PLC to VFD speed control Omron 3G3mv

[mordred]

currently operating machine that is currently using a CJ1m-CPU22
this sends an analog output to FR-FC inputs on the drive then links the next drive from AM-AC to FR-FC on the nexct drive. We then modify the speed reference scale parameter so that when we enter a % of full speed the speed reference will generate a speed change of 20% from one drive to the next in order to maintain a 20% increase in speed from one conveyer to the next one. This worked out rather well so here is my question.

For one reason or another we replaced the first motor with a hydraulic motor. Now I want to remove the first drive in the panel and I'm concerned that the speed reference that the second drive will recieve from the PLC may be altered throwing off the speed reference scale. When the drives are wired in this configuration is ther any change in the output from the PLC as it passes thru one drive to the next? Or should it remain at the same voltage from one drive to the next. The only reason I would like to know is to know how much time I should set up for the job
If it does change then it would hve to be done on a weekend. If not then I can remove it during one of the breaks.

 

[Lancie1]

Mordred,

Your description seems to be of a single analog signal from the PLC that controls all the drives. (You mentioned voltage, but it could also be a miliamp current signal.) If the signal is being passed from drive terminal to drive terminal, then No, the PLC is not changing signals betweens drives. To do that would require a separate signal to each drive, with a dedicated PLC analog output for each drive. If there is only 1 PLC output for all drives, then the 20% speed increase (above the speed signal) has to be programmed into each drive.

If the signal is daisy-chained as you described, then when you remove the first drive you will need to rewire and reroute the signal wires so that they still connect to the second drive. If the hydraulic motor is the new first drive set to run a "normal" speed", then the second drive should still have the correct scaling to run 20% above the first, as long as you re-connect the signal wires.

 

[mordred]

Thanks Lancie that was what I had thought but wanted to make sure before I changed anything and yes it is daisy chained so I will have to relocate the wires from drive one to drive 2