Adapting the Formula for Planar Spiral Inductors’ Inductance Computation to the New Oval Geometric Shape, Ideal for Designing Wireless Power Transfer Systems for Smart Devices

Claudia Pacurar (), Vasile Topa, Claudia Constantinescu, Calin Munteanu, Marian Gliga, Sergiu Andreica and Adina Giurgiuman ()
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Claudia Pacurar: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania
Vasile Topa: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania
Claudia Constantinescu: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania
Calin Munteanu: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania
Marian Gliga: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania
Sergiu Andreica: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania
Adina Giurgiuman: Department of Electrotechnics and Measurements, Faculty of Electrical Engineering, Technical University of Cluj-Napoca, 26-28 G. Baritiu Street, 400027 Cluj-Napoca, Romania

Mathematics, 2025, vol. 13, issue 3, 1-23

Abstract: The most used spiral inductors, in the available scientific literature and in our research activities, so far, have been those with square, hexagonal, octagonal, and circular geometric shapes. Geometry plays an important role in the efficiency of these inductors when used in wireless power transfer. In this article, a new geometric shape is designed by combining the square and the circle to create an oval shape of a planar spiral inductor. Inductors with this new shape are designed, numerically modelled, and practically constructed for experimental testing. The formula for inductance computation for planar spiral inductors is adapted for this new oval shape. New geometric coefficients, required for inductance computation formula, have been determined. The new formula for inductance computation is validated both analytically, by comparing the results with those from numerical modelling, and experimentally, by comparing with measurements, for a wide range of oval spiral inductors. Five sets of different oval spiral inductors are optimally designed, numerically modelled, practically constructed, and experimentally tested. By designing this new shape for planar spiral inductors, the inductance is increased 2.16 times compared to square, 1.84 times compared to hexagonal, 2.12 times compared to octagonal, and 2.52 times compared to circular shapes. The new oval spiral inductor design will be very useful for constructing wireless power transfer systems for pacemakers, smartphones, smartwatches, and/or any other type of smart device.

Keywords: spiral inductor; oval shape; inductance formula; optimal design; numerical modelling; planar electromagnetic technology; geometrical coefficients; experimental measurements (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2025
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