This paper investigates a 3-D coupled-field finite-element method (FEM) used in simulation of temperature distributions in air-cooled asynchronous induction motors. The temperature rise in motors is due to Joule’s losses in stator windings and squirrel cages, and heat dissipation by air convection and solid conduction. The Joule’s losses calculated by 3-D eddy-current field analysis are used as the input for the thermal field analysis, which is deeply dependent on accurate air fluid field analysis. Moreover, a novel multi-component fluid model is proposed to deal with the influence of rotor rotation upon the air convection. A test prototype is designed and manufactured. The good agreement of the temperature distributions between the simulated and measured results validates the proposed methodology.