トランス損失

の一次巻線が 変成器 is energized, the magnetic flux generated by the coil flows in the iron core. Because the iron core itself is also a conductor, an electric potential will be induced on the plane perpendicular to the magnetic field lines. This electric potential forms a closed loop on the section of the iron core and generates a current. It looks like a vortex so it is called "vortex". This "eddy current" increases the loss of the 変成器 and increases the temperature rise of the 変成器's iron core heating 変成器.
The losses caused by "eddy currents" are called "iron losses". In addition, a large amount of copper wire is needed to wind the 変成器. These copper wires have resistance. When the current flows, the resistance will consume a certain amount of power. This part of the loss is often consumed as heat. We call this loss "copper loss". . Therefore, the temperature rise of the 変成器 is mainly caused by iron loss and copper loss.  
Due to the iron loss and copper loss of the 変成器, its output power is always less than the input power. For this reason, we introduce an efficiency parameter to describe this, η=output power/input power.