471,948. Dynamo - electric machines. PESTARINI, G. M. May 4, 1936, No. 12617. [Class 35] Rotary transformers : exciting.-A machine of the metadyne type has two stator windings producing fluxes displaced by 90‹ electrical, each stator winding being supplied from an exciter, the current from which is controlled by a number of stator windings excited from selected sources. The object of the invention is te reduce the number of stator windings on the main machine by providing the necessary field windings on the exciters, which may be similar to those described in Specification 449,924. As shown in connection with a transformer 1, the primary brushes a, c of which are connected to a constant voltage supply 2, the four polar projectors producing a two - pole field each have an exciting winding 6 fed from the exciter 4 and a winding 7 fed from the exciter 5. The exciters may be ordinary generators working unsaturated or machines of the Krõemer type, but are preferably constant current machines of the Krõemer or metadyne types. The winding 6 produces a resultant flux in the direction of the secondary commutating axis d-b and the winding 7 a fiux in the primary axis c-a. The field winding 8 of the exciter 4 is separately excited and serves to control the output current of the main machine, and the field winding 9 carrying the main primary current functions as a primary stabilizing winding. The field winding 10 of the exciter 5 is in the circuit of a speedregulating device which may be an unsaturated shunt machine connected across the supply 2, the action being the same as that described in Specification 404,734. The winding 11 carrying the output current of the main machine functions as a secondary stabilizing winding. If the main machine is to operate as a generator, the primary brushes a, c, may be short-circuited or connected together through the exciter winding 9. The winding 10 of the exciter 5 may be omitted since speed regulation is not required but another stator winding connected across the main secondary brushes b, d may be provided to reduce the primary current of the main machine. In a modification, Fig. 2, the exciter 14 supplies the winding 12 on oppositely arranged poles 26, 27 of the main machine, and the windings 13 on the remaining poles 24, 25 are fed by the exciter 15. The exciters have windings 16, 17, carrying the main primary current and windings 18, 19 carrying the main output current. The exciters are metadyne generators with their primary brushes either short-circuited or connected together through a low resistance field winding. Field windings 22, 23 on the exciters are connected together and to a source of direct current and act to determine the value of the main output current. Windings 21, 22 may be connected to a regulator machine as described in connection with the winding 10, Fig. 1. In a modification of this arrangement the main machine acts as a generator, the primary brushes being connected together through stator windings on the exciters replacing the windings 20, 21. Windings 16, 17 are replaced by windings connected across the main brushes d, b. Each exciter may have two additional windings namely, a winding in the primary axis connected across the secondary brushes, and a winding in the secondary axis carrying the primary current. These windings serve to reduce the primary currents of the exciters. Additional windings, e.g. stabilizing windings may be provided on the poles of the main machine if the number of ampere turns is not too great. Specifications 400,416, 404,739, [both in Group XXXVII], 417,517, and 424,082 also are referred to.