GB1343358A - Homopolar electrical machine wherein the space between the rotor and stator is filled with liquid metal - Google Patents

Abstract

1343358 Homopolar machine ANVAR, AGENCE NATIONALE DE VALORISATION DE LA RECHERCHE 19 Nov 1971 [20 Nov 1970] 53953/71 Heading H2A In a homopolar generator or motor having a plurality of rotor discs 1 separated by stator partitions 4 and in which liquid metal fills the space between the stator and rotor, insulation (shown by double lines) isolating the facing radial surfaces of the rotor discs and stator partitions so as to form a current path through the machine outer gap 9-10, to the stator and thence radially inwards, along a stator partition 4 and across an inner gap 12-7, to the hub 8 of the next rotor disc, cumulative build-up of pressure in the liquid is prevented by causing the liquid on both sides (rather than on just one side) of each rotor disc to rotate. Since the annular body of liquid 15 to the right of each disc is electrically directly in parallel with the disc itself, when the machine is in use this body of liquid is forced, by the induction motor principle, to rotate at the same speed as the disc so as to develop across it a back e.m.f. which equals the rotor e.m.f., the centrifugal forces causing a high pressure to appear at the periphery of the body of liquid. For similar reasons the body of liquid 16 to the left of each disc, being directly in parallel with a stator partition 4 across which there is no voltage, would normally be constrained to remain stationary so that no back e.m.f. appeared across it. According to the invention, however, this left hand body of liquid 16 is also caused to rotate so as to build up a pressure which balances that on the right hand side. The net e.m.f. across the left hand body of liquid 16 must still be zero, and to allow for this the outer portion 16b only of the liquid 16 is compelled to rotate in the same direction as the adjacent rotor disc 1, the inner portion 16a then necessarily rotating in the opposite direction so that the e.m.f.'s across the inner and outer portions mutually cancel. The outer liquid portion 16b is caused to rotate with the disc 1 either by using fan blades fitted to the disc, or, using the induction motor principle again, by exposing at least the outer and inner peripheries of the portion 16b to a conductive annulus rotating with the rotor, e.g. by fixing a conductive annulus to the disc 1 over its insulation, or by removing an annulus of insulation from the disc itself, either over the whole of the surface portion adjacent the portion 16b or just over a thin strip at the interface 17 between liquid portions 16b and 16a. The liquid is mercury or a mercury amalgam.