Rotordynamic Analysis of 500 000 r/min 2 kW Ultra-High-Speed Machine for Portable Mechanical Antenna

Bi-directional wireless communication between the earth's surface and underground or undersea facilities is infeasible because of the conventional electrical antenna's (CEA) excessive power requirement and enormous size. The most promising and power-efficient solution to this problem is using a mechanical-based antenna (AMEBA) that enables the ULF-VLF (0.03-10 kHz) communication in these conductive media. However, one of the main challenges in developing the AMEBA is designing its transmitter, i.e., the ultra-high-speed (UHS) rotor, which rotates the polarized permanent magnet (PPM) in a wide range of frequency. Because of the high rotating frequency and high load inertia of PPM, the UHS rotor's design becomes more critical in terms of Rotordynamic and vibration issues. This paper presents a detailed Rotordynamic analysis of a 2 kW, 500000 r/min UHS AMEBA rotor, which can generate transmitting frequency up to 8333 Hz. First, the UHS rotor's design is presented, which meets the torque and speed requirement of the AMEBA system. The impact of the different rotor materials on the rotor's undamped natural frequency is studied. Then, considering the AMEBA application, other rotor dynamic characteristics such as critical speed, bearing selection, Campbell diagram, and unbalance harmonic responses are investigated using 3-D finite element analysis (FEA). Finally, the UHS AMEBA rotor prototype is built, and an experiment of impulse hammer testing is performed to validate the rotor's undamped natural frequencies.