Solar City H6 inverter question DC volts on AC lines

[oldryder]

Recently finished install of 12kw array feeding two Solar City H6 Inverters. We were going thru start up of the inverters as per the manual. Utility guy was out to start everything and noticed there was about 30vdc per inverter (total of 60 vdc) on the AC line after the DC disconnects were closed. This was with no AC supplied to the inverters and the AC disconnect off. The dc voltage gradually decreased to zero over about a minute after the DC disconnects were opened. Inverters appeared to boot up normally after DC discconnects were closed. Both inverters performed the same way. Looking for an explanation as the utility guy did not want to energize the inverters until this was explained. Thx in advance to anyone that can provide info. mark in MN

[jflorey2]

If nothing was connected it's not a big deal. It's just one of the input filter caps starting off at an odd voltage. That can happen in non transformer inverters.

If there is something there with a load on both lines (say a 10K power resistor) then there's a problem.

[oldryder]

Thx for the reply. I have arranged for another user to test one of his inverters under the same conditions and see if it exhibits the same thing. Ultimately I need to have an explanation that satisfies the EE at the utility and your response will help.

[bcroe]

I suspect, that is normal operation. With DC connected, the
inverter tests for a line connection, and not finding it, leaves
a bit of very low energy charge on the line.

To drain off such energy from non operating circuits, bleeder
parts are sometimes built in, apparently not in this case. For
a 240VAC output, I would put in series a couple small incandescent
bulbs (the resistance curve of incandescent makes a good beeder)
and wire them to the offending circuit. A couple 75W work, a pair
of 6W night lights are probably enough to remove any leftover
charge instantly. I use this 4 bulb setup for my 400V array to
eliminate static charges, and only light on real energy.
Bruce Roe
PVtestLt.JPG

[SunEagle]

It almost sounds like "Induction" where an electrical device gets charged through a magnetic field and then dissipates when it gets grounded. Those inverters may be "charging up" and a meter will measure that charge as a low voltage until is dissipates.

[oldryder]

Problem resolved. Added a temporary bleed resistor (incandescent bulbs as suggested) and DC volts disappeared seemingly instantly when the "bleed resistor" was connected across each AC line to ground. This was enough to make the EE at the utility happy. System is up and running without difficulty.

Many thanks to SolarFanatic. hid advice was exactly right.