Nonlinear Analysis of Magnetic Bearings for Space Technology

The high magnetic energy stored in rare earth-cobalt magnets allows the design of lightweight motors and magnetic bearings for high-speed rotors. Magnetic bearings are not subject to wear and with the ability to operate under high vacuum conditions, they appear ideal for applications requiring high rotational speeds such as 100 000 r/min. Important applications are for turbomolecular pumps, laser scanners, centrifuges, momentum rings for satellite stabilizations, and other uses in space technology. This paper presents a two-dimemsional nonlinear numerical analysis of the magnetic fields in a magnetic bearing, based on magnetostatic assumptions and finite-difference iterative techniques.     

Marangoni convection in a liquid layer under the simultaneous action of a transverse magnetic field and rotation

Asymptotic stability characteristics with respect to the onset of Marangoni convection in a liquid layer under the simultaneous action of a large transverse magnetic field and a large rate of rotation are investigated. In certain parameter ranges there is a decrease in critical Marangoni number for increasing magnetic field and rotation depending on the coupling between interfacial perturbations and rotation.     

Performance evaluation of IRI-2007 at equatorial latitudes and its Matlab version for GNSS applications

International Reference Ionosphere (IRI) model is the widely used empirical model for ionospheric predictions, especially TEC which is an important parameter for radio navigation and communication. The Fortran based IRI-2007 does not support real-time interactive visualization and debugging. Therefore, the source code is converted into Matlab and is validated for the purposes of this study. This facilitates easy representation of results and for near real-time implementation of IRI in the applications including spacecraft launching, now casting, pseudolite based navigation systems etc. In addition, the vertical delay results over the equatorial region derived from IRI and GPS data of three IGS stations namely Libreville (Garbon, Africa), Brasilia (Brazil, South America) and Hyderabad (India, Asia) are compared. As the IRI model does not account for plasmasphere TEC, the vertical delays are underestimated compared to vertical delays of GPS signals. Therefore, the model should be modified accordingly for precise TEC estimation.     

A Minimax Filter for Systems with Large Plant Uncertainties Using Measurements Corrupted by Colored Noise

A minimax filter is derived to estimate the state of a system, using observations corrupted by colored noise, when large uncertainties in the plant dynamics and process noise are present.     

Bénard-Marangoni instability in a rotating liquid layer subjected to a transverse magnetic field

The problem of controlling the onset of convective instability in a liquid layer due to the joint action of buoyancy and interfacial tension mechanisms by means of rotation and magnetic field is considered. Selected stability characteristics delineating the effects of both these stabilizing agencies and those of interfacial curvature and gravity waves as well as those of typical boundary conditions are illustrated.     

Electromagnetic Fields in Solid-Rotor Induction Motor

The most elementary type of rotor for the polyphase induction machine is the solid-iron rotor, which offers advantages in ease of manufacture, in high torque per ampere at standstill, in withstanding high rotational stresses, and in operating in unusual environments. Since conventional induction machine theory has proven inadequate for such machines, the need has arisen for improved methods of investigation. It is the purpose of this paper to present an approximate three-dimensional nonlinear numerical analysis for the solid-rotor induction motor, based on magnetostatic assumptions and finite-difference iterative techniques.     

Solid-Rotor and Composite-Rotor Induction Machines

The feasibility of constructing composite rotors in the laboratory for use on a 60- to 120-Hz supply has been established and the experimental results with such rotors have been published for the first time. Results obtained from the tests made on a three-phase induction motor with different solid-iron as well as composite rotors are presented. These are compared with the theoretically predicted characteristics based on existing analytical as well as numerical analyses.     

End Leakage of Aerospace Homopolar Alternators

An accurate knowledge of the magnetic field distribution is of great importance in finding the best designs for electrical machinery. It is the purpose of this paper to present a new numerical method for the determination of three-dimensional flux distribution in the end zone of a highspeed aerospace homopolar alternator, and for the calculation of end leakage reactance. The new analysis is applied to an experimental 95 kVA, 115/200 V, 3400 Hz, 40 800 r/min, three-phase, wye-connected, homopolar alternator.