Quote Originally Posted by Lloyd Barnes View Post
Thanks for the heads up on this. Have spoken with the motor supplier and done some further research.
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Can I check my understanding. As I understand it (be gentle I'm, still learning this stuff!) running the driver for the NEMA34 at 48v is going to generate a much lower torque. Rather than the 8.7nm its capable of, it's probably going to be running somewhere closer to 4.5-5nm. Speed however shouldn't change? Is that right?
Ok seen as nobody answered this here goes.! . . . . However first let me point out that suppliers will always want to sell you what they have in stock or highest profit margin they'll never recommend what's best for you if they don't have it on stock.! . . . So if today they have 48V psu's then "This what you need Sir".!!!

Torque and speed are both proportional to Voltage so both will be affected to some degree. However low voltage affects speed more than torque esp if Motor inductance is high, which is often the case with larger motors hence why 23's are often used.

The higher the Inductance of the motor the more voltage you'll require to get the same speed/torque than motor with lower inductance. Then we have how the motor is connected to factor into the mix.! . . Bi-polar Parallel or Series wired.?
Most large motors are 4 wire motors internally wired in series which means they'll require much more voltage than 8 wire motor which can be parallel wired.

Series wired motor will provide higher torque down low in the speed curve but torque will drop off quickly as the rpm rise. To get higher speeds out of series wired motor will require much much more voltage.
Parallel wired motors will have lower torque down low but carry it much higher up speed curve and in general give more balanced torque/speed curve using less voltage.

So in your case if you'd used nema 23 wired parallel with 48V and 2:1 you'd be better off than using series wired 8Nm 34 running on too low voltage.
Personaly I'd just fit the 34 with 2:1 with what you have got and see how it goes. IF doesn't work out just give it more volts.