Stepper Power Question

[TimothyMoulder]

Greetings all!

I'm setting up a system with some Automation Direct stepper drives, I was wondering about the power supplies.

The system uses a STP-DRV-80100 driver and STP-MTRH-34127, a total of 4 sets. Up to two may be in motion at any given time. The motors have a nominal current of roughly 6.5 amps, and half that when idle.

I want to connect 2 power supplies in parallel to feed these beasts. The STP-PWR-4810 provides 48 VDC at 10 amps, so combined gives 20 amps. The StP-PWR-7005 provides 70 VDC at 5 amps, so total of 10 amps.

Now, according to the documentation, to get maximum torque, this requires the 70 VDC drive. Which is odd because that is the motor needs 6.5 amps, not sure where the rest of the current is coming from.

So for 4 of these, which is best: 48 volts at 20 amps or 70 volts at 10 amps?

Any thoughts?

Thanks!

Tim Moulder

 

[keithkyll]

Now, according to the documentation, to get maximum torque, this requires the 70 VDC drive.

70 Volts. Don't confuse Amps with Torque.

 

[TimothyMoulder]

Thanks Keithkyll,

So can someone explain this to me? How does 70VDC at 5 amps support a drive/motor combination that needs 6.5 amps to function, without overloading the power supply?

 

[keithkyll]

Good explanation from Gecko.
There won't be a continuous load of 6.5 Amps. The large capacitor is the most important part with steppers.
I used that drive and motor combination a few years ago (one of each). The only issue was overvoltage from the power supply when it's idle. If you stop with all windings off, the unregulated voltage will rise above 80 Volts and trigger an overvoltage fault in the drive. Add a resistor across the supply to give it a little load. Don't remember what I used. Try 4700 Ohm, 3-5 Watt wirewound. You won't need this if you stop with a little current for braking.

 

[TimothyMoulder]

Thanks again, that was helpful!