Xantrex/Onan Surging

 I live off-grid and use both PV/battery and generator power.  I used a
cheap Yamaha portable gas generator successfully for years and then
decided to get a 'nicer' stationary Onan RS12000 in 2004.  It ran well
for a short time and then started surging when charging through a
Xantrex SW 4024 (120v only).  The surging starts shortly after start-
up and is about a 1Hz cycle with AC Hz cycling between 57 and 63 Hz.
After several technician visits and replacement of the governor
control board as well as the main control board, Cummins has declared
that nothing is wrong and that the inverter/charger is the problem -
it still surges. I upgraded recently (after a lightning strike) to the
XW4024 (120/240v) with hopes that the two legs would help.  Same
problem - maybe worse. I usually need to keep the charge rate down
near 1,500W (on a 10kW generator!!) or else it will surge out of
acceptable Hz range and the inverter will disconnect.

I also use (as backup when the Onan will not run) a relatively crude
welder/generator a backup without any surging issues.

I am wondering if there is an inherent response incompatibility
between the Xantex charge controllers and the Onan governor
controller.  Are the natural frequencies of the controllers too close
and a harmonic is created (forgive what might be a stupid conclusion -
I am a mechanical guy)? Is there a simple fix/test? A way to dampen
the response?

Or did running with only one leg for some time do permanent damage to
something?

Help!!

Thanks,

Tim

  On Mon, 29 Dec 2008 19:15:14 -0800 (PST), timothysrourke



Yes.  basically the Xantrex and generator are fighting with each other with
time constants just right to oscillate.  If you'll find and post the URL of
the manual for that generator, I'll help you figure out what to do. Preferably
the service manual where it shows the governor setup.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
I'm going crazy. Wanna come along?

 
Thanks. The manual is not avail on-line.  I have scanned the top-level
schematic (pdf), but it does not appear that I can attach a file.
Ideas?

 On Tue, 30 Dec 2008 16:03:28 -0800 (PST), timothysrourke



If it's not too huge, just attach it to an email.  I'm on dial-up so be
gentle.  My email address is on the home page of my website.  Just go there,
click "email john" and you have it in a spam-proof format.

If it's larger than a couple of MB, drop me an email and I'll point you to my
private file stash.
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
Okay, okay, I'll take it back ... UNfuck you!

 

I wonder if you have any thoughts applicable to my situation.

I've had a similar problem for years with my Kohler 12RZ and a pair of
SW5548's.  The generator has an electronically controlled governor.  After
swapping control boards, and carefully adjusting the manual mixture control
in the LP fuel line, the surging, which is worse at higher outputs, is at a
point where, although audible, it does not seem to affect anything (other
than clocks that are tied to AC frequency), and no longer causes the
inverters to disconnect the generator, which it did initially.

I limit the draw from the generator (40A per leg to the chargers; 45A per
leg total), but this is still at about 90% of the generator rated output.

I don't have access to the schematics just now -- I may in a few weeks,
though.  (I'm not sure if the schematics for the governor are in the
manual).

Any ideas as to what to look for to try to improve things?  Or, since it
seems to be tolerable, should I just ignore it.
--ron