Poweflex 40 - F4, and F71 Faults?

We have approx 100 PF40 conveyors in our building. Occasionally one stops without a fault being sent to the PLC. We reset/start the conveyor and it runs OK.

When I check the PF40 Fault Queue I always see: F4 F71 F4, indicating DC Buss Undervoltage, followed by the Comm Loss. We are using Profibus, and when I run Profitrace, the buss checks out normal.

I'm wondering if the motor startup load can momentarily bring the AC Buss down along with the DC Buss, enough to cause the Comm Card to glitch, resulting in the F71 Fault?

TIA for your feedback...

You can get an F4 DC bus undervoltage when you have a lost or intermittent incoming phase, because the DC bus ripple becomes excessive for the load on the drive. It can also be an early indicator that the DC bus caps are starting to fail. But yeah, the comm card is powered from a DC/DC power supply that is tapped off of the main DC bus, so if the main DC bus goes wonky, the PSU for thee comma card may wink out.

Thanks, That's helpful!

Is there a diagnostic I can run to check the health of the DC Buss Caps?


Most of the Drives in my building are 5 years old, and they run 20 hours per day, 7 days per week, so many are > 30,000 hours.