A major turning point in the development of DC machines took place in 1864, when Antonio Pacinotti described for the first time the ring armature with its symmetrically grouped coils closed upon themselves and connected to the bars of a commutator, the brushes of which delivered practically non-fluctuating current. The first commercially successful DC motors followed the invention by Zénobe Gramme who, in 1871, reinvented Pacinotti's design. In 1873, Gramme showed that his dynamo could be used as a motor, which he demonstrated to great effect at exhibitions in Vienna and Philadelphia by connecting two such DC motors at a distance of up to 2 km away from each other, one as a generator. (See also 1873 : l'expérience décisive [Decisive Workaround] .) COUNT 5
QSN1 What made Pacinotti's motor an important advancement? ANS1 non-fluctuating current QSN2 Who created a motor similar to Pacinotti? ANS2 Zénobe Gramme QSN3 How far from each other were the motors in Gramme's demonstrations? ANS3 2 km QSN4 Besides a motor, what did Gramme use the other device for? ANS4 generator QSN5 In what two cities did Gramme conduct his demonstrations? ANS5 Vienna and Philadelphia