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PLC Unitronics communication with another company's frequency converter


Patko

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I use PLC unitronics US10-B10-T42 and a frequency converter from NORD. The frequency converter contains an absolute encoder for positioning. The connection is via MODBUS RS485.

I thought it would be easier but I can't get advice on how to get the necessary command from the PLC to the frequency converter. What format should it be. I've seen that a periodic or aperiodic coil / register must be used but I don't know what it should look like in a ladder, what all has to be there.

I also looked at the examples Unitronics Unilogic Examples \ UniLogic Examples_V1.30 Rev 52 \ Communications \ MODBUS RS485 \ UniStream_070_Modbus_RS485_Master_Aperiodic but I don't know if this is exactly what I need.

If someone was dealing with such a communication and sent me an example for inspiration or could help me, I would be grateful.

well thank you

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  • MVP 2021

Nord frequency converters have a specific command structure for control.

Some settings are configured only from the local control panel.

Please send the full marking (nameplate fotos) of NORD frequency converter and the type of motor and encoder.

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For testing I have borrowed a test station that has a frequency converter and a motor (the label is in the pictures test_Station). We will use two frequency converters and two motors for the application itself, on one of them there will be an absolute sensor (configuration in pictures NORD1,2,3,4,5)

test_station_VFD.jpg

test_Station_engine.jpg

NORD5.jpg

NORD1.jpg

NORD2.jpg

NORD3.jpg

NORD4.jpg

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Unfortunately, now I do not have the opportunity to tell you in more detail. I'll try to do it later.

However, you should now try to read the instructions and start the connection of the NORDCON program with the frequency converter.

This is important for further connection to the Unistream.

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  • MVP 2021

Hi, i look for some manuals and find

https://www.nord.com/media/documents/bw/bu0050_gb_3111.pdf

As i see MODBUS RTU is supported on SK540E and bove - please see p.61.

USS protocol implemented on SK 530E is like Siemens Profibus. Not supported by Unistream.

You must ask NORD support about 530E communication, but  i think only CANopen is possible to use with Unistream.

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Yes, you are right according to this pdf and MODBUS RTU is only supported from version SK540E.  : /.  In this case, should I buy another module on UniStream or does it need to be solved on the NORD side?

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Unistream side not support Profibus.

You can use one of embedded to Unisream protocol, please find all possible on Unitronics site

https://www.unitronicsplc.com/unistream-series-unistream7/#1449515771593-63d974b6-05ac1451602511853

Or try to find some protocol converter

But i think change inverter to the upper model needed.

I do not know about your application. Maybe use Unitronics Servo product is the best way.

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Tomorrow I will take over with the sales representative and technical support from the Nord, because they assured me that there will be no problem with MODBUS RTU and it seems that it will be.  Engines with selected VFDs are already ordered but it probably won't work ...

Thanks for the advice, I'll let you know what the solution was.  If necessary, do you have an example of how to do it to communicate properly?

 

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I called with technical support from NORD and currently it is so that all VFDs can communicate via MODBUS RTU. This PDF is old, and it is true that at that time only VFD versions 540E and above could do it, but then they updated the processors and all VFDs can do it.

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Great, than you can find info  about Modbus communication in this PDF.

Please post some info about needed control algo and maybe we can find solution for your system.

P.S. Thanks for info about NORD drive modbus update. I found this problem in the past (500 series) and must migrate to Lenze drive and CANopen. 

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We are going to make an automated rack (warehouse) with 12 positions. We will have two engines and two VFDs. One motor will control the "elevator" up and down and the other motor will pull and slide the drawer.

The motor for controlling the "elevator" will have an absolute sensor that will position the individual positions.

Everything will be controlled via VFD, but the PLC must be the master through which the position is entered, and through the ladder and sensors it will automatically select whether to pull or slide the drawer and thus send a command whether the motor should go backwards or forwards.

You are welcome, I was happy to provide this information. :)

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I try to find info about your absolute encoder with embedded CANopen.

https://www.nord.com/media/documents/bw/ag_0100_en_3216_screen.pdf

In this manual present CANopen encoder feedback commisioning and on p.69 present info about possible preprogrammed fixed position (63 for 530E VFD).

I think best way to control this application is operate with preprogrammed in VFD fixed positions. Then in PLC you can use 4 bit binary coding for 16 absolute  position changover. In this case no modbus connection needed. One problem - find way (parameters on VFD)  for fixed position program and switch via VFD logic input and program logic VFD outputs - in position, VFD ready (OK).

P.S Yes you can program and change current positions via fieldbus (CANopen, MODBUS). But it is not easy way.

p.p.s Second VFD positioning must be controled with two proximity sensors?

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When I spoke with technical support from NORD, they told me that they would set the exact positions through VFD and according to the agreement I would just send the value of the position. For example, position 2 will be in drive 2650 but I will only send number 2 from the PLC to the drive.

Only one position will be positions 1-12. When the drawer is pulled out, the motor stop (positioning) is controlled by inductive sensors.

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  • MVP 2021
1 hour ago, Patko said:

2 will be in drive 2650 but I will only send number 2 from the PLC to the drive

Yes, this is exactly the option I was talking about. In practice, the position number can be selected by inputs or by communication network.

As I mentioned above, the signals that need to be transmitted from the frequency converter to the PLC are "movement completed in the desired position", "frequency converter in good condition", if necessary, you can transmit more errors of the frequency converter.

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Hello kratmel,

 

I finally have the right VFD. But I can't start communication. status is 3, which indicates an error. Through NORDCON I set the source of the control word USS, baud rate I have set the same in VFD and in PLC.

image.png.4d711669e17407c3915b76e6a7d3393f.png

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Hi, USS is not Modbus.... But as i see on p.61  if modbus is present - VFD select needed protocol in auto mode (it is strange USS must be selected).

 

I think you must try to do RS485 modbus connection via PC and standard modbus software (like Qmodbus or another free modbus soft).

Then you can see is it communication work and how VFD respond to your command.

 

Then you can try to do all possible mode.

The frequency inverter can process 2 versions of the Modbus protocol.
1. Communication via Bus IOs: If the frequency inverter is to be accessed via Bus IO Bits, the functions
must be assigned in parameters (P480) and (P481). The source for the control word and the setpoints
(P509/P510) must be set to "Control terminals". (For details: see "Coil list")
2. Process data communication: If process data is to be exchanged or parameters changed, the source for
the control word and the setpoints (P509/P510) must be set to "USS". The definition of the parameters is
made in the parameters (P543) to (P548). (For details: see "Process data")

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Some quastions:

1) PC to RS485 converter present on table?

2) Modbus evaluation software on PC is installed?

I do not know is it Modbus option present in your VFD.

You say

On 3/15/2022 at 9:46 AM, Patko said:

I called with technical support from NORD and currently it is so that all VFDs can communicate via MODBUS RTU. This PDF is old, and it is true that at that time only VFD versions 540E and above could do it, but then they updated the processors and all VFDs can do it.

But if this option is enabled - NORD must declare from what SW version for 530E  this option is enabled. I do not find any document about it....

p.s. I can run Anydesk... post me about it in PM.

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1. Yes I have a PC and VFD connection, via USB (pc) -RS232-RJ12 (vfd). I use NORDCON 2.8.6.1 software

2. Yes,  I downloaded and installed the QModBus 0.2.1 software

3. I asked the support who lent me the VFD, I will call him again to confirm it.

4. VFDs with a new processor all have the option of communication via MODBUS RTU

 

I sent you anydesk in a private message.

Thank you

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