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VFD question: Will SVC cause issues if you use Acorn 0-10v?(answered)
Posted: Tue Sep 19, 2017 7:07 am
by frijoli
I have always used Sensorless Vector because of it's ability maintain torque at slow speeds. Night and day over V/Hz.
However, I have never used a VFD with analogue input and encoder feedback from the external controller. My gut feeling is that the Sensor-less vector algorithm inside the VFD and the external controller will cause a conflict/problem.
Am I overthinking this and it's perfectly acceptable to use with the Acorn analogue input?
Thanks in Advance!
Clay
Re: VFD question: Will SVC cause issues if you use Acorn 0-10v?
Posted: Wed Sep 20, 2017 1:15 pm
by frijoli
Just FYI, I spoke with a drive specialist for a VFD manufacturer, and the consensus is that you should NOT run a drive in Vector mode if you have an encoder and external controller controlling the speed.
This is what I suspected, but now I am comfortable that it is correct.
Clay
Re: VFD question: Will SVC cause issues if you use Acorn 0-10v?(answered)
Posted: Sat Sep 23, 2017 6:46 pm
by martyscncgarage
frijoli wrote: ↑Tue Sep 19, 2017 7:07 am
I have always used Sensorless Vector because of it's ability maintain torque at slow speeds. Night and day over V/Hz.
However, I have never used a VFD with analogue input and encoder feedback from the external controller. My gut feeling is that the Sensor-less vector algorithm inside the VFD and the external controller will cause a conflict/problem.
Am I overthinking this and it's perfectly acceptable to use with the Acorn analogue input?
Thanks in Advance!
Clay
Most VFDs, can be programmed sensorless vector. The 0-10vdc signal just tells the VFD at what frequency to run at. The VFD still controls the torque at lower RPM.
The spindle encoder is only there for the control to synchronize axis movement with the spindle speed for tapping and threading as well as to display accurate RPM.
The control is not maintaining spindle speed RPM by using the encoder feedback.
Perhaps Centroid staff will add to the discussion.
Marty
Re: VFD question: Will SVC cause issues if you use Acorn 0-10v?(answered)
Posted: Sun Sep 24, 2017 1:20 pm
by union7
Yes, I believe the analog signal speed input to the VFD is just a unidirectional, open loop, "pilot" signal to tell the VFD's internal closed loop process what speed to target. No different than manually twiddling a keypad potentiometer when in Sensorless Vector Mode.
Re: VFD question: Will SVC cause issues if you use Acorn 0-10v?(answered)
Posted: Mon Sep 25, 2017 6:11 am
by frijoli
That's curious that they would monitor but not control the speed.(closed loop)
If that's the case then SVC is the way to go.
Re: VFD question: Will SVC cause issues if you use Acorn 0-10v?(answered)
Posted: Mon Sep 25, 2017 7:04 am
by diycncscott
Yes. It is open loop except for CSS applications on Lathes. This is typical on pretty much all non-servo spindle motor/drive system and is the reason for sensorless vector control from the VFD in the first place.
The encoder will not effect the behavior of the VFD because:
1. The encoder only comes back to the control (not the VFD).
2. The VFD will always follow the speed command from the control -it only adjusts it's output to make sure the motor is meeting the speed command of the control (not some other internal reference).
Re: VFD question: Will SVC cause issues if you use Acorn 0-10v?(answered)
Posted: Mon Sep 25, 2017 9:38 am
by martyscncgarage
diycncscott wrote: ↑Mon Sep 25, 2017 7:04 am
Yes. It is open loop except for CSS applications on Lathes. This is typical on pretty much all non-servo spindle motor/drive system and is the reason for sensorless vector control from the VFD in the first place.
The encoder will not effect the behavior of the VFD because:
1. The encoder only comes back to the control (not the VFD).
2. The VFD will always follow the speed command from the control -it only adjusts it's output to make sure the motor is meeting the speed command of the control (not some other internal reference).
Thanks for the clarification Scott!
Marty