Torque-ripple in AC switched reluctance generators

In this paper a switched reluctance machine is used as an AC switched reluctance generator. Each phase resonates with a parallel capacitor and the circuit is tuned to match the generation speed. It is shown that in each phase of the experiments energy flows from the prime mover to the machine and the opposite within each cycle. The superposition of all the phase energy flows results in unidirectional energy transfer from the prime mover to the machine. The resultant torque associated to this function shows a ripple that is reduced with the number of phases of the machine. A machine model based on Finite Element data is used to illustrate the torque involved in the generation process. An experimental set-up with a four-phase machine is used to test the simulations. The phases are star connected and the energy obtained charges a battery bank by rectifying the AC voltage. As the resonant frequency can be fitted to a specific rotor speed by changing the capacitance, the system can generate energy at variable speed. It may be suitable for small wind mills to load batteries in isolated sites.