Renewable Energy Questions/Discussion > Automation, Controls, Inverters, MPPT, etc
Inverters pull lots of Amps from Batteries
ChrisOlson:
--- Quote from: Wolvenar on January 18, 2012, 05:20:43 am ---@ChrisOlson
This is an interesting addition that I have not heard a lot about.
I am curious how well this setup works for you
--- End quote ---
The only way I can describe how it works is "awesome".
--- Quote ---What is the loss of the "autotransformer" in your system?
--- End quote ---
It's a Xantrex T240 and I don't know the exact figures. But I think it's pretty negligible. Our house is totally electric - electric range, electric clothes dryer, electric 240 volt water heaters. We have everything electric because my wife has a phobia about having any sort of gas line coming into the house. She won't have it. The 240 volt loads are always leg balanced so those are taken off ahead of the transformer. The inverters put out their sine waves 180° from one another for the 240 split phase power. The transformer is used in "stepdown" configuration where the the 240 output of the inverters is stepped down to 120 VAC and this keeps the loads on the inverters perfectly balanced at all times.
I got the master's Peak Load Management programmed to bring the gen online if the load on the inverters goes over 20 amps (4.8 kW) for more than 2 minutes. They'll normally run the clothes dryer, or the electric range without the gen coming online. But if my wife turns on more than one thing, or I'm doing welding in the shop continuously, then the gen will start, the inverters switch the load over to the gen and the inverters "help out" with any load above what the gen can deliver. So, basically, we have a 6 kW gen and 8 kW of inverter power, so we have a 14 kW service in our house. When the load goes below 20 amps the master watches it and if the load stays below 20 for five minutes it then looks at bank status and if the bank needs charging it does a maintenance charge on the bank. If the bank status is still good it just shuts it off without charging the bank.
So I dunno. We like it. Haven't had a single problem with it since we put the new system in last year.
I theory, you could do it without a load balancing transformer. But then the master inverter might be carrying more load than the slave. And if the gen comes online, the legs on your gen are also unbalanced without a transformer and you would never be able to get full capacity out of your system when needed. If the water heater is going and pulling 4,500 watts, plus my wife plugs in her confounded infrared cooker thing on 120 volt that draws like 1.5 kW, then you got unbalanced load with one inverter delivering 3.75 kW and the other one at 2.25 kW. Now - my wife goes all out and plugs in a roaster or slow cooker on 120 volt, plus the 'fridge starts and the well pump starts. Your master inverter kicks out due to overload. With the transformer, the load stays balanced and the inverters never kick out.
Personally, I wouldn't be without it.
Edit: the other option for 120/240 split phase is to get a Xantrex XW, which has load balancing built in. But we wanted 14 kW service (with the gen) and got the SW Plus inverters brand new, plus the T240, generator start and aux load modules, remote control module for the master, AC Conduit boxes, and the whole shebang for a better price than two new XW's with all the bells and whistles. The XW's are a little over $4 Grand each with the AC panels and gen start. We got our setup for $6,500, and the SW-series inverters have a reputation for being damned near indestructible.
--
Chris
Watt:
Here is a link on Outbacks transformer and wiring. Might help understanding a bit about how they work for some of us.
http://www.outbackpower.com/pdf/archives/fw-x240_rev_b.pdf
I can't get the thing to finish loading but had it saved on my favorites.
DBCollen:
I thought the problem was with my internet connection. I have spent the last 3 days trying to download the flexmax 60 and Mate manuals from outback, no luck, gets part way through the download and stops with an IO error. Finally downloaded them from other sources just fine. Outback must be having trouble with thier servers.
RichHagen:
I downloaded the flexmax manual in pdf format from their site to review for possible use in a project I am involved with a few days back without incident. (except for the 150VDC (- deregulation) open circuit voltage limit in the manual) Rich
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