1000 ft of AWG22 wire is about 19-20 ohms
Based on some stuff on N8LP's website, I'm going to guess that the
motor current for a single element is about 300 mA. I'm going to
guess that they use standard 2 phase motors, so 150mA per winding.
The voltage drop in the cable is going to be about 3 Volts, which
seems quite low.
It might be that a higher voltage is used to get the di/dt to be fast
enough to get reasonable step rates (on most stepper drives, you need
substantially more voltage than you'd calculate from the winding
resistance, so that you can get the current up high enough fast
enough.. the voltage waveform looks like a spike with a back porch...
see, e.g., TV horizontal flyback waveforms)
The series L from the cable is going to be substantial, even with the
twisted pair, and the driver has to charge the entire transmission
line up, too. I seem to recall something like 0.5 to 1
microhenry/meter for twisted pair of "reasonable size".. Call it 200
uH total. Then, you've got that surge suppressor with a ferrite bead
and some parallel C (0.001 uF).
I can easily see the driver electronics being unstable/unpredictable
into this sort of load, especially if it's one of those slick PWM
drivers like the ones from Allegro that try to drive constant current.
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