Abstract: A current sense transformer is provided for which includes a bobbin; the bobbin includes a winding portion for supporting a coil of wire. The winding portion includes a horizontal substantially flat base portion, a horizontal substantially flat top portion and a step portion. The step portion is disposed on top of the horizontal substantially flat base portion. The horizontal substantially flat top portion is disposed on top of the step portion substantially in parallel to the horizontal substantially flat base portion. The top portion has a central recess, raised portions on its upper surface separated from each other, and a ridge on one side of its lower surface. The central recess and the raised portions cooperate to accept a magnetic core, such that the core is substantially flush with the raised portions.