Magnetic circuit

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

A simple dynamic model for eddy currents in a magnetic actuator

Abstract: This paper presents a simple dynamic model of eddy currents in a magnetic actuator. The model is based on the application of Maxwell's equations to a homogeneous ferromagnetic conductive material. The resulting diffusion equation is solved in two dimensions for a cross-sectional cut through a rectangular bar; boundary conditions are imposed by a sinusoidally varying actuator coil current. The utility of the new modeling approach is illustrated by predicting the dynamic performance of a magnetic bearing actuator. The predictions are found to be in good agreement with measured values. The model provides a new and convenient method of modeling the relationships among voltage, current, force, and flux in magnetic circuits containing eddy currents.

Characteristic Analysis of Claw-Pole Machine Using Improved Equivalent Magnetic Circuit

Abstract: Magnetic field analysis of claw-pole machines using improved equivalent magnetic circuit (EMC) is presented in this paper. On the basis of 3-D geometry, improved EMC, which consists of magneto motive-force (MMF) source and permeance considering main and leakage flux distribution, is composed and field analysis is performed. Nonlinear characteristics of magnetic core are considered for precise analysis results. Three-dimensional finite element analysis (FEA) is performed to verify calculated results and flux density in rotor and stator areas are compared. In addition, calculated and experimental back-EMF versus MMF of field and rotor speed is compared. From the verification with calculated and experimental results, it is proved that improved EMC compared with 3-D FEA provided reasonable results in initial design of claw-pole machine having asymmetric structure.

A Novel Structure for Low-Loss Radial Hybrid Magnetic Bearing

Abstract: This paper proposes a novel radial hybrid magnetic bearing (RHMB), which has integrative magnetic pole boards and continuous working air gaps that reduce the hysteresis and eddy-current losses of the traditional homopolar structure. Its configuration and working principle are introduced. The bias and control magnetic circuits of the RHMB are analyzed with the equivalent magnetic circuit method. Mathematical models, from which the force-displacement and force-current relationships are derived, are built. The method for the rudimentary design of RHMB parameters is illustrated, through which a prototype RHMB for a reaction flywheel system is designed and assembled. Its performance and characteristics are calculated and analyzed with the obtained models and relationships. The results show that in its air gaps, the novel RHMB can generate a continuous and uniform bias magnetic field, which reduces the hysteresis and eddy-current losses and enhances the radial load capacity and axial passive resilience. The bias fluxes of all poles are decoupled from each other at all times. Although the control fluxes of the two channels are slightly coupled when the rotor is not in the central position, the coupling force-current stiffness is very low and can be ignored. These attributes simplify the design of the control system. The novel RHMB is especially suitable for high-speed and low-loss circumstances. A pair of RHMBs are used for the reaction flywheel, and for maintaining suspension of the rotor at the spin speed of 0-6000 rpm.

Magnetic-field-resilient superconducting coplanar-waveguide resonators for hybrid circuit quantum electrodynamics experiments

Abstract: Superconducting coplanar-waveguide resonators that can operate in strong magnetic fields are important tools for a variety of high-frequency superconducting devices. Magnetic fields degrade resonator performance by creating Abrikosov vortices that cause resistive losses and frequency fluctuations or suppress the superconductivity entirely. To mitigate these effects, we investigate lithographically defined artificial defects in resonators fabricated from Nb-Ti-N superconducting films. We show that by controlling the vortex dynamics, the quality factor of resonators in perpendicular magnetic fields can be greatly enhanced. Coupled with the restriction of the device geometry to enhance the superconductors critical field, we demonstrate stable resonances that retain quality factors ≃105 at the single-photon power level in perpendicular magnetic fields up to BâS¥ ≃20mT and parallel magnetic fields up to B⥠≃6T. We demonstrate the effectiveness of this technique for hybrid systems by integrating an In-Sb nanowire into a field-resilient superconducting resonator and use it to perform fast charge readout of a gate-defined double quantum dot at B=1T.