A high capacity power transformer (1) includes a housing (3) having top and bottom ends. A top board (32) extends outwards from four sides of the top end of the housing (3). A bottom board (33) extends outwards from four sides of the bottom end of the housing (3). A frame (4) is connected between each of four sides of the top board (32) and a corresponding one of four sides of the bottom board (33). An outer wallboard (5) envelops and is fixed to each frame (4). A sound absorbing material layer (6) is mounted to an inner face of each outer wallboard (5) facing the housing (3). The sound absorbing material layers (6) are connected to each other and surround four sides of the housing (3). The outer wallboards (5) are connected to each other and surround the four sides of the housing (3).
