A design for a winding is based on a material of low electrical resistance, such as copper, and of a diameter typically greater than 90 mm, intended to generate a magnetic field in an electrical contact for a medium voltage vacuum circuit-breaker. The winding includes a hollow cylinder including helical slots that are empty of material, arranged in parallel around its longitudinal axis, and that open out both to the hollow and to the outside of the cylinder. The angular length of each helical slot is equal to at least 360°. The design makes it possible to increase the level of the axial magnetic field (AMF) obtained by the winding(s) incorporated into an electrical contact of a vacuum circuit-breaker while improving uniformity, symmetry of the field, and production cost.