624,952. A.C. motors. GILBERT, G. July 16, 1947, Nos. 18974 and 23732. [Class 35] The rotor of a synchronous motor, in which either the stator or rotor may be permanently magnetized, comprises a pair of axially-spaced discs a, b, fixed on a single shaft c and having mutually staggered teeth f, f<SP>1</SP>, whilst the diametrically-opposed stator pole-pieces g, p, each carry a pair of pole-plates m, k and o, n respectively, lying in the same planes as the discs, the teeth on opposite pole-plates being mutually staggered with respect to the teeth on the associated rotor disc. In the form shown, the rotor is polarised by a permanent magnet d between the discs, whilst the A.C. fed coil j excites the stator. In a modification the rotor may be excited by a stationary A.C. coil and the coil j is replaced by a permanent magnet. In either form the permanent magnet may be replaced by a D.C. excited coil.