A 4 MVA saturable reactor for VLF

This paper describes the design and testing of a 4 megavolt-amp saturable core reactor. The reactor is designed to operate in the range of 14-30 kHz (VLF) at voltages up to 37 kV (rms) and currents up to 110 A (rms). The reactor is tunable over the range of 30 millihenries down to 2.8 millihenries by applying a control current up to 120 A. This reactor is a replacement for a reactor built over 40 years ago and therefore had to match the same inductance versus control current profile. The previous reactor was designed with a ferrite core. The new reactor is designed with a nanocrystalline core. The gap in the nanocrystalline core is cut at various angles to produce a profile that matches the previous reactor. This paper will detail the core material advantages over ferrite material and describe the first order approximation for determining the gap profile.