A three-phase-two-phase transformer (1, 20) comprising a magnetic circuit, three-phase windings, and two-phase windings, wherein: the magnetic circuit comprises a first column (3; 4), a second column (4; 3), and a third column that are magnetically connected together; and the three-phase windings consist in a first winding of n 1 turns around the first column (3; 4), a second winding of n 1 turns around the second column (4; 3), and a third winding of n 1 turns around the third column; the transformer being characterized in that: the two-phase windings consist in a fourth winding of n 2 turns around the first column (3; 4), a fifth winding of n' 2 turns around the first column (3; 4), a sixth winding of n 2 turns around the third column, and a seventh winding of n' 2 turns around the third column; the fourth winding and the seventh winding are connected in series and form a first two-phase phase, and each of the fourth and seventh windings (9, 12) presents a corresponding winding direction for a current (I 1) flowing in the first two-phase phase, with magnetic potentials (n 2 I 1, n' 2 I 1) in the same direction; and the fifth winding and the sixth winding are connected in series and form a second two-phase phase, and each of the fifth and sixth windings (10, 11) presents a corresponding winding direction for a current (I 2) flowing in the second two-phase phase, with magnetic potentials (n 2 I 2, n' 2 I 2) in the same direction. the magnetic circuit comprises a first column (3; 4), a second column (4; 3), and a third column that are magnetically connected together; and the three-phase windings consist in a first winding of n 1 turns around the first column (3; 4), a second winding of n 1 turns around the second column (4; 3), and a third winding of n 1 turns around the third column; the transformer being characterized in that: the two-phase windings consist in a fourth winding of n 2 turns around the first column (3; 4), a fifth winding of n' 2 turns around the first column (3; 4), a sixth winding of n 2 turns around the third column, and a seventh winding of n' 2 turns around the third column; the fourth winding and the seventh winding are connected in series and form a first two-phase phase, and each of the fourth and seventh windings (9, 12) presents a corresponding winding direction for a current (I 1) flowing in the first two-phase phase, with magnetic potentials (n 2 I 1, n' 2 I 1) in the same direction; and the fifth winding and the sixth winding are connected in series and form a second two-phase phase, and each of the fifth and sixth windings (10, 11) presents a corresponding winding direction for a current (I 2) flowing in the second two-phase phase, with magnetic potentials (n 2 I 2, n' 2 I 2) in the same direction. the two-phase windings consist in a fourth winding of n 2 turns around the first column (3; 4), a fifth winding of n' 2 turns around the first column (3; 4), a sixth winding of n 2 turns around the third column, and a seventh winding of n' 2 turns around the third column; the fourth winding and the seventh winding are connected in series and form a first two-phase phase, and each of the fourth and seventh windings (9, 12) presents a corresponding winding direction for a current (I 1) flowing in the first two-phase phase, with magnetic potentials (n 2 I 1, n' 2 I 1) in the same direction; and the fifth winding and the sixth winding are connected in series and form a second two-phase phase, and each of the fifth and sixth windings (10, 11) presents a corresponding winding direction for a current (I 2) flowing in the second two-phase phase, with magnetic potentials (n 2 I 2, n' 2 I 2) in the same direction.