In 1866, Werner Siemens, using an electromagnet, created a machine that transformed mechanical energy into electric called a DC generator or dynamo. It had the ability to self-induce because it removed from the rotor’s own winding the voltage needed to generate the magnetism.
When a continuous electrical voltage is applied at its terminals, the rotor is in motion, similar to that of the electric motor.
The dynamo was developed by the Italian Antonio Pacinotti, however, according to some historians, he presented the invention to a workshop to obtain the patent and the owner, the Belgian Zenobe-Theophile Gramme, patented it with his name in 1871, after making some improvements.
The large ring at the top of the Gramme machine is a permanent magnet and at the bottom there is a magnet and, between the magnet poles, a disc attached to a handle. Next to this crank are coils consisting of copper wires with coils around a circular shaped iron core.
By turning the crank, the copper coils cross the uniform magnetic field, thus generating electric current. It is known that, by the principle of electromagnetic induction, this current will be alternated, but, with the use of the commutator, the current obtained was continuous.