Understanding Tiny Cooling Fan starting voltage

There are those factors that affect the start voltage? Start voltage means "Tiny Cooling Fan" minimum operating voltage operation is more a fan of the merits of a feature, usually a low friction coefficient net fan, and a bathroom with a lower operating voltage of the fan in the Hall IC to lower electric start.
Affect the fan starting voltage of factors:
1. Winding design is appropriate.
2. "Tiny Cooling Fan" hysteresis loss silicon steel sheet size.
3. Hall lC minimum operating voltage.
4. transistor magnification level.
5. magnetization intensity rubber magnet.
6. "Tiny Cooling Fan" blade weight.
7. The low coefficient of friction bearings.
8. transistor saturation voltage level.
9. Is there a reverse protection diode.