A distribution transformer (10; 200; 220; 300; 320; 350) having a primary side for receiving input voltage and current from a source and a secondary side for providing output voltage and current to a load, the distribution transformer (10; 200; 220; 300; 320; 350) comprising: a ferromagnetic core; at least one winding structure (22; 226), each winding structure (22; 226) comprising a primary winding for connection to the source and a secondary winding for connection to the load; a power electronic module operable to reduce variations in the output voltage of the distribution transformer (10; 200; 220; 300; 320; 350), the power electronic module comprising a plurality of semiconductor switching devices; characterized in that the distribution transformer (10; 200; 220; 300; 320; 350) comprises a pocket (100; 240; 330) defining a cavity and having connectors electrically connected to the at least one winding structure (22; 226), the connectors being disposed in the cavity, the power electronic module being removably mounted in the cavity of the pocket (100; 240; 330), the power electronic module comprising a plurality of connectors adapted to slidably engage the connectors of the pocket (100; 240; 330), the power electronic module being movable between a removed position, wherein the power electronic module is located outside the pocket (100; 240; 330), and an installed position, wherein the power electronic module is disposed in the cavity of the pocket (100; 240; 330) and the connectors of the power electronic module engage the connectors of the pocket (100; 240; 330) so as to electrically connect the power electronic module to the at least one winding structure (22; 226), wherein the distribution transformer (10; 200; 220; 300; 320; 350) additionally comprises cooling structures (116, 128, 132) for conveying and dispersing heat from the power electronic module, the cooling structures (116, 128, 132) extending outwardly from a portion of the pocket (100; 240; 330) and/or a portion of a housing of the power electronic module. a ferromagnetic core; at least one winding structure (22; 226), each winding structure (22; 226) comprising a primary winding for connection to the source and a secondary winding for connection to the load; a power electronic module operable to reduce variations in the output voltage of the distribution transformer (10; 200; 220; 300; 320; 350), the power electronic module comprising a plurality of semiconductor switching devices; characterized in that the distribution transformer (10; 200; 220; 300; 320; 350) comprises a pocket (100; 240; 330) defining a cavity and having connectors electrically connected to the at least one winding structure (22; 226), the connectors being disposed in the cavity, the power electronic module being removably mounted in the cavity of the pocket (100; 240; 330), the power electronic module comprising a plurality of connectors adapted to slidably engage the connectors of the pocket (100; 240; 330), the power electronic module being movable between a removed position, wherein the power electronic module is located outside the pocket (100; 240; 330), and an installed position, wherein the power electronic module is disposed in the cavity of the pocket (100; 240; 330) and the connectors of the power electronic module engage the connectors of the pocket (100; 240; 330) so as to electrically connect the power electronic module to the at least one winding structure (22; 226),