The behaviour of screening systems in the superconducting a.c. generator

Abstract

Contents C'K A simple model is used to analyse the screening properties and interactions of both single and double cylindrical screens in the superconducting alternator. It is shown that interaction with a closed field winding can seriously degrade the screening effectiveness. A simple technique is described for estimating the direct and quadrature axis time constants required in the 'heteropervious' screen proposed by the author. ObersichtEs wird ein einfaches Modell benutzt, um die Schirmeigenschaften und die Wechselwirkungen sowohl yon Einzel-als auch yon Doppelabschirmzylindern im Turbogenerator mit supraleitender Erregerwictdung zu analysieren. Es stellt sich heraus, dab Wechselwirkung bei geschlossener Erregerwicklung die Schirmleistung sehr beeintrAchtigen kann. Ein einfaches Verfahren wird beschrieben, um die Liings-und Querachsen-Zeitkonstanten abzusch~tzen, die ffir den vom Yerfasser vorgeschlagenen asymmetrischen (,,heteropervious") Schirm erforderlich sind. List of SymbolsNd, Nq f J S(f) T T t E magnetic vector potential, Wb[m magnetic flux density, T peak value of sine-distributed flux-density: radial and circumferential components, T normalised flux-density permeability of free space, H/m resistivity, ~m thickness of screen, m radian frequency, rad/s double screen interaction factor number of pole-pairs d-and q-axis armature currents number of effective turns on d-and q-axis armature coils frequency, Hz V:S screening-ratio frequency-response function time constant, s time constant as reduced by closed field winding, S electric field strength, Vim R L c~, c~ -1 number of equivalent conductors per radian linear current density, A/m in peripheral direction (current flows axially) resistance, inductance, H Fourier transform and inverse Subscripts I inner 2 outer D d-axis Q q. axis