I have a strict requirement1 to drive a stepper motor with an L/R (Constant Voltage) driver but the problem is, nobody seems to commercially make these anymore due to their inefficiencies compared to the chopper-type drivers.
Reading up on how the chopper drivers work, it seems like you give it a current limit and the board uses feedback via a sense resistor to "chop" the voltage on/off to maintain a constant current at the specified limit, independent of motor speed.
This current limiting mechanism got me thinking: If I were to make the current limit high enough such that this limit could never be met, even at max output voltage (supply rail minus some small drop), would I have effectively turned the chopper driver into an L/R constant voltage driver?
For clarity, here are the specs for the stepper motor I need to drive:
2-phase, Bi-polar 1,600 steps/revolution Winding Inductance: 80mH - 150mH Winding Resistance: 160 - 220 ohm Operating Voltage: 15V - 35V
By the way, if somebody knows of a true L/R constant-voltage driver that meets the above specs, that would be ideal!
1The reason it's a strict requirement is that the flight hardware uses an L/R drive and we must Test Like You Fly, a NASA guideline which states that you should test equipment on the ground in the same form, fit and function as flight hardware.