Studies on Decreasing Methods of Iron Losses of Powder Cores

Through previous studies of materials for iron powders insulated with the resin, we have developed anode reactor powder cores which are used to protect Thyristor Valves for HVDC (High-Voltage Direct Current) transmission systems. However, their core losses are not necessarily low. Then, further studies on insulating methods of iron powders and annealing conditions of the powder cores were carried out to decrease the core losses. As the results, we have developed much superior powder cores which show higher specific resistivity than 5 Omega m by researching suitable interfacial activators and rust preventive in the insulation materials. Further, by studying on annealing conditions of these new powder cores, we have been able to decrease the core losses. Although the specific resistivity decrease with the annealing process, it can be maintained more than 0.01 Omega m which is considered to be minimum value to maintain their core losses at low level, as the newly developed powder cores show higher specific resistivity than 5 Omega m before annealing.