5W«5 



Figure 68. — Gramme's 1876 type (T atelier dynamo for use with arc lights. From Revue industrielle, 



February 9, 1876, p. 57. 



magnets grouped in the form of a triangle on each 

 side of the armature, and each group had a common 

 pole-piece. This machine weighed 700 kg. and 

 measured 0.90 meter square by 0.65 meter high. 

 There were 180 kg. of copper wire on the electro- 

 magnets and 40 kg. on the armature. This large 

 generator normally produced a light of 500 Carcel 

 units, but it was claimed that this amount of light 

 could be almost doubled by increasing the speed of the 

 generator. The smaller machine weighed 183 kg. 

 and measured 0.55 meter square by 0.60 meter 

 high. There were 47 kg. of wire on both armature 

 and field. The armature on the small arc-light 

 machine was what Gramme termed dedouble, that is, 

 there were two windings on the single core with a set 

 of commutator bars on each side of the form (fig. 66).^^ 

 These two windings could then be connected so as to 

 double the current or to double the voltage. The in- 

 tensity of the arc light at 900 r.p.m. was 200 Carcel 

 units. Small lecture magnetos using Jamin's com- 

 pound magnets also were produced at this time (fig. 

 67). 



Later improvements enabled Graixime to reduce the 

 cost and increase the efficiency of his generators still 



'8 Alfred N. Breguet, "Note sur la machine Gramme a 

 I'anneau dedouble," Revue industrielle, 1876, vol. 5, pp. 106-110. 



Figure 69. — Gramme's 1877 type d' atelier 

 dynamo for use with arc lights. From Revue 

 industrielle, May 2, 1877, p. 173. 



384 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



