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 5 arranged in one of two phases of the main transformer 2M on the input side in order to control a voltage or a current and second control equipment 6 arranged in one end of a primary coil 2c of the teaser transformer 2T on the input side in order to control a voltage or a current, the control equipment 5 and 6 controlling an output voltage of the main transformer 2M and an output voltage of the teaser transformer 2T individually.