Planetary Variator, functioning as subsystem for variable or reversible transmissions, able to vary continuously the transmission ratio, wherein said variator comprises a ring wheel, two or more planets mounted around a central shaft and a sun wheel, so that each component, namely the ring wheel, the central shaft and the sun wheel form an interface with other transmission components; - wherein the ring wheel is an axisymmetric body around the axis of the central shaft with a rolling surface shaped according the tractrix curve, and that this surface is preferably hardened or coated to withstand tractional and compressive forces; - wherein the sun wheel is principally the same as the ring wheel but the inner and outer diameter of the tractrix curve may differ from the diameters of the ring wheel; - wherein the planets comprise a planet wheel with basically a conical rolling surface, preferably hardened or coated to transmit tractional and compressive forces, mounted freely rotational around a planet fork by means of radial and axial bearings or bushings and that the virtual top of the mentioned cone coincides with the intersection of the axis of the central shaft with the axis of the hinge of the planet; - wherein each planet fork of one Planetary Variator can rotate freely around a hinge joint of which the axis is perpendicular on the central shaft axis and parallel to the planet wheel plane and that each planet fork and each planet wheel is designed not to interfere with each other for all applicable inclination angles between the planet axis and the central shaft axis; - wherein the ring wheel, planets and sun wheel are squeezed against each other so that the rolling surfaces are in contact with each other and that the contact pressures are high enough to transmit the required torque;; - wherein the tractrix curve of ring and sun wheel have both the same length parameter L as the length from the rolling contact point of the planet wheel to the intersection of the hinge axis with the central shaft axis, where L is used in the tractrix equation +/-x+c = L*(cos α+ In|tan (α/2)|), with c an arbitrary constant and α the inclination angle between the tangent in the contact point and the axis of the central shaft; - - and wherein the shape of the rolling surfaces of the planet wheels, which is basically conical, deviates slightly from this theoretical shape in a convex way in order to optimize the contact pressure distribution; characterized in that: the central shaft is moved axially with a defined speed in relation to the squeezing force and transmitted torque, in order to change the transmission ratio. - wherein the ring wheel is an axisymmetric body around the axis of the central shaft with a rolling surface shaped according the tractrix curve, and that this surface is preferably hardened or coated to withstand tractional and compressive forces; - wherein the sun wheel is principally the same as the ring wheel but the inner and outer diameter of the tractrix curve may differ from the diameters of the ring wheel; - wherein the planets comprise a planet wheel with basically a conical rolling surface, preferably hardened or coated to transmit tractional and compressive forces, mounted freely rotational around a planet fork by means of radial and axial bearings or bushings and that the virtual top of the mentioned cone coincides with the intersection of the axis of the central shaft with the axis of the hinge of the planet; - wherein each planet fork of one Planetary Variator can rotate freely around a hinge joint of which the axis is perpendicular on the central shaft axis and parallel to the planet wheel plane and that each planet fork and each planet wheel is designed not to interfere with each other for all applicable inclination angles between the planet axis and the central shaft axis; - wherein the ring wheel, planets and sun wheel are squeezed against each other so that the rolling surfaces are in contact with each other and that the contact pressures are high enough to transmit the required torque;; - wherein the tractrix curve of ring and sun wheel have both the same length parameter L as the length from the rolling contact point of the planet wheel to the intersection of the hinge axis with the central shaft axis, where L is used in the tractrix equation +/-x+c = L*(cos α+ In|tan (α/2)|), with c an arbitrary constant and α the inclination angle between the tangent in the contact point and the axis of the central shaft; - - and wherein the shape of the rolling surfaces of the planet wheels, which is basically conical, deviates slightly from this theoretical shape in a convex way in order to optimize the contact pressure distribution; characterized in that: the central shaft is moved axially with a defined speed in relation to the squeezing force and transmitted torque, in order to change the transmission ratio. the central shaft is moved axially with a defined speed in relation to the squeezing force and transmitted torque, in order to change the transmission ratio.