Siemens Step 7 Classic, Profibus, G120C VFD: Speed reference values

AutomationTechBrian

Lifetime Supporting Member
Join Date
Jul 2013
Location
St. Cloud, MN
Posts
669
I'm trying to figure out how to read the actual speed reference value from the move blocks, writing to a DB that is being sent to the VFD. For instance the following speeds come up as the machine is running:

(hex)

1500
EB00
CAAB
3555

I know the decimal equivalents:

5,376
60,160
51,883
13,653

But now I can't look at those values and make any sense of what the actual speed reference is. And are the values working in percent of a max speed parameter, or 60hz? If it is, which parameter? Is anybody versed enough to give me some insight?

Brian
 
This was one of the few days I didn't bring their laptop home with me, so I'll have to wait until next Wednesday when I'm there again. What I might do, however, is put a Fluke clamp-on meter on a motor lead, and switch it to reading Hz. Then, I'll trend the output to my bluetooth notepad and watch for the 4 different speeds. I should be able to figure out the scaling from that.
 
For STEP7 Classic you should use the STARTER software to go online with the drive and observe parameters.

If you have a setup with ethernet to the PLC and from the PLC to the G120C you have profibus, then you can get access to the drive by routing, so you dont need a profibus card in your PC.

STARTER is a bit quirky, but after using it a little bit it is quite OK.
You can see what setpoint is sent to the drive, how the setpoint is scaled, and you can browse the setpoint channel graphically so that you can see how the setpoint is generated.
Without STARTER it is a pain to troubleshoot Siemens drives. There literally thousands of parameters.

You can have the STARTER project integrated into the STEP7 project. That is nifty way to backup all the parameters together with the PLC program.
 
Brian

Im posting some screenshots- show us what you have here

and let us know what is in parameter P2000

Also like L D said- show us where you get your values from

drv1.jpg drv2.jpg drv3.jpg
 
Last edited:

Similar Topics

I really struggle with STL in Siemens Step 7 Classic. I'll learn chunks, but then I don't use it enough to retain and build on the knowledge. When...
Replies
17
Views
3,144
I've been working for a customer with Siemens Step 7 (classic) PLC automation, using a Siemens Field Service Laptop, and V5.6 of Simatic Manager...
Replies
5
Views
2,942
Had to do my first live troubleshooting under pressure today with Siemens Step 7 Classic (v5.6). There was a contactor that wasn't pulling in and...
Replies
9
Views
2,480
Hello, I am trying to configure a Siemens OPC server using the following siemens documentation...
Replies
12
Views
8,180
Good Morning, Hoping someone with some Siemens experience can give me a hand with this one. Customer has a S7-200 cpu, which has a 6GK7...
Replies
0
Views
214
Back
Top Bottom