Instrument transformer cores: nanocrystalline or silicon steel?
For class 0.2S/0.5S metering CTs, nanocrystalline toroidal cores are the default: very high permeability gives low phase error in a small core. Silicon steel remains competitive for protection CTs and larger ratios where saturation behaviour matters more than accuracy.
Selection checklist
Accuracy class, rated primary/secondary current, burden, dimensions, insulation requirement (epoxy coated or cased), and operating temperature range.
