Characterization and Modeling of High-Value Inductors in ELF Band Using a Vector Network Analyzer

• Published in: IEEE transactions on instrumentation and measurement 2013-02, Vol.62 (2), p.415-423
• Main Authors: Garcia Salvador, Rosa M., Gazquez Parra, José A., Castellano, N. N.
• Format: Article
• Language: English
• Subjects: Coils; Cores; extremely low frequency (ELF) measurement; Frequency measurement; Ground penetrating radar; Impedance; inductor model; Inductors; Transmission line measurements; transmission lines; vector network analyzer (VNA); Windings
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2012.2215141

Characterization and modeling of high-value inductors (hundreds to thousands of henrys) are complex problems, exacerbated when working in the extremely low frequency (ELF) range. This paper details the measurement and characterization of inductors using a vector network analyzer that has a bottom operating frequency of 5 Hz. Using this device, we establish a strategy for measuring the impedance of high-inductance coils-with or without a high-permeability core-and propose a mathematical model that can explain the behavior of these high-inductance coils, which incorporate long lengths of winding wire, as a function of working frequency. These inductors were constructed as part of a research project on ELF electromagnetic fields. The importance of making a complete characterization derives from the need to exploit the largest possible amount of energy captured by the coil, which acts as a sensor. We propose a mixed model of concentrated and distributed parameters that fits the experimental results with an error of about 2% for the frequency range of 5-500 Hz, as part of the characterization process. The effects of the magnetic core on inductance and winding resistance, as a function of frequency, have been characterized in terms of concentration of the magnetic field.