Magnetic circuit

About: Magnetic circuit is a research topic. Over the lifetime, 15707 publications have been published within this topic receiving 118099 citations.

Design Synthesis of Switched Flux Hybrid-Permanent Magnet Memory Machines

Abstract: This paper develops a design methodology for switched flux (SF) hybrid permanent magnet memory machines (HPMMMs). The memorable flux is achieved due to the variable magnetization level of low coercive force (LCF) permanent magnets (PMs) Thus, the associated excitation loss is negligible, resulting in high efficiency operation over a wide speed range. A general hybrid PM magnetic circuit is modeled, which is characterized by spoke-array NdFeB PMs and LCF PMs sandwiched between an outer stator ring and an inner stator pole. Based on the magnetic circuit, the design conflicts within the stationary side are unveiled. Thereafter, the machine configuration is introduced, followed by a description of the design procedure. First, the optimal stator pole number is determined based on one-phase machine models. In addition, a simplified permeance function is utilized to analytically optimize the rotor number, accounting for different ratios of the slot opening to NdFeB PM thickness. The electromagnetic performance of the machines with alternate stator/rotor pole combinations are compared. The design guidelines for LCF PMs are presented. Finally, the theoretical analysis is verified experimentally on the prototype machine.

Improvements of single sheet testers for measurement of 2-D magnetic properties up to high flux density

Abstract: Due to structural limitation, the currently proposed apparatus based on a single sheet tester (SST) cannot measure magnetic properties along arbitrary directions (so-called 2-D magnetic properties) of silicon steel at high flux densities. In this paper, significant improvements are carried out on magnetizing windings and auxiliary yokes of a double excitation type of SST. Furthermore, crosswise overlapped H-coils are introduced so that even an ordinary single-excitation type of SST can be applicable to the measurements of 2-D properties. It is demonstrated that 2-D magnetization property up to 1.9 T can be measured by using the newly developed SST's.

Design and Realization of a Novel Compact Fluxgate Current Sensor

Abstract: A new closed-loop magnetic current sensor is presented in this paper. The sensor consists of two toroidal magnetic cores. One core works in fluxgate principle for the measurement of dc and low-frequency ac, and the other one is used as a current transformer for higher frequency application. Based on the simulation results, a prototype was designed, and the test results have a good agreement with the simulation results. The closed-loop configuration with a magnetic core and a feedback winding in the sensor improved the sensitivity of the sensor, eliminated the offset and drift related to temperature, and greatly reduced the error caused by magnetic hysteresis phenomenon. It can measure currents up to 20 A, with an accuracy of 0.5%, and a 50 kHz small signal bandwidth.

Characterization of induction motors in adjustable speed drives using a time-stepping coupled finite element state space method including experimental validation

Abstract: This paper describes how a comprehensive time-stepping coupled finite element phase flux linkage-based state-space modeling approach can be used for the characterization of induction motors in adjustable-speed drives. The model implemented the faster indirect and iterative coupling approach based on the curl-curl nondiffusion equation rather than the direct coupling approach, which is based on the curl-curl diffusion equation. The model presented in this paper is capable of rigorously modeling the effects of magnetic nonlinearities and space harmonics due to the machine magnetic circuits' topology and winding layouts, time harmonics resulting from electronic switching of inverters, as well as the synergistic interaction between these time and space harmonics. This includes the presentation of a unique approach for the calculation of electromagnetic torque by means of a concept of energy balance computed from instantaneous magnetic field solutions calculated at each time sample in an at cycle. This approach reveals higher content of torque ripples than given by more conventional approaches to torque calculations. The results of motor drive performance simulations and corresponding test results are shown to correlate well here with current waveforms and torque averages. This includes sinusoidal excitation and six-switch inverter excitation with pulsewidth modulation switching pattern, respectively.

Analysis and Optimization of Thrust Characteristics of Tubular Linear Electromagnetic Launcher for Space-Use

Abstract: Release-launch is a fundamental operation in space platform. Not like traditional land-base launcher, space-base launcher is more flexible and more efficient. Tubular linear electromagnetic launcher (TLEML), which provides higher force density, simple structure and no unilateral magnetic force, compared with the flat linear electromagnetic launcher, is more suitable for space platform. It can easily meet the demand such as little volume, light weight and high control precision. This paper analyzes and optimizes the thrust characteristics of tubular linear permanent magnet synchronous motors (TL-PMSM) for electromagnetic launcher, including different topologies, interior permanent magnet (IPM) and surface-mounted permanent magnet (SPM). First, build up the finite element model for the two kinds of TLEML and calculate the magnetic field. Then thrust force fluctuation figures are obtained by finite element analysis considering the pole/arc ratio, the pole pitch and the inner diameter/outer diameter ratio of the stator. The result shows that it can improve the thrust characteristic and decrease the cogging force by optimizing the parameters of the motor.