PURPOSE: To enable the transportation limit to be satisfied even if employed for the new AT system by placing the iron core and windings for the main seat in one tank and placing the iron core and windings for the T seat in the other tank, and connecting these thanks by means of a duct which are threaded with the two leads for connecting the primary winding groups in a T connection.

CONSTITUTION: Placed in a tank 21 for the main transformer is the main transformer content consisting of primary windings 2A, 2B for the main seat and a secondary winding 4 and a tertiary winding 5 for the main seat which are wound around the iron core for the main seat (not shown in the figure), and placed in a tank 22 for the teaser transformer is the teaser transformer content consisting of primary windings 3A, 3B for the T seat not a secondary winding 6 and a tertiary winding 7 for the T seat which are wound around the iron core for the T seat (not shown in the figure). And the two tanks 21, 22 are connected by a connecting duct 23, through which a connecting lead 24 for M1 and a connecting lead 25 for M2 are passing. With this constitution, the leakage impedance characteristics are satisfied and the operational inconvenience is eliminated, and the insulation classes of the secondary and tertiary windings and the circuit can be reduced by half. In addition, because of the two-tank system, the transportation to the installation site is easy.