Analysis of No-Load Operation of Cup Winding Permanent Magnet Synchronous Machine in Flywheel Energy Storage Application

The flywheel energy storage system (FESS) with no-load loss as low as possible is essential owing to its always running in no-load standby state. In this article, cup winding permanent magnet synchronous machine (PMSM) is presented in FESS application in order to eliminate nearly its total no-load loss. First, the principle and structure of the cup winding PMSM is put forward based on the special structure of FESS rotor. Then, in order to accurately and quickly calculate the no-load loss of the PMSM, the no-load magnetic field analytical model of the machine is established to calculate the flux density, flux linkage, back electromotive force and no-load loss accurately, which are verified by the finite-element method. Finally, a 27 MJ/200 kW FESS prototype is manufactured and tested, which verifies the theoretical analysis correctly and proves that the FESS with cup winding PMSM feature the excellent characteristics of low power consumption and high efficiency.