0-10V signal drop with shield grounded

[BradC]

We have constructed a new vibrator control station with local pots on the panel and remote pots on a wireless system. We are running 6 AB 525 VFD's we have no problem using the local pots which use the 10V signal from the VFD. When we switch to the remote is where we have issues. The 10v signal is generated in the remote control receiver. It is set up for 0v=0hz and 10v=60hz. With one VFD on it runs at 52hz with the pot all of the way turned up. As you turn more on the speed drops even more, to about 28hz with all of them on. By some expermenting I have found if I disconnect the shield on all of the wires it brings it back up to around 56hz with them all running. I measured voltage on the shield to ground and it has 0-dc and 4.8v ac. I am running a 3 strand 18 ga straight wire foil wrapped with a bare wire drain. Looking for ideas on what could be causing this. The local pots are using the same kind of wire.

 

[Tinine]

Schematic of what you have?
You say that the 10v is generated on the remote unit. There is a common ground, right? Or are you feeding some sort of differential input?


Craig

 

[BradC]

I don't have a schematic that I can upload easy. The remote control have a 0-10v output card and it shares all of the commons. The remote control is mounted on the side of the control cabinet and is grounded to the control cabinet.

 

[dummy_bit]

If you are using the remote, how are you disconnecting the main pots from the VFD? The main is sourcing 10V from the VFD and your remote is also sourcing 10v? When you are sending 0 - 10VDC to the VFD, you have to tie 0VDC to pin 4 I believe (SINKING). It appears there may be a mix of sourcing and sinking causing abnormal voltage issues here, without actually seeing the schematic.

 

[BradC]

We have relays to switch between local and remote.

 

[BradC]

I believe you tie to terminal 4 for sinking or sourcing of the 24v controls.