Pump control via frequency converter

[ashaw99]

Hello,

I am currently trying to integrate a pump into a wider system using a frequency converter to control the pump.

The frequency converter is a PowerXL DC1 Variable Frequency Drive from EATON (manual attached) and the pump is 

I have designed the attached block diagram to attempt to control the pump system, however, when it is used the pump does not turn on. Does anyone have any advice in this matter?

Thank you!

Asha

[GerdW]

Hi ashaw,

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@ashaw99 wrote:

I have designed the attached block diagram to attempt to control the pump system, however, when it is used the pump does not turn on. Does anyone have any advice in this matter?

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How do you connect with your VFD (variable frequency drive)?

Which protocol does it use/expect?

Does it really understand your command consisting of just a float number converted to string?

Suggestion:

I mostly used smaller VFDs with an analog input, so setting a speed required only to output the corresponding voltage signal…

[ashaw99]

Hello,

Thank you for your quick reply!

To answer your questions:

1. It connects via ethernet cable

2. It uses Modbus, but I have read this can also be operated using VISA Serial communication. Would it be better to install and use a Modbus library (like this?.. https://www.ni.com/en/support/downloads/tools-network/download.modbus-master.html#374378 )

3. I will look into this further

At the moment it seems that the VISA setup is wrong and I should be using a Modbus library. Do you think this is the right direction?

Thank you!

[GerdW]

Hi ashaw,

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@ashaw99 wrote:

1. It connects via ethernet cable

2. It uses Modbus, but I have read this can also be operated using VISA Serial communication. Would it be better to install and use a Modbus library (like this?.. https://www.ni.com/en/support/downloads/tools-network/download.modbus-master.html#374378 )

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• "Ethernet cable" is the physical layer in the communication: pure copper wires…
• "VISA" is a library to handle communication over different communication protocols using a unified API: serial, GPIB, TCP/IP…
• "Modbus" is a protocol that defines the way of organizing data/messages. Those messages can be transported using several communication protocols, one of them being TCP/IP. So most probably your VFD supports "Modbus/TCP"…

So the answer is:

Yes, you can use VISA functions to transfer your Modbus messages. But you need to use more functions than just VISAWrite to define the proper messages!

Yes, use one of those available (and free) Modbus libraries. I made good experiences with the NI Modbus library available in VIPM!