Electrophoretic Dielectric Coatings for Magnetic Switches

In high magnetization rate magnetic switches, the insulation requirements are severe and in high average power applications the thermal management of core losses is a serious design issue. We have been investigating the possibility of using electrophoretic (BP) coating techniques to provide a viable alternative to dielectric films for insulation in such switches. The EP process is analogous to electroplating and as such offers advantages over other coating techniques including: excellent edge coverage, thicker coatings in areas of higher electric field stress, and the possibility of detecting and repairing any coating flaws or weak points in a secondary processing step. A continuous foil EP coating machine which is capable of coating Metglas at a rate of several feet/minute with a 2-24 /spl mu/m thick methyl methacrylate coating has been constructed. In order to determine the dielectric strength of the coating in a wound geometry, capacitors have been wound with coated Metglas conductors and DC breakdown distributions have been obtained. Mean breakdown strengths in excess of 1 MV/cm have been observed. Experiments to demonstrate the effect of the second coating step on the breakdown distributions have also been conducted. In addition, the magnetic properties of small scale coated magnetic switch cores have been measured. Experiments have also be conducted on coated material at elevated temperatures. The results of these experiments will be presented.