Schneider 6848 Incorrect AC1/Load power reading causing surging/oscillation

corusco

The title states the critical issue that I'm having, but I think it's worth some background here. So please bear with me while I try to explain the situation.

This 6848 was installed by a local install company and was working relatively well for about 5 months. Unfortunately the L1-CL terminal on the relay board was not correctly torqued, and it eventually developed a high enough resistance that the conductor and lug overheated and turned to a black crisp. The terminal lugs and the large film capacitor directly above the terminals needed to be replaced, but the board didn't look damaged other than some discoloration of the FR4 right around the bad terminal. 

After reinstalling the board, I noticed on the SCP display that the Load was at around 4kW (also checked in the Insight dashboard). This would have been unlikely on its own, as the load would have only been around 1-1.5kW, but the inverter breakers were still set to grid bypass, so I'm not expecting that the current sensors on the board have anything to tell the inverter about power. 

When the inverter was then inline, enabled, and set to grid support mode, the power control would be very unstable - swinging from 100W to 4kW, back and forth, and would not settle. The transformer flux noise was also super audible. It was clear that something else had been damaged in the overheat event, or otherwise connected to it. I noticed the plastic around lower current transducer near the board was also somewhat deformed, so I've also replaced that, as well as the MLCCs below the terminal lugs. The incorrect power reading and the unstable control however, persist.

Does the unit have ways of calculating AC power other than the CTs near the relays and lugs? Does anyone have schematics to indicate other components that could have been damaged that would affect the CT signal like this? Any other ideas for diagnosis? I can also put up a link to a vid that shows the swinging power control if it would help.

Thanks for taking a look at my issue. 

Dave Angelini

What XW?    XW+  or XW pro. 

Who did the repair work?

XW measures all inputs, outputs and several other key points to capture/process data.

No Schematics!

corusco

Thanks for your response, Dave.

It’s an XW Pro. I forget the XW+ shares the number, sorry.

I did the repair work. I have both IR and hot air rework stations, as well as a selection of irons for this sort of thing.

I do see the other CTs at the upper part of the relay board which I think would make sense to have a signal for the trafo output, and understand there would be other points in and out of the DC stage. A key point of the failure I see is that the load power doesn’t seem to go through the AC board at all in bypass (that seems right), but there is a Load Power signal produced (logically V*I sensed near the output, but an implausible value here) anyway.

And sorry if I missed a rule of no schematics on the forum!

 Thanks again!

Dave Angelini

No rule about schematics on the forum.  There just are not many out there for XW. Quite a few block diagrams. I have been given partial schematics for changing boards during field testing for Schneider. They have guarded the schematics as policy. Their choice.

So no warranty? How old is it?  Good soldering with safe anti static practiced right?  Was it doing the same thing before you were in there?

I would run it as offgrid for additional symptoms. No AC1 or AC2