Thermal analysis of Lundell alternators used in automobiles is presented. An analytical thermal model for Lundell alternators is proposed, and procedures for acquiring the model parameters are elucidated. Based on the thermal model, the temperature profile of an operating Lundell alternator can be predicted analytically. The predicted alternator temperatures are found to be consistent with the experimental measurement. The presented models and measurement methods are useful for embedding switched-mode power electronics into the alternator with low manufacturing cost.