Magnetic circuit

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

Optimum geometry for torque ripple minimization of switched reluctance motors

Abstract: This paper briefly describes an approach to determine the optimum magnetic circuit parameters to minimize low speed torque ripple for switched reluctance (SR) motors. For prediction of the torque ripple, normalized data obtained from field solution and a neural network approach is used. Comparison of experimental results with computations illustrates the accuracy of the method. The optimization method is briefly described and some results are presented.

Magnetic domains in thin-film recording heads as observed in the SEM by a lock-in technique

Abstract: In a thin-film magnetic recording head, a magnetic circuit made from two Permalloy thin films, one above the other, is magnetized by a spixally plated thin-film copper coil which is located (together with insulating layers) between those two films. The magnetic domains in a thin Permalloy film can be studied by type-2 magnetic constrast using backscattered electrons (BSE) in the scanning electron microscope (SEM) provided that the film has a smooth surface and is deposited on a flat substrate. In practice, the upper Permalloy film follows the contours of the underlying layers. This gives a topographic signal which is large enough to mask the type-2 magnetic contrast signal in its simple form. The domain walls can, however, be seen if the magnetic recording head is excited with a sinusoidal current and if the video waveform is processed with a lock-in amplifier referenced either to the fundamental or to the second harmonic of the excitation frequency. This lock-in image processing technique has now been applied to obtain images of the magnetic domains both from the upper Permalloy film of an incompletely fabricated head and also from the exposed cross sections of the Permalloy films in an operational thin-film head.

Electric current sensing device of the magnetic field compensation type

Abstract: An electric current sensing device for measuring a primary current of relatively high intensity. The device includes a magnetic circuit that is coupled with a primary conductor and with a measuring coil that is connected to a current source through an associated control circuit. The magnetic circuit includes an air gap which accommodates a magnetic field detector that is electrically connected to an input of the control circuit for controlling a magnetic field compensating current that is supplied to the measuring coil. The device also includes a printed circuit that is arranged to both minimize electromagnetic interference between the measuring current circuit and the control circuit input, and improves heat dissipation of the printed circuit, thus optimizing the size ratio of the maximum primary current to the bulk of the device and improving performance of the same.

A novel transverse flux machine for vehicle traction aplications

Abstract: A novel transverse flux machine topology for electric vehicle traction application using ferrite magnets is presented in this paper The proposed transverse flux topology utilizes novel magnet arrangements in the rotor that are similar to Halbacharray to boost flux linkage; on the stator side, cores are alternately arranged around a pair of ring windings in each phase to make use of the entire rotor flux that eliminates end windings Analytical design considerations and finite element methods are used for an optimized design of a scooter in-wheel motor Simulation results from Finite Element Analysis (FEA) show the motor achieved comparable torque density to conventional rare-earth permanent magnet machines This machine is a viable candidate for direct drive applications with low cost and high torque density

Method for estimating core losses in switched reluctance motors

Abstract: SUMMARY The prediction of switched reluctance motor (SRM) performance requires knowledge of core losses. However, the calculation of iron losses in SRM is especially complex first because the flux waveforms are nonsinusoidal and different parts of the magnetic circuit have different waveforms and second because they are conditioned by the type of control used. This study proposes an analytical method for calculating core losses that comprises simulation of the SRM using finite element analysis to determine the magnetization curves, and SRM modeling, which enables transient simulations with the associated electronic power converter run under different control strategies. The flux density waveforms in the different parts of the SRM are derived from the flux density waveform of the stator pole that is obtained from the transient simulation. The specific core losses (in W/kg) are separated into three parts (hysteresis losses, classical eddy current losses and excess losses) and calculated using the waveforms and time derivatives of the local flux density. The core losses for each part of the SRM’s magnetic circuit can be estimated using the calculated values for specific hysteresis losses, specific classical eddy current losses and specific excess losses for each zone. Adding these individual losses yields the total core losses. The method was applied to three-phase 6/4 SRM, and the calculated results were compared with experimentally obtained measurements. Copyright # 2010 John Wiley & Sons, Ltd.