GB1256757A - - Google Patents

Abstract

1,256,757. Homopolar machines; slip rings for dynamo-electric machines. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 15 May, 1970 [9 June, 1969], No. 28980/69. Heading H2A. In a homopolar machine of the kind in which the rotor 1 and stator 5 have annular, seriesconnected, conducting paths formed by the rotor and a copper tube 8, the tube 8 is located in the air gap 6 adjacent the rotor so that the path of the load current defines a toroidal volume lying substantially in the air gap whereby no flux due to load current is present in the ferromagnetic material of the stator. As shown, rotor 1, which is cup-shaped, forms part of a variable speed drive and is located with its base adjacent a similar rotor 3, the two rotors being secured to shafts 2, 4 and located in annular air gaps 6, 7 in the toroidal stator 5 which carries two field coils in annular cavities. 11, 12. Connection is effected between the bases of the rotors and between the ends of the side walls and the tube 8 by conducting liquid, e.g. an alloy of sodium and potassium and to facilitate the latter connections, the side walls increase in diameter towards the open ends of the rotors. Except where connections are required, the exposed surfaces of the rotors, the tube 8 and adjacent parts of the stator 5 are covered with a thin layer of insulating material. The liquid is introduced through a passage 13 and flows as a result of centrifugal force, through passages 18 to a trough 19 at the open end of rotor 1 and through passages 20 to the space between rotors 1, 3 and from there through passages 22 to a trough 23 at the open end of rotor 3. The liquid is then drawn off through passages 24 and re-circulated through the passage 13. A suitable gas such as nitrogen, fills the parts of the system not occupied by liquid. To maintain a connection between the open ends of the rotors, particularly rotor- 3, and the tube 8 at low speed, an outwardly extending flange 27 is provided which is slotted to retain the liquid. In operation, the shaft 2 is driven so that rotor 1 acts as a generator and produces current which flows through rotor 3 and causes rotation thereof. The drive between the shafts 2, 4 is controlled by varying the currents in the two field coils.