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Motor Command/Actual quadrature current
#1
I am using the PMAC Tunning Pro to plot the Command and the Actual DAC/Current to my AC servo motor. The problem is that in any case the Actual DAC/Current is always zero and only the Cmd. DAC/Current changes in different conditions. Could you please explain me the reason.

Also, I want to access to the Command and Actual Current value for further processing (such as calculating the motor torque). How can I get these variables?

I am using PMAC clipper controller.
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#2
In PMAC Plot you can select the "Servo Cmd Out" checkbox when selecting the relevant waveforms that you want to plot. This checkbox will give you access to "ServoCmd Output" and "Current" waveforms. Where's current control happening in your system, on the Clipper or 3rd party amplifier?
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#3
(11-03-2017, 04:14 AM)nicorubies Wrote: In PMAC Plot you can select the "Servo Cmd Out" checkbox when selecting the relevant waveforms that you want to plot. This checkbox will give you access to "ServoCmd Output" and "Current" waveforms. Where's current control happening in your system, on the Clipper or 3rd party amplifier?

The current control is on the Clipper. The signal then is transferred to the amplifier. I know that I can get the plot with PMAC Plot or PMAC tuning Pro, but it just gives me a graph. What I need is a variable which I can get/access to process it.
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#4
Try Mx75 which under my Clipper configuration shows as "Actual quadrature current", I've used that before to try and gauge how close I was to the max motor rating that I was configuring, it proved to be very useful. Also see Mx77 "Quadrature current-loop integrator output" that may help you.
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#5
(11-13-2017, 10:27 AM)nicorubies Wrote: Try Mx75 which under my Clipper configuration shows as "Actual quadrature current", I've used that before to try and gauge how close I was to the max motor rating that I was configuring, it proved to be very useful. Also see Mx77 "Quadrature current-loop integrator output" that may help you.

Thank you for your suggestion. In my configuration, it is Mx02. Do you know how to access it from LabVIEW (PMAC panel) for further processing?
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#6
The PMAC only has access to actual current information if it is performing "direct PWM" control of the motor, closing a digital current loop with current feedback from a "power block" drive.

This is rarely done with the Clipper, unless you have the Clipper Stack integrated drive. Is this your configuration?
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#7
(11-17-2017, 12:13 PM)curtwilson Wrote: The PMAC only has access to actual current information if it is performing "direct PWM" control of the motor, closing a digital current loop with current feedback from a "power block" drive.

This is rarely done with the Clipper, unless you have the Clipper Stack integrated drive. Is this your configuration?

I am not sure what exactly is my Clipper Controller. I just know that the PMAC is Clipper. Maybe it is not what you mentioned and that's why the actual current signal is always zero in my system. Only the commanded current varies when I move the motor.
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#8
What amplifiers/drives are you using? What is the command signal from the Clipper to the amplifier?
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#9
(11-21-2017, 09:58 AM)curtwilson Wrote: What amplifiers/drives are you using? What is the command signal from the Clipper to the amplifier?

I am using XGT servo AC servo drive (XDL servo motor). It was installed before I came my lab so I just use it. I don't know exactly what is the command signal from the Clipper to the amplifier. How can I check it? (So sorry about my ignorance)
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#10
That is not a direct-PWM power block drive. LSIS does not sell drives of that type. The PMAC will not get any actual current information from the drive, as the current loop is closed within the drive.
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#11
(11-27-2017, 10:58 AM)curtwilson Wrote: That is not a direct-PWM power block drive. LSIS does not sell drives of that type. The PMAC will not get any actual current information from the drive, as the current loop is closed within the drive.

Thank you for your answer. Is that the reason why the actual current signal always is zero? So can I get the actual current information directly from the drive instead of from the PMAC controller?
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#12
Yes, that is why the value in the actual current register is always zero. If you are not in direct-PWM mode, that register is not used.

You will have to get the drive documentation to see if there is a way to get that information from the drive. Even if you can, it will be very difficult to synchronize it with the PMAC information.
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#13
I see. Thank you so much for your help.
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