Inverters Grrrrr.

niel

Re: Inverters Grrrrr.

i hate to say it, but ng and propane are fossil fuels.

ChrisOlson

Re: Inverters Grrrrr.

Panamretiree wrote: »

When I hear about NG and propane being better than fossil fuels, in the short term maybe; however, the BTU content of NG and propane is far less than gas, diesel or a #2 type stove oil, and last but not least, bunker C - good old black gold. If you do the calks on BTU for each of them, not quantity, NG and propane are far more expensive than the rest

Yes, it is. Our Honda gasoline generator emits less CO2/kWh than our EcoGen propane generator did. That's because it's more thermally efficient.

There is no "free lunch" with fossil fuels. Only the efficiency of the device that burns them can be altered.
--
Chris

Panamretiree

Re: Inverters Grrrrr.

niel wrote: »

i hate to say it, but ng and propane are fossil fuels.

That they are, hope there aren't too many disillusioned people out there.

ChrisOlson

Re: Inverters Grrrrr.

Panamretiree wrote: »

That they are, hope there aren't too many disillusioned people out there.

I hate to tell you this, but there's LOTS of disillusioned people out there. The LPG and NG industries have pushed their product as "clean burning". When it actuality, diesel fuel is cleaner burning in a modern diesel engine than propane is in a gas cooktop.
--
Chris

Panamretiree

Re: Inverters Grrrrr.

ChrisOlson wrote: »

Yes, it is. Our Honda gasoline generator emits less CO2/kWh than our EcoGen propane generator did. That's because it's more thermally efficient.

There is no "free lunch" with fossil fuels. Only the efficiency of the device that burns them can be altered.
--
Chris

Did a survey for the Dorchester pen in New Brunswick because the system was being pressured to switch to NG from Bunker C because the NG pipeline was less than a mile away. The pen used $4M worth of Bunker C each year, Going to a #2 diesel fuel the cost went up to $10M per year, NG went through the roof at $20M per year. Dorchester pen is still using bunker C.

Cheers

Ernest

ChrisOlson

Re: Inverters Grrrrr.

Panamretiree wrote: »

The pen used $4M worth of Bunker C each year, Going to a #2 diesel fuel the cost went up to $10M per year, NG went through the roof at $20M per year

Yep. Better than 90% of the megawatt class diesel standby and prime generators run on either Bunker B or Bunker C HFO. There's a reason for that.
--
Chris

ChrisOlson

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
--
Chris

mtdoc

Re: Inverters Grrrrr.

ChrisOlson wrote: »

But I'm sorry to say that stacked GVFX's with gen support is not one of the viable options. That configuration is not even supported by Outback.
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Chris

Oh no- Not that old yarn again! Run away, run away....:p

It's the woman in house that is going get tired of not being able to do things because there's no power

I guess it's a good thing there aren't a lot of women on this forum...

Thankfully this is not an issue for my wife - she appreciates the idea of conservation and often gets on me to turn off lights, etc..

verdigo

Re: Inverters Grrrrr.

Well. I'v certainly got a lot for my money with this thread. If I had to pay consultants for all this information I could probably afford to buy a Radian and the bigger XW6048 and just see which one I like better. There is a lot of good information in the thread to refer back to and a lot to digest. I really appreciate all the good input from folks who live with these systems. This forum has become my version of porn. I do want to make the right call on an inverter. I think I would be better off buying more inverter than I can use initially.

My immediate plans are for a smallish 464 ah battery bank because I'm a retailer for Interstate battery, and as I have read I will probably kill my first set. I am thinking a 3 kw pv array to keep my charge rate at 10% or a little better. In a backup scenario I can get by in the short term on mostly 120 volt loads. I could heat water in the day time and using my old Honda em2500 I could run a space heater or a small air conditioner part time depending on the season.

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

Anyway. I'm going to have to read this thread a few more times to comment anymore without sounding like an idiot

Thanks again for all the input.

mtdoc

Re: Inverters Grrrrr.

Good luck verdigo.

Despite all the hoopla, varying opinions and finer points of disagreement - the reality is that any of those choices - XW, Radian or GVFX 3648s will do what you want and none are the wrong choice - so don't sweat it!

Have fun!

ChrisOlson

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
--
Chris

vtmaps

Re: Inverters Grrrrr.

ChrisOlson wrote: »

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

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

ChrisOlson

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.
--
Chris

Cariboocoot

Re: Inverters Grrrrr.

ChrisOlson wrote: »

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
--
Chris

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.

ChrisOlson

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
--
Chris

john p

Re: Inverters Grrrrr.

There is NO WAY that an auto transformer can clean up a MSW to look like a TSW..
Its something many of us have tried over the years and it just cant and doesnt work. If you think it does you need to adjust the o/scope so can show small sections of the wave form. You will see just about identical output to input..

mike95490

Re: Inverters Grrrrr.

ChrisOlson wrote: »

....
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 .....

ONLY, if the inverter will stay running. Many will see the big inductive load of a transformer, and crash.

ChrisOlson

Re: Inverters Grrrrr.

john p wrote: »

There is NO WAY that an auto transformer can clean up a MSW to look like a TSW..
Its something many of us have tried over the years and it just cant and doesnt work. If you think it does you need to adjust the o/scope so can show small sections of the wave form. You will see just about identical output to input..

Nope. An inductive load tends to smooth the "steps" of a MSW. And when you run it thru an auto-transformer it is physically impossible to precisely vary the flux in the core to imitate the "steps" so it smooths it further when the collapsing flux field induces the current in the secondary winding as the primary is switching polarity. It is not a mystery. It is a fact about how transformers work. And as I said, you don't get a perfect true sine wave. But it cleans it up enough so stuff don't buzz.

I could never get my bench grinder in the shop to start on our old MSW inverter. It would just hum and barely turn. But if I turned on the drill press first, and had it running, the bench grinder would fire right every single time.

If you try it with a square wave inverter that has no steps, then you're going to get square wave output from the transformer too, with the square corners rounded off. So it's not going to work that well with the very cheap MSW inverters that you can buy for 30 bucks off the shelf at Walmart. But it definitely works on the higher end MSW inverters like a DR/TR.
--
Chris

Cariboocoot

Re: Inverters Grrrrr.

Anybody got popcorn? This should be interesting.

ChrisOlson

Re: Inverters Grrrrr.

Cariboocoot wrote: »

Anybody got popcorn? This should be interesting.

Well, they say a picture is worth a thousand words. Only a good movie is deserving of popcorn.

I could demonstrate this with the MSW inverter in our fifth wheel camper with that bench grinder. It would take a bunch of extension cords running from the camper to the shop to do it. LOL!
--
Chris

ggunn

Re: Inverters Grrrrr.

ChrisOlson wrote: »

Nope. An inductive load tends to smooth the "steps" of a MSW. And when you run it thru an auto-transformer it is physically impossible to precisely vary the flux in the core to imitate the "steps" so it smooths it further when the collapsing flux field induces the current in the secondary winding as the primary is switching polarity. It is not a mystery. It is a fact about how transformers work. And as I said, you don't get a perfect true sine wave. But it cleans it up enough so stuff don't buzz.

I could never get my bench grinder in the shop to start on our old MSW inverter. It would just hum and barely turn. But if I turned on the drill press first, and had it running, the bench grinder would fire right every single time.

If you try it with a square wave inverter that has no steps, then you're going to get square wave output from the transformer too, with the square corners rounded off. So it's not going to work that well with the very cheap MSW inverters that you can buy for 30 bucks off the shelf at Walmart. But it definitely works on the higher end MSW inverters like a DR/TR.
--
Chris

I agree. A basic characteristic of an inductor is that you cannot instantaneously change the current through it, so the corners of any sort of square wave or stepped function are unavoidably somewhat rounded when passed through a transformer under load.

nsaspook

Re: Inverters Grrrrr.

How well it works depends on the transfer function of the transformer when acting as a bandpass filter. How much the odd harmonics at 3,5,7..etc will be reduced depends on the slope of the filter( big and heavy normally means faster high frequency rolloff), loading and the type of load (reactive or resistive). 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.

BB.

Re: Inverters Grrrrr.

Yep, filtered energy (after the MSW output) has to go somewhere. Either as useful work (filament light bulbs, resistance heaters) or as "wasted energy--aka heat" (circulating currents in transformers, induction motors, etc.).

-Bill

NorthGuy

Re: Inverters Grrrrr.

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).

ChrisOlson

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.
--
Chris

Cariboocoot

Re: Inverters Grrrrr.

Difference between masking the spike with its mirror image presented by the transformer (the electrical equivalent of "noise cancellation") and utilizing the energy as is done with a true sine wave inverter (Voltage spike turned into current; equivalent power available, not wasted as heat).

Short form: we don't want anyone thinking all they have to do is put an autotransformer on an MSW inverter's output and the get pure sine wave. It's not that simple.

BTW, you can also have horrible experiences with motors connected to inverters through transformers, as the residual magnetism in a motor can back-feed through the transformer and raise the Voltage at the inverter's output.

I'm a bit pressed for time today, but you guys can argue it amongst yourselves.

ChrisOlson

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.
--
Chris

ChrisOlson

Re: Inverters Grrrrr.

Cariboocoot wrote: »

Short form: we don't want anyone thinking all they have to do is put an autotransformer on an MSW inverter's output and the get pure sine wave. It's not that simple.

No, it certainly is not, as that's not how it works. And you still have to put up with the losses that are inherent in it. Just pointing out that most MSW inverters can be "cleaned" up with either an induction motor or a transformer so things like ceiling fan motors don't buzz. And as Mike noted, it takes a decent inverter to even handle the transformer. Just the act of connecting a transformer - with no load at all connected to it - to an inverter can put such an inrush load on an inverter than it can kill or crash the inverter. Like the transformer in my old copper-wound Lincoln welder pulls over 150 amps inrush when it magnetizes the core, just by throwing the switch on. Few inverters will handle that.
--
Chris

NorthGuy

Re: Inverters Grrrrr.

ChrisOlson wrote: »

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.

I searched for square waves and transformer pictures, and I found this document. Looks like a square wave put through a transformer remains a square wave with quite sharp edges - rise and fall time is only 5us. Certainly depends on the transformer, but it's not much of a smoothing by any means. They say that bad transformers would hava a slower rise and fall time at the edges.

Transformer is certainly different from an inductive load. If no load is connected on the other end, it doesn't consume any power. When you connect a load to the secondary, I think the power factor on the primary should be the same as if the load was connected directly without a transformer (assumong it was 1:1 transformer). So that if you connect a heater to the secondary, the whole system will have power factor close to 1. If you connect a motor, you get a power factor of 0.6 or so.

That's what I always believed, but I must confess I never could get a good understanding of the transformers.

BB.

Re: Inverters Grrrrr.

Transformers (and induction motors, etc.) have a whole bunch of design criteria that affect how they perform. Transformers tend to work better" at high frequencies (why a 50Hz transformer should work fine on 60Hz, but a 60 Hz transformer may not work as well on 50 Hz). And why aircraft use 400 Hz AC vs low frequency AC (smaller/lighter transformers).

But, you can have construction/material choices that will affect high frequency performance, etc.

-Bill