Realistic litz wire characterization using fast numerical simulations

Zhang, Richard Y.; White, Jacob K.; Kassakian, J.G.; Sullivan, Charles R.

doi:10.1109/apec.2014.6803390

Cited by 40 publications

(44 citation statements)

References 18 publications

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“…In general, a wide range of pitches can work well, and the choice of pitch may be left to the litz wire manufacturer based primarily on practical considerations. Numerical simulations of the effects of pitch reported in [26] provide more insight into the effects of pitch and may lead to more specific guidance. A possible concern in this regard is turns that are close to an air-gap.…”

Section: Discussion and Alternativesmentioning

confidence: 97%

“…Such a turn might be subject to a strong field just through a fraction of one twist of the wire. The twisting of litz wire works to reduce proximity effect when voltage induced by the flux through one half twist is canceled by the same flux going through the next half twist, linked in the opposite sense [26]. If the flux at the next half twist is much lower because it is not as close to the gap, this principle is undermined.…”

Section: Discussion and Alternativesmentioning

confidence: 97%

“…To illustrate the behavior that can occur with a more controlled construction, the simulation tool described in [26] was used to simulate the same three constructions, but with the 25 and 125 strand simply twisted bundles having an ideal structure in which all the strands stay at the same radius throughout the length. The results are shown in Fig.…”

Section: Experimental Measurementsmentioning

confidence: 99%

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Simplified design method for litz wire

Sullivan

Zhang²

2014

2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014

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150

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A simplified approach to choosing number and diameter of strands in litz wire is presented. Compared to previous analyses, the method is easier to use. The parameters needed are only the skin depth at the frequency of operation, the number of turns, the breadth of the core window, and a constant from a table provided in the paper. In addition, guidance is provided on litz wire construction-how many strands or sub-bundles to combine at each twisting operation. The maximum number of strands to combine in the first twisting operation is given by a simple formula requiring only the skin depth and strand diameter. Different constructions are compared experimentally.

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Section: Discussion and Alternativesmentioning

confidence: 97%

Section: Discussion and Alternativesmentioning

confidence: 97%

Section: Experimental Measurementsmentioning

confidence: 99%

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Simplified design method for litz wire

Sullivan

Zhang²

2014

2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014

Self Cite

150

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“…FEM) [7], [17], [18], or both [13]. However, 3D methods are complex to implement and demand for very high computational cost, which limit the number of strands to less than hundred [7], [18]. For larger HF litz wires, massive parallel computing is required [17].…”

Section: A Computation Methodsmentioning

confidence: 99%

“…• A non-integer number of pitches is used, leading to circulating currents inside the HF litz wire [7], [16]. Alternatively, local variations (along distances that are similar to the pitch length) of the external magnetic field also create additional losses [12].…”

Section: Introductionmentioning

confidence: 99%

Litz wire losses: Effects of twisting imperfections

Guillod

Huber

Krismer

et al. 2017

2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL)

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Abstract-High-Frequency (HF) litz wires are extensively used for the windings of Medium-Frequency (MF) magnetic components in order to reduce the impact of eddy current losses that originate from skin and proximity effects. Literature documents different methods to calculate eddy current losses in HF litz wires, however, most of the computation methods rely on perfect twisting of the strands, which is often not present in practice. This paper analyzes the implications of imperfect twisting on the current distribution among the different strands of HF litz wires and the corresponding losses by means of a fast 2.5D PEEC (Partial Element Equivalent Circuit) method. The effects of different types of twisting imperfections (at the bundle-, subbundle-, or strand-level) are examined. It is found that imperfect twisting can lead to increased losses (more than 100 %). However, perfect twisting of the strands, which is difficult to achieve, is often not required, i.e. suboptimal twisting is sufficient. Analytical expressions are given for distinguishing between critical and uncritical imperfections. The experimental results, conducted with a 7.5 kHz / 65 kW transformer, reveal a reduction of the error on the predicted losses from 52 % (ideal HF litz wire model) to 8 % (presented model) and, thus, confirm the accuracy improvement achieved with the proposed approach.

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An Efficiency Optimization Method of Static Wireless Power Transfer Coreless Coils for Electric Vehicles in the 85 kHz Band Using Numerical Analysis

Yamada

Imura

2022

IEEJ Transactions Elec Engng

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Wireless power transfer (WPT) has been attracting a lot of attention in recent years for its ability to greatly improve the convenience of our lives. Moreover, WPT for Electric Vehicles (EVs) has become an important key to the spread of EVs. The efficiency of WPT using magnetic field resonant coupling can be evaluated by the kQ product, but the optimal coil design method to maximize the kQ product at a specific frequency has not yet been established. In this paper, taking the Test station GA‐WPT1 and the Test station VA‐WPT1/Z3 of SAE J2954, which is officially defined as the standard for WPT while the electric vehicle is stationary in October 2020, as examples, the coil parameters that maximize the kQ product in the case of the coreless are determined according to the proposed method. An efficiency of 99.13% was obtained with a transmission distance of 200 mm and the number of turns of N1 = 34 and N2 = 30. Also, since all analyses can be derived immediately except for the analysis of the Litz wire to be used, the optimization time could be reduced significantly compared with the electromagnetic field analysis. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

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Realistic litz wire characterization using fast numerical simulations

Cited by 40 publications

References 18 publications

Simplified design method for litz wire

Simplified design method for litz wire

Litz wire losses: Effects of twisting imperfections

An Efficiency Optimization Method of Static Wireless Power Transfer Coreless Coils for Electric Vehicles in the 85 kHz Band Using Numerical Analysis

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