Stead Fast Engineers Pvt. Ltd. Manufactures Electrolytic Grade Copper DC Choke. Stead Fast Engineers Pvt. Ltd is an ISO9001:2000 certified company that also offers induction furnaces, spares for crucibles, panels and cranes. Electrolytic Grade Copper DC Choke reduces the AC riffles on DC bus, dv / dt and dl rates and the DC bus transient over voltage. The Electrolytic Grade Copper DC Choke absorbs voltage / current spikes. The Electrolytic Grade Copper DC Choke is used in all types of heavy industries like refineries, metal processing etc.