Abstract: The present disclosure relates to power transformers and medical devices having the same. A power transformer may include a first magnet comprising a first magnetic core and a first winding and a second magnet comprising a second magnetic core and a second winding wound around a side wall of the second magnetic core. The first magnetic core may include an annular body, and the first winding may be wound around a side wall of the annular body. The second magnetic core may include a groove extending from an end surface of the second magnetic core. The first magnet and the second magnet may be contactless. At least part of the annular body may be embedded in the groove. The first winding and the second winding may be at least partially overlapped along an axial direction of the second magnetic core.