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Identifying material properties of a dielectric motor

Identifying material properties of a dielectric motor Purpose – The purpose of the paper is to define a methodology for identifying the electric conductivity and permittivity of lossy dielectric materials employed in a class of small dielectric motors, knowing the motor torque. Reference is made to data measured on an existing prototype. Design/methodology/approach – The motor operates because of the interaction between a rotating electric field, generated by a three‐phase system of electrodes, and the charge density induced at the surface of the rotor, which lags with respect to the field. The stator and the rotor are hollow cylinders made of dielectric materials. A finite‐element model of the motor has been developed. For a given set of material properties, the time‐averaged value of starting torque acting on the rotor is evaluated by means of the Maxwell stress tensor. Findings – A family of curves of starting torque vs conductivity for different values of rotor permittivity are obtained. Each curve is well approximated by a Lorentz distribution. Originality/value – A field model of the motor was exploited to estimate the conductivity that gives rise to a prescribed value of the starting torque. The solution of the underlying inverse problem, which is ill‐posed, can give an helpful insight for maximizing the torque. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering Emerald Publishing

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Publisher
Emerald Publishing
Copyright
Copyright © 2005 Emerald Group Publishing Limited. All rights reserved.
ISSN
0332-1649
DOI
10.1108/03321640510598148
Publisher site
See Article on Publisher Site

Abstract

Purpose – The purpose of the paper is to define a methodology for identifying the electric conductivity and permittivity of lossy dielectric materials employed in a class of small dielectric motors, knowing the motor torque. Reference is made to data measured on an existing prototype. Design/methodology/approach – The motor operates because of the interaction between a rotating electric field, generated by a three‐phase system of electrodes, and the charge density induced at the surface of the rotor, which lags with respect to the field. The stator and the rotor are hollow cylinders made of dielectric materials. A finite‐element model of the motor has been developed. For a given set of material properties, the time‐averaged value of starting torque acting on the rotor is evaluated by means of the Maxwell stress tensor. Findings – A family of curves of starting torque vs conductivity for different values of rotor permittivity are obtained. Each curve is well approximated by a Lorentz distribution. Originality/value – A field model of the motor was exploited to estimate the conductivity that gives rise to a prescribed value of the starting torque. The solution of the underlying inverse problem, which is ill‐posed, can give an helpful insight for maximizing the torque.

Journal

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic EngineeringEmerald Publishing

Published: Sep 1, 2005

Keywords: Electrically operated devices; Numerical analysis; Electrical conductivity

References