Trigonometric interpolation at sliding surfaces and in moving bands of electrical machine models

Purpose To propose trigonometric interpolation in combination with both sliding-surface and moving-band techniques for modelling rotation in finite-element electrical machine models. To show that trigonometric interpolation is at least as accurate and efficient as standard stator-rotor coupling schemes. Design/methodology/approach Trigonometric interpolation is explained concisely and put in a historical perspective. Characteristic drawbacks of trigonometric interpolation are alleviated one by one. A comparison with the more common locked-step linear-interpolation and mortar-element approaches is carried out. Findings Trigonometric interpolation offers a higher accuracy and therefore can outperform standard stator-rotor coupling techniques when equipped with an appropriate iterative solver incorporating Fast Fourier Transforms to reduce the higher computational cost. Originality/value The synthetic interpretation of trigonometric interpolation as a spectral-element approach in the machine's air gap, the efficient iterative solver combining conjugate gradients with Fast Fourier Transforms. The unified application to both sliding-surface and moving-band techniques.