Steady-state operation modes of three-phase induction machines canbe efficiently simulated by 2D nonlinear time-harmonic finite-element models, although only induced currents with respect to the fundamental air-gap field are correctly taken into account.This technique does not generalise to single-phase inductionmachines. An approach based on multiple rotor models and a spectraldecomposition of the air-gap field enables to consider higherharmonic air-gap field contributions. In a capacitor-motor model,the first, third and fifth forward and backward rotating componentsgive raise to different frequencies in the rotor which result indifferent eddy-current effects. The torque dip due to the thirdharmonic is accurately simulated.