Inverters Grrrrr.

Re: Inverters Grrrrr.

Another thing about vertigo's proposed installation is that us guys could probably get by on a couple marine deep cycles, a 250 watt inverter and a single CFL that don't work unless you tap on it. It's the woman in house that is going get tired of not being able to do things because there's no power. For better than 7 years we scrimped on every watt and I even had to get up at 3:00 in the morning in the dead of winter to start a stubborn gas charger because the batteries were dead. We couldn't afford the stuff we got today because it (especially solar panels back then) was astronomically expensive.

In the long term the price of inverters really has not gone up. A SW4024, back in the day, was around $2,500 new. There was no such thing as MPPT controllers because nobody could afford one, even if you knew what it was. So the price of RE stuff has come down, or remained constant, in the face of inflation. So it's easier today to afford a "comfortable" and reliable system than it was 10 years ago, simply because there's more to choose from and it's all pretty good stuff.

I know my wife thoroughly enjoys FINALLY being able to do what she wants in the house, when she wants to do it. She doesn't even know if or when the generator starts to help out with the loads. She had problems understanding the menus in the SCP, and since it's on the kitchen wall she figures it's important and she needs to know about it. So I renamed the XW system components from the defaults so it's easier for her to understand. And she knows that we check the fuel in the generator once a week, and if the gauge shows below half we grab the can and fill it up.

When your woman is happy, so are you for the most part. So most of what I have learned about how to make this all work is because of what she has wanted over time. If it was up to me I'd live in the shop and sleep in an old recliner and eat some junk food I found and heated up on the top of the woodstove. And I'd be perfectly happy with that. But my wife is a little more demanding
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Chris

Re: Inverters Grrrrr.

verdigo wrote: »

A question for Chris. Will the XW inverter be able to use my 120 volt generator to feed both legs using my auto transformer?

Yes. I use our old Trace T240 transformer with our Champion generator, which is 120V only. It works fine. It should work fine with the Radian inverter too.

Split phase power consists of two sine waves that are 180 degrees out-of-phase with one another. The amplitude of each sine wave is such that there is 120V between either one at peak and the reference (neutral, or zero line). Because one sine wave will be at full 120 positive when the other is at full 120 negative, the total difference, or potential, between the two sine waves is 240.

All an auto transformer does in step-up mode is generate a mirror image of the 120V input to the primary winding. So the output of the secondary to neutral is still 120V but it's 180° out-of-phase with the input. So you get 120V from the generator "hot" to neutral, you get 120V from the transformer secondary output to neutral, and you get 240V between the generator output and the transformer secondary output. The PSX-240 has such heavy windings and core that it's very efficient and the inverter basically can't tell the difference between the transformer on a 120V generator and a true split-phase generator.

Edit:
Interesting thing about an auto-transformer; you can hook one up to a modified sine wave inverter and get almost (but not quite) pure sine wave output from the transformer secondary to neutral
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Chris

Re: Inverters Grrrrr.

vtmaps wrote: »

Doesn't that mean that the transformer runs hotter (and less efficiently) because it is dissipating the non-sine wave energy?

Not totally sure. The transformer primary buzzes quite a bit on MSW. I just happened to think of it because some people don't need a big system for backup when they have grid power. Schneider still builds and sells the Trace DR re-designed as the TR
http://www.schneider-electric.com/products/ww/en/7000-solar-off-grid-and-back-up/7010-inverters-chargers/7655-tr/?BUSINESS=7

There's a couple that lives off-grid on their farm near us that have had a Trace DR inverter powering all their stuff for 21 years. Lots of folks don't consider these because they're MSW and therefore considered "second class". But they run most things fine and they are pretty solid and reliable inverters.
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Chris

Re: Inverters Grrrrr.

Cariboocoot wrote: »

You've tested this with a scope? It would be an interesting thing to see.

I suspect what you're really seeing is THD "dilution", not correction.

Never looked at it on the scope. But due to the way the magnetic field collapses on the primary when it switches polarity 120 times/sec it induces a smoother sine wave curve from the secondary. You can get the same effect by hooking up an induction motor to a MSW inverter.

It came to mind because the couple I mentioned above have the old heavy duty Trace transformer (not the T240 - can't remember the model of it) for their well pump. The fellow that put their system in 21 years ago (and he's still putting in off-grid systems in the North Woods here) set it up so the 120V stuff is powered from the transformer instead of the inverter. Their ceiling fans don't even buzz and they got an electric 'fridge and everything - 21 years and still running fine
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Chris

Re: Inverters Grrrrr.

Anybody got popcorn? This should be interesting.

Re: Inverters Grrrrr.

nsaspook wrote: »

That odd harmonic energy still will be present as high levels of reactive fields surrounding the core and will cause IR losses in the inverter, transformer windings and heating of the core iron due to saturation/hysteresis/eddy-currents during heavy loads.

I would say that's almost a given. I'm just pointing out that it was a "trick" used by that installer for years on the old DR inverters when he installed them in off-grid homes and cabins in the Wisconsin North Woods. I talked to him not too long ago and he's since switched to installing Magnum PAE's in places that need 240V for a well pump. But there's over 100 installations he did over the years that are still running with those old DR's and the old Trace transformer that was rated for 6 kVA.

I believe (but don't remember for sure) that the model number used to be a T220. The T240 replaced it, but was only rated 4500 VA instead of 6000 VA.
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Chris

Re: Inverters Grrrrr.

NorthGuy wrote: »

I don't know much about transformers, but I always thought that the voltage on the output of the transformer is the exact replica of the input waveform (given frequency is high enough).

NorthGuy - the voltage or peak of the sine wave will be approximately the same (there's a small amount of insertion loss). But the waveform is not due to hysteresis in the core.
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Chris