PLCoblems

AB VFD

5 posts in this topic

Not sure exactly what model I have, but I'm 99% sure it's an AB Powerflex.  I need to increase the Hz from 60 to 80 to attempt to increase the speed on a grinding mill, but I have 0 experience on setting VFDs.  Any help is appreciated.

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Revised:  It's a Powerflex 520 Series.  I need to increase the voltage to get 120%, so instead of 60 Hz, I need 72 Hz.  I know it's not sustainable, we are trying to test something.  Is it possible and if so how can I do it?

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How is it getting its speed command?  Pot, typed in, analog input?

As a quick start:

Parameters 43/44 are the min/max frequency.  Parameters 47, 49, and 51 tell where each of the 3 possible speed references is.  Parameters 62-68 will tell you if any inputs are configured to select a particular speed reference.  If the speed reference is "preset frequency", look to parameters 410-425.

This manual may be useful:
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/520-um001_-en-e.pdf

 

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MOST AC induction motors are capable of 100Hz continuous-duty operation.  Before you jack up the maximum VFD speed output, gather data on the motor and how much it is loaded already.  If the application is already fully loaded, increasing the speed headroom will do nothing for you.  

There are a number of questions to answer prior to making the change.  How is the VFD commanded?  It could be a speed pot, an analog output from the HMI via the PLC, an Ethernet/IP register from the PLC.  Pull out the electrical schematics, go through the PLC program, pull out the VFD user manual.

http://literature.rockwellautomation.com/idc/groups/literature/documents/td/520-td001_-en-e.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/520-um001_-en-e.pdf

PFlex 520 AC VFDs have parameter P044-Max Freq (typical is 60Hz).  Once you have proven that you will not burn up the motor, and once you have insured yourself that the motor is not fully loaded already, with the machine stopped, change parameter P044 and whatever else is needed (for expanding the maximum signal coming into the drive).  

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Parameters 43 and 44 were Frequency, I was able to set the maximum to 72, and eventually to 90.  I will be looking into the motor to see what it is rated to.

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