Magnetic circuit

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

Design Considerations for Magnetorheological Brakes

Abstract: Design considerations for magnetorheological (MR) brakes are discussed for different geometries. A complete modeling in terms of torque density, efficiency, bandwidth, and controllability is presented. The model assigns a desired magnetic flux density over the fluid surface. The magnetic circuit dimensions and the necessary power can be calculated in consequence. The analysis focuses on a single disc and on a single drum brake and highlights the interdependence of the measures of performance as a function of the dimensions. The proposed models have been validated using finite-element analysis, the results demonstrate that both brakes are equivalent in terms of torque density but drum brakes are more reactive and require less power. The analysis has subsequently been extended to multiple-layered brakes with several fluid gaps in parallel. The performance are globally improved by increasing the number of gaps. Finally, the paper considers the influence of the MR fluid characteristics and housing material.

Electrically isolated power and data coupling system suitable for portable and other equipment

Abstract: An electrically isolated combined power and signal coupler is usable for a portable medical monitoring device attachable to a patient in a medical environment. A power coupling system transfers power between a power source and a powered device separated by a physical and electrical isolation barrier. The system comprises a power coupler including in a first device, a first section of a magnetic circuit including a first core section of magnetically permeable material of cross-sectional area substantially larger at an isolation barrier interface than within a first winding located on the first core section. The first section of magnetic circuit being suitable, in a docking mode, for positioning adjacent to a second section of magnetic circuit in a second device to form a completed magnetic circuit used to transfer power between said first and second device. The second section of magnetic circuit including a second core section with a second winding magnetically coupling with the first winding via the completed magnetic circuit in the docking mode for the power transfer. The first core section comprises at least one substantially planar core section at the isolation barrier interface for positioning adjacent to a corresponding substantially planar core section of said second section of magnetic circuit at the isolation barrier interface to form the completed magnetic circuit without a device containing the second section of magnetic circuit enveloping a significant portion of the substantially planar core section.

Compact inductor with stacked via magnetic cores for integrated circuits

Abstract: An on-chip inductor device for Integrated Circuits utilizes coils on a plurality of metal layers of the IC with electrical connectors between the coils and a magnetic core for the inductor of stacked vias running between the coils. The magnetic core is made from a series of stacked vias which are deposited between each metal layer of the IC having a coil. The magnetic core desirably includes an array of magnetic bars comprising the magnetic core. The via material of the magnetic core may be both magnetic and electrically conductive. The magnetic and electrically conductive via material may also be used for the planar coil electrical connectors or other electrically conductive parts of the IC, or both, thereby lessening fabrication steps. Films of magnetic material may be formed at the ends of the inductor to provide a closed magnetic circuit for the inductor. A high Q factor inductor of small (e.g., transistor) size is thus obtained. The materials and processes which enable the on-chip inductor device are compatible with ordinary IC fabrication methods.

Design and control of axial-flux brushless DC wheel motors for electric Vehicles-part I: multiobjective optimal design and analysis

Abstract: We have applied multiobjective optimal design to a brushless dc wheel motor. The resulting axial-flux permanent-magnet motor has high torque-to-weight ratio and motor efficiency and is suitable for direct-driven wheel applications. Because the disk-type wheel motor is built into the hub of the wheel, no transmission gears or mechanical differentials are necessary and overall efficiency is thereby increased and weight is reduced. The dedicated motor was modeled in magnetic circuits and designed to meet the specifications of an optimization scheme, subject to constraints such as limited space, current density, flux saturation, and driving voltage. In this paper, two different motor configurations of three and four phases are illustrated. Finite-element analyses are then carried out to obtain the electromagnetic, thermal, and modal characteristics of the motor for modification and verification of the preliminary design. The back-electromotive forces of prototypes are examined for control strategies of current driving waveforms.

Collector-less D-C motor

Abstract: A permanent magnet rotor operates within the air gap of a stator magnetic circuit which has a stator winding. Current through the winding is controlled by a selectively energized semiconductor switch, which is energized over a portion of rotor rotation and in synchronism therewith. The air gap included in the magnetic circuit is non-uniform along its length, increasing to a maximum intermediate the extent of a pole, for example between 10 to 50 electrical degrees, and then decreasing to a minimum over the remainder to 180 electrical degrees over a pole. The winding is energized to cause rotation of the rotor while the permanent magnet is within a predetermined angular range, resulting in storage of magnetic energy which is released as torque upon further rotation of the rotor in another angular range. The timing of energization of the winding by a control circuit can be used to control motor speed.