A contactless magnetic gear with an efficient closing of magnetic flux lines that enhances the maximum torque capability and the efficiency and simultaneously reduces the magnetic pollution outside. It can be used as a reducer for a rotating axle or transmission tree in any kind of machine, providing a fixed velocity ratio between the input and output axles -if the torque is below a limit- and torque limiter function -sliding-.
1. A contactless magnetic gear provided with at least two wheels, both provided with magnets fixed to them, these magnets being regularly distributed along circles concentrically to the wheels themselves, characterized by being the radial section of at least one of the wheels "U" shaped, made of a magnetic permeable material conforming a magnetic flux circuit except for the gap where the magnets of the other wheel pass through. 2. The contactless magnetic gear of the previous claim characterized by being at least one of the wheels radially segmented. 3. A contactless magnetic planetary gear characterized by being provided with at least two gearing wheels according to any of the previous claims.