Patent GB-1140021-A (GB)
Title: Electrical machine of disc-type construction
IPC: H02K19/16
Filed: 1966-01-21
Abstract: 1,140,021. Alternators; core constructions. LLOYD DYNAMOWERKE G.m.b.H. 21 Jan., 1966 [21 Jan., 1965; 31 July, 1965], No. 2857/66. Heading H2A. An electrical machine of the planar air gap type has three discs (two stator and one rotor, or vice versa), and in at least one air gap flux paths of different magnetic conductivity are provided; at this air gap at least one A.C. winding is provided in radial winding grooves of a disc; an annular exciting winding is provided of such a diameter that it lies within the compass of this air gap; and one of the discs bordering this air gap at its side facing it has an inner disc part, and, concentric thereto but traversed by the magnetic flux in the opposite direction, an outer disc part, the A.C. winding extending radially over the entire air gap region. As shown in Figs. 1 to 3, two stator discs 36 are provided; each stator disc has a laminated portion where it faces the air gap, and an annular exciting winding 53, Fig. 2, or 54, Fig. 1. Each stator disc also has an A.C. winding 55, Fig. 2, in the laminated region, as can be seen in Fig. 1. The central rotor disc 50, Fig. 1, consists of an inner disc part 51, Fig. 3, separated by a non-magnetic ring 44 from an outer disc part 52; the magnetic flux traverses the inner and outer parts in opposite directions, as shown by the arrow loops in Fig. 1. The inner disc part has teeth 38 and grooves 40 in its surface, and the outer disc part has teeth 37 and grooves 39, the teeth of one part being located opposite the grooves of the other. In a modification of the above embodiment the non-magnetic ring in the rotor disc is omitted, and the teeth and grooves of one part are respectively aligned with the teeth and grooves of the other part; in this case the A.C. winding in the stator is modified in the manner shown in Fig. 5, where (assuming clockwise threading), the conductor is taken from the end of an even slot in the inner section of the stator face to the next odd slot in the outer section, and back from the next even outer slot to the next odd inner slot, and so on. In a separate modification of the first embodiment, only one annular exciting winding is provided, and in this case it is in a groove in the rotor, radially inwardly of the non-magnetic ring 44. In another embodiment the central disc is stationary and is laminated throughout its axial length; it incorporates one annular exciting winding forming a non-magnetic separating ring and two A.C. windings-one adjacent each face. Each of the two axially outer, rotor, discs has its face adjacent the air gap formed with uninterrupted radial teeth and grooves. If the A.C. windings have different pitches this machine may be used as a single-armature frequency-converter. The rotor discs in this embodiment are not laminated. The laminations of the central stator may be provided by rolling up a sheet in the form of a spiral with an adhesive layer between the convolutions, the adhesive being later heat-treated. In a modification of this embodiment the central stator is formed from an assembly of individual segmental winding cores, each being axially laminated, or consisting of ferrite; the A.C. winding is single and covers each winding core over its entire length. In another embodiment, Fig. 11, the rotor 34 is again the central member; on its lower face it has two sets of mutually-displaced grooves and teeth as illustrated in Fig. 3 and, axially above these, a non-magnetic separating ring 44. Within the ring 44 an exciting winding 41 is provided. On its upper face, the rotor has four claw poles: two of these, diametrically opposite, extend from the centre, one of them, 42, being shown in radial cross-section on the right of Fig. 11; the other two, interdigitating with the first two, extend from the periphery towards the centre, one of them, 43, being shown in radial cross-section on the left of Fig. 11 (taken at right-angles to the right-hand crosssection). The upper stator disc 35 is laminated axially throughout and carries A.C. windings in radial winding slots. The lower stator disc 36 is partly laminated, carries an A.C. winding, and has spiral cooling grooves 47 closed by a plate 48; it also has a wedge-shaped iron ring 49 adjustable in a slot to vary the reluctance of the disc. This machine may be driven by an external motor and in its stator discs two currents of different frequency and/or number of phases may be generated. Alternatively the machine may be used as a single-armature frequency-converter, in which case the upper part of the rotor co-operates with the upper stator disc 35 as a synchronous machine with heteropolar excitation, while the lower part of the rotor co-operates with the lower stator disc 36 as a modulation machine with monopolar excitation. In the embodiment where the central disc is stationary, the two outer discs have channels through their hubs for circulation of cooling gas, and cooling devices are provided in the gas stream at each end of the machine. Radially-extending cooling tubes are provided in the central disc.