Analog signals exchange - VFD->LOGO

[rQx]

Hi!

I have a VFD and a Siemens LOGO.
The VFD send the speed feedback 0-10V to my LOGO.
The LOGO send the speed setpoint 4-20mA to the VFD.

How would you set this up regarding that we use two power supplys (the VFDs and the LOGOs). Both power supply are grounded so the -24VDC have the same potential.

The examples in the manuals only state how to connect a 2-wire sensor with the same supply as the LOGO/VFD.

Naturally it works if I pull a wire from the logo to the VFD and the other way around since it have both ends grounded. But is this the best/a good solution?

Should I maybe connect the 0V on both ends?

What I am worried about is that if I connect and have reference to ground it will get noise from the VFD.

/Tim

 

[osmanmom]

post the diagram

 

[rQx]

Here is a drawing of my concern, and a jpg of the manual

 

[Bering C Sparky]

What type of drive are you using?

I know on the Siemens Micromaster440 drives they have an option to use an external power supply source.

Not sure if all do, but would think they would give you this option for when your using the drive in conjuction with PLCs.

I tried to download the quick start quide to post for you but we are in rough seas and I dont think the satlink dish is having a good time of it, as I cant load the PDF.

If you can download the "Siemens Micromaster440 Quick Start Guide" you can see an example of this on page #42.

BCS

 

[rQx]

Thanks I'll look into it. The VFD is a Parker 650V.

 

[osmanmom]

If T1 are Parker VFD the 0V cannot go to GROUND.

 

[osmanmom]

please refer the attachment

 

[rQx]

please refer the attachment

You can ground the 0V of the parker drive, but you mean in this case we shouldn't? I also noticed that you removed the grounding of our power supply, what is the meaning of this? We don't want floating reference thats why we connect it to ground.

I understand the analog input from VFD to LOGO analog input. Since we use power from the VFD we have to have reference to the 0V of the VFD aswell to the LOGO.

But the analog signal from the LOGO analog ouput, here it's using power from external power supply (supply of the analog output module) to the VFD. You mean that the current will flow from LOGO to VFD analog input, to VFD 0v and back to the analog output module?

I had one thought that I should connect the 0V of the VFD with the 0V of the power supply to get the same reference and then have it grounded only on one side (the power supply side)

 

[osmanmom]

yes you correct

i'm wrong

 

[osmanmom]

Base on User Manual the Parker SSD 650 Control Terminal 0V can connect earth/ground,

but if we refer to page 10-1 (attachment EARTH-2),

how to separately the earth ?

 

[rQx]

This is when we have two drives, but maybe it applies to when we have one VFD and one power supply also. I think that this:

I should connect the 0V of the VFD with the 0V of the power supply to get the same reference and then have it grounded only on one side (the power supply side)

Is the most correct

 

[osmanmom]

you using LOGO current output to VSD as analog input as speed reference AIN2

may i know

 

[rQx]

Yes, that is correct