It is known, that the alternator self-excitation is possible at capacitor loading . From this follows, that the alternator excitation by means of capacitors connected to one or several stator windings, as from simple excitation winding is located on a rotor, is possible.In the report the excitation of the automobile alternator with claw pole rotor by means of capacitors connected to stator windings at rotor open excitation circuit is considered. Thus, for comparison the alternator idle characteristics are received both at excitation by means capacitors, and by means of a simple excitation winding. Besides the other electrical parameters of the alternator with claw pole rotor by experimental way are determined. On the basis of the received data the alternator digital model was developed, it takes into account the magnetic circuit saturation, by using of the received experimental idle characteristics.On the basis of digital model the idle characteristics and load characteristics were calculated that confirms the adequacy of digital model to the real alternator. The digital model can be used for design and calculation a voltage regulator at excitation by stator winding. For excitation current creation the real alternator the inverter can be used, output alternating current of which should be equal to the frequency and current phase of the capacitor connected with the stator winding. The considered excitation principle can be used in electrical machine with claw pole rotor in a motor mode.