A press-clamp for an electric transformer winding formed by an upper plate having a free inner face with a first concentric circular protrusion, and an outer face joined to a concentric nut that can be screwed along a threaded bolt; a clamping force sensor having a ring-shaped body; and a lower plate having a peripheral wall defining a cavity with a second concentric protrusion and housing the ring-shaped body of the clamping force sensor and the upper plate by its inner face, the ring-shaped body of the clamping force sensor placed concentrically when aligned with the first protrusion and the second protrusion.