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KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 12:20pm 25 Jul 2010

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OK so both the Efergy I have and the Envi (with either of the two clamps and senders) reads 128-135W when no power is flowing, ie inverters are shut down at night, still showing a 128-135W load.
I spoke to both the Envi/Trec people and the Efergy people and the answer was
"we are aware of this issue with transformerless type GTI's"

WTF? Why i cannot even begin to comprehend.

What I do know is if I throw the switches they go back to 0W.

manufacturer claims a 7W standby power for each inverter......is this some wierd power factor thing going on here???

Karl

Luck favours the well prepared

GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127

Posted: 02:36pm 25 Jul 2010

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Hi Karl,

this is a common problem with measuring current with a CT, can't tell which way the current is flowing, as is the way with all of these common clamp type sensors. The inverter still has some high frequency switching happening, and the CT is responding to the current that is flowing in and out of the inverter. I have seen a similar problem with SMA, Latronics and Sunprofi GTI's. Once the GTI shuts down completely and the relays open, then the switching stops and the currents should drop to 0. In my own logging programs for the CC128 I noticed a time period where the inverter seemed to continue supplying power, yet it should not have been. This is like ghost power, and happened in the mornings and evenings. After time I just ignored it, as I realized what was happening. These power measuring devices are only guides, and the only important readings are those on the utility measuring kWh meter. On my own systems, the readings amounted to about 0.1kWh per day of ghost power.

I was initially really concerned as I did think that the GTI was faulty. I was able to record at a high enough rate to conclude that the power readings coincided with pulsing noise the inverter made during this time, and the inverter was actually drawing power from the grid into the capacitors, and then pumping the power back out again, at about 0.5Hz. Mine is not too bad, but a friends was more noticeable. It is probably a feedback issue that effects the PWM cct in low power conditions.

The TL GTI have a lower grid impedance so the measured currents would be higher.

Gordon.

become more energy aware

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:00pm 25 Jul 2010

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Hi Karl

I have had a similar problem with mine a transformer less GTI and I had to put isolating relays on the input and output to solve the problem. I think it is to do with the Islanding senses circuit.

All the best

Bob

Foolin Around

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 10:04am 26 Jul 2010

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isolating relays ....
mmmm complicated
i'm happy with ghost readings in that case!

Luck favours the well prepared

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