forum.cncdrive.com

Hi all!

I recently acquired a DG4S-16035 drive, a breaking circuit, an encoder signal converter, a UC300ETH-5LPT and the UCCNC software all from CNCdrive.

For power supply, I found at the junkyard a large transformer (about 50 pounds) to witch I attached four large 1500uf capacitors and a bridge rectifier. The transformer has many possible configurations. I found one that give’s me an output of 76V.

I would like if possible to drive 3 large servos from this power supply. I am still bench testing and the servos have no loads on them.
Also, for now, I can only test one servo at a time since I only bought one drive.



Here is a summary of the specs from my three servos:


And this is what they look like:


They are quite large! The biggest weighs more than 50 pounds!

The results of my bench tests so far are quite encouraging! But that said, I have no idea if I'm getting the most of my servos. Should I try with a higher voltage? Something like 120V? Could the drive and the braking circuit or even the servos take it?

Also, I noticed that if I try to push the speed over 1200 RPM, I get an error and both LED on the drive light up. Would a higher voltage give more torque to my servos?

Has I continue with this project, I am sure many more questions will rise up!

Thank you for your support!

- Blaise

With servos the rotational speed is proportional to the supply voltage and the torque is proportional to the supply current.

If the motor gets higher voltage it runs faster, so if the supply voltage is higher to the drives then the drive can run the motor to a higher maximum speed.

The torque and current works a bit different, because the current in the motor coil in the static state could be simplified as I=U/R, where the U is the voltage the motor gets and the R is the motor coil resistance.
Usually servo motors have low coil resistances from a few Ohms to even fractions of one Ohm.
And so even on low voltage the motor is able to supply it's full torque, because of the low resistance of the coil.
It makes no difference in max. torque if you will use 20 or 120 Volts. The motor is able to produce it's full torque in both cases and the torque limit will be defined by the current limit you set in the drive.

Thank you CNCdrive for your quick reply!

So just to be clear, with my current configuration, there is no risk of supplying 120V to the drive?
What would be the uptimum supply voltage to get the most out of my servos?

What about the braking circuit BRKC-180? Will one of them in parallel to the power supply suffice?

Thank you for you precious help!

- Blaise

I did more tests and tuning today using Servoconfigurator.
I raised the power supply voltage to 92 volts and ajusted the PWM in Servoconfigurator to match the motor “voltage at peak torque”. Then keeping Servoconfigurator on top with the diagnostic tab active, I jogged the servo in UCCNC at 100% velocity.

I then adjusted the velocity in the axis configuration page and jogged again raising velocity until a point where the error would accumulate rapidly.

I don’t know if this is a good way to go about tuning and trying to get the most of my system.

hi Blaise can show me more pic of your cnc machine please? and videos?