Trace FET problems [RE-wrenches]

[Tom Elliot]

Todd,

You may not have any damage.  My current unit shows itself at greater than
5% THD between 3 and 6 amps of AC load, which is the range I use the most.
It has experienced one genset out of gas which appeared to be a possible
cause of the problem the tech discovered in my older unit.  As of now it is
all I have to go on but I certainly hope to hear more definitively from the
Trace folks when they've had a chance to chew it over.

Does your o-scope show THD?  For an example of what mine looked like, both
the waveform and the spectrum.

One thing that got me really interested in what was happening was the
headset and microphone on my computer.  When the microphone was turned on I
got a strong hum except right after the current unit was installed (and
before the genset ran out of gas).  When it was first installed I got no hum
at all, after the genset out of gas the hum had returned (it had been
persistent on my previous inverter, the one with the blown FETs, also, but I
had dismissed it).

Bottom line is you may have nothing wrong with your unit but it will be
difficult without testing the FETs.  Even my old one with the burned FETs
produced power just fine, but not in spec I guess, maybe more like a
modified sine wave.

Tom Elliot
Guffey Energy Works
Solar Energy Education
http://www.wagonmaker.com


----- Original Message -----
From: "Todd Cory, Bald Mt. Solar" <toddcory at jps.net>
To: "Wrenches" <RE-wrenches at topica.com>
Sent: Saturday, July 08, 2000 4:27 PM
Subject: Trace FET problems [RE-wrenches]


> Ok, now I am wondering if my old type 1, 4024 (SN 2711) has bad FETS. I
> am curious how this condition would show up... the unit appears to be
> operating fine in all modes. It has never had a generator hooked up to
> it, but has faithfully been operating without interruption in a grid
> interactive mode continuously for nearly 5 years now. Would the unit's
> efficiency be affected by bad FETS or just high THD?
>
> I do have an oscilloscope however I wonder what kind of sine wave trace
> I would see with bad transistors? From the TTW on this unit in HP, I
> remember the trace being a series of steps formulation the sine wave
> approximation.
>
> Thanks for the feedback fellow techies!
>
> Todd
>
> P.S. Anyone else discover the "Tech Menu" available beyond the user and
> set up menu's? There are a bunch of readouts in there that I don't
> understand... Anyone deciphered them? It is helpful to see the heat sink
> temperature readouts.
> --
> Todd Cory
> KE6SXS
> toddcory at jps.net
> Bald Mountain Solar
> P.O. Box 689
> Mt. Shasta, Ca. 96067
> (530) 926-1079
>
>
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