You *can* try to run a 100A motor that is rated for 0.01V. Your drivers will probably start cutting out at 1.2A so you will have 1% of it's design torque available to do things. If you have a motor that has 100X the needed torque (and it still steps) that's a fine solution. It's also a waste. You have a 12V supply, why put a 3V motor on it?
Here's the math:
Take your steps per mm on the motor. (Marlin firmware config.h)
Take the max rational speed (say 100 mm / sec) (experience)
The steps and the speed will give you the revolutions per second. (math)
Every time you complete 4 steps you go through one cycle of micro stepping drive. (Allegro or TI or Sanyo driver chip data sheet)
You are diving the motor at revs/sec x steps / 4. For a 1.8 degree motor that's 200 steps / 4 = 50 times the revs per second.
The driver chip puts a constant current into the motor (Allegro or TI or Sanyo data sheet). The curet is set by the Vref.
The normal driver boards have a chip rating of 2A maximum (data sheet again).
The normal driver boards have a thermal cut-out / self protect. That cuts in after extended run at about 1.2A (many user's experience).
The normal driver boards are not super duper well designed for thermal performance (50 years of doing this stuff for a living).
From your motor data sheet you can get three basic numbers:
1) The resistance of the winding
2) The inductance of the winding
3) The rated current through the winding
You will find that the rated current and resistance give you the voltage of the winding (E=IR, ohms law).
The reactance of the winding is 2 * pi * frequency * inductance in Henries (EE 201)
The magnitude of the impedance of the winding is square root of reactane squared plus resistance squared (EE201)
The voltage on the winding will be the current times the magnitude of the impedance.
Most of these motors have an inductance in mHy that's about 1.4X the resistance in ohms regardless of what the specific numbers are. That gives them all a common point that the reactance starts to matter.
You can go through the numbers for a number of motors and you get a fairly consistent result, If you have about 30% more voltage than the "voltage rating" on the motor, you can drive it just fine with the typical chips.
Next up is the temperature rating on the motors. They have what's known as a "class B" insulation rating for the most part. That's a 135C rating. Its measured by an odd technique (winding resistance change) so the real inner temperature is a bit higher. When the inside of the motor is 135C, it's outside is pretty warm. That bothers many people. They tend to cut the current back because of it. If you cut the current in half you loose half the torque. You also need half the voltage. Your 3V motor is now a 1.5V motor ....
That's the first layer. There's a lot more, I suspect that's enough for now.
Here's the math:
Take your steps per mm on the motor. (Marlin firmware config.h)
Take the max rational speed (say 100 mm / sec) (experience)
The steps and the speed will give you the revolutions per second. (math)
Every time you complete 4 steps you go through one cycle of micro stepping drive. (Allegro or TI or Sanyo driver chip data sheet)
You are diving the motor at revs/sec x steps / 4. For a 1.8 degree motor that's 200 steps / 4 = 50 times the revs per second.
The driver chip puts a constant current into the motor (Allegro or TI or Sanyo data sheet). The curet is set by the Vref.
The normal driver boards have a chip rating of 2A maximum (data sheet again).
The normal driver boards have a thermal cut-out / self protect. That cuts in after extended run at about 1.2A (many user's experience).
The normal driver boards are not super duper well designed for thermal performance (50 years of doing this stuff for a living).
From your motor data sheet you can get three basic numbers:
1) The resistance of the winding
2) The inductance of the winding
3) The rated current through the winding
You will find that the rated current and resistance give you the voltage of the winding (E=IR, ohms law).
The reactance of the winding is 2 * pi * frequency * inductance in Henries (EE 201)
The magnitude of the impedance of the winding is square root of reactane squared plus resistance squared (EE201)
The voltage on the winding will be the current times the magnitude of the impedance.
Most of these motors have an inductance in mHy that's about 1.4X the resistance in ohms regardless of what the specific numbers are. That gives them all a common point that the reactance starts to matter.
You can go through the numbers for a number of motors and you get a fairly consistent result, If you have about 30% more voltage than the "voltage rating" on the motor, you can drive it just fine with the typical chips.
Next up is the temperature rating on the motors. They have what's known as a "class B" insulation rating for the most part. That's a 135C rating. Its measured by an odd technique (winding resistance change) so the real inner temperature is a bit higher. When the inside of the motor is 135C, it's outside is pretty warm. That bothers many people. They tend to cut the current back because of it. If you cut the current in half you loose half the torque. You also need half the voltage. Your 3V motor is now a 1.5V motor ....
That's the first layer. There's a lot more, I suspect that's enough for now.