The Conversion of an Induction Motor to a Synchronous Alternator for Wind Power Application

This study was conducted to analyze and record the procedures necessary to convert a ten horsepower three phase induction motor into a ten pole three phase synchronous alternator, suitable for use n a wind energy conversion system. It was undertaken in response to the high cost of commercially produced wind energy machines. A search of current literature revealed little in the area of motor or generator redesign, and no specific instructions regarding the conversion of an induction motor to a synchronous alternator.Methods: The redesign process was conducted using a locally obtained ten horsepower motor and common motor repair materials. A method based on experimentation was used to determine the alternator design parameters. The processes of machining, fitting, winding, baking, assembly, and testing were conducted in the instructional laboratories at the University of North Dakota.Results: The redesigned machine was tested for power output and found to operate satisfactorily as an alternator. The output voltage when the machine was operated at full load was lower than anticipated. The machine showed no signs of excessive internal temperature when operated at full load for periods greater than one half hour. The power conversion efficiency was calculated at 71.7 percent. The results of the study indicate that the original objectives were met.Conclusions: The conclusions reached from this study were that: (1) a motor or generator is designed to operate most efficiently at its rated speed. A change in rated speed will not take full advantage of the iron in the machine from a magnetic standpoint, and (2) any individual with an interest in mechanical and electrical machines, and access to a lathe and milling machine, could perform the motor to generator conversion.Recommendations: Based on the research conducted during the study, it was recommended that further research be conducted in the following areas: (1) the design of the field for both 12 and 117 volts, depending on the connection scheme, (2) the establishment of the relationship between the air gap length and the output terminal voltage, (3) the establishment of the relationship between the pole shoe shape and the output voltage wave-form, (4) the alternator with a field current regulator designed to be fully excited at below rated rotor speed, (5) permanent magnets in the rotating field, (6) the repulsion induction motor as a direct current generator, (7) an excitation system for an induction generator that would not ’*equire utility company power.