[kNucklBustr]

I have a 48v/7.3A PS running Nema 23 stepper motors thru a 540 Gecko driver rated at 3.5A/motor.
Stepper motors:
1) 2.55v/3.5A bipolar
2) 4.17v/2.8A bipolar (has resistor at DB9)
3) 2.55v/3.5A bipolar

If I understand correctly, these motors at holding are drawing their respected current.
Total 3 steppers - 9.8A

Under-powered ?

[ger21]

With a Gecko drive, the motor will never see more than 2/3 of their rated current. 9.8 x 2/3 = 6.5 amps. Also, I believe that the G540 has an internal 7 amp fuse. If it draws any more than 7 amps, the fuse will blow.

[Fastest1]

Go back and read the G540 manual. I am pretty sure all of the DB9's will require the current set resistor. Each stepper has its own resistor.

When you say underpowered, for what? No clue what you are using them on however the G540 is successfully used on machines at the hobby/home shop level all of the time.

[kNucklBustr]

With a Gecko drive, the motor will never see more than 2/3 of their rated current. 9.8 x 2/3 = 6.5 amps. Also, I believe that the G540 has an internal 7 amp fuse. If it draws any more than 7 amps, the fuse will blow.

Does the 2/3 of rated current apply to any drive ?

Does 2.8A stepper motor still need a resistor ?

I have another separate drive and stepper on the same PS. Stepper motor is 5.44v-6.8A, driver 6A. Im suspecting this motor is not working properly.
And thinking of connecting its own separate PS.

On a very large 1990s Grizzly mill/drill- 4 axis.

[awerby]

On a large machine like your mill-drill, those little 23-frame steppers may well be too small, especially if they're used to drive the axes directly, rather than geared down in some way. Big heavy machines like this, when they're sold as CNC tools, often come with 42-frame servos. The combination of the G-540 and NEMA 23 steppers is great for small and relatively light machines, but there's a limit to what it can do.

[kNucklBustr]

On a large machine like your mill-drill, those little 23-frame steppers may well be too small, especially if they're used to drive the axes directly, rather than geared down in some way. Big heavy machines like this, when they're sold as CNC tools, often come with 42-frame servos. The combination of the G-540 and NEMA 23 steppers is great for small and relatively light machines, but there's a limit to what it can do.

Actually the XYA run very well with these motors. Geared down 2:1. A is direct. Original acme screws. They arnt speed demons, but this is a 1750lb mill/drill. The bed alone needs a hoist.
They were originally intended for a 9x26 lathe.
The Z is the prob. Its a 3250 Nema42. also geared down 2:1. It skips steps.
Thats why I think it needs its own PS.
btw- thanks for the offer, but Ill pass.