Current rise time: L/R Constant
It appears that current rise time is depend on the L/R constant (coil inductance/resistance). This means with the same power some motors will react faster then an other. In graph below the formula is shown and the current rise against time.
So it's obvious to have a low L/R constant for better results. Motors I found so far have a L/R between 2 and 10 [mH/ohm].
Lowering L/R Constant
By adding an extra resitance, the L/R could be lowered and the voltage could go up, so the current rise time will react faster. So your motor could run faster at higher step frequencies. Because torque is lineair to current, you have more torque left at same speed :)
Windings
When you buy a motor, sometimes you have more winding options, see picture below.
| Connections | Example | Resistance | Inductance | Current | voltage | Holding Torque |
|---|
| Unipolar | 2 & 4 | Nameplate | Nameplate | Nameplate | Nameplate | Nameplate |
| Bipolar Series | 3 & 5 | X2 | X4 | X0.707 | X1.414 | X1.414 |
| Bipolar Half Coil | 1 | Nameplate | Nameplate | Nameplate | Nameplate | Nameplate |
| Bipolar Parallel | 6 | X0.5 | Nameplate | X1.414 | X0.707 | X1.414 |
This will result in different torque-speed outputs:
