Air-gap Magnetic Density Research Articles

Study of Axial-Flux-Type Superconducting Eddy-Current Couplings

A theoretical physical model of axial-flux-type superconducting eddy-current coupling is systematically investigated. A mathematical description of a high-field superconducting bulk magnet used as the magnetic field source is modeled based on the physical superconducting mechanism. Thereafter, a practical two-dimensional (2-D) magnetic equivalent circuit model for the analytical calculation of magnetic field distribution in this coupling design using Schwarz–Christoffel mapping is proposed to predict the air gap magnetic density and the transferred torque, taking nonlinear effects of the magnetic materials into consideration. Finally, a 1/6 section 3-D model of the proposed superconducting eddy-current coupling is designed and analyzed via finite element method. The calculation results by the proposed analytical model are verified with those issued from the finite element method. Also, the efficiency of superconducting eddy current couple is analyzed theoretically.

Fast Calculation Model and Theoretical Analysis of Rotor Unbalanced Magnetic Pull for Inter-Turn Short Circuit of Field Windings of Non-Salient Pole Generators

Inter-turn short circuit of field windings (ISCFW) may cause the field current of a generator to increase, output reactive power to decrease, and unit vibration to intensify, seriously affecting its safe and stable operation. Full integration of mechanical and electrical characteristics can improve the sensitivity of online monitoring, and detect the early embryonic period fault of small turns. This paper studies the calculations and variations of unbalanced magnetic pull (UMP), of which the excitation source of rotor vibration is the basis and key to online fault monitoring. In grid load operation, ISCFW are first calculated with the multi-loop method, so as to obtain the numerical solutions of the stator and the rotor currents during the fault. Next, the air-gap magnetic field of the ISCFW is analyzed according to the actual composition modes of the motor loops in the fault, so as to obtain the analytic expressions of the air-gap magnetic motive force (MMF) and magnetic density. The UMP of the rotor is obtained by solving the integral of the Maxwell stress. The correctness of the electric quantity calculation is verified by the ISCFW experiment, conducted in a one pair-pole non-salient pole model machine. On this basis, comparing the simulation analysis with the calculation results of the model in this paper not only verifies the accuracy of the electromagnetic force calculation, but also proves that the latter has the advantages of a short time consumption and high efficiency. Finally, the influencing factors and variation law of UMP are analyzed by means of an analytic model. This develops a base for the online monitoring of ISCFW with the integration of mechanical and electrical information.

A Model for Analyzing a Five-Phase Fractional-Slot Permanent Magnet Tubular Linear Motor with Modified Winding Function Approach

This paper presents a model for analyzing a five-phase fractional-slot permanent magnet tubular linear motor (FSPMTLM) with the modified winding function approach (MWFA). MWFA is a fast modeling method and it gives deep insight into the calculations of the following parameters: air-gap magnetic field, inductances, flux linkages, and detent force, which are essential in modeling the motor. First, using a magnetic circuit model, the air-gap magnetic density is computed from stator magnetomotive force (MMF), flux barrier, and mover geometry. Second, the inductances, flux linkages, and detent force are analytically calculated using modified winding function and the air-gap magnetic density. Finally, a model has been established with the five-phase Park transformation and simulated. The calculations of detent force reveal that the end-effect force is the main component of the detent force. This is also proven by finite element analysis on the motor. The accuracy of the model is validated by comparing with the results obtained using semianalytical method (SAM) and measurements to analyze the motor’s transient characteristics. In addition, the proposed method requires less computation time.

Design of disk type PM synchronous generator based on halbach

This paper expounds the application merits of disk type PM synchronous generator in small-scale wind power generation .The characteristics of the disk type PM synchronous generator were analyzed and 8P, 200W disk type generator with 90 degree Halbach magnet structure was designed. Simulation and calculation are carried out by using finite element method. By comparing the 90 degree Halbach magnet structure and the traditional magnet structure of the disk type generator, the results shows that the 90 degree Halbach magnet structure can improve the air gap magnetic density, reduce the leakage of main magnetic circuit and the loss.

Finite Element Method Simulation and Comparison of a Segmented-PM Motor and a Whole-PM motor

A permanent magnet synchronous motor (PMSM) with rotor embedded segmented permanent magnet was analyzed. The structural features and flux weakening principle are introduced. The shape of the rotor is optimized to get a sinusoidal air gap magnetic density waveform and reduce the toque ripple. The whole-permanent-magnet (PM) motor and the segmented-permanent-magnet motor are compared from the aspects of the no-load performance, the rated load performance and the flux-weakening performance by finite element method (FEM)The theoretical analysis and simulation by FEM indicate the availability and validity of flux-weakening for the segmented-PM motor.

Analysis of Magnetic Field for Micro Axial-Flux Electromagnetic Generator

This paper reports on the magnetic field distribution and magnetic circuit calculating method of micro generator. A micro axial-flux electromagnetic generator is designed as size of Φ6mm×3mm. Traditional magnetic circuit analysis methods are used to retrieve the air-gap magnetic density on no-load micro generator in operation. FEA is done for the micro generator model using magnetic field numerical simulation software. The main parameters of no-load magnetic field and the waveform of induced EMF are obtained. Comparing the results obtained from the magnetic circuit analysis and numerical simulation, the error of air magnetic density is less than 2.54% and the error of the maximum value of induced EMF is less than 2. 68%. The results suggest that magnetic circuit analysis methods can be used for magnetic field analysis of micro axial-flux electromagnetic generators, and be helpful to provide guidance for designs.

Design of Brushless Electric Excitation Synchronous Machine

Brushless electric excitation synchronous machine is a new kind of AC machine. There are two sets of windings with different pole numbers on the stator. It eliminates the brushes and slip rings. The air gap magnetic density of brushless electric excitation synchronous machine is achieved based on Ansoft. And the influence of stator windings with different pole numbers on coupling capability is analyzed. All the results are investigated to provide the guide for the optimal design.

A New Approach to Research the Transverse Edge Effect in Linear Induction Motor Considering the Edge Fringing Flux

In this paper, we propose a new approach to analyze the transverse edge effect using the vector electric potential. The edge fringing flux is considered by separating the air-gap magnetic density created by stator current and secondary eddy current, respectively. The variations of the total thrust force, the magnetization inductance and the secondary resistance varying with the air gaps, the stator widths and the end portion widths were studied.

Study on Electromagnetic Exciting Force Characteristics and Electromagnetic Noise of Permanent Magnet DC Motor

Electromagnetic exciting force is the key to generate electromagnetic noise. The characteristics of electromagnetic exciting force and the causing of electromagnetic noise were analyzed after the power was off for cooling fan Permanent Magnet DC (PMDC) motor. Time-stepping finite element method was selected to calculate its several parameters, such as air gap magnetic density harmonics generated by the stator and rotor, torque ripple and unbalanced magnetic pull at its different speed.Experiment on unloading vibration noise was carried out to confirm the validity of electromagnetic exciting force analysis. The results show: electromagnetic force amplitude keeps constant while the motor speed changing. Torque ripple decreases while the motor speed down. A kind of electromagnetic noise called howling noise produced by PMDC motor used in car cooling fan is mainly due to resonance. So the best way to eliminate this motor’s noise is to improve the order of electromagnetic waves and avoid the electromagnetic resonance.

Analysis of Cogging Torque of PM Motor with Radial Magnetic Field and Parallel Magnetic Field

This paper provide two methods to analyze the cogging torque of PM motor with radial magnetic field and parallel magnetic field, FEM method and Analytic method. The FEM model and Analytic model of PM motor with radial magnetic field and parallel magnetic field are founded. We analyze the model in both methods. From the result of analysis. The air-gap magnetic density of PM motor can be analyzed. We can find the cogging torque of radial magnetic field PM motor is much heavily than the cogging torque of parallel magnetic field PM motor. The result of Analytic method is close to the result of FEM method. The Analytic method is useful in analyze the cogging torque of PM motor.