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Inverter won't accept AC input
By magneticanomaly, Section Controls Posted on Wed Dec 24, 2008 at 03:32:22 AM MST
problem with inverter-charger

I have an off-grid solar power system I built that has been up and running for about three months. Have about 800W pvs, lots of second hand batteries from standby system via scrapyard, and Outback FX2524 inverter.
I have a lovely 50 year old 500 lb 120VAC 1800RPM 3KW generator driven by 1-cyl Wisconsin engine, that I have used to run my machine shop for 20 years. But the FX2524 does not like it. When I try to use charge function on the FX 2524, it is almost impossible to get it to accept the AC from the generator. The FX gives error message saying that the AC frequency is BOTH too high, and too low. I do not know the exact frequency I am running at, but I can adjust the generator RPM over a wide range, and SOMETIMES the inverter will "lock in" and accept it, but often not at all.
I've tried Outback Tech Support, they basically gave up and said I need a new generator. I tried their Forum, and found another guy with a much fancier generator, and same problem.
Any ideas much appreciated!

Inverter won't accept AC input | 12 comments (12 topical)

Re: Inverter won't accept AC input (3.00 / 0) (#1)
by Madscientist267 on Tue Dec 23, 2008 at 09:09:39 PM MST

Stab in the dark here, as I'm not familiar with the exact model you're dealing with...

How does it react to grid input? May seem like a stupid question, but could have been overlooked (wasn't mentioned as already excluded) and could help pinpoint source waveform vs inverter issue... Just my 2c...

Steve

Re: Inverter won't accept AC input (3.00 / 0) (#2)
by Airstream on Tue Dec 23, 2008 at 09:32:18 PM MST

Older units had no/low concepts of the low noise electronics require. Looking at an oscilloscope trace of the units output could be very enlightening or even frightening from sawtooth waveforms or resonances in the windings throwing some peculiar spikes down the output lines.

If the generator is unloaded when dedicated to the inverter have you tried placing an AC resistance load in parallel with the inverter input - say a 60 or 75 watt bulb, and/or maybe a small value 440V motor run capacitor across the outputs too as a filter network? I'd say once of the whole-house surge protectors as an output filter too but the antique power plant might eat it as a snack...

Re: Inverter won't accept AC input (3.00 / 0) (#3)
by laskey on Tue Dec 23, 2008 at 10:58:25 PM MST

It sounds like your gen's frequency is oscillating. Your gen is not controlling it's frequency tight enough for your inverter to be happy. I think this because you can get it to lock by messing with the RPM adjustment. You need to source (or build yourself) a frequency synchonizer... a device that detects the frequency out of the gen, and automatically adjust the gen's RPM up or down as required to provide a stable frequncy out. Heck it probably has one on it that just needs some maintainence, they usually come with one.

[ Parent ]

Re: Inverter won't accept AC input (3.00 / 0) (#4)
by Colaman on Wed Dec 24, 2008 at 03:17:12 AM MST

Single cylinder? With a honkin great big flywheel? (I take it that's a yes with a 500lb mass)

It's quite possible that the speed is varying too much between power strokes. Seeing as a single cylinder engine has three non-power-producing strokes, it's quite possible.

Only real solution to that is to add extra mass to the system to keep the speed variation down as much as possible. I take it that it's not direct-drive, so put extra mass on the generator head side of the drive system if possible to give a bit of inertia as it spins faster. Another motor with a small drive pulley (unloaded, just spinning) run off the same drive belt might help.

Re: Inverter won't accept AC input (3.00 / 0) (#7)
by wpowokal on Wed Dec 24, 2008 at 07:13:54 AM MST

Ok I will throw my two bobs worth in here, the motor you describe will exhibit varying frequency, single cylinder.

Those motors have 'B' class governors, meaning they are slow to react to load so speed droops. Generally they do not respond well to starting large loads because of this. As others have stated some inverter/chargers may/will handle it but for my money you are drawing a long bow.

allan down under
"Dream as if you'll live forever, live as if you'll die today." James Dean
[ Parent ]

Re: Inverter won't accept AC input (3.00 / 0) (#5)
by halfcrazy on Wed Dec 24, 2008 at 03:38:46 AM MST

the outback inverters can be real fussy i use a lot of magnum energy inverters and i can tell you they will lock on to anything i have a lister diesel with the flywheels "wieghs like 1200 pounds" and it locks right on no problem but i am almost positive the outback wouldnt. Hm maybe i see an experiment here.
I would say if you have a nice low rpm older generator i wouldnt buy another i would either make outback work with you or buy a magnum.

Re: Inverter won't accept AC input (3.00 / 0) (#6)
by MattB on Wed Dec 24, 2008 at 06:31:38 AM MST

I sometimes have similar problems with my similar system.. FX3624 I think, 50+ year old 2500W generator powered by a 2 cyl Fairbanks (worn out)...

That charger draws a lot.. puts about 55A into the batteries, so it's pulling well over 1kw off the generator. If that generator isn't running just right, the charger in the inverter will bog it down, lowering RPMs to a point where the inverter no longer likes it's power.

I generally have to get the generator running, and sit next to it and make adjustments right when the charger starts to kick in and keep the RPM up to speed. It can be quite frustrating...

I pretty much wrote it off as needing to rebuild that generator... the motor just isn't as powerful as it once was.

Maybe try a different generator if only as a diagnostic tool, and measure the exact output of the one you have...

Re: Inverter won't accept AC input (3.00 / 0) (#11)
by tomtmook on Thu Dec 25, 2008 at 09:27:45 PM MST

Can you drop the charge current on the Outback? Maybe not draw so much load that it slows the generator RPMs down?

[ Parent ]

Re: Inverter won't accept AC input (3.00 / 0) (#8)
by RUFUS on Wed Dec 24, 2008 at 08:27:21 AM MST

Just a thought
Would you consider going D.C. with the output?
An old doll like that with a lot of freq variation
shove the output through one of those
big three phase bridge rectifiers rated 1200A.
and charge your batteries directly, you have to
babysit the thing anyway, just thinking out loud

RUFUS

Re: Inverter won't accept AC input (3.00 / 0) (#9)
by electronbaby on Wed Dec 24, 2008 at 02:37:23 PM MST

This is the reason why I built my axial flux listeroid gen. The Outbacks have been known to be fussy while synching to a generator. Outback states this in the manuals, if you havent seen it, I would go back and read more carefully. You also could search it on their site, quite possibly on their forum. I used an MX on the DC side of the generator so you wouldnt have to baby sit it as much. This works very well. There are others that have done the same Im sure.
Have Fun!! RoyR KB2UHF
[ Parent ]

Re: Inverter won't accept AC input (3.00 / 0) (#10)
by tanner0441 on Wed Dec 24, 2008 at 03:38:59 PM MST

Does the generator have electronic AVC or is it an Isontal Regulator? I had a similar problem with a microwave oven the timer looked like a fruit machine. When I looked at the output on a scope there was more noise and rubbish than I had ever seen. The scope wouldn't lock had to do single sweep.

Isontal regulators are a set of contacts controling the excitation, and there are small capacitors across the contacts, they suffer from heat.

I built a filter with a big coil out of a welder and three 400V 55Uf capacitors.

Brian.

[ Parent ]

Re: Inverter won't accept AC input (3.00 / 0) (#12)
by magneticanomaly on Mon Jan 19, 2009 at 09:45:52 AM MST

Problem solved!

Steve Higgins engineer at Outback told me that the freq too high AND too low is the message the inverter gives for EITHER fault.

And I got a "Kill-A-Watt", which told me that my genset is not turning at 58 HZ until voltage is up at 135. I had not tried pushing the governor up that high.

Inverter locked on to 135 V @ 58 HZ with no problem, stayed with it through freq variations from 57.8 to 60.1.

Check your frequency! Thanks, Steve.

John

[ Parent ]

Inverter won't accept AC input | 12 comments (12 topical)

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