The present invention allows individual control of an output voltage of a main transformer and an output voltage of a teaser transformer while utilizing output characteristics of the respective transformer when a Scott connected transformer has control equipment arranged on the input side thereof, including first control equipment arranged in one of two phases of the main transformer on the input side in order to control a voltage or a current and second control equipment arranged in one end of a primary coil of the teaser transformer on the input side in order to control a voltage or a current, the control equipment controlling an output voltage of the main transformer and an output voltage of the teaser transformer individually.