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Old November 15th, 2018, 03:07 PM   #1
United States

Cydog is offline
Join Date: Feb 2018
Location: Maryland
Posts: 285
RS Logix 5000 / PF 525 -CommFreqCnt -0 CommLogixCnt-0 will not start ?

Good Afternoon ,

I'm in the process of building this panel with 17 - PowerFlex 525 drives in them. I appreciate your help before. The issue I have now is that some drives will not start. I took notice that the ones that will not start , in the controller tags , that CommFreqCnt is 0 and CommLogicCnt is 0 . The ones that will start have a 1 in each one of those.

Could you guys explain what CommFreqCnt and CommLogicCnt mean , and could that be the reason those drives will not start ?

Thanks so much , again.
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Old August 5th, 2022, 07:56 AM   #2

zan778 is offline
Join Date: Sep 2020
Location: Matão
Posts: 5
Hi there. I know I'm a bit late, but it is nice to leave a response to someone facing this in the future...

"CommLogicCnt" and "CommFreqCnt" are status indicator bits regarding if the drive is commanded by the Active Comm. and if its speed reference is commanded by the Active Comm. With both these bits on false state, you won't be able to start the drive nor give it a speed reference via network, only wired or via HMI.

I've stumbled upon a problem with some old PF 525 that used to be wired directly on IO to start and get speed reference, but someone has put them into ETH/IP network, and did a lazy job.

In my case, the "CommLogicCnt" was set to 1, but the "CommFreqCnt" was zeroed. It could start remotely via ETH/IP but it wouldn't accept any frequency value I'd input on the ControlLogix. The drive had been operating with fixed frequency since (min freq set to 50Hz).

I've had to pay a visit to see the VFD, and notice the old wiring to start and command the drive was still there, and it got no jumper cables on the terminals 1 and 11.

I removed all of them and put the jumper between 1 and 11 terminals, as the manual states, and the same way the PF 525 comes from shipping, out of the box. Voila, both bits were set, and the drive was full responsive on the ETH/IP network.

So I recommend you to double check your parameters, set them do default, or run a Startup Wizard using CCW nowadays, and go see the wiring.

Links below:


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Old August 5th, 2022, 11:13 AM   #3
James Mcquade
United States

James Mcquade is offline
Join Date: Oct 2007
Location: Nashville, Tennessee area
Posts: 3,361
several questions.
how are you communicating to the drives?
are you using shielded cable to the motors?
are the motors 230 or 480 volt?
what is the distance from the vfd to the motors?

try this, power all drives off except 1, get it running. then do the rest.
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