Variation Range of Different Inductor Topologies with Shields for RF and Inductive Sensing Applications.

In this study, different planar inductor topologies were studied to evaluate their characteristic parameters' variation range upon approaching Fe- and Cu-based shield plates. The use of such materials can differently alter the electrical properties of planar inductors such as the inductance, resonant frequency, resistance, and quality factor, which could be useful in multiple devices, particularly in inductive sensing and radio-frequency (or RF) applications. To reach an optimal design, five different square topologies, including spiral, tapered, non-spiral, meander, and fractal, were built on a printed circuit board (PCB) and assessed experimentally. At the working frequency of 1 MHz, the results showed a decrease in the inductance value when approaching a Cu-based plate and an increase with Fe-based plates. The higher variation range was noticeable for double-layer topologies, which was about 60% with the Cu-based plate. Beyond an intrinsic deflection frequency, the inductance value began to decrease when approaching the ferromagnetic plate because of the ferromagnetic resonance (FMR). It has been shown that the FMR frequency depends on the inductor topology and is larger for the double-layer spiral one. The Q-factor was decreasing for all topologies but was much faster when using ferromagnetic plates because of the FMR, which intensely increases the track resistance. The resonant frequency was increasing for all double-layer topologies and decreasing for single-layer ones, which was mainly due to the percentage change in the stray capacitance compared to the inductance variation. The concept of varying inductors by metal shielding plates has great potential in a wide range of nondestructive sensing and RF applications.

PCB-Based Planar Inductive Loops for Partial Discharges Detection in Power Cables.

Partial discharge (PD) diagnosis tests, including detecting, locating, and identifying, are used to trace defects or faults and assess the degree of aging in order to monitor the insulation condition of medium- and high-voltage power cables. In this context, an experimental evaluation of three different printed circuit board (PCB)-based inductive sensor topologies, with spiral, non-spiral, and meander shapes, is performed. The aim is to assess their capabilities for PD detection along a transmission power cable. First, simulation and experimental characterization are carried out to determine the equivalent electrical circuit and the quality factor of the three sensors. PD activity was studied in the lab on a 10-m-long defective MVAC cable. The three PCB-based sensors were tested in three different positions: directly on the defective cable (P1), at a separation distance of 10 cm to 3 m (P2), and on the ground line (P3). For the three positions, all sensors' outputs present a damped sine wave signal with similar frequencies and durations. Experimental results showed that the best sensitivity was given by the non-spiral inductor, with a peak voltage of around 500 mV in P1, 428 mV in P2, and 45 mV in P3, while the meander sensor had the lowest values, which were approximately 80 mV in P1. The frequency spectrum bandwidth of all sensors was between 10 MHz and 45 MHz. The high sensitivity of the non-spiral inductor could be associated with its interesting properties in terms of quality factor and SFR, which are due to its very low resistivity. To benchmark the performance of the designed three-loop sensors, a comparison with a commercial high-frequency current transformer (HFCT) is also made.

Partial discharge detection with on-chip spiral inductor as a loop antenna.

In this paper, a pioneer partial discharge (PD) loop antenna sensor is presented and examined. It is made of a 70-turn square planar inductor with a side length of 1.8 mm, which is fabricated on top of a silicon substrate in complementary metal oxide semiconductor technology. The microsensor ability to detect corona PD is demonstrated once connected in series with a 60 dB gain amplifier. The behavior is studied at different separation distances from the line through which the PD pulses flow. At 5 cm away, a damped sinusoidal induced voltage with an amplitude of about 100 mV has been measured. The output signal spectrum is highly concentrated around a central resonance frequency of ∼5 MHz. The microsensor response is compared with those of other industrial sensors from Techimp, i.e., horn antennas and high-frequency current transformer sensors. The presented on-chip sensor can be considered a non-intrusive competing solution compared with other heavy and expensive commercial sensors due to its lightweight, compact size, and low cost. In addition, it shows an acceptable signal to noise ratio compared with other commercial electromagnetic wave-based sensors.