Re: [CAD_CAM_EDM_DRO] Servo motor questions

cnc_4_me wrote:

> 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.
>

Most likely. The resistance of the motor will be low, something like 1
ohm or so. The high voltage rating is needed to overcome the back EMF
generated by the motor while it's turning. What will happen when you
drive it at 80V is that it will run about half as fast as it would when
driven with 160V. You should also note whether that current rating is
continuous or peak.

I have some motors with similar continuous ratings. One thing I noticed
was that the voltage rating is higher than you could ever need if you're
operating the motor within its speed and current ratings. The peak
current is about 40A, armature resistance about 1 ohm, and back EMF at
full speed about 100V. If you add the max back EMF plus 40V across the
armature (at full current), it's only 140V, but the motor is rated for
160V. That's just a little bit of insurance - they made sure the max
voltage is high enough that even at full speed and full torque, you
can't break down the wire insulation.

> 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.
>

Either can be done, but it's probably easier to slot the motor mounting
holes. Less parts to worry about, less chance of something getting
stuck somewhere and changing the tension, little chance of the thing
loosening up, etc. Just my opinion, but simpler is often better.

- Steve