Dielectric Losses in Dry-Type Insulation of Medium-Voltage Power Electronic Converters
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Date
2020-09
Publication Type
Journal Article
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Abstract
Newly available Medium-Voltage (MV) Silicon-Carbide (SiC) transistors are setting new limits for the design space of MV converters. Unprecedented blocking voltages, higher switching frequencies, higher commutation speeds, lower losses, and high temperature operation can be reached, which, however, create new challenges for the electrical insulation. In particular, the dielectric losses can become significant for MV converters operated at higher switching frequencies. Moreover, the evaluation of the dielectric losses is a key element for assessing the insulation stress and for insulation diagnostics. Therefore, this paper analyzes the modeling and the computation of dielectric losses with PWM voltages. After a review of the dielectric loss mechanisms occurring in polymeric insulation materials, scalable analytical expressions are proposed for the losses produced by PWM voltages. Afterwards, the dielectric losses of a Medium-Frequency (MF) transformer, employed in a 25 kW MV DC-DC converter (7 kV to 400 V) operated at 48 kHz, are analyzed and measured in detail. With epoxy resin, the insulation losses represent a significant share, i.e. up to 17 %, of the total transformer losses. As shown, the transformer performance can be significantly improved with a silicone elastomer insulation. Finally, design guidelines are provided for the selection of insulation materials.
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published
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Volume
8 (3)
Pages / Article No.
2716 - 2732
Publisher
IEEE
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Date collected
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Subject
Dielectrics and Electrical Insulation; Dielectric Losses; Medium-Frequency Transformers; Medium-Voltage Transformers; Silicon carbide; DC-DC power converters
Organisational unit
03869 - Franck, Christian / Franck, Christian
03573 - Kolar, Johann W. (emeritus) / Kolar, Johann W. (emeritus)