Self-Excitation Scheme Employing the 2nd-harmonic of Armature MMF for AC-Generators

For ac-generators, a new self-excitation scheme has been proposed. The generator employing this scheme behaves as a flat-compound machine without any automatic voltage regulators. The stator of the generator is provided with an armature winding which generates the fundamental and 2nd-harmonic mmfs. The rotor is equipped with a field winding and a harmonic winding. Letting the current flow in the stator armature winding, the ac voltage is induced in the rotor harmonic winding due to the 2nd-harmonic component of armature mmfs. By connecting the harmonic winding to the field winding through a rectifier circuit, self-excitation of the generator is obtained. This excitation scheme is both self-excited and brushless, and no exciter is required. Additionally, the voltage regulation due to the load variation can be improved by selecting a capacitance of a condenser connected to the terminals of the armature winding.In this paper the operating principle and circuit configuration of the generator are explained, and the experimental results using a 1kVA prototype machine are shown. Then, the generator caracteristics are theoretically clarified by approximate analysis, and appropriateness of the theory and the usefulness of the proposed scheme are experimentally confirmed.