This study investigates the deformation behavior of transformer windings under the combined influence of magnetic and thermal coupling

with a particular emphasis on the role of thermal stress. A 3D model of a 35 kV single-phase oil-immersed scaled transformer is established

and a calculation method is proposed that simultaneously considers electromagnetic force and thermal stress. An improved turbulence model and finite element analysis are used to compute the dynamic coupling among the magnetic field

temperature

and deformation. A dedicated test platform equipped with 24 temperature sensors and 16 distributed fiber-optic vibration sensors is developed

and thermal rise and short-circuit tests are conducted to validate the simulation results. The contribution and mechanism of thermal stress in the deformation process are analyzed in detail

as well as its impact under cumulative effects. The results reveal that as the current increases

the influence of thermal stress on deformation decreases from 96.3% to 33.8%

but it significantly increases winding distortion and vibration frequency. Under cumulative short-circuit conditions

the transformer's short-circuit withstand capability is reduced by approximately 25%. The experimental findings strongly support the accuracy of the simulation analysis and demonstrate that thermal stress is a non-negligible factor in winding deformation.