Date of Award

1997

Document Type

Master Thesis

Degree Name

Master of Engineering (Research)

Department

Electrical & Electronic Engineering

First Advisor

Dr. Noel Barry

Abstract

This dissertation describes various methods of maintaining a collar levitated in a vertical axis, using the well-known principle of electromagnetic induction between two circuits. The advantages of closing the magnetic loop around the collar, to obtain large radial flux cutting the collar and, therefore, large lifting forces for a given induced current, are considered in depth.

The ideal magnetic circuit and the equivalent electrical circuit are used in developing a model for two topologies of core (both an open and closed-circuit core) levitating a nonmagnetic conducting collar above a coil. Various affects that degrade the performance of the levitation rig from the ideal, are discussed, and then incorporated into the model.

Particular emphasis is placed on the levitation of a collar, highlighting the differences that occur when levitating a collar, as opposed to levitating a ring. In particular the distribution of the flux over the height of the collar is considered, as an accurate description of this distribution leads directly to a good model for the levitation system.

The mutual inductance of mutually coupled coils and the coupling coefficient between these coils is also considered at length. This is necessary, as it is the accurate definition of the mutual inductance that defines the accuracy of the model. Care is taken to maintain the theory as general as possible. In this way the resulting model is not tied to any particular topology and it is a relatively simple task to apply the model to any application.

Emphasis is placed on the practicality of the model. Therefore, many experiments have been carried out, and the results from these are compared with those obtained from the model. Also, throughout the development of the model, demonstrative experiments are carried out to show the validity of some of the more crucial parts of the theory. The theory results are also compared with the results obtained from a electrodynamics simulation package. In all of the results obtained, a good agreement is found across a range of levitated distances, different frequencies of operation, various weights of the levitated member and various types of materials.

The dissertation closes by considering some applications of the electrodynamics levitation system, in particular, its application to Load Cells and Magnetic Bearings.

Access Level

info:eu-repo/semantics/openAccess

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