Purpose <p>The turbocharger rotor system assisted by an electric motor can reduce emissions and improve energy utilization efficiency under high-speed and high-load conditions. To improve the stability of the electrically assisted turbocharger (EAT) at high speeds, this study investigates the vibrations of an EAT rotor system supported by ball bearings and an elastic ring squeeze film damper (ERSFD). The ERSFD is installed on the outer ring of the ball bearings, together forming the support system of the EAT rotor system. The vibrations of the EAT rotor system under unbalance excitation are investigated through theoretical and experimental studies.</p> Method <p>The theoretical model of the EAT is developed using the lumped mass method. The elastic ring in the ERSFD serves to provide elastic support and segment the oil film. The oil film force of the ERSFD is derived based on the short bearing approximation, taking into account the deformation of the elastic ring. Experimental tests were conducted under simulated operating conditions of the EAT rotor system.</p> Results and Conclusions <p> The results demonstrate the system’s stability under this support system and validate the theoretical model. Then, the theoretical model is used to investigate the structural parameters of the ERSFD. Supporting the system with an ERSFD effectively suppresses the sub-synchronous vibrations of the EAT rotor system, and the system’s stability can be further enhanced through optimal design of the number and height of the bosses in the elastic ring. This study proposes a novel feasible approach for designing support systems in EAT rotor systems.</p>