PowerFlex 525 -- SLC 5/05 -- EEM Instruction

Maximuse

Member
M
Join Date
Apr 2013
Location
Ontario
Posts
51
Hi all,

I have a pretty simple application that I can't seem to get straight in my head. I have a 525 which is set to start/stop based on discrete I/O (terminals on drive). However, I need to vary the Commanded Frequency via E/IP.

From what I understand I can't use DataLinks because I'm communicating via SLC 5/05, please correct me if I'm wrong there. So it appears my only option is to use explicit messaging via EEM instruction. I've tracked down parameter P047 (Speed Ref) and I know I need to set it to '15' = E/IP. However, I don't know where to go from there. What parameter do I write to for the actual frequency reference?
 
If everything else on the drive is controlled with discreet IO, can you not keep it simple and control the speed the same way via a 0-10V output or 4-20mA?
 
Rob, unfortunately there is no room in the rack to add an analog output card and no panel space to expand the rack. It's a dog's breakfast in there. The VFDs I'm adding are taking the place of two old DC drives which is why I have existing discrete I/O available for start/stop. Up until now they have had to open the panel and physically adjust the pot on the drives whenever they changed parts on the line.

Tarik, I've read that KB article many times (and many others). I've got a pretty good handle on how to write to parameters explicitly, I just can't figure out which parameter to write to! It seems so simple and I'm embarrassed I haven't been able to figure it out yet.
 
I'm not gonna get this all right, but I think you're on the wrong path. A SLC does not have EthernetIP abilities (you're just using ethernet - no IP). So you DO NOT want to set the speed ref to 15.

I think you want to set speed ref 1 to Preset Freq. Then, you want to set your datalink to write the freq to Parameter A410 (Preset 0).

I need to go, so I'm missing some details. You'll need to make sure the drive uses Speed Ref 1. and need to figure out how the preset speed follows preset 0 and not the other preset speed values.

Something like that. I am fairly confident that you do not want to be trying EthernetIP.
 
I did it using a ML1400 about 4 years ago- should be the exact same on a SLC 5/05.

There is another knowledgebase article that includes sample code. I just copied that and it worked flawlessly. Do a search for MicroLogix and 525.

Edit:
See articles 721115, 567393, 52205

Thinking about this some, you may not be able to both write values using E/IP and control it with hardwired I/O. It's worth a try still, but you may have to control it entirely from E/IP if you want to remotely control the speed.
 
Last edited:
rupej said:
Thinking about this some, you may not be able to both write values using E/IP and control it with hardwired I/O. It's worth a try still, but you may have to control it entirely from E/IP if you want to remotely control the speed.
Click to expand...


Same here with the ML1400. Yes, you can use both hard wire and messaging at the same time.


Attached is a setup shot of the write speed from ML1400 to PF525.

ML1400-PF525.jpg
 
So according to KB article 721115
https://rockwellautomation.custhelp.com/app/answers/detail/a_id/721115

It seems really straightforward to write to parameter P041 (Accel Time 1) using an explicit message. I must be totally missing the boat here because I'm thinking it should be equally simple to write the commanded frequency somewhere. I just can't figure out which parameter number that would be.

Padees, thanks for posting your solution. Do you remember what the setting of P047 (Speed Ref) had to be to make this work? Was it necessary to send 3 words of data to the drive or was that just additional information that your particular application required? Also has anyone used the EEM instruction instead of the MSG instruction? The EEM seems much more intuitive since you just need to set the Instance # to the Parameter # in the drive you're trying to change (which again -- I can't find).
 
P047 is set to EtherNet/IP.
Not sure if 3 words are totally necessary, but I was reading/writing other parameters.


For the message to work, you first need a timeout message.

timeout.jpg
 
Last edited:
Gotcha. The EEM seems to do away with writing the initial Timeout value and as I've said I think would look more intuitive for an end user. So I'd prefer that but in the end I may have no choice but to use the MSG.

On that note, how did you choose N17:22 to be the speed reference word? Is that just hardcoded into the drive at that specific location?
 
Last edited:
I believe N41:2 is hard coded in the drive as write speed. I just used N17:20 with size element of 3 on the ML side, so N17:22 writes speed.


There are 2 other drives on this that use N27 and N37 on the ML1400 side. Just a goofy way to organize things.
 
Right sorry I meant N41:2 not N17:22, good clarification. One other thing, in that same KB article 721115 it states that frequent writing of parameters via explicit messaging will cause premature failure of the drive due to repeated access to the non-volatile memory. The KB article states to set parameter C121 (Comm Write Mode) to '1' = RAM only. Have you done this? If not, how long have your drives been operating and how often are you accessing NV memory?
 
This was done about 6 years ago, a couple years before 721115 came out. This particular machine changes speed on two drives 4 times per cycle, and cycles are around 2 minutes each. Running 2 shifts since then, I haven't heard of any issues. Although, I have been out of that loop for 4 months now. I do have the original setup programs and C121 was never changed from default.
 
Last edited:
Never heard about the non-volatile failure thing. Kinda scary. I coded mine to write all values every 250ms via a message regardless of if they changed. I haven't gotten a call back yet :confused:
 

Similar Topics

L
Scaling issue- Powerflex 525 on SLC devicenet
I'm having a strange issue where the operator can input a desired speed in 0-110%, and the scaling will correctly translate that in Hertz to the...
Replies
6
Views
2,253
ASF
A
J
SLC 5/04 - 1761-NET-ENI - Powerflex 525`
I have decided that instead of upgrading the drives & plc at the same time on my project i would just do the drives for now as just getting them...
2
Replies
23
Views
8,933
Firejo
Firejo
S
SLC 5/05 controlling Powerflex 525 drives over Ethernet ???
Going back to a 15 year-old project and upgrading the drives to PowerFlex 525. SLC 5/05 was controlling three non-AB drives with analog (for...
Replies
6
Views
9,419
beanpole_ecc
B
M
Changing a PowerFlex 525.
Hi to all. We need to change a bad powerFlex 525 to a new one. How do you save the configuration to install in the new one? Thank you all for...
Replies
5
Views
207
James Mcquade
J
T
Teacher needs some help with Powerflex 525.
Im trying to teach a couple of labs on VFDs at a community college. We have some motor control trainers with P525s and 3 phase motors from...
Replies
0
Views
123
tim_callinan
T
Back
Top Bottom