Transposition effects on bundle proximity losses in high-speed PM machines

Reddy, Patel Bhageerath; Jahns, T.M.; Bohn, Ted

doi:10.1109/ecce.2009.5316037

Cited by 73 publications

(33 citation statements)

References 12 publications

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“…The model in (2) assumes ideal winding transposition. However, manufacturing variation in the turn-to-turn transposition may increase the losses [37], [38]. This effect is neglected in this study.…”

Section: Winding Loss Modelmentioning

confidence: 99%

High-Frequency Characterization of Losses in Fully Assembled Stators of Slotless PM Motors

Millinger

Wallmark

Soulard

2018

IEEE Trans. on Ind. Applicat.

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PostprintThis is the accepted version of a paper published in IEEE transactions on industry applications. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. IEEE transactions on industry applicationsAccess to the published version may require subscription. N.B. When citing this work, cite the original published paper. © © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Abstract-The recent emerge of wide band-gap (WBG) power transistors enables higher switching frequencies in electrical motor drives. Their full utilization from a system point of view requires quantification of the corresponding time-harmonic motor losses. As an initial step, this paper presents a unique study of stator losses for three different commercially available non-oriented silicon-iron (SiFe) steel grades (with lamination thicknesses 0.1, 0.2 and 0.3 mm). The investigations cover a wide frequency range (10-100 kHz) at different levels of DC-bias (up to 1.6 T). Iron losses are identified from measurements on fully assembled stators, deploying a novel technique. By utilizing fully assembled stators, no additional samples are required. Manufacturing influence is inherently incorporated. Results show that measured iron losses are twice as high at 10 kHz compared to Epstein test results, which emphasizes the need to incorporate manufacturing influence on iron losses at high frequencies. The level of DC-bias is also observed to have a significant impact on iron losses (up to 30 %). Even though thinner laminations are known for reducing iron losses, the reduction is much lower than anticipated in the studied frequency range due to skin effect. Using 0.1 mm lamination gauge instead of 0.3 mm reduces losses by 50 % at 10 kHz, while the same substitution at 100 kHz only reduces losses by 30 %. Future work includes loss separation in complete converter-fed machines.

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Section: Winding Loss Modelmentioning

confidence: 99%

High-Frequency Characterization of Losses in Fully Assembled Stators of Slotless PM Motors

Millinger

Wallmark

Soulard

2018

IEEE Trans. on Ind. Applicat.

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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%

“…Many different twisting schemes exist for HF litz wires [6], [14], [18], featuring different bundle structures, radial and/or azimuthal permutations, etc. However, most litz wires are constructed with the following twisting schemes:…”

Section: B Considered Twisting Imperfectionsmentioning

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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“…Experimental characterization procedures, like those described in [3], require intricate test equipment, as well as many litz wire samples to be manufactured and prepared over a meaningful range of construction parameters. On the other hand, general-purpose three-dimensional numerical simulations can often be very computationally expensive, requiring the use of "high-throughput computing [with] distributed computer resources" [4]. For these reasons, existing litz wire optimizations have largely focused on balancing the number of strands, assuming ideal litz wire construction that successfully equalizes the current through each strand [1], [5], [6].…”

Section: Introductionmentioning

confidence: 99%

Realistic litz wire characterization using fast numerical simulations

Zhang

White

Kassakian

et al. 2014

2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014

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Abstract-The losses of realistic litz wires are characterized while explicitly accounting for their construction, using a procedure that computes the current-driven and magnetic-field-driven copper losses using fast numerical simulations. We present a case study that examines loss variation in one-and two-level litz wires as a function of twisting pitch, over a wide range of values and in small increments. Experimental confirmation is presented for predictions made by numerical simulations. Results confirm the capability and efficiency of numerical methods to provide valuable insights into the realistic construction of litz wire.

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Transposition effects on bundle proximity losses in high-speed PM machines

Cited by 73 publications

References 12 publications

High-Frequency Characterization of Losses in Fully Assembled Stators of Slotless PM Motors

High-Frequency Characterization of Losses in Fully Assembled Stators of Slotless PM Motors

Litz wire losses: Effects of twisting imperfections

Realistic litz wire characterization using fast numerical simulations

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