Calculation and analysis of torsional vibration of electrical propulsion system under a short-circuit-induced impulse load

  Objectives  For an electrical propulsion system, the transient torque induced by short-circuit faults is so large that it will exert a greater impact on the safety of shipboard electric propulsion system. In order to evaluate the problem, a simulation method for analyzing the torsional vibration of a propulsion system under a short-circuit-induced torque impulse is proposed in the time domain.

  Methods  Based on the torsion vibration analysis theory, a time-domain model is developed, and the system response to a transient torque impulse induced by a short-circuit is expressed. Then by using the proposed simulation model, the natural frequencies and response to the transient torque impulse for an electrical propulsion system are calculated and analyzed.

  Results  The simulation results show that the dynamic characteristics of the system have a prominent role in the transmission of torque impulse, and components at frequencies above the first resonance frequency see a substantial reduction, so the torque response of the propeller is mainly based on the first resonance frequency component. If an elastic coupling is inserted into the propulsion motor and the shafting, the torque response of the system can be significantly decreased. The peak value increases with motor speed, and vibratory torque can reach several times the value of the mean torque, causing the gears to rattle and the torsion vibratory stress to grow as a result.

  Conclusions  The proposed simulation modeling method is suitable for analyzing the torsional vibration response of an electrical propulsion system under a short-circuit-induced impulse load, and a numerical calculation should be carried out to check the reliability of the system during the design process.