  This paper studies hidden oscillations appearing in electromechanical systems
with and without equilibria. Three different systems with such effects are
considered: translational oscillator-rotational actuator, drilling system
actuated by a DC-motor and drilling system actuated by induction motor. We
demonstrate that all three systems experience hidden oscillations in sense of
mathematical definition. But from physical point of view in certain cases it is
quite easy to localize there oscillations.
