Magnetic circuit

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

A High-Frequency and High Spatial Resolution Probe Design for EMI Prediction

Abstract: In this paper, a simple and accurate equivalent circuit of the magnetic probe is proposed. Based on the equivalent circuit, a high-frequency probe for near-field measurements is proposed, manufactured, and tested. To increase its working frequency, its parasitic inductance and capacitance are reduced by using a small loop aperture and a tapered transition. The working frequency of the probe is up to 30 GHz. At the same time, sidewall metallization and bottom-vias are used in the probe, which result in a good performance of electric field suppression. The transmission section of the probe is optimized at high frequencies by using via fence and coax-thru-hole vias. The magnetic field probe is built on a four-layered printed circuit board with Rogers substrate. The loop aperture size of the probe is $250\,\,\mu \text{m}\,\,\times 250\,\,\mu \text{m}$ , so it has a high spatial resolution and is helpful to measure the detailed magnetic field from a small device. The probe is calibrated by a standard coplanar waveguide with a backside ground (CPWG). Finally, a near-field scanning system with the fabricated probe is set up to test the magnetic field above an unknown CPWG and microstrip line. From the near-field scanning results, it can be concluded that the probe can accurately measure the magnetic field over a wide frequency band.

Radial magnetic bearings: An overview

Abstract: Radial magnetic bearings (RMBs) are one of the most commonly used magnetic bearings. They are used widely in the field of ultra-high speed and ultra-precise numerical control machine tools, bearingless motors, high speed flywheels, artificial heart pumps, and molecular pumps, and they are being strengthened and extended in various important areas. In this paper, a comprehensive overview is given of different bearing topologies of RMBs with different stator poles that differ in their construction, the driving mode of electromagnets, power consumption, cost, magnetic circuits, and symmetry. RMBs with different poles and couplings between the two bearing axes in the radial direction responsible for cross-coupling generation are compared. In addition, different shaped rotors are compared, as the performances of magnetic bearing-rotor systems are of great concern to rotor constructions. Furthermore, the parameter design methods, the mathematical models and control strategies of the RMBs are described in detail. From the comparison of topologies, models and control methods for RMBs, the advantages, disadvantages and utilizable perspectives are also analyzed. Moreover, several possible development trends of the RMBs are discussed.

Fully integrated matrix magnetic recording head with independent control

Abstract: A matrix array of recording heads, wherein each head is independent from another both in terms of its magnetic circuit and excitation conductors. Each individual head has a planar magnetic circuit and an helical coil wrapped around the lower part of the magnetic circuit. The matrix array is collectively fabricated using full thin film technology on non-magnetic substrates. Preferably, the heads are aligned in an oblique lattice with the write gaps aligned along rows and offset by a constant value along columns. Each individual head is connected to the control electronics through interconnects to the backside of the wafer, allowing independent control of the write parameters. The die forming the device is shaped on its edges and top surface to optimize head/medium positioning and minimize wear.

Optimization of Voice Coil Motor to Enhance Dynamic Response Based on an Improved Magnetic Equivalent Circuit Model

Abstract: This paper presents an optimization of voice coil motor (VCM) used in ultra-precision motion stages based on an improved magnetic equivalent circuit (MEC) model. The modified MEC model takes into consideration the nonlinear saturation effect of ferromagnetic material by segmentation, and estimates the magnetic flux density in air gap of VCM in a more precise way. The results of experiment, finite-element analysis, and MEC model are compared to validate the correctness of the improved MEC method. A new optimization criterion is used to measure dynamic response and heat dissipation of VCM simultaneously. The geometric parameters of VCM are optimized, and the resulting VCM is proved to have a better dynamic response and lower heat dissipation.

Magnetic circuit for a non-contact charging device, power supply device, power receiving device, and non-contact charging device

Abstract: Disclosed is a magnetic circuit for non-contact charging devices which is provided with a coil, a coil yoke positioned on the rear side of the coil, and a magnetic absorption means positioned in the hole of the coil yoke but separated by a magnetic gap in an in-plane direction and/or the thickness direction.