The loss of transformer include iron loss and steel loss. The iron loss is that the primary winding swift on. The coil produce flux which flow in iron core to create energy loss. The copper loss is that copper wire create energy loss by winding transformer. When the current flow through these copper wire that will loss certain energy with self resistance. The loss will change into heat. We usually call this kind of heat as copper loss.
The iron loss often occur in the inside disc of transformer by hysteresis and eddy current caused by alternating magnetic field lines through the core lead to losses. At the earliest the material of transformer iron core is made of soft wrought iron which is easy magnetized and demagnetized. At the beginning of 20th century, it was discovered that put a little silicon or aluminum in iron would decrease the magnetic circuit loss and increase magnetic permeability. Transformer core material has developed to the latest energy material — amorphous magnetic material which reduces the iron loss of transformer.
Copper loss is copper winding that flow current in transformer winding out of its own resistance will loss partial electrical energy then change into heat. Because of mostly transformer adopt copper winding. So the winding loss is copper loss. Also we can say no-load loss. There are many element affect transformer. Such as silicon steel sheet property, processing technology and structure of iron core. The transformer with lower no-load loss is manufactured. On the one hand, the silicon steel sheet with lower unit loss is used. On the other hand to improve the structure and improve the level of manufacturing technology. However, it is not possible to reduce the no-load loss simply by using silicon steel sheet with lower unit loss, which will increase the manufacturing cost of iron core. By improving the structure and improving the manufacturing technology level, the no-load loss can be reduced which can save materials, cost and energy. Only when the structure and technology level have been improved that can be the silicon steel sheet with lower unit loss be used.