Measurement and Characterization of High Frequency Losses in Nonideal Litz Wires

Roßmanith, H. P.; Doebroenti, M.; Albach, Manfred; Exner, D. W.

doi:10.1109/tpel.2011.2143729

Cited by 88 publications

(61 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This ideal construction is difficult to realize with a large number of strands (more than six). and is commonly found in commercially available HF litz wires [2], [6], [12]. These twisting schemes ("PT" and "BW") feature correct twisting in azimuthal direction since imperfect azimuthal twisting is uncommon for HF litz wires.…”

Section: B Considered Twisting Imperfectionsmentioning

confidence: 99%

“…5(d) depicts a hybrid twisting scheme, which is also commonly found: the "BW" twisting scheme is used at the strand-level and all other levels (e.g. top-level) employ perfect twisting ("PT") [6], [12].…”

Section: B Considered Twisting Imperfectionsmentioning

confidence: 99%

“…Over the years, different calculation methods have been proposed for the calculation of the losses, which rely on analytical and/or numerical calculations [6]- [11]. However, it is found that the measured losses are often larger than the values computed with the aforementioned methods [1], [2], [12]. Different effects can explain such deviations:…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, terminations can add an impedance mismatch between the strands which leads to undesired circulating currents [2], [12], [14].…”

Section: Introductionmentioning

confidence: 99%

“…Alternatively, local variations (along distances that are similar to the pitch length) of the external magnetic field also create additional losses [12]. Such local variations are typically produced by the fringing fields of air gaps.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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)

View full text Add to dashboard Cite

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.

show abstract

Section: B Considered Twisting Imperfectionsmentioning

confidence: 99%

Section: B Considered Twisting Imperfectionsmentioning

confidence: 99%