Chassis ground current and voltages [RE-wrenches]

[Christopher Freitas --- OutBack Power]

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The voltage you are seeing when the inverter chassis ground is
disconnected is normal - the AC output filter causes the 120 VAC to be
"split" +/- 60 VAC or so from the chassis.  This is true for both the
old Trace products and the newer OutBack inverters (funny how that is,
huh?) 

When the ground wire is reattached to the chassis - the capacitor in the
AC output filter which is connected from the AC output neutral to the
chassis gets discharged - causing a momentary spark and the typical
reaction from the installer (which I can't include here). This spark
only occurs if the inverter is running when the connection is made, BTW.


As far as the current in the ground conductor - it is not normal 60 Hz
AC current - it is high frequency "noise" current (which is mostly why
typical clamp meters won't measure it).  There is no real power flowing
- just RF being shunted to ground.  

I'll go a measure a couple of inverters and will report it here -
although I think the numbers mentioned are typical from my experience.  

This is pretty common with large power devices - many large filters in
motor drives and UPS warn of it on a sticker next to the ground terminal
and are also UL or ETL listed.  

Christopher Freitas
OutBack Power Systems
cfreitas at outbackpower.com
19009 62nd Ave NE 
Arlington WA 98223 USA 
Tel 360 435 6030
Fax 360 435 6019
www.outbackpower.com 

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