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High power transformer with controllable leakage inductance

auxiliary power converter
Fig. 1. Topology for the auxiliary power converter.
  With the electrification of railways, more power density and a more efficient auxiliary power converter used for lighting, fan, and compressor are in great demand. A 30kW converter transferring a 500-1000V dc voltage to a three- phase 380V ac voltage with 150% overload is proposed. The topology is illustrated in Fig. 1. consisting of one dc-dc stage and one dc-ac stage. The dc-dc stage will transfer a 500-1000V voltage to 600-800V and serial half bridge resonant LLC converter is adopted because it can stand high voltage for primary side.
  This paper focuses on the transformer design for the dc-dc stage. The transformer turns ratio is selected to be 0.563 based on the input and output voltage range. UI Core is selected based on needed leakage inductance. Different winding structures' impact on leakage inductance is analyzed and finally leakage inductance is achieved by properly breaking the interleaved winding structure without sacrificing too much winding loss.
  The transformer turns number is determined based on the transformer loss volume trade-off and core loss winding loss trade-off. Different core loss density's impact on transformer design is also analyzed based on a similar method.

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