The Magnetic Characteristics of Tape Wrapped Cylindrical Ferromagnetic Laminations for Frequencies Below 50 KHz,

The leakage magnetic fields from magnetic devices are known to create EMI problems for sensitive shipboard VLF receivers and sonar equipment. Devices which contain ferromagnetic cores can be particularly significant EMI offenders because of the high flux densities available in their magnetic circuits. This memorandum discusses the magnetic characteristics of various laminated cores found in shipboard equipment with source frequencies extending into the VLF band. Test results are presented for an open tape cylindrical lamination containing an axial and radial air gap. Although this is a more complicated magnetic circuit, its behavior is shown to be identical to predictions derived for simple lamination shapes without air gaps for frequencies up to 50 kHz. Author