The given summary of doctoral thesis is devoted to system of excitation of alternating-current salient poles synchronous motors from energy of the third harmonic of a magnetic field. In system of excitation of the given type the principle of compounded self-excitation, i.e. self-acting change of excitation current is applied at change of a load current. To conclusive virtues of excitation systems from third harmonic of a magnetic field it is possible to attribute: the opportunity of self-regulation, that the given system is the integral part of an electromagnetic system of the machine, ability of speeding up of excitation and operating speed.