Leakage reactance variation in dry-type transformers due to spacer positioning: A FEM and experimental study

Leakage reactance is a fundamental electrical parameter in transformers that directly affects voltage regulation, efficiency, and short-circuit performance. In dry-type transformers, the physical configuration of the windings plays a critical role in determining leakage reactance. Spacers placed between turns of the low-voltage winding to improve cooling also influence the electromagnetic behaviour of the winding. However, the extent to which the position of these spacers affects reactance remains underexplored. This study presents a detailed analysis of the impact of spacer positioning on leakage reactance in the low-voltage winding of a dry-type transformer. Using the finite element method, seven distinct cases are examined, each representing a different location of a single spacer placed between the winding turns. The simulation results provide data on how leakage reactance varies with spacer position, revealing the complex interaction between winding geometry and leakage reactance. The results show that spacer placement has a non-linear effect on leakage reactance; it even leads to a slight decrease. Overall, leakage reactance varied by about 10% across the different spacer positions, with the highest increase observed when the spacer was nearest to the high-voltage winding side. Additionally, one of the simulated cases is verified through experimental measurements to validate the simulation model.