In this thesis work the temperature distribution in the frame bolts of a 5 MVA, 115 kV, 60 Hz, three-phase five-limbs shunt reactor is obtained utilizing the finite element method (FEM) and the commercial ANSYS Maxwell software. This because the reactor actually failed while it was running, the failure occurred progressively as the screw insulation was damaged and caused an unwanted temperature rise. A time-harmonic analysis is performed to compute the magnetic field distribution in the reactor and the power losses in the frame bolts. A three-dimensional (3-D) shunt reactor model is utilized, and Maxwell’s equations are solved utilizing scalar and vectorial magnetic potentials. The 3-D electromagnetic shunt reactor model is validated by comparing the value of inductance measured in the laboratory with the value of inductance computed in the 3-D FE simulation. In addition, the core losses computed in the FE simulation are compared with the core losses measured in the laboratory. This thesis work is important for transformer manufacturers which requires an adequate shunt reactor model to analyze it under different operation conditions and to optimize the actual design.