Modelling Thomson Coils With Axis-Symmetric Problems: Practical Accuracy Considerations

This paper assesses factors that impact the simulation accuracy of a 2-D finite element (FE) transient axis-symmetric model of a Thomson coil (TC) actuator. Three-dimensional FE analysis (FEA) is used to show that geometric differences between a planar coil and the intrinsic assumptions of a 2-D axial model may result in important differences in coil inductance. It is then shown that inductance and resistance compensation of the 2-D model can be used to produce an accurate prediction of the TC performance. Detailed parameters of a prototype TC test system are used as inputs in the compensated 2-D axial model and excellent agreement is observed between 2-D FE simulations and experimental results. It is also shown that armature vibration modes explain the presence of apparent speed oscillations in the experimental results not present in numerical simulations. The compensated 2-D axis-symmetric model shows a good accuracy compared with experimental results for the investigated scenarios, even when an armature flexing is considered.