Pf 755

Has any body ever seen this?



I have been thru the parameters and don't see a way to correct it

My assumption at this time is what ever is transmitting or reading the temp is disconnected.

Any advice would be appreciated

Thank you

What do you mean "correct it"? Do you know it is incorrect?

What is the value of P944? This is in actual degrees and will be easier to make sense of.

Keith

Hi Kamenges, Thank you for your response, it's 104 degrees in the MCC container.

Compared to the seven other PF755s in the MCC I get this


I have compared the Parameters of the ones reading correctly to the one reading incorrectly



Before I yank it out and return it to MidCoast, I wanted to be sure.

In assuming the way I am here, I always assume it was something I did. I have learned that when I cannot discern any notable differences in the way I set these up, I need to be check by some one who has more knowledge/experience than I do.

I have done the work, going thru the drive manuals, researching the internet, requesting guidance from the distributor. Haven't had a response yet, So I decided to check my work here.

Does the value ever change, or is it always exactly -36.0 ?

I don't know the details of these circuits but years ago I did work on a big PowerFlex 700 whose heatsink sensor was disconnected, and it gave a fixed negative number. It's been a long time (and I no longer work for that employer) so I don't recall the details.

In general if it's an RTD, then you have a damaged feedback circuit. If it's a thermocouple, it's wired backwards.

This is from the PF750 programming manual:

168 HeatSinkUnderTmp

ResettableFault

Bit 2

“PwrStrucFlts”

Heatsink temperature sensor is reporting a value below -18.7
°C (-1.66 °F) or the sensor feedback circuit is open.
See P943 [Drive Temp Pct] and/or P944 [Drive Temp C]

Theoretically, you should be seeing a fault because of this, since you are below -18.7 degrees. I would guess your initial assessment is correct; the sensor is not connected to the feedback circuit.

Keith

Yes. Heat sink sensor is disconnected or defective. It's an NTC thermistor, meaning the resistance changes in the inverse of the temperature change. So if the sensor becomes disconnected, the "infinite" resistance is interpreted as a very cold temperature by the processor.


https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/479654/loc/en_US#__highlight

Thanks to everyone for the assist

I know which direction to take now