Abstract: A device for automatic excitation of brushless electrical machines, comprising: an A.C. exciter feeding a power converter built around controlled rectifiers disposed on a machine shaft; a converter control circuit employing optoelectronic elements with light-emitting diodes, composed of a booster unit, an inverter unit, and a unit intended for transfer of the converter into a non-controlled rectifier mode; and a photodetector receiving light signals from a stationary light source and located on the machine shaft. The device permits continuous control from boosting modes to inversion.