VFD to PLC
VFD to PLC
(OP)
So I have 3 VFDs being run off of a PLC. I am Mechanical and new to this stuff but I think I need 1digital 1analog to each of the motors.. digital for ON/OFF and then the analog is 4-20 so i can control the speed though that, correct? I have external sensors that will be recording the rate and flow of my pumps. I just need to know is 1DO and 1AO each is enough to control the pumps... I am running a Wago PLC and the VFDs are Baldor VS1SP series.
Thanks for your time I hope u can help
Mech
Matt
Thanks for your time I hope u can help
Mech
Matt





RE: VFD to PLC
FYI, in today's industrial environments, many VFD's are being controlled via a network cable such as Ethernet, Devicenet, Profibus, etc. There are no digital or analog "wires" going to the drive.
RE: VFD to PLC
A lot of jobs could be adequately run by selecting slow, med, fast, faster, if you know what I mean.
Anyway this would result in speed control with only digital outs which are often more available or cheaper.
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD to PLC
But all that aside, assuming you have some other valid reason for having the PLC, you can usually do on-off control through the analog input as well, eliminating the DI altogether. What you do is program the VFD t turn itself off if the AI drops below some threshold value, and wake up to run if it increases above it. So for example, let's say you are using 0-10VDC as your speed command. First you program the AI speed response to vary from 0-100% speed on the AI going from 1-10V, then tell it that if it is even below 1V, shut down. It's done all the time, I'm sure the Baldor drive has that capability.
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RE: VFD to PLC
RE: VFD to PLC
Its just that I have not played with these before and we dont have a PLC guy so I am left with the task.... even if it is more than i can chew. Right now we are assigning addresses to the PLC. We have two PLCs, a master and a slave and i am having one hell of a time getting them to talk to each other.... any ideas. Its a Wago PLC
Mech
Matt
RE: VFD to PLC
I'm sorry, but I am not familiar with Wago PLC's. I have been in your shoes before though. I am a PLC tech for a steel mill. We have mostly allen bradley's and some large siemens plc's. For someone familiar with these PLC's it is simple to get tyhe communcations working. But for the novice, you will probably have a hell of a time. What I did before I had any experience or training, is had my local distributors help me out. Find out who is a distributor in your area for Wago, call them up and they should be able to get an Engineer down there to help you out.
RE: VFD to PLC
That was my thinking as well and I contacted the distributor in November and the soonest they could get a Engineer out to me is Jan 15 ... This is a time sensitive project that must be completed by the 1st of Jan.
And what is everyones take on Wago. Its seems people dont like it to much
RE: VFD to PLC
1- DO to command the VFD to Run / Stop,
1- AO to command the VFD speed,
1- AI for the VFD speed feedback signal to the PLC,
1- AI as your process input,
1- DI as a Run/Stop command to the PLC, and
1- DI as a feedback from the VFD for Run / Fault status. But I would do it with a little more than that, or do serial communications to the VFD.
Generally, if you are wanting to do serial communications between a PLC and a VFD, the best approach is to use a VFD/combo from a PLC mfr., such as Siemens, A-B, Schneider etc. because they make it easy for the novice. The difficulty you would have with something like a Wago PLC (I didn't know they even made them!) is that any direct serial communications will need to be done via the serial port and you will need to write commands in the PLC code that the VFD comm port can understand. For experienced programmers this is a no-brainer, but for a novice it can be daunting.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD to PLC
RE: VFD to PLC
*[link]itsmoked[/link] comes to mind...
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD to PLC
RE: VFD to PLC
http://www.contactify.com/c27d0
Ed
RE: VFD to PLC
I take it that you have the software, do you know how to upload the files or have a copy? Like Jraef said, you could possibly email an Engineer the file, have him write the code and send it back electronically for a fee. If you have to install new hardware, than some harware configuration will be needed. But maybe someone could walk you through that over the phone. The best solution is to get someone there at the site.