The main sources of car speaker electromagnetic interference and space power transformer stray electromagnetic waves. Common specifications EI power transformer, ring type and R-type, whether it is still leaking from the electromagnetic point of view, these three transformers have advantages and disadvantages from the quality point of view, we can not simply judge the merits. EI transformer is the most common, the most widely used transformers, magnetic coil radiation leak and the main source of the gap E between type I core. EI transformer magnetic leakage is directional, as shown below, three directions X, Y, Z-axis, Y-axis direction of the coil axis of the strongest interference, Z-axis direction of the weakest radiation X-axis direction between Y between Z, so try not to make the Y-axis is parallel with the circuit board when in actual use. R-type transformers can be seen as a simple circular cross-section of the toroidal transformer, but in the coil winding techniques are different, thermal conditions better than the toroidal transformer, the core expands gradually close involute type, R type transformer electromagnetic leak situation is similar with toroidal transformer. Since each turn line length is shorter than the ring-type transformer, the core can close around the system, and therefore the minimum copper loss in the three types of transformers R-type transformers.