What kind of inverter is more reliable? A transformer based one or Non Transformer one??
rollandelliott
Solar Expert Posts: 834 ✭✭
What kind of inverter is more reliable? A transformer based one or Non Transformer one??
I just started welding and there are two types of welding machines basically ones that use a transformer and are huge or smaller new inverter design welders. It seems like the newer machines with OUT a transformer have a bad repuation of failiong early.
I'm wondering if the same is true of solar grid tie inverters???
I just started welding and there are two types of welding machines basically ones that use a transformer and are huge or smaller new inverter design welders. It seems like the newer machines with OUT a transformer have a bad repuation of failiong early.
I'm wondering if the same is true of solar grid tie inverters???
Comments
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Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
The difference is low frequency transformer versus high frequency transformer. The use of a high switching frequency inverter allows a smaller transformer, but there still is a transformer.
A low frequency transformer design has no semiconductor devices on the output side so there is less vunerable electronics that may be subjected to high voltage surges due to lightning strikes on the power grid. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
I'd say it's not a valid comparison.
In the welding case, you are comparing the durability of transformers to the durability of inverters (and rectifiers). Inverters are less durable components than transformers so they may be at a disadvantage.
In the solar case, all products must have inverters. The presence of a transformer (or lack thereof) really doesn't affect the longevity of the inverter component that has to be there in any case.
To put in another way...
In the welding case, adding an inverter (and rectifier) means adding things that are more likely fail.
In the solar case, removing the transformer just means one less component that can fail (even if it as more reliable type of component). -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
RCinFLA has a very valid point re lightening surges etc. Output transformers are usually wired to isolate the internal electronics from direct connection with the AC output. Not so with non output transformer designs. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
lightning induced power on a transformer will backfeed into the primary side of the transformer from the secondary as transformers are not one way. lightning will still damage the electronics. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer olightning induced power on a transformer will backfeed into the primary side of the transformer from the secondary as transformers are not one way. lightning will still damage the electronics.
Agreed, it's most certainly capable of doing that, but if the spike is equal and in sync on both AC output terminals of the xformer, as could sometimes be expected depending on how the cables were run, and if those spikes are not too big, some protection would be provided over that of spikes fed directly into the output FETs. Higher voltage spikes of course would arc right across from primary to secondary as if the xformer wasn't even there. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer orollandelliott wrote: »What kind of inverter is more reliable? A transformer based one or Non Transformer one??
I just started welding and there are two types of welding machines basically ones that use a transformer and are huge or smaller new inverter design welders. It seems like the newer machines with OUT a transformer have a bad repuation of failiong early.
I'm wondering if the same is true of solar grid tie inverters???
I haven't heard of any transformerless (non isolated) grid tie inverters having a lower reliability issue than their isolated counterparts. I would be interested to hear of any.
The thing about transformerless GT inverters is that their efficiency can be a few percent better than isolated types.
I do not know of any non-isolated battery based inverters though, if that is what you mean. I would also be interested to hear of any of those.
High frequency (small xformr) or low frequency (large xformer) types...
(or maybe I just haven't quite woken up yet ?)
boB -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
The history of "transformerless" solar inverters is pretty short so not much empirical evidence to go on yet. I can tell you though that in the field of consumer electronics, when that industry changed over to "switching" type power supplies (from the good old step-down transformer) failures went way up. Hey - but it saved the manufacturers weight and cost.... My take on it is that a heavy transformer made for 60hz naturally absorbs or filters out higher frequency spikes and surges. Switching supplies and worse - transformerless designs are more susceptible to these disturbances which are then passed to the low voltage electronics on the secondary side which get toasted. I don't care if the transformer type inverter is a heavy beast to lift one time onto the wall, I think its chances of lasting ten years are much higher. I'm not saying that transformerless designs cannot be robust, but it is in their nature to operate at higher frequencies and therefore be susceptible to higher frequency noise. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
I always wondered why the the the two types of inverters were about the same price? The heavy sma inverters must have a ton of copper wire in them to make them that heavy. A novice like me would think that would make them more expensive? Maybe the electronics used in " non transformer" inverters is expensive, so it is a wash? -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer orollandelliott wrote: »I always wondered why the the the two types of inverters were about the same price? The heavy sma inverters must have a ton of copper wire in them to make them that heavy. A novice like me would think that would make them more expensive? Maybe the electronics used in " non transformer" inverters is expensive, so it is a wash?
A lot of the weight in any low frequency transformer is the steel core. That is not nearly as expensive as copper, although in the form it it used for transformer cores it is not exactly cheap either.
And, yes, the rest of the electronics required for transformerless does affect the cost and price. Another factor is that the price is based partially the competition, and the two types are direct competitors.SMA SB 3000, old BP panels. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oI'm not saying that transformerless designs cannot be robust, but it is in their nature to operate at higher frequencies and therefore be susceptible to higher frequency noise.
Where are you getting that transformerless solar inverters operate at higher frequency than isolated ones? Both create a 60hz sine wave, and both use capacitors and filters to smooth the wave. I'm no inverter engineer, but I would guess the frequencies are pretty much the same. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oWhere are you getting that transformerless solar inverters operate at higher frequency than isolated ones? Both create a 60hz sine wave, and both use capacitors and filters to smooth the wave. I'm no inverter engineer, but I would guess the frequencies are pretty much the same.
Reread RCinFLA's post #2. In "transformerless" there is a transformer and it works at high frequency so it can be small. After that transformer the power must be converted to 60 hz, thus the need for electronics on the output of the transformer.
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oReread RCinFLA's post #2. In "transformerless" there is a transformer and it works at high frequency so it can be small. After that transformer the power must be converted to 60 hz, thus the need for electronics on the output of the transformer.
--vtMaps
I believe there is some confusion here. The more recent type of solar grid tie inverter is a non-isolated, also called a non-grounded inverter. This means that it is not isolated
by a transformer, either large or small. They will both typically use high frequency for the PWM to make the low 50/60 Hz low frequency part.
The non-isolated are also non-grounded because you do not ground the positive or negative PV array lines. An isolated with transformer
inverter is typically grounded on the PV negative line somewhere. That's where GFP comes in. There was an article about this recently
in Solar Pro magazine that explains it pretty well. There are some gotchyas on the non-isolated inverter as far as their internal
ground fault protection goes.
The non-isolated one may not use a transformer but both types will usually incorporate inductors, which looks sorta like a transformer.
boB -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oI believe there is some confusion here.
Thanks for clarifying that
--vtMaps 4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
In transformerless designs, the power is transferred from the input to the output using a relatively small circuit running at frequencies of 20khz to 100khz (above the audio range). The circuit topology can be a switched capacitor, or a switched inductor, or even a transformer (but being so small - the inverter is still referred to as being transformerless as there is no large heavy transformer). The circuit is transferring the power in little small packets at high frequency as opposed to large packets at 60hz. Modern high-speed transistors that minimize the switching losses make this possible and save a lot of cost because the components are much smaller. The switching energy packet size is constantly adjusted to achieve the desired output voltage in sync with the grid, and then smoothed with output inductors to give a nice 60hz sine waveform. All very wonderful, but tends to be more susceptible to power surges than the big old large, slow circuits.
Capacitors are a key element in any of these circuits, and the electrolytic type is generally used as it is the smallest and cheapest in the larger sizes needed for power circuits. However, capacitors specs do not typically address the range of frequencies each part is suitable for and it is very common for electrolytics to get put into these switching type power supplies at frequencies far above what the parts are good for. Specs like dissipation factor that determine the cap's frequency range are rarely given or used. I've seen manufacturers like Matsushita and Panasonic take 10 years and dozens and dozens of design iterations to figure out this error. As the electronics industry pushed the switching frequencies higher and higher, not many designers thought about the effect this would have on electrolytics and had horrendous failure rates (well, maybe failing after 5 years is a good thing as planned obsolescence). Even then, most of the time they still just use "high quality" electrolytics instead of going to something like a film cap (bigger and more expensive) that is inherently better at high frequencies. For example, after several years of pronouncements of how reliable their caps were, Emphase finally redesigned their microinverter to eliminate the electrolytics altogether. Personally for reliability, I like that big heavy SMA inverter. (even though I've had some of those fail due to buzzing or loose transformer windings). My experience is that long term reliability in power circuits is not easy. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Lot of good info in this thread.
As for what type is more reliable... the transformer type by far.
That is the one with the big honking 60 cycle transformer on its output.
Reason = They provide an isolated output enabling you to ground the neutral.
The MSW inverter must have complete output isolation.
Just one little momentary touch to anything and your inverter is gone.
I use both types but when it is a MSW the first thing following the inverter is an isolation transformer. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Thanks for Sharing. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Transformerless inverters are not the same as MSW. I believe he is asking about inverters like the Sunny Boy TL series and REFUsol. As to which type is more reliable in the long run, that's hard to say because TL inverters have not been in the field that long.Lot of good info in this thread.
As for what type is more reliable... the transformer type by far.
That is the one with the big honking 60 cycle transformer on its output.
Reason = They provide an isolated output enabling you to ground the neutral.
The MSW inverter must have complete output isolation.
Just one little momentary touch to anything and your inverter is gone.
I use both types but when it is a MSW the first thing following the inverter is an isolation transformer. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Its not easy to give an absolute answer as to what type of inverter is the most reliable. Im assuming we are talking about "normal" battery driven inverters.
I test hundreds of them every year, all types ,many never seen for sale to the public.. And my conclusions are as follows.
Transformer types are on average less efficient .
Transformer types will in most cases start difficult loads easier.
Non transformer types are more reliable and tollerant to output shorts
Non transformer types come in two types the more common high frequency switching type ,usually above 20khz and the far supperior low frequency switching type ,around 2khz. By design the low frequency types can handle difficult starting loads at least equal to transformer types and are very tollerant to output shorting.
Transformer types can sometimes be "noisy" so need to be placed where they cant easily be heard.
Transformer types and low frequency non transformer types all tend to be more reliable that the "everyday" high frequency switching types, Reason : They are designed for heavy duty use and all the components in them are opperating well within their limits. High frequency switching types are built to the lowest price possible and many of the components,especially the caps are opperating at or over their design limits..
Ya get what ya pays 4. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
No, the original question posted was about grid-tied inverters.Im assuming we are talking about "normal" battery driven inverters. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oNo, the original question posted was about grid-tied inverters.
I do not know of any battery based transformer-less inverters. Just grid tie.
It can technically be done but I haven't heard of any. If there is one or more of these, please let us know.
boB
PS... I haven't looked for one, either though. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oI do not know of any battery based transformer-less inverters. Just grid tie.
It can technically be done but I haven't heard of any. If there is one or more of these, please let us know.
boB
PS... I haven't looked for one, either though.
1000w transformer battery input inverter will weigh about 60lb and be about the size of 2 shoeboxes. Its how they all were in 70,s ande 80,s .But most were less than 500w.
1000w transformerless battery input inverter will weigh about 6 lbs and be about half the size of a shoe box -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Mabe I should have read the original post before rambling on.
I cant help much with the original question as my experience is limited to destroying 4 x1.5k brand new grid tie inverters in one day.Now no one will give me any more to experiment with. But I did eventually(4 grid tie and 3 battery inverters later) get a battery input inverter to act as the "grid" to keep the grid tied inverter working from the solar panels.. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Sunny Island, Sunny Boy.Mabe I should have read the original post before rambling on.
I cant help much with the original question as my experience is limited to destroying 4 x1.5k brand new grid tie inverters in one day.Now no one will give me any more to experiment with. But I did eventually(4 grid tie and 3 battery inverters later) get a battery input inverter to act as the "grid" to keep the grid tied inverter working from the solar panels.. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer oSunny Island, Sunny Boy.
And what would be the challenge and what would I have learnt from them? They are designed to do that. The ones I had(took) were not designed for that.The ones I used were going to simply be installed and their performance verified.And as they were sitting there one whole day the next morning temptation got the better of me.
Iknew almost nothing about grid tied inverters up to this time.Now I know a little. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o1000w transformer battery input inverter will weigh about 60lb and be about the size of 2 shoeboxes. Its how they all were in 70,s ande 80,s .But most were less than 500w.
1000w transformerless battery input inverter will weigh about 6 lbs and be about half the size of a shoe box
Hi John. I was looking for a brand and model possibly. Just because it is small and light-weight does not mean it is transformer-less.
I have never heard of one is why I was wondering what you (or anybody) had seen for one of these.
thanks,
boB -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Bob in the context of transformer or non transformer in an inverter. A transformer one is one that has a very large and heavy laminated transformer.ie the old type of transformer you use for say 12v to 240v or the slightly lighter toriodal transformer.
And usually old style simple switching DC to supply the transformer with a square wave..or some variation to vaguely resemble a sine wave.
Transformerless ones do technically use very small ,usually no more than a few turns of heavy wire on a air core.,but sometimes on an iron core. But they are considered transformerless.
Industrial inverters in many cases use a larger version of that very small transformer because the low switching speed but are still also considered transformerless. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
We know what transformerless vs. transformer inverters are; he was asking if you could give him a specific example of a transformerless battery inverter.Bob in the context of transformer or non transformer in an inverter. A transformer one is one that has a very large and heavy laminated transformer.ie the old type of transformer you use for say 12v to 240v or the slightly lighter toriodal transformer.
And usually old style simple switching DC to supply the transformer with a square wave..or some variation to vaguely resemble a sine wave.
Transformerless ones do technically use very small ,usually no more than a few turns of heavy wire on a air core.,but sometimes on an iron core. But they are considered transformerless.
Industrial inverters in many cases use a larger version of that very small transformer because the low switching speed but are still also considered transformerless. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
I don't believe that U.L. would approve a non-isolated battery based inverter system or a non-isolated GTI for U.S. market. It might be possible to get by U.L. if the manufacturer can prove a double or triple failure false-safe scheme. Back in the 50's, 60's and 70's there was transformerless AM radios and T.V.'s the design of which would not be U.L. approved today. Those over fifty may remember the fun when the plastic volume control or tuner knob broke off or was loss.
I think there are such types of inverters in Europe. Most all multi-KW commercial U.P.S units use 400-500 vdc battery stack of AGM batteries, but still have isolation transformers for safety.
If you have a DC voltage greater then sinewave peak (plus some additional voltage for switching losses) you can make a battery based or PV GTI totally transformer-less.
For 240 vac system you need a minimum D.C. voltage of 370 vdc + switching and high freq filter losses, or at least about 380 vdc to account for possible high end line grid voltage of 260 vac rms. You can put a bunch of batteries or PV panels in series to do this. It is about the same voltage on hybrid auto battery packs. Just don't come in contact with the DC voltage. Unlike A.C. it can lock up your muscles so you can't let go.
As for a GTI PV system made with a high voltage, transformerless, PV stack, it does not give much operating room factoring in all the variables that cause Vmp & Voc voltage variation and stay within the window of 400 vdc min. for Vmp and 600 vdc max for Voc. The 600 vdc max put you within the U.L. acceptable limit for residential/customer distribution voltage. -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Transformer-less or "ungrounded" grid tie inverters are becoming pretty popular in the US after EU started doing this...
Here is one link that talks about it.
http://www.solarworld-usa.com/system-designers/~/media/Global/PDFs/Grounded-vs-Ungrounded.pdf
There was a decent article in Solar Pro magazine a couple of issues ago about this very thing. It's mainly an NEC thing.
There is a list of ungrounded (transformer-less or non-isolated) inverter companies here...
https://homepower.com/articles/ungrounded-pv-systems/page/0/2
I don't think I would want to use a non-isolated battery based inverter, myself.
boB -
Re: What kind of inverter is more reliable? A transformer based one or Non Transformer o
Actually, there are several of them. REFUsol and the TL line of SMA Sunny Boy's, for example.I don't believe that U.L. would approve a ... non-isolated GTI for U.S. market.
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