A speed changing apparatus for changing an input speed to an output either greatly slower or faster, the apparatus has a coaxial pair of ring gears that includes a large ring gear having a pitch diameter A and a small ring gear having a pitch diameter D. Each electromagnet of a magnetic bearing for supporting a rotary shaft of a circulation fan 3 includes excitation coils. The spring arrangement comprises a spring that extends along a predetermined length of the rod and an elastic band that is looped through the length of the rod down the interior of the spring and around the exterior of the rod.