PowerFlex Continues Running after Stop Command

[Controls_SLuG]

We are an OEM of reinforcing fiber dispensing machines for asphalt production.

I am experiencing an intermittent issue with several machines where the PowerFlex 525 VFD keeps running after Stop is true and Start is false. During these random occurrences, the Speed Reference and Commanded Speed drop to zero, but the Speed Feedback goes up to approximately 32 HZ and the motor continues to spin until it faults with a F006 Motor Stalled fault.

We use a 480VAC, 3-phase, 0.4KW PowerFlex 525 drive (A-B 25B-D1P4N104) using FW ver. 7.001.
Our PLC's are A-B Micro850 (A-B 2080-LC50-24QBB). We use Ethernet/IP for speed and Start/Stop commands. Parameters P046 (Start Source 1) is set to 5 (Ethernet/IP) and P047 is 15 (Ethernet/IP). The PLC is programmed using CCW and I am using the RA defined UDFB for control of the PF525.

Most of the time these machines work as designed, with the drive stopping when the Stop instruction is enabled. Occasionally the drive will keep the motor running until the fault occurs. If this occurs on one of our machines when it is filled with our fiber product, a catastrophic machine failure will occur.

Has anyone else seen this issue or have any suggestions to eliminate this problem?

 

[JeremyM]

What stop mode are you using?

If the motor is driving something like a horizontal motion conveyor, this can happen if the drive isn't set to coast to stop.

 

[Controls_SLuG]

Stop Mode (P045) = 0
Ramp, CF
The PF 525 drives a gearmotor that slowly rotates a vertically oriented cylinder that normally contains our fiber product. but these machines are currently empty.
I am not getting a DC Bus Overvoltage fault (Regenerative Voltage) that occurs when the ramp Decel is too short a duration.

 

[El Guapo]

I noticed you said you were "experiencing an intermittent issue with several machines". Are these machines connected in any way that would impact each other?

has there been any recent changes to the drives or machines that you are aware of or this just started happening randomly to multiple machines?

Also I'm curious as to what your accel and decel parameters are?

 

[Controls_SLuG]

Each VFD is connected on an individual network that are not interconnected to other machines. All the EIP devices on each machine are hardwired to the PLC through an unmanaged switch in each panel. Each main panel is connected to a remote HMI via a WLAN created by an industrial AP in the main panel and a WLAN client in each remote. Each machine has a unique SSID to eliminate any possibility of crosstalk between units.

We have seen this problem occur randomly in many machines since we changed to this new EIP networked control system. 6 months ago.

 

[Controls_SLuG]

Hello JeremyM. I changed the Stop Mode (P045) from Ramp, CF (0) to Coast, CF (1) as you recommended. I have not seen the drives running on after they receive the EIP signal to stop..

Thanks for the advise.