Double Analog output problem PowerFlex40

lukas.m

Member
L
Join Date
Mar 2012
Location
Slovakia
Posts
3
Hello,

I am controling 2 motors with 2 PowerFlex 40 frequency drives trough Allen-Bradley PLC and RSLogix 5000. When I send information for analog output to only frq. drive n.1 it works normal, but when I send information for analog output to both of them, frq drive n.1 will stop and only frq. drive n.2 works.

P.S.: This is my first post so I hope someone understand it a little bit.
 
We will need a lot more information before we can help you.
How have you got the analog signals wired to the drives from the PLC, or are you sending the analog signals on a network?
 
When I send information for analog output to only frq. drive n.1 it works normal, but when I send information for analog output to both of them, frq drive n.1 will stop and only frq. drive n.2 works.
Click to expand...
Just guessing based on the above, but this could mean that you are using one Analog Voltage Output to feed two drives. If the drive inputs at wired in series, the voltage will be split between the two drives and the result will be half-speed or no speed. For series drive inputs, you need to use an analog current output. For a voltage output, you need to wire the drive inputs in parallel.
 
I am sorry for late response.

I got them connected to Analog I/O card 1769-IF4XOF2 , two separate connections, Local:1:O.Ch1Data and Local:1:O.Ch0Data. I cant see where is a problem.
 
The problem may be in that the channels are not isolated from each other. The analog inputs to the drive may possibly need isolated inputs derived solely from the drive's power.
 
in the past i have connected two drives using common voltage between the two using 0 to 10vdc and isolated commons using 4 to 20 ma
 
I don't vote for bernie's diagnosis in this case, because the symptoms are not symmetrical.

OP needs to clarify "when i send information" - just how is the information sent? perhaps there is underlying PLC code that we don't know about.
 
bernie_carlton said:
The problem may be in that the channels are not isolated from each other. The analog inputs to the drive may possibly need isolated inputs derived solely from the drive's power.
Click to expand...

If the output card channels are not isolated, having the voltage common wire connected to each drive input common terminal should take care of that. I am without easy access to manuals to confirm this.

As Alan said 'How have you got the analog signals wired to the drives from the PLC...?'
 

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