Figure 51. — Pacinotti's ring armature, as used 

 in a motor, with a field produced by electro- 

 magnets. Pacinotti found he could use the 

 machine as a generator by replacing the field 

 electromagnets with permanent magnets. 

 From La Lwniere electrique, 1882, vol. 7, p. 15, 

 fig. 14. 



But the inherent advantages of the drum armature 

 were greater. After it was discovered that the coils 

 could be inserted in slits on the core and better 

 methods of laminating the core and of winding the 

 coils were introduced, the drum armature was 

 put to use; it has remained in use to the present time. 

 But the production of current in all these early 

 generators was hampered considerably by the lack 

 of sufficiently strong fields. Charles Wheatstone had 

 introduced electromagnets into the generator that 

 he used for his telegraph of 1845, but this arrangement 

 was generally deemed too clumsy as it required 

 chemical cells in addition to the generator itself.''^ 

 In 1864, Henry Wilde patented a generator in which 

 a magneto was substituted for the chemical cells 



(fig. 57). The current from the magneto was then 

 used to excite the electromagnet field coils of another 

 generator. One motor drove both magneto generator 

 and electromagnet generator.*" A few years later 

 William Ladd simplified the double structure by 

 combining the two separate fields in one unit (fig. 58). 

 Wire was wound around permanent bar magnets 

 which were placed parallel to and above each other. 

 An armature was rotated between each pair of poles 

 at the end of the magnets. One armature provided 

 current for the coils on the permanent magnets and 

 so added to the latter's field while the output current 

 was taken from the other armature.*' 



When demonstrated at the Paris Exhibition of 

 1867, both Wilde's and Ladd's machines produced 



'9 British patent 10665 (May 6, 1845). 



s» British patent 3006 (June 4, 1864); Henry Wilde, "Experi- 

 mental Researches in Magnetism and Electricity," Philosophical 

 Magazine, 1866, ser. 4, vol. 32, pp. 148-152, and 1867, ser. 

 4, vol. 34, pp. 81-104; Les Mondes, 1866, vol. 11, pp. 319-324, 

 373, 629-636; vol. 12, pp. 24-26; Theodose du Moncel, 

 Expose des applications de releciricite, Paris, 1872-1878, ed. 3 

 (5 vols.) vol. 2, pp. 226-230. 



SI William Ladd, "On a Magneto-Electrical Machine," 

 Philosophical Magazine, 1867, ser. 4, vol. 33, pp. 544-545; 

 "On a New Form of Dynamo-Magnetic Machine," Reports of 

 the British Associaticn for the Advancement oj Science, 1867, vol. 

 37, pp. 13-14; "On a Further Development of the Dynamo 

 Magneto Electric Machine," Reports of the British Association 

 for the Advancement of Science, 1868, vol. 38, pp. 19-20; Du 

 Moncel, op. cit. (footnote 80), vol. 2, pp. 230-234. 



PAPER 30: DEVELOPMENT OF ELECTRIC-kL TECHNOLOGY IN THE 19TH CENTURY: III 



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