General Principles of Electric Machines

Electrical machines are the result of an application Intelligent of the principles of electromagnetism and in particular of Faraday's law of induction. Electrical machines are characterized by having intertwined electrical and magnetic circuits. Throughout the historical process of its development, they played a leading role, which determined the movement of all electrical engineering, thanks to its application in the fields of generation, transport, distribution and use of electrical energy.

Electrical machines perform an energy conversion of a form to another, one of which, at least, is electric. Based on this point of view, strictly energetic, it is possible to classify them into three fundamental types:

1. GENERATOR: That transforms mechanical energy into Electric. The action is developed by the movement of a coil in a magnetic field, resulting in an induced e.m.f. that when applied to an external circuit, produces a current that interacts with the field and develops a mechanical force that opposes the movement. Consequently, the generator needs a mechanical input energy to produce the corresponding electrical energy.

2. MOTOR:That transforms electrical energy into mechanical energy. The action is developed by introducing a current into the machine by means of an external source, which interacts with the field producing a movement of the machine; then an induced f.e.m. appears that opposes the current and that is therefore called counter-electric force. Consequently, the engine needs an input electrical energy to produce the corresponding mechanical energy.

3. TRANSFORMER:That transforms an electrical energy of input with certain magnitudes of voltage and current in other output electrical energy with different magnitudes.

Generators and motors have mechanical access and therefore they are machines equipped with movement, which is normally rotation; on the contrary, transformers are electrical machines that have only electrical access and are static machines. Each machine in particular, complies with the principle of electromagnetic reciprocity, which means that they are reversible, being able to function as a generator or as a moto.

Citation

Universidad Politecnica de Madrid: Maquinas Electricas