Design and Manufacture of a High-speed Rotor in a Flywheel Demonstrator

A high-speed flywheel demonstrator with 28 kW rated power was designed and built. The rotor is made of steel, which contains 0.5 kWh energy capacity at the maximum revolution speed of 24 000 min(-1). This paper presents the mechanical issues regarding the design and manufacturing of this steel rotor. During the hardening process, an unpredicted damage occurred in the rotor due to overloaded thermal stress. The analysis of this damage and the solution are presented. After assembling the rotor components of the drive machine and the magnetic bearings, the rotor was tested at 120 % overspeed. The designed rotor passed the test successfully up to the speed of 28 800 min(-1) for 2 minutes according to standard IEC 60034-1. After assembled in the complete system, the rotor was also successfully driven up to the maximum operating speed of 24 000 min(-1), suspended by magnetic bearings.