An electric motor comprising a stator of the type having polar expansions of the wound type, a rotor chamber defined by a sealed case, closed by a sealing ring, a permanent magnet rotor, housed inside the rotor chamber and a shaft connected to the rotor. The electric motor comprises a valve which allows outflow of fluid from said rotor chamber; the valve is formed by a through bore provided on the sealing ring and an opposing wall for closing the bore; the wall is provided in a wall of a sealing ring holding disc which is form coupled to the sealing ring.