Experimental Studies on Speed-Dependent Vibrations of a 30,000 rpm Switched Reluctance Machine

The absence of current-carrying conductors or permanent magnets on the rotor makes the switched reluctance machine (SRM) a strong candidate for high-speed applications. This paper presents experimental vibration measurements on a 30,000 rpm SRM at various speeds under no load, conducted by mounting two accelerometers-one on the bearing housing and the other on the external housing. The SRM is run at speeds ranging from 1,000 rpm to 30,000 rpm, and the vibrations captured by the accelerometers are analyzed in the frequency domain to obtain the dominant frequencies at various operating speeds of the machine. The obtained dominant frequencies are related to the natural frequencies of the machine components, as well as the rotational frequency and the frequency of electromagnetic excitation (radial force). At lower speeds, the natural frequencies of the machine components are observed to be dominant, while at higher speeds, it is primarily the speed or radial force frequencies and their harmonics that prevail. The RMS acceleration increases with rotor speed, but the vibration is significantly higher at certain intermediate speeds when the natural frequencies of the machine parts–namely the stator, cooling jacket, and rotor assembly–are excited by speed or radial force excitation. The dominance of the rotational frequency component with increasing speed indicates the importance of proper dynamic balancing of the rotor in high-speed SRMs.