For transient finite element analysis of eddy-current fields in solid rotors which have invariant material properties, it is convenient to use the Eulerian formulation where only a fixed mesh is needed when modeling motion effect. However, in the Eulerian formulation, a convection-diffusion equation instead of the pure diffusion equation has to be solved. Furthermore, when the rotor rotates at high speeds, the eddy-current fields usually have sharp transition layers over a period of time, thereby making it difficult to solve these fields accurately and effectively. To obtain a high-resolution numerical solution efficiently, an adaptive discontinuous Galerkin method is proposed and numerical examples are reported to showcase the accuracy and effectiveness of the proposed method.