For my application I need a torque of \$\tau=0.87 \, Nm \$ and a speed of \$ w=140 \, RPM \approx 14.65 \, rad/s \$. This gives me a mechanical power \$ P_m=12.75 \, W\$. $$ P_m=\tau w $$ I have selected this stepper motor, which gives me the desired speed torque characteristics. Now, I want to double check that the motor will generate enough electrical power to match or exceed the mechanical power requirements (\$P_m<=P_e\$). $$P_e=UI$$ From the motor spec \$I=6.37\$, \$R=0.3\$. As recommeded here, I obtain \$ U=IR\$; this gives me a value \$U=1.91 \, V\$.
Now this gives me an electrical power of \$P_e \approx 12 \, W\$, which is lower than my \$ P_m\$. Looking at the graph I would expect a \$P_e\$ considerably higher than my \$P_m\$ requirement. Question: why is \$P_e\$ not higher?