Single-phase self-excited inductor alternators for renewable energy electric conversion systems

Single-phase inductor alternators have been shown to be suitable for use with renewable energy electric conversion systems for small power applications. Since both the field and the ac output winding are on the stator, these alternators, in respect of construction and maintenance, have all the advantages of self-excited induction generators presently being employed with renewable energy sources. An attempt has been made in this paper to modify the stator winding design of conventional inductor alternators, to reduce the field power requirement by reducing the number of field winding coils and also to feed this winding by self-excitation, so that their suitability for the proposed applications could be further enhanced. Taking the induced EMF of a conventional single-phase inductor alternator as the bench mark value, the EMF of the new design is calculated and compared. Such calculations are made by determining the EMF of each coil separately, which leads to the assessment of the number of possible parallel paths of the ac output winding. A simple microcontroller based MOSFET chopper circuit has been developed for the filed current control of the inductor alternator. Test results obtained on an alternator wound with the proposed winding design are presented. A dc motor for initial test purposes and then a bio-mass gasifier based diesel engine to demonstrate the application with renewable energy sources, have been used as prime-movers for the alternator.