GB190723881A - Improvements in Dynamo-electro-machines for Installations subject to Short Circuits and the like - Google Patents

Abstract

23,881. Felten & Guilleaume - Lah - meyerwerke Akt.-Ges. Oct. 31, 1906, [date applied for under Patents Act, 1901]. Distributing; converting alternating and direct currents.-The exciting - circuits of continuouscurrent generators subject to large back electromotive forces or short-circuits are so arranged as to limit the load current automatically to a predetermined maximum. Fig. 1 shows a generator driven by a motor, the two being placed between the supply mains and the arc lamps l. The motor is shunt-excited by a coil f, and has on the axis of its driving-brushes a an over-compensating coil c and a shunt coil g, both of which oppose the armature field along the axis a-a. The load current traverses a coil h, the field of which opposes those of the coils c, g, and the generator field coil i is excited by brushes b placed along the axis of the shunt coilf. An increase in the load current accordingly reduces the exciting potential at the brushes b, and the current is thus automatically limited. The two machines may be combined into one when one of them has twice as many poles as the other, or when its field axis is shifted by one half of the pole-pitch with regard to the other, as shown in Fig. 2. In this form, the winding i, Fig. 1, is combined with the winding g, which, as before, generates an electromotive force at the brushes b in opposition to that generated by the load current in the coil h. The armature field in the direction a-a is neutralized by the com- . pensating - winding c. The invention is also applicable to alternating-current installations, or for transforming from alternating to direct-current or vice versa, as shown in Fig. 3, in which the direct-current motor M drives the alternator G. The load current passes through a series alternating-current motor x, which is coupled to a direct-current dynamo y by which the opposing- current in the coil h is supplied.