4.3.- ELECTRICAL MACHINES

Electric generators transform mechanical energy into electrical energy, while electric motors transform electrical energy into mechanical energy. In turn, electric motors are classified into DC motors and AC motors. Unlike the previous ones, the transformers conserve the same type of energy, only transforming the voltage levels. The operation of electrical machines is based on the principles of electromagnetism.

The first electromechanical generator was built by Faraday based on the electromagnetic induction phenomenon. Some time later, Ampère developed the first permanentmagnet generator. But it was Galileo Ferraris who took the final step with the discovery of the rotating magnetic field.

An important aspect in electrical machines is the type of drive used to control them. Nowadays, the use of variable frequency drives and PLCs for the advanced control of squirrel-cage induction motors, servomotors, DC motors, etc. Is very frequent. The variable frequency drives allow precise control of the torque and speed of rotation of these machines. They have different types of protections, such as overcurrent and overload protections. In addition, variable frequency drives usually have digital and analog signals for the automation of different processes in which the corresponding electric motor will take part. More economical and simple are the electronic starters for electrical machines. This type of drive allows the start of a high-power electric motor, reducing starting transient currents. Other more conventional drives, still used for their low cost, are manual star-delta starters. The star-delta starter reduces the starting currents of the squirrel-cage motors, causing less disturbances and transient imbalances in the electrical grid.