| Abstract |
This paper proposes a new plastic mold structure for medium-frequency molded transformers used in solid-state transformers (SSTs), aiming to enhance both the cooling performance of windings and insulation capabilities. In medium-frequency transformers for 6.6-kV SST, high-voltage insulation performance is required between the primary and secondary windings. Therefore, insulation should be provided by molding around the windings. In contrast, an effective cooling method for windings is necessary because copper losses in the windings also increase as the operating frequency rises.In this paper, temperature rise in the windings, which is a problem in medium-frequency molded transformers, is addressed by applying plastic molding only to the high electric field generating part in a structure that allows efficient cooling. Experimental results show that the developed transformer, which has a power density of 12.6 kW/L, continuously transmit 37.5 kW with a maximum transmission efficiency of 99.2\%. In addition, partial discharge tests of the developed transformer show that it has sufficient insulation performance for SST with a 6.6-kV input. |
