GB774195A - Improvements in electrical generators - Google Patents

Abstract

774,195. Permanent magnet generators. PRINCIPAL SECRETARY OF STATE FOR FOREIGN AFFAIRS. July 20, 1955 [June 23, 1954], No. 18458/54. Class 35. An electrical generator comprises a wound salient pole stator and a rotor having a plurality of radially-extending permanent magnets each provided with a pole piece, the pole pieces being separated by gaps. Referring to Fig. 2, the rotor comprises six permanent magnets 6 seated on the faces of a hexagonal portion of the rotor shaft 2, and each magnet is provided with a pole piece 8 of rhombic shape. A disc 12 of diameter equal to the outer diameter of the pole pieces and of material of good conductivity, such as copper or brass, is pressed on to the shaft 2 on either side of the hexagonal portion and the discs are connected together by six copper tubes 14 which pass through the spaces between adjacent magnets and into apertures in the discs 12 where they form good electrical contact with the discs. Each pair of adjacent copper tubes together with the parts of the two discs between them form a loop of high conductivity surrounding one of the magnets; in consequence of these loops the mechanical effort required to turn the rotor varies comparatively little with the electrical load. The rotor may be completed by potting with a suitable plastic, such as a synthetic epoxy resin, which fills all the interstices including the gaps between adjacent pole pieces. The short-circuited loops may be arranged around the pole pieces instead of around the magnets; thus the gaps between the pole pieces may be filled with a non- magnetic metal instead of potting resin. The generator may be hand- or foot-operated, the rotor being operated through gearing from a pair of handles or pedals.