An electromechanical system is composed by two subsystems with distinct origins: one of a mechanical nature and another of electromagnetic nature. The energies in the system have also different origins. Some of them are mechanical, as kinetic and potential, and others are electromagnetic, as magnetic and electrical. For a proper description of an electromechanical system dynamics it is not sufficient to describe each subsystem separately. Coupling terms must be considered in the system dynamics. These terms characterize the mutual influence between the two subsystems and the interplay of the energies of the system. The objective of this paper is to analyze from an energetic point of view an electromechanical system. This paper shows how the dynamics of an electromechanical system can be constructed by the definition of the energies that are present in the system and their interplay using the Lagrangian method. To exemplify, an electromagnetic loudspeaker will be analyzed. Its dynamics will be constructed and numerical integrated in order to make an energetic analysis.

Power quality maintenance is a concern that has currently reached all levels of electric systems. This concern is mainly due to the increased connection of nonlinear devices and loads with high sensitivity to power quality disturbances on distribution, transmission and generation complexes. However, to enable power quality measurements on medium (MV) and high voltage networks, voltage transducers are necessary. There are different types of voltage transducers commercially available. The inductive voltage transformers (IVTs) are most commonly used for MV systems. However, it is well-known that some types of voltage transducers may not present a linear transformation ratio for harmonic frequencies, including IVTs. Therefore, to overcome this nonlinearity of voltage transducers, the IEC published a technical report addressing guidelines and recommendations regarding the use of instrument transformers for power quality applications (IEC/TR 61869-103). In this context, this paper is aimed at performing a frequency response test on three MV IVTs using the mentioned IEC document in order to guarantee accurate harmonic voltage measurements. Moreover, a laboratory structure at the Federal University of Uberlândia is implemented for evaluating the frequency response on MV transducers.