A Harmonic Current Injection Method to Reduce Torsional Vibrations on Mounting Feet of SPMSM

Motor mounting feet are crucial components that directly transmit vibrations to external systems. This paper investigates the effects of harmonic current injection on the vibrations of mounting feet in surface-mounted permanent magnet synchronous motors (SPMSMs) with elastic supports. First, the sensitivity of mounting feet to different forces and the characteristics of the forces caused by harmonic currents are analyzed. The analysis reveals that the harmonic currents induce both radial and tangential forces at comparable levels, with the mounting feet more sensitive to the 0th-order tangential components of them. This sensitivity makes the harmonic current injection method effective only for adjusting the torsional vibrations of mounting feet. Next, it is demonstrated that the harmonic currents and torsional vibrations exhibit a highly linear relationship. Based on this, a method for accurately calculating the optimal harmonic currents to suppress the torsional vibrations is proposed. Finally, finite element analysis (FEA) and experiments are conducted on a 3-phase SPMSM to validate the theoretical analysis and calculation method. After injecting the calculated harmonic currents, torsional vibrations of mounting feet can be reduced by over 92% under varying speed and torque operating conditions.