VFD won’t follow speed reference input from PLC

[Kcorbelli]

Working on 2 VFDs for two motors, they follow any speed command when local and in hand. Once I try to give a Speed reference from my PLC they both only go to the minimum frequencies. No matter what speed command I input. What could be causing this? VFD is PowerFlex 525 Allen Bradley

 

[Jim3846]

depends on your setting for P40 thru P45, start there

 

[Kcorbelli]

P046- 2 trm blk
P047- 3 serial/DSI (HMI)
P049- 6 4-20input

Have drawings with all VFD settings and checked in VFD itself and it matches

 

[widelto]

How do you change speed reference when using PLC .?
Are you using speed reference thru ethernet or thru other means like 4-20 mA for instance. ?

 

[Kcorbelli]

4-20 signal out!

 

[joseph_e2]

Are you using t062-t068 to use a digital input to select a speed reference? If not, the default (speed ref 1) will be used. In your case, that's the Serial/DSI. Is that how you're doing it? What PLC are you using?

 

[Kcorbelli]

Yes that is how I’m doing it and it’s an Allen Bradley PLC. Cannot get either Moyer to go above minimum frequency

 

[joseph_e2]

What model PLC? Does it have Ethernet? If so, I would switch from Serial/DSI to Ethernet, unless you have a compelling need not to.

 

[Kcorbelli]

I believe it’s a contollogix 1756. The VFD does have an Ethernet option. I can try

 

[joseph_e2]

I'm curious how the PLC is connected to Serial/DSI?

 

[JunQ]

1. Check if the VFD setting is <1 “Speed Ref 2"> on whichever of T062 - T068 selected as PLC reference.
2. Check that terminal block signal and 4-20mA current when running.
3. Check PLC program or analog module settings if no current on wire or not match expected.
4. Check wiring.