

The thermal analysis is necessary for the design and safe operation of the homopolar inductor machine (HIM) applied in the flywheel energy storage system (FESS). However, due to its unique three-dimensional (3-D) structure, the thermal analysis of HIM relies on the 3-D finite element analysis (FEA) or computational fluid dynamics (CFD), which is time-consuming and computationally inefficient. To facilitate the thermal analysis and design of HIM, a fast and accurate analytical model is essential. In this article, the novel 2-D and 3-D hybrid thermal networks combined with a coupled iterative analysis method are proposed to predict the temperature of HIM. First, the structure, operation principle, and material properties of HIM are illustrated. Second, the heat sources of HIM, including iron loss, rotor eddy current loss, rotor air friction loss, copper loss, and bearing loss, are fully analyzed and investigated. Third, the proposed hybrid thermal model (HTM) and coupled iterative analysis method are demonstrated and applied to predict its temperature. The proposed thermal model and analysis methods are explained in detail. The influences of different speeds and operation conditions on the temperature rise of HIM are analyzed based on the proposed thermal model and FEA. Finally, the temperature of an HIM prototype is tested, which proves the accuracy of FEA and the proposed method. The proposed HTM can quickly and accurately predict the temperature of HIM, which provides a new idea for the temperature prediction of this kind of machine.

Study on a Novel Hybrid Thermal Network of Homopolar Inductor Machine

The change rate of the exciting current of the homopolar inductor machine (HIM) would be affected by the time constant of exciting winding (EW). The smaller the time constant is, the faster the exciting current changes, which is help to build or eliminate the excitation magnetic field of HIM quickly. To reduce the time constant of EW, some methods are proposed and investigated in this article. First, the mathematical model of the time constant of EW is established based on the equivalent circuit method. Afterward, the factors affecting the time constant of the EW, including the resistivity of the winding, the equivalent air-gap length of the HIM, and the cross-sectional area of the winding, are investigated. Moreover, several methods are proposed and analyzed to reduce the time constant of the EW. Finally, the theoretical analyses are verified by simulations and experiments.

Investigation on the Method for Reducing the Time Constant of Exciting Winding of Homopolar Inductor Machine

Permanent magnetic bearings (PMB) are used nowadays in many applications ranging from turbomachinery to energy storage flywheels due to their simple construction, no contact, and no wear The calculation of the magnetic force is of great significance in the optimal design progress However, the current magnetic force expression obtained by the equivalent magnetic charge model is a multidimensional integral with a complex integrand In order to simplify the calculation under the premise of ensuring accuracy, the equal distribution sequence Quasi-Monte Carlo method (QMC) is used to calculate the magnetic force between two ring magnets in this paper Based on Monte Carlo method (MC), it is proposed to solve the multidimensional integral by using a sequence of low-discrepancy irrational numbers that are more uniform than the randomly generated point distribution to avoid aliasing of projections and have a faster rate of convergence The integral is programmed in MATLAB using MC and QMC and verified using the finite element method (FEM), then the results are compared with the data in published literature The results show that QMC has higher accuracy and better repeatability than MC, and the calculation efficiency is higher The results of the proposed method are in good agreement with FEM and published literature, and the required time is shorter than FEM, which is a more suitable method for magnetic force calculation in some cases

Calculation and Verification of Magnetic Force in a Radial Permanent Magnetic Bearing based on Quasi-Monte Carlo Method

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