338,977. Naamlooze Vennootschap Hengelosche Electrische en Mechanische Apparatenfabriek, and Booden, A. Aug. 30, 1929. Alternating-current induction machines.-In a short-circuit rotor for a three phase motor, the short-circuiting rings are subjected to a current displacement effect solely by rigid and non- subdivided magnetic material which is arranged on the rings or in their proximity and is so disposed that the current of the rotor windings does not flow in series through it. Fig. 1 shows a rotor with inner and outer cage windings 2, 1 of different inductances and resistances and shortcircuiting rings 5, 3 separated from the end of the rotor by spacers 6, 4. An iron ring 7 is secured to the ring 3 by means of screws. In an alternative form, the iron ring consists of an annular channel which shrouds the inner ring 5. In the form shown in Fig. 2, the inner shortcircuiting ring of the outer winding 1 consists of a flat copper ring 3, optionally stamped to the same pattern as the core discs, and the iron ring 7 constitutes an end plate for compressing the core. Flow of the rotor currents in the iron rings may be prevented by insulating them from the short-circuiting rings or core by a layer of varnish. Specifications 236,609, 246,437 and 267,670 are referred to.