Line harmonic current effects study of a 33 kW, 3-Phase 60 Hz, 12-pulse transformer using "Double-2D" FEA model

This paper presents an analysis of the skin and proximity effects produced by line frequency harmonic currents in a 33 kW 12-pulse rectifier transformer using its "Double-2D" FEA model. The model is first validated with experimental data obtained from a series of standard impedance voltage tests with a proof-of-concept transformer prototype. Good agreement is observed between model results and experimental data. The model is then used to study the 12-pulse harmonic current conditions and represent the associated winding losses as equivalent resistances. It is seen that harmonic current losses account for as much as 8-11% of the secondary winding and 4-6% of the total winding power loss, indicating their significance in this application.