E型硅钢片又称壳型或日型硅钢片，它的主要优点是初、次级线圈共同一个线架，有较高的窗口占空系数(占空系数Km：铜线净截面积和窗口面积比);硅钢片对绕组形成保护外壳，使绕组不易受到机械伤损伤;同时硅钢片散热面积较大，变压器磁场发散较少.但是它的初次级漏感较大，外来磁场干扰也较大，此外，由于绕组平均周长较长，在同样圈数和铁芯截面积条件下，EI型铁芯的变压器所用的铜线较多。
E type silicon steel sheet also called shell type or type of silicon steel sheet, its main advantage is the primary and secondary windings of a common wire frame, high duty factor (window duty factor: Km copper wire net area and window area ratio); silicon steel sheet to form a protective shell of winding, the winding is not easy due to mechanical injury; at the same time, silicon radiating area is large, the transformer magnetic field divergence is less. But first it large leakage inductance, the external magnetic field interference is large, in addition, because the winding average circumference is longer, in the same number of turns and core area under the condition of using the EI type iron core transformer copper more.