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Modeling the behavior of a homopolar motorBelarde, Gianetta Maria. Engel, Thomas G. January 2008 (has links)
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on September 16, 2009). Thesis advisor: Dr. Thomas G. Engel. Includes bibliographical references.
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Study of homopolar DC generatorBaymani Nezhad, Mehdi January 2013 (has links)
The aerospace and marine sectors are currently using or actively considering the use of DC networks for electrical distribution. This has several advantages: higher VA rating per unit volume of cable and ease of generator connections to the network. In these systems the generators are almost exclusively ac generator (permanent magnet or wound field synchronous) that are linked to the dc network via an electric converter that transforms the ac generator output voltage to the dc rail voltage.The main objective of this project is to develop a Homopolar DC Generator (HDG) that is capable of generating pure DC voltage and could therefore remove the need for an electric converter and ease connection issues to a dc electrical distribution network. The project aim is to design, build and test a small technology demonstrator, as well as electromagnetic modeling validation.In Chapter 1, the initial generator concepts proposed to fulfill the aforementioned requirements of DC generator are presented, as well as an obscurity in electromagnetic induction law faced at the beginning of this project. Also the advantages, disadvantages and different applications of Homopolar DC Generators are covered in Chapter 1. In Chapter 2, Faraday's law of induction and the ways of using it properly are discussed using some example. The preliminary design calculations to construct the prototype HDG are presented in Chapter 3. Also the prototype construction and assembly procedure are discussed in this chapter. In this project, magnetostatics and current flow Finite Element (FE) simulations were used to assess the prototype HDG. In Chapter 4, the results of 2D and 3D-FE simulation are presented; furthermore the limitations of the FE simulations to assess the HDG performance are included. In Chapter 5, the results of the practical tests are demonstrated and assessed, as well as comparison between some of the results obtained practically and those obtained using FE-modeling. Using sliding contacts in the HDG is obligatory so some definitions corresponding to electrical contact resistances are given in Chapter 5. Final chapter is conclusions including the results assessments, future works to design, simulation and construction of the HDG.
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Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing SystemWadhvani, Vishal Ashok 2011 May 1900 (has links)
Magnetic bearings are increasingly being used in a wide variety of applications in the industry such as compressors, turbines, motors, generators etc. Also, there are different types available depending upon their construction. The research presented here investigates a high temperature permanent magnet biased magnetic bearing system which is jointly being researched by National Aeronautics and Space Administration (NASA) and Electron Energy Corporation (EEC). The purpose of this research was to develop a permanent magnet biased magnetic bearing system using high temperature (HT) permanent magnets (PM) developed by EEC. This system was designed for high performance, high temperature (1000F) and high speed applications. The entire system consisted of two radial bearings, two catcher bearings, one axial thrust bearing and a motor. The central rotor shaft is powered by a high temperature permanent magnet motor to be able to run at the designed conditions of 20,000 rpm. This thesis documents the design of a feedback control law that stabilizes this HTPM biased AMB levitated system and summarizes efforts to build a test rig for the HT tests of the machine. A decentralized PD control law is used to achieve successful levitation. An existing PD analog controller with single input single output (SISO) control law for each axis (previously used for a flywheel test rig) is used as a feedback controller for this HTPM magnetic bearing system. Modeling and simulation of the resulting closed loop system is done in Matlab to test for stability and an iterative approach leads to optimum values of proportional and derivative gain pairs. The notch filter locations are also determined through this closed loop iterative simulation.
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Circular sensor array and nonlinear analysis of homopolar magnetic bearingsWiesenborn, Robert Kyle 25 April 2007 (has links)
Magnetic bearings use variable attractive forces generated by electromagnetic
control coils to support rotating shafts with low friction and no material wear while
providing variable stiffness and damping. Rotor deflections are stabilized by position
feedback control along two axes using non-contacting displacement sensors. These
sensor signals contain sensor runout error which can be represented by a Fourier series
composed of harmonics of the spin frequency. While many methods have been
proposed to compensate for these runout harmonics, most are computationally intensive
and can destabilize the feedback loop. One attractive alternative is to increase the
number of displacement sensors and map individual probe voltages to the two
independent control signals. This approach is implemented using a circular sensor array
and single weighting gain matrix in the present work. Analysis and simulations show
that this method eliminates runout harmonics from 2 to n-2 when all sensors in an ideal
n-sensor array are operational. Sensor failures result in reduced synchronous amplitude
and increased harmonic amplitudes after failure. These amplitudes are predicted using
derived expressions and synchronous measurement error can be corrected using an
adjustment factor for single failures. A prototype 8-sensor array shows substantial
runout reduction and bandwidth and sensitivity comparable to commercial systems.
Nonlinear behavior in homopolar magnetic bearings is caused primarily by the
quadratic relationship between coil currents and magnetic support forces. Governing
equations for a permanent magnet biased homopolar magnetic bearing are derived using
magnetic circuit equations and linearized using voltage and position stiffness terms.
Nonlinear hardening and softening spring behavior is achieved by varying proportional control gain and frequency response is determined for one case using numerical
integration and a shooting algorithm. Maximum amplitudes and phase reversal for this
nonlinear system occur at lower frequencies than the linearized system. Rotor
oscillations exhibit amplitude jumps by cyclic fold bifurcations, creating a region of
hysteresis where multiple stable equilibrium states exist. One of these equilibrium states
contains subharmonic frequency components resulting in quasiperiodic rotor motion.
This nonlinear analysis shows how nonlinear rotor oscillations can be avoided for a wide
range of operation by careful selection of design parameters and operating conditions.
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Nonlinear Dynamics of a Rotor Supported by Homopolar Magnetic Bearings with SaturationKang, Kyungdae 2010 December 1900 (has links)
An objective in the design of high performance machinery is to minimize weight
so magnetic bearings are often designed to operate slightly lower than the magnetic
material saturation. Further weight reduction in the bearings requires operation in the
nonlinear portion of the B-H curve. This necessitates a more sophisticated analysis at the
bearing and rotordynamic system levels during the design stage. This dissertation
addresses this problem in a unique manner by developing a fully nonlinear homopolar
magnetic bearing model.
The nonlinear dynamics of permanent magnet-biased homopolar magnetic
bearing (PMB HoMB) system with 2-dof rigid and 4-dof flexible rotor is analyzed. The
dynamic behavior of the rotor-bearing system is examined in the feedback control loop
that includes low pass filter effects.
An analytical magnetization curve model is proposed to predict the nonlinear
magnetic force under the influence of the magnetic flux saturation more accurately. The
modified Langmuir method with the novel correction terms for the weak flux region is used to curve-fit the experimental magnetization data of Hiperco 50. A new curve fit
model of the B-H curve is shown to have significantly better agreement with the
measured counterpart than conventional piecewise linear and other models. PMB HoMB
characteristics with flux saturation, such as forces depending on the rotor position and
bearing stiffness, are compared with these other models.
Frequency response curve, bifurcation diagram, Poincare plot, and orbit plot are
utilized to demonstrate the effects of the nonlinearities included in the 2-dof rotorbearing
system.
Due to heavy static loads applied to the rotor, it operates within the magnetic flux
saturation region at the bearing clearance. The voltage saturation in the power amplifier
of the magnetic bearing introduces lag in the control loop and the response of the heavily
loaded 4-dof rotor-bearing system shows that limit cycle stability can be achieved due to
the magnetic flux saturation or current saturation in the amplifier; otherwise the system
would experience a destructive instability. These simulation results provide the first
explanation of this commonly observed limit cycle which is referred to as ‘virtual
catcher bearings’.
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Design and analysis of a novel low loss homopolar electrodynamic bearingLembke, Torbjörn A. January 2005 (has links)
<p>A novel homopolar electrodynamic bearing, together with a suitable permanent magnet drive, have been developed for high-speed applications where low losses and high reliability are essential and exclude the use of ball bearings, and yet where active magnetic bearings offer a too complex system solution. Considered applications are small turbomolecular vacuum pumps, and maintenance free flywheels for energy storage in remote telecom and satellite systems. Other upcoming areas where these bearings offer interesting technical and economic solutions are compressors for fuel cells and heat pumps, applications which normally suffer from short bearing lifetime.</p><p>Unlike active magnetic bearings, forces are produced in electrodynamic bearings without any control electronics, thanks to stabilizing eddy currents induced by permanent magnets. In the novel homopolar concept eddy current losses are reduced to a minimum using a homopolar design with ring magnets instead of multipole or Halbach arrays.</p><p>Currents and forces are simulated using steady state 3D-FEM analysis, which can take velocity into account using an implemented Minkowski transform. From these results an analytical model has been developed, and the results are compared. The results are converted into useful rotordynamic data that is easily understood by machine engineers.</p><p>The bearing has been experimentally tested in a rebuilt turbomolecular vacuum pump up to 90,000 rpm. Bearing forces have been accurately measured on a specially designed spring suspended scales, in which the bearing rotor is powered with the permanent magnet drive. Comparison of measured data with results from the 3D-FEM analysis shows excellent agreement.</p>
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High temperature, permanent magnet biased, homopolar magnetic bearing actuatorHossain, Mohammad Ahsan 30 October 2006 (has links)
The EEC (Electron Energy Corporation) in conjunction with the National Aeronautics and Space Administration is researching the magnetic bearings for an alternative to conventional journal or ball bearings. The purpose of this research was to design and develop a high-temperature (1000úF) hybrid Magnetic Bearing using High Temperature Permanent Magnets (HTPM), developed by the EEC for high performance jet engines at high speeds that supply loads of 500 lbf. Another objective is to design and build a test rig fixture to measure the load capacity of the designed bearing. The permanent magnet bias of the Homopolar radial magnetic bearing reduces the amount of current required for magnetic bearing operation. This reduces the power loss due to the coil current resistance and improves the system efficiency because the magnetic field of the HTPM can suspend the major portion of the static load on bearing. A high temperature radial magnetic bearing was designed via an iterative search employing 3D finite element based electromagnetic field simulations. The bearing was designed to produce 500 lbf of force at 1000úF and the design weight is 48 lbs. The bias flux of the Homopolar radial bearing is produced by EEC HTPM to reduce the related ohmic losses of an electromagnetic circuit significantly. An experimental procedure was developed to measure actual load capacity of the designed bearing at the test rig. All the results obtained from the experiment were compiled and analyzed to determine the relation between bearing force, applied current and temperature.
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Design and analysis of a novel low loss homopolar electrodynamic bearingLembke, Torbjörn A. January 2005 (has links)
A novel homopolar electrodynamic bearing, together with a suitable permanent magnet drive, have been developed for high-speed applications where low losses and high reliability are essential and exclude the use of ball bearings, and yet where active magnetic bearings offer a too complex system solution. Considered applications are small turbomolecular vacuum pumps, and maintenance free flywheels for energy storage in remote telecom and satellite systems. Other upcoming areas where these bearings offer interesting technical and economic solutions are compressors for fuel cells and heat pumps, applications which normally suffer from short bearing lifetime. Unlike active magnetic bearings, forces are produced in electrodynamic bearings without any control electronics, thanks to stabilizing eddy currents induced by permanent magnets. In the novel homopolar concept eddy current losses are reduced to a minimum using a homopolar design with ring magnets instead of multipole or Halbach arrays. Currents and forces are simulated using steady state 3D-FEM analysis, which can take velocity into account using an implemented Minkowski transform. From these results an analytical model has been developed, and the results are compared. The results are converted into useful rotordynamic data that is easily understood by machine engineers. The bearing has been experimentally tested in a rebuilt turbomolecular vacuum pump up to 90,000 rpm. Bearing forces have been accurately measured on a specially designed spring suspended scales, in which the bearing rotor is powered with the permanent magnet drive. Comparison of measured data with results from the 3D-FEM analysis shows excellent agreement. / QC 20101026
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High Temperature, Permanent Magnet Biased Magnetic BearingsGandhi, Varun R. 2009 May 1900 (has links)
The Electron Energy Corporation (EEC) along with the National Aeronautics and
Space Administration (NASA) is researching magnetic bearings. The purpose of this
research was to design and develop a high-temperature (1000�F) magnetic bearing
system using High Temperature Permanent Magnets (HTPM), developed by the EEC.
The entire system consisted of two radial bearings, one thrust bearing, one motor and 2
sets of catcher bearings.
This high temperature magnetic bearing system will be used in high
performance, high speed and high temperature applications like space vehicles, jet
engines and deep sea equipment. The bearing system had a target design to carry a load
equal to 500 lb-f (2225N). Another objective was to design and build a test rig fixture to
measure the load capacity of the designed high temperature radial magnetic bearing
(HTRMB) called Radial Bearing Force Test Rig (RBFTR).
A novel feature of this high temperature magnetic bearing is its homopolar
construction which incorporates state of the art high temperature, 1000 �F, permanent
magnets. A second feature is its fault tolerance capability which provides the desired
control forces even if half the coils have failed. The permanent magnet bias of the radial magnetic bearing reduces the amount of
current required for magnetic bearing operation. This reduces the power loss due to the
coil current resistance and also increases the system efficiency because magnetic field of
the HTPM is used to take up the major portion of the static load on the bearing. The bias
flux of the homopolar radial bearing is produced by the EEC HTPM to reduce the related
ohmic losses of an electromagnetic circuit significantly.
An experimental procedure was developed using the Radial Bearing Force Test
Rig (RBTFR) to measure actual load capacity of the designed bearing at the test rig. All
the results obtained from the experiment were compiled and analyzed to determine the
relation between bearing force, applied current and temperature.
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High temperature, permanent magnet biased, homopolar magnetic bearing actuatorHossain, Mohammad Ahsan 30 October 2006 (has links)
The EEC (Electron Energy Corporation) in conjunction with the National Aeronautics and Space Administration is researching the magnetic bearings for an alternative to conventional journal or ball bearings. The purpose of this research was to design and develop a high-temperature (1000úF) hybrid Magnetic Bearing using High Temperature Permanent Magnets (HTPM), developed by the EEC for high performance jet engines at high speeds that supply loads of 500 lbf. Another objective is to design and build a test rig fixture to measure the load capacity of the designed bearing. The permanent magnet bias of the Homopolar radial magnetic bearing reduces the amount of current required for magnetic bearing operation. This reduces the power loss due to the coil current resistance and improves the system efficiency because the magnetic field of the HTPM can suspend the major portion of the static load on bearing. A high temperature radial magnetic bearing was designed via an iterative search employing 3D finite element based electromagnetic field simulations. The bearing was designed to produce 500 lbf of force at 1000úF and the design weight is 48 lbs. The bias flux of the Homopolar radial bearing is produced by EEC HTPM to reduce the related ohmic losses of an electromagnetic circuit significantly. An experimental procedure was developed to measure actual load capacity of the designed bearing at the test rig. All the results obtained from the experiment were compiled and analyzed to determine the relation between bearing force, applied current and temperature.
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