The invention relates to a high-power air-core inductor (20) prepared by coiling hollow bars made of an electrically conducting material. The coil includes at least two windings (21, 22, 23) arranged coaxially one in the other, the windings being connected in series so as to preserve the same winding direction, the induction coil having a mean radius A, a half section in a plane including the axis of the coil, which is square in shape, and the side B of which is such that the relation 2A = 6B = 6A is satisfied.
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