Servo motor questions

If you have a servo motor rated at 160 volts, 10 amps, 5nM, and you are driving it with a Gecko 80 volt 20 amp drive. What happens to the 5nM torque rating. Since the voltage you are driving it with is so low, can you make the 10 amps required for 5nM of torque.

Also, how is the belt usually tensioned for a Nema 34 or 42 motor. Are the 4 motor bolt holes slotted. Or is an idler used.

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