VPI Varnishing Technology Effects on Frequency Characteristics of an Air Core Inductor Used in LISN Circuit Application

Abstract

-The functional characteristic of LISN circuit, which is used for measurements of conductive noise in mains power line, is basically related to frequency characteristics of passive elements like inductors used in the circuit as well as the frequency response of inductors is highly related to the resins used in the varnishing process. The significant problem in determination of an inductor's frequency characteristic is the intrinsic resistance, inductance and parasitic capacitance. In this triplet, the parasitic capacitance is the major limiting factor of inductor's frequency range. This capacitance depends on inductor design parameters and materials filling the spaces of coil like resin and its coherency after curing process. In this paper, two similar inductors were designed and built. The first inductor was not varnished while the second one was varnished with VPI technology. VPI, or Vacuum, Pressure, Impregnation technology is one of the most reliable methods performing good insulating conditions for electrical circuits and windings based on resins. The measured results show that implying varnishing technology does not significantly affect the frequency response. However, due to mechanical solidity aspects and improved environmental protection, it is better to varnish the inductors.

CM and DM conducted EMI modelling of PMSM VSD system with non‐ideal LISN

“…Both inductors have a Teflon bobbin, and the vacuum pressure impregnation (VPI) process is used to improve the stability of the structure of them to be suitable for use in industrial environments. However, as stated in [14], using the VPI process increased the parasitic capacitance of the inductors due to the existence of resin among coil layers and its insulation coefficient, which is about 2.5 times of the air. C 1 is a 3 μF plastic body capacitor, C 2 is an 8 μF metal body capacitor.…”

Optimal Design of Single-Layer and Multi-Layer Air-Core Inductors Considering Uncertainty Factors

“…A IR-CORE inductors are widely used in EMI filters [1], power electronic converters [2], and line impedance stabilization networks (LISNs) [3] with the advantage of avoiding hysteresis and eddy-current losses and holding large currents without saturation. However, because of their inherent capacitance (stray capacitance), the inductive behavior of air-core inductors is constrained up to the first selfresonant frequency (SRF), limiting the potential performance of designed applications at high frequency.…”