Hi, After reading many notes and other reading materials, I do find that the core selection is to be made based on the Core Geometry method or Kg core approach. Even though much literature do describe this, I am but lost how to find this Kg core value from the core datasheets, or how to calculate it. Another stumbling block that came across me is the Mean Length per Turn. I cannot find this parameter in the datasheets nor a way to calculate these. ie I am using EPCOS cores, but I am unable to find any Kg core, MLT values, or any way to calculate it. Any ideas, how this is to be done ? Best Regards, Manu --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .