Magnetic bearing eddy current effects on rotordynamic system response /
The recent growth of magnetic bearing applications in the chemical, utility and aerospace industries requires more accurate design tools to insure reliable and effective operation as components of the overall rotor bearing system. Vibrations of magnetic bearing supported or active vibration controll...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742145601&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The recent growth of magnetic bearing applications in the chemical, utility and aerospace industries requires more accurate design tools to insure reliable and effective operation as components of the overall rotor bearing system. Vibrations of magnetic bearing supported or active vibration controlled rotors are affected by the stiffness, mass, damping and external force factors of conventional rotors plus the dynamics of the control-feedback components, i.e. sensors, controllers, power amplifiers and actuators. The coupled electromechanical system (EMS) then governs critical speeds, unbalance response and stability. This system response is especially sensitive to eddy current induced fields as revealed by the results of this dissertation. This dissertation combines eddy current field modeling with rotor and EMS modeling to examine the effects that eddy currents may have on overall system closed loop stability. The methodology is confirmed via a gas turbine engine simulator rig, with a single magnetic bearing. Time harmonic magnetic field simulations are conducted to predict the eddy current induced field lag effect, as characterized by a Bd, (dynamic B field due to control AC)/B,, (static B field due to bias DC) frequency response functions. Nonlinear magnetic field analyses are performed to examine magnetic position and current stifffiesses and operating points on the B-H curve. The material permeability changes with flux density, and has a significant effect on the amount of eddy current induced field lag. The dissertation identifies the remarkable result that system stability may be significantly influenced by laminated stator conductivity and permeability. Since a third order transfer function (TF) showed the most accuracy in fitting the measured and simulated [ ] frequency responses, it is the best representation for eddy current induced field lag effects. A one dimensional model of a homopolar magnetic bearing is developed and yields results close to test in the linear operating range. Results presented in this dissertation should aid in designing magnetic bearings by illustrating how eddy currents may change system stability and by presenting a total system modeling methodology. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xvi, 130 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |