NO. 2 



HISTORY OF ELECTRIC LIGHT SCHROEDER 



29 



Hollander, in 1842, and by Pacinnotti, an Italian, as shown by the 

 crude motors (not dynamos) they had made. Gramme's armature 

 consisted of an iron wire core coated with a bituminous compound 

 in order to reduce the eddy currents. This core was wound with 

 insulated wire coils, all connected together in series as one single 

 endless coil. Each coil was tapped with a wire connected to a commu- 

 tator bar. His first machine, having permanent magnets for fields, 

 was submitted to the French Academy of Sciences in 1871. Later 



Alteneck's Dynamo with " Drum " Wound Armature, 1872. 



The armature winding was entirely on the surface of the armature 

 core, a principle now used in all dynamos. 



machines were made with self-excited field coils, which were used in 

 commercial service. They had, however a high resistance armature, 

 so that their efficiency did not exceed 50 per cent. 



Von Hefner Alteneck, an engineer with Siemens, invented the 

 drum wound armature in 1872. The wires of the armature were all 

 on the surface of the armature core, the wires being tapped at frequent 

 points for connection with the commutator bars. Thus in the early 

 seventies, commercial dynamos were available for use in arc lighting, 

 and a few installations were made in Europe. 



