Results 1  10
of
12
Analysis of eddycurrent losses over conductive substrates with applications to monolithic inductors and transformers
 IEEE Transactions on Microwave Theory and Techniques
, 2001
"... Abstract—In this paper, a closedform integral representation for the eddycurrent losses over a conductive substrate is presented. The results are applicable to monolithic inductors and transformers, especially when such structures are realized over an epitaxial CMOS substrate. The technique is ver ..."
Abstract

Cited by 7 (0 self)
 Add to MetaCart
Abstract—In this paper, a closedform integral representation for the eddycurrent losses over a conductive substrate is presented. The results are applicable to monolithic inductors and transformers, especially when such structures are realized over an epitaxial CMOS substrate. The technique is verified against measured results from 100 MHz to 14 GHz for spiral inductors. Index Terms—CMOS substrate losses, eddy currents, monolithic inductors, monolithic transformers, spiral inductors, spiral transformers. I.
Prediction of rotating losses in heteropolar radial magnetic bearings
"... Previously, thin plate assumptions have been used to obtain a onedimensional eddy current model for predicting the stationary, transformertype losses in magnetic bearings built out of laminated material. Using similar assumptions as in the 1D eddy current model, rotating losses can be predicted f ..."
Abstract

Cited by 3 (2 self)
 Add to MetaCart
Previously, thin plate assumptions have been used to obtain a onedimensional eddy current model for predicting the stationary, transformertype losses in magnetic bearings built out of laminated material. Using similar assumptions as in the 1D eddy current model, rotating losses can be predicted for a laminated heteropolar radial magnetic bearing. The thin plate model of rotating losses yields a hybrid analyticalboundary element model that is computationally inexpensive to implement. Predictions from this model compare favorably to losses experimentally measured in rotor rundown tests.
Optimal Solutions to the Inverse Problem in Quadratic Magnetic Actuators
, 1996
"... The formulation of currenttoforce relationships for magnetic actuators proceeds in a fairly straightforward fashion from Maxwell's equations for magnetostatic problems. However, the inverse problem of determining a set of currents to realize a desired force is less well understood. Historically, t ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
The formulation of currenttoforce relationships for magnetic actuators proceeds in a fairly straightforward fashion from Maxwell's equations for magnetostatic problems. However, the inverse problem of determining a set of currents to realize a desired force is less well understood. Historically, this problem has been relatively neglected because actuators were built in symmetric geometries where a viable solution could be intuited. Recently, calls for both optimal actuator performance and fault tolerance have necessitated the formulation of general solution methodologies for magnetic actuators. This dissertation explores such formulations for magnetic actuators whose currenttoforce relationships are homogeneous quadratics. Two inverse strategies are considered: a generalized bias linearization approach that yields solutions which are easily implemented and faulttolerant; and a direct optimal approach that realizes low power loss. The examples of the class of actuators addressed are radial magnetic bearings and the magnetic stereotaxis system.
A wide bandwidth model for the electrical impedance of magnetic bearings
"... Magnetic bearings are often designed using magnetic circuit
theory. When these bearings are built, however, effects not
included in the usual circuit theory formulation have a
significant influence on bearing performance. Two
significant sources of error in the circuit theory approach
are the neglec ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
Magnetic bearings are often designed using magnetic circuit
theory. When these bearings are built, however, effects not
included in the usual circuit theory formulation have a
significant influence on bearing performance. Two
significant sources of error in the circuit theory approach
are the neglect of leakage and fringing effects and the
neglect of eddy current effects. This work formulates an
augmented circuit model in which eddy current and flux
leakage and fringing effects are included. Through the use
of this model, eddy current power losses and actuator
bandwidth can be derived. Electrical impedance predictions
from the model are found to be in good agreement with
experimental data from a typical magnetic bearing.
OneDimensional Analytical Constant Parameter Linear ElectromagneticMagnetomechanical Models of a Cylindrical Magnetostrictive (TerfenolD) Transducer
"... ABSTRACT: A method is presented for including motional and eddy current effects when analytically modeling electrical impedance functions of cylindrical magnetostrictive transducers. To approximate eddy current effects, onedimensional analytical constant parameter linear electromagnetic models of a ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
ABSTRACT: A method is presented for including motional and eddy current effects when analytically modeling electrical impedance functions of cylindrical magnetostrictive transducers. To approximate eddy current effects, onedimensional analytical constant parameter linear electromagnetic models of a cylindrical magnetostrictive transducer are developed. Maxwell's equations are solved for the magnetic field strength as a function of radial position. Closed form expressions for magnetic flux as a function of radial position are then derived, from which transducer electrical impedance functions are formulated. Two different physical models of the transducer are considered. The first model results in the classic eddy current solution for a rod in a wound wire solenoid. The second physical model includes the effects of a conducting external cylindrical housing. Motional effects are incorporated into the electromagnetic models via the magnetomechanical model, which is a frequency and load dependent, complex valued expression for the "dynamic magnetic permeability " of the magnetostrictive material within the transducer. The functional form for this dynamic magnetic permeability is derived by comparing the transduction equations for the magnetostrictive material with those for the transducer containing the material. Electrical impedance functions for both physical models are compared with an experimental measurement for a particular magnetostrictive transducer (using TerfenolD) in its low
"NullE" Magnetic Bearings
, 2002
"... Using electromagnetic forces to suspend rotating objects (rotors) without mechanical contact is often an appealing technical solution. However, in real life magnetic suspensions have to satisfy many engineering performance requirements beyond the simple compensation for the rotor weight. These typic ..."
Abstract
 Add to MetaCart
Using electromagnetic forces to suspend rotating objects (rotors) without mechanical contact is often an appealing technical solution. However, in real life magnetic suspensions have to satisfy many engineering performance requirements beyond the simple compensation for the rotor weight. These typically include adequate load capacity and stiffness, low rotational loss, low price, high reliability and manufacturability. With recent advances in permanentmagnet materials, the magnitudes of the required forces can often be obtained by simply using the interaction between permanent magnets. While a magnetic bearing based entirely on permanent magnets could be expected to be inexpensive, reliable and easy to manufacture, a fundamental physical principle known as Earnshaw's theorem maintains that this type of suspension cannot be statically stable. Therefore, some other physical mechanisms must be included.
Effect of Magnetic Hysteresis on Rotational Losses in Heteropolar Magnetic Bearings
, 2004
"... This paper extends a method for predicting rotational losses for laminated rotors of heteropolar magnetic bearings by using an eddycurrent model to include the effect of magnetic hysteresis in the rotor material. It compares the modeling results to the experimental data that were used earlier to as ..."
Abstract
 Add to MetaCart
This paper extends a method for predicting rotational losses for laminated rotors of heteropolar magnetic bearings by using an eddycurrent model to include the effect of magnetic hysteresis in the rotor material. It compares the modeling results to the experimental data that were used earlier to assess the loss model neglecting hysteresis. The correction to the total electromagnetic loss in the rotor due to the hysteresis is significant at rotational speeds below 6000 revolutions per minute (RPM), where the model including hysteresis effects provides much better agreement with existing experimental data.
A Thin Plate Model for Predicting Rotating Losses in Magnetic Bearings
"... Previously, thin plate assumptions have been used to obtain a onedimensional eddy current model for predicting the stationary, transformertype losses in magnetic bearings built out of laminated material. Using similar assumptions as in the 1D eddy current model, rotating losses can be predicted f ..."
Abstract
 Add to MetaCart
Previously, thin plate assumptions have been used to obtain a onedimensional eddy current model for predicting the stationary, transformertype losses in magnetic bearings built out of laminated material. Using similar assumptions as in the 1D eddy current model, rotating losses can be predicted for a laminated heteropolar radial magnetic bearing. The thin plate model of rotating losses yields a hybrid analyticalboundary element model that is computationally inexpensive to implement. Predictions from this model compare favorably to losses experimentally measured in rotor rundown tests.