[Beekeep52]

Can you apply more voltage (78 VDC verses 60 VDC) to a DQ860MA controller than the stepper motor requires by just setting the amperage of the motor with the DIP switches on the controller?

[joeavaerage]

Hi,
no. The maximum voltage of the drive is 80VDC, you be wise not to exceed it.

As a stepper motor decelerates it will generate voltage will will be pushed back into the drive as it is, so even if the power supply is only 80V its entirely possible that it will see spikes
of 90V or more as the steppers decelerate.

You may have seen with servos and VFDs they talk about a 'braking resistor'. This is a big kick arse resistor that is electronically switched directly across the power supply (shorting it out!)
at the moments when the motor is decelerating and back generating a voltage high enough to do damage. The resistor is to provide a place for that extra energy to go while the motor decelerates.

Craig

[Beekeep52]

I think you misunderstood what I am asking. Years back I built a 6 axis machine that I am overhauling. It has 3 motors that are rated for 60 VDC and 3 motors that are rated for 78 VDC. What I want to know is it alright to supply 78 VDC to all the new controllers or is there a risk of damaging the motors that are rated for 60 VDC or does the controller vary the voltage to control the amperage set by the DIP switch. I am mounting the new controllers adjacent to the motors that they control and want to know if I must wire the machine with two power supplies. At 78VDC I am not exceeding the controllers maximum 80 VDC.

Greg Ferris

[joeavaerage]

Hi Greg,
yes I did misunderstand.

There is no problem applying a higher supply voltage to a driver, up to its rated voltage input. The only time the full voltage is actually applied to the stepper is for a few
microseconds when it first switches. The current in the stepper winding increases rapidly until it reaches its rated max current whereon the driver uses PWM to cut the
applied voltage to maintain but not exceed that max current. Most steppers have a winding resistance of lets say 1 Ohm, and lets say a max current of 4A, then the continuous
voltage applied by the stepper drive is 1 x 4 =4V, despite the power supply to the drive being 60V or 78V or 80V or whatever.

Craig

[Beekeep52]

Thanks Craig.
I suspected that that was the case but couldn't find the answer in the driver manual.
One would think that they would include that info as another selling point.

Greg