Power device for motor (D) of wheelchairs for disabled persons, in which the wheelchair (C) comprises a support frame that supports the wheelchair seat, the device comprising (D): - a motor module (10) comprising a main tube (1) in which a steering column (1a) is inserted, supporting a handlebar (3) in its upper position and associated in a lower position with a fork (2) to the which is articulated a wheel (4) provided with electric motor and brake, both operated by means of controls mounted on the handlebar (3), characterized in that the device (D) also comprises: - an intermediate frame (20) mounted detachably in the engine module (10) and adapted to be detachably fixed on the support frame of the wheelchair (C), such that the intermediate frame (20) is placed in an intermediate position between the engine module ( 10) and the wheelchair (C), - first inclination adjustment means (90) placed between the engine module (10) and the intermediate frame (20) to adjust the inclination of the main tube (1) of the motor module with respect to the intermediate frame (20), and - second inclination adjustment means (100) placed between the intermediate frame (20) and the wheelchair support frame (C) to adjust the inclination of the intermediate frame (20) with respect to the chair support frame wheel； wherein the intermediate frame (20) has substantially a "U" shape comprising a transverse or cross member (21) and a pair of arms (22) substantially orthogonal to the cross member (21)； the first inclination adjustment means (90) are mounted on the crossbar (21) of the intermediate frame and the second inclination adjustment means (100) are mounted on end sections (22b) of the arms of the intermediate frame, the second means Tilt adjustment (100) comprises a joint comprising: - a cylindrical sleeve (26) adapted to adjust an upright (M) of the wheelchair support frame (C)； - a tubular element (28) having a cylindrical conduit (28b) adapted to accommodate the end sections (22b) of
