Current Transformer Current Transformers, 115 Series 115 Series Information Terminals Are Brass Studs No. 8 32 with One Flat Washer, Lockwasher and Regular Nut. The Transformer Winding Is Arranged So That the Turns Are Fully Distributed Between All Taps.It Has a Frequency Range of 50-400 Hertz, It Has a 600 Volt Insulation Level