Current Source Inverter Drive of an Ironless Motor for Flywheel Batteries

In this paper, the performances of a Current Source Inverter (CSI) drive for a flywheel battery based on an ironless machine are assessed. The ironless machine is chosen to limit eddy currents when the flywheel is disconnected from both energy source and loads. However, ironless machines have low phase inductances values and low current filtering capability. Hence, the current ripple can be reduced only with a high switching frequency in a Voltage Source Inverter (VSI), increasing the switching losses. On the other hand, a CSI has an intrinsic control of output current, thus ensuring a low current ripple even at lower switching frequency. In this paper, the performances of VSI and CSI drives for a flywheel battery are compared in terms of output torque ripple and total inverter losses. Results show that the CSI outperforms VSI in terms of current ripple and losses.