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. "韦德betvlctor" hysteresis loss silicon steel sheet size.
3. Hall lC minimum operating voltage.
4. transistor magnification level.
5. magnetization intensity rubber magnet.
6. "韦德betvlctor" blade weight.
7. The low coefficient of friction bearings.
8. transistor saturation voltage level.
9. Is there a reverse protection diode.