extruder motor problem SD2

Hi everybody!

I have a problem with extruder motor, it block during printing and become very hot (fan blocked also!).

Now if I demand extruder of 100mm, motor work like a clock .

I seen into wiki that Conventional NEMA-17 motors (as used in most RepRaps) are the Y, Z and extruder motors SM42HT33-1334A
Model confirmed to be working: NEMA 17 Stepper Motor 4.5kg*cm

Also I understand that X and Y Motor is 12v and extruder motor is 3v ????
Because SM42HT33-1334A have this characteristics  :
Rated Voltage : 2.8
Current/Phase : 1.33
Resistance/Phase : 2.1
Inductance/Phase : 2.5
Holding/Tprque : 30/2200
#Of Leads : 4
Rotor Inertia : 35
Weight : 0.22
Length : 33

Thanks!