Purpose It takes long time for estimating a copper loss in the coil winding of the motor by using the finite element method (FEM). The purpose of this paper is to calculate fast the copper loss by zooming method. Design/methodology/approach The authors adopt the “zooming method” to FEM. The authors compare the accuracy and the calculation time with zooming method and normal FEM. Findings The zooming method contributes to speeding up and the high accuracy of calculation. In the results, the 43-fold speed increase is achieved in the calculation of synchronous motor compared to usual FEM. Practical implications The AC copper loss calculation of 3D motor analysis can be calculated in practical computation time. Originality/value The main advantage of employment of zooming method is significantly reduction of the computation time in the loss calculation of the coil winding.