Due to the high saturation fl ux density of iron powder (950...1600 mT) these ring cores are very suitable for output chokes carrying high DC currents. Another application is found in lamp dimmers as ballast choke. The cores are made of electrolytic iron powder, mixed with a small amount of resin for insulation. They are coated with polyamide 11 (thickness 0.1 - 0.3 mm). The isolation voltage between core and winding is up to 1500 V.