Based　on　the　characteristics　of　three-phase　three-limb　transformer　magnetic　circuit,　the　relationship　among　its　inductances　is　analyzed,　and　a　new　mathematical　model　and　an　equivalent　circuit　model　are　proposed.　The　proposed　model　can　reflect　the　structure　characteristics　of　three-phase　three-limb　transformer　magnetic　circuit.　Compared　with　existing　three-phase　three-limb　transformer　models,　the　new　model　can　clearly　demonstrate　the　roles　of　each　current　component　in　inducing　winding　voltage.　The　equivalent　circuit　model　is　more　simple　and　intuitive　than　existing　models　and　is　easy　for　qualitative　analysis　and　calculations.　The　proposed　model　is　verified　through　comparison　with　the　traditional　nonlinear　three-limb　transformer　model.　As　an　example　for　application,　the　simplified　calculation　model　for　three-phase　three-limb　transformer　with　external　faults　is　discussed.　©　2011　State　Grid　Electric　Power　Research　Institute　Press.