Woodward MFR1 situation

jolio ST

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Join Date
Oct 2004
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central CDC
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292
The company I worked in recently has a lot of projects requiring the use of the Woodward Multi-function relay or MFR. It's job is to do basic protection to the generator. Now I am trying to figure out how do I program the following PLC programs so as to enable communication between the MFR15 and the PLC. I need some help on the communication between AB SLC 5/03, Modicon PL7Pro. I have tried the "read var" instructions on PL7 but I could not even get a reading from the MFR15. I have yet to try on my RSlogix500.

Anyone has done this before? can you guide me through? I'm really stuck in this situation and my deadline for shipment is near.

Thanks in advance.

regards
Sherine T.
 
hello joilo ST;

from the Woodward MFR 15 webpage (http://www.woodward.com/pdf/ic/03247.pdf);

MFR 15 package SYN-I provides a Modbus RTU slave (RS-485, 2 wire)connection, which would allow you to exchange data with your PL7 and A-B (through a MVI card). We connect to protection relays and prower meters on a regular basis in our projects (plant construction and control), so I know this is a very easy way to do this.
If you use other packages (SY and SYN) that do not offer Modbus, use the programmable analog outputs (3) to get the basic data you require.
Hope this helps,
Daniel Chartier
 
Dear Daniel

Thank you. I had noted the wiring diagram on MFR15 package SYN-I, which is the Modbus RTU. There are 5 terminal points there (X1, X2, X3, X4 & X5). I made a check with the wiring technician and he said that he has wired up X3, X4, X5. But I thought it should be X1, X2 and X3. Is there a difference?

And also, my main worry is that I could not get my PLC to read data from the MFR. I am unsure about the addressing of the MFR for the various protection faults. Can you advice?

regards
Sherine T.
 
Hello Sherine;Looking at the Woodward connection diagram:

Woodward_RTU.jpg


I would say that I would conect to terminals X1 (Tx/Rx+), X2 (Tx/Rx-), and X3 (Gnd) to establish a RS-485 2-wire bus.

As far as requesting data from the relay, you must first have the Modbus mapping of the relay (ask Woodward); this will tell you in which registers are the values you need to request. Then you must determine which Modbus function is needed to read the registers you need (probably functions 3 and 4) . Then you program the Modbus requests in the master PLC. Modbus is native to modicon PLCs, so the PL7 should have then imbedded 9I have not worked with these PLCs so you will need to ask anotehr expert). For the A-B platforms (SLC and Controllogix) there is a Prosoft MVI Modbus master card; communication requests are configured and there are great programming examples to follow. Once you understand the pattern, it is easy.
Hope this helps,
Daniel Chartier
 
Modbus is native to modicon PLCs

Believe me, even they do not get it right (Schneider).

Have communicated with many Woodward devices from Omron PLCs over the years using both Modbus RTU and Woodward Servlink. Setting up communications protocols is really easy with CX-Protocol for Omron PLCs.

Modbus RTU is a standard communications method used to connect to almost anything. J Bus is basically the same 1 address removed.

Yes, connection via RS485 is really simple. I would, however, suggest using an RS232 port on the PLC and a communications adaptor/isolator from RS232 to RS485. Have had chips sizzle on comms units before due to different voltage levels in both devices. One voltage has been floating at a different level than the other. Normally use the Adam 4520 from Advantech. Really easy to use and set up, and of course is isolated.

By the way, I normally supply 24VDC to my PLC through a switch mode power supply. This gives isolation to the PLC. Never ground the negative from a switch mode as once you do that you lose isolation. Consequently an isolator on the comms line is required.

Cannot help you on the PLC side as I have not used this PLC.

You can obtain all addressing details from manuals available at www.woodward.com. If I remember correctly you have to join but that is no problem. The manual library is extensive. A couple of years ago you had to contact you Woodward local office for a password. Thanfully they have finally started to catch up with modern technology and practices.
 
Last edited:
suggest using an RS232 port on the PLC and a communications adaptor/isolator from RS232 to RS485... Normally use the Adam 4520 from Advantech

That just might work. But I have run out of time to get that, and the panel is very very cramp (Clients claim they do not have more space). The panel is going to be packed today so it leaves me with no choice but to continue on site. Do you think AB SLCs need the Adam 4250?

For the other project, I do have a prosoft 3150-MCM module for the AB SLC 5/03. I'll be trying to set up the communication with the woodward MFR later. But I have tested out the signals sent out by the MFR using Modscan, and it is doing o.k.

I thought it should be X1, X2 and X3

I have to eat my words. X3 to X5 is fine for direct termination.

regards
Sherine T.
 

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