To solve the safety problems such as excessive vibration and shaft fault occurred during variable frequency transformation of electric feed pump

the multi-lumped masses model of the pump rotor-gear-front pump rotor was established

and the finite element model was established by ANSYS. The torsional vibration frequencies and modes of the shaft system were calculated by using the transfer matrix method and the finite element method respectively. According to the calculation results

the dangerous sections of the shafting system were determined. The detailed frequency conversion speed control system model was built up by using the MATLAB/Simulink platform

and the output harmonics of the high voltage inverter were simulated as the faulty source of the fault. Finally

the finite element model was applied to calculate the torque response of the dangerous sections due to the output harmonics of the inverter

and combining with the S-N curve

the fatigue life loss of the shaft system was obtained. The results show that

the dangerous cross section of the shafting system locates at the front end of the feed pump coupling and the front end position of the front pump shaft

respectively. The torsional stress of the shaft caused by the harmonic of the inverter is 5 MPa and 1 MPa

which is far away lower than the fatigue limit o f50 MPa at the dangerous section

so life loss of the rotor will not occur.