Three-phase high frequency transformer design for a three-phase current-fed dc/dc converter with active clamp

In this paper, a new three-phase three-leg high frequency transformer is proposed for three-phase dc-dc converter and operating principle of a three-phase current-fed dc/dc converter with active clamp is introduced. The three-phase dc/dc converter transfers power in the discontinuous current mode through transformer leakage inductances and a single common active clamp branch is employed for zero-voltage switching (ZVS) in all active switches. In other words, single- phase current-fed dc/dc conversion concept is extended to the three-phase current-fed dc/dc converter by employing commonly used three-phase full bridge converter topology. However, three- phase transformer was constructed by connecting three discrete single-phase transformers with delta-delta winding and resulted in more volume and material cost. Therefore, a new three-phase three-leg high frequency transformer is designed and three discrete cores are integrated into single transformer core. The proposed transformer is analyzed in the several operating modes of the converter and its design rules are derived. And confirmed by simulation.