Fast 3D Transient Electromagnetic FEA for e-NVH Analysis of Induction Machines

Three-dimensional (3D) transient electromagnetic finite element analysis (FEA) of induction machines (IMs) main-tains the highest fidelity by accurately taking into account the 3D effects, such as the stator end windings, rotor cage rings, radial ventilation ducts, stator and/or rotor skewing, etc. It may take a very long computation time for each operating point due to the lengthy numerical transient before the steady state is reached as well as the large number of mesh elements. The problem becomes even more challenging when the detailed noise, vibration, and harshness (NVH) performance of the machine needs to be evaluated, which requires a relatively large number of time steps $(T_{stop}-T_{start})/T_{step}$ and a relatively small time step size $T_{step}$ determined by the range of the electromagnetic force frequency of interest. This paper presents the theoretical analysis of the numerical transient in electromagnetic FEA of IMs based on the complex vector model. The root cause and key parameters in determining the numerical transient settling time are identified. A generalized fast 3D transient electromagnetic FEA for e-NVH analysis of IMs by effectively shortening the prolonged numerical transient, reducing the finite element mesh, and speeding up the steady-state harmonic force data generation is proposed. An NVH case study based on a representative traction IM has been conducted to verify the theoretical analysis and proposed framework.