Transient and small perturbation behaviour of superconducting turbogenerators

Abstract

An improved method is used capable of calculating any form of generator transients. In this method, based on a two-dimensional model, solid conducting parts of the rotor are represented by multiple thin conducting layers. The resulting non-linear differential equations are solved numerically for the recently proposed new rotor arrangement with independently rotatable (free) outer rotor. The results are compared with the previously accepted arrangement having rigid connection of outer to inner rotor showing that the free outer rotor arrangement greatly relieves the inner rotor of transient torques and that its steady-state stability, although inferior to the rigidly fixed outer rotor configuration, is nevertheless quite adequate: it compares very favourable with that of the conventional generator, being markedly superior on underexited operation.

Superconducting AC generator with a magnetic steel outer rotor

“…B Q r\ refers to the product of the flux density at the axial centre of an air-cored machine and the square of the effective winding radius of the superconducting rotor winding, k r is a geometric factor relating to the effect of the environmental screen on the flux density at the armature winding \j/, the internal-power-factor angle, is a function of synchronous reactance and externalpower-factor angle. A two-dimensional analysis of the magnetic fields inside the generator, assuming the superconducting field winding to be represented by an infinitely long sinusoidal current sheet K o Sin 6, gives the environmental screen factor, k r , [3,7,8] as (2) k r = i + M-…”

“…13 where the variation of synchronous inductance is expressed as a ratio of the equivalent inductance for the generator with a nonmagnetic outer rotor, for design 1 of Table 2. The limiting value of synchronous inductance as the permeability tends to infinity is L s = L s (8) with L so being the synchronous inductance of the equivalent generator but with a nonmagnetic outer rotor.…”

Study of Screens for Superconducting A.C. Machines. Part A: Simplified Determination of Time Constants for Screens of Superconducting Machines

“…For instance Fourier transform methods are prefered to study frequency resfonses [15) or losses, during operations under known speeds [16 ,whereas multiple thin sheet representations are preferred, when the speed is unknown [12], [13].…”