Squirrel-cage Induction Generator with Distributed and Fractional-Slot Concentrated Winding for Small Hydro Generation

This work addresses the design of nonconventional winding structures with in mind reliability and maintainability of electric machines for small renewable energy production in developing countries or remote places. Squirrel-cage induction machines are at the core of the study, aiming at the most robust and pertinent structure in a very constrained context. Mostly used for PM motors, distributed and fractional-slot concentrated windings are uncommon for induction machines especially in generation mode. A comparison between different windings is proposed for a squirrel-cage induction machine, considered alternatively as a motor and a generator. Various slots/pole/phase integer or fractional, single layer and double layer are simulated; their performances are compared on the basis of the average electromagnetic torque as well as the copper losses in rotor bars. A special focus on tooth-winding is made considering its easy assembling property. Results show that more torque can be obtained in generator mode thanks to harmonics.