PVI-5000-OUTD-US 5000 watt Inverter

mradtke

Hello,

Most of you have probably read my chain (rant?) titled "Fronius MPP Hunting" in the "Grid Connected Solar Electric and Wind" forum. I talked about this inverter there, but perhaps this is the appropriate place to post a review.

Power-one does not seem to have a large presence in the US inverter market yet. They produce a series of wind and solar inverters as well as a number of other power products. As I write this, their inverters are available directly from them. Their web site is: http://www.power-one.com.

The Power-One PVI-5000-OUTD-US 5000 watt Inverter, and its 6000 watt sibling have dual independent MPP tracking inputs. They are unique in the US inverter market in that they are transformerless in design (UL 1741 certified). The dual inputs allow the most efficient use of dissimilar arrays, or arrays with different orientations. The transformerless design yields a somewhat higher efficiency than the transformer isolated designs that are familiar in the USA. These inverters have a 96-97% conversion efficiency over most of their power range.

The increase in efficiency has a price though. Most installers are not familiar with the transformerless design and my be reluctant to make the wiring modifications necessary to meet code. I believe that the result is an overall safer system than is traditionally tolerated. My installer was open to change.

These related inverters include an attached DC disconnect and wiring box, as well as software for data collection and analysis.

I found that the unit was well constructed. It is convection cooled and very quiet in operation. During our 70-80 degree afternoons the inverter has only been warm to the touch while inverting about 3800 watts. I will have to report again when our temperatures get over 100 degrees and the inverter is handling more power as well. The Power-One folks seem very friendly and offered good support during the installation.

I'll add to this report as my experience grows. Please feel free to ask questions or add your comments.

Thanks for reading this,
Mike

LucMan

Re: PVI-5000-OUTD-US 5000 watt Inverter

This is my experience with Power One inverters,( just the facts.)
In June 2007 I had a 5.2KW grid tied BP PV system installed at my home (26 200watt panels- two 13 panel strings). The contractor originally had specified that they were installing 2 Xantrex inverters. When the system was completed I had 1 Magnatec Aurora PVI 3000 (Power One) and 1 SMA 3800 inverter. After a month of operation I noticed that the daily output of the Magnatec inverter was approximately 800-1000 watts less than the SMA on a full sun day. Also noticed that the output at my solar noon was considerably less than than the SMA.
I don't want to go into a long story about all the problems that had transpired with the solar contractor during the installation because it would just take to long and serve no purpose.
I called the solar contractor and asked him to replace the Magnatec with another SMA inverter as the Magnatec was not as efficient as the SMA.
They came and replaced the PVI 3000 with a SMA 2500. This solved the problem and both systems output were within a few watts of each other at solar noon and for the day.

mradtke

Re: PVI-5000-OUTD-US 5000 watt Inverter

LucMan,

Thank you for your comments.

You have pointed out an advantage of having two inverters. Everything else being equal, that provides a good way to check some of the system operation. If you read my long chain on my Fronius inverter, you may notice that it took me quite a while to notice the problem.

Because I was so easily fooled by the Fronius, I have been watching the Power-One very closely. Everything seems right on with it and all indications are that it is performing better than expected taking both the Fronius oscillation and the modest increase in efficiency into consideration. However, it will be a few more months before I can make a direct comparison since my system didn't come online until about June 1 of 2008. I am basing my conclusions on the daily readings of my non-billing AC meter, not the on board inverter measurements.

Of course, that begs the question. Do you have two non-billing meters? Did you take independent voltage and current measurements? Or, did you use the internal measurements of two very different inverters?

I haven't heard any comments specifically about Power-One or SMA, but I have been warned that inverters have poor and often optimistic measurement hardware.

If you are using a single non-billing meter as I suspect did you record daily readings for your old mismatched inverters in June 2007? Did you record the readings again with the matched inverters in June 2008? If you did both of those things, how about taking a look at that data and posting again?

You mentioned that your two strings are identical, but why would they ever have had different inverters, and why did you end up with a SMA 3800 and a SMA 2500? I would have expected identical inverters all along, unless your arrays have different orientations. Do they?

I didn't know that the PVI 3000, which is transformerless, was certified in the USA in 2007. The SMA 3800 and 2500 are transformer type inverters. These two inverter types use very different wiring on the DC side. How did your installer deal with this? Did (do) you have two DC disconnects? How were the disconnects wired? How were the strings wired?

Thanks,
Mike

LucMan

Re: PVI-5000-OUTD-US 5000 watt Inverter

to answer your questions:
The display readings were verified as being accurate with a voltmeter & Fluke clamp on amp meter.



Of course, that begs the question. Do you have two non-billing meters? None
Did you take independent voltage and current measurements?
Yes with separate Fluke clampon and voltmeter. P=E x I



If you are using a single non-billing meter as I suspect did you record daily readings for your old mismatched inverters in June 2007? Did you record the readings again with the matched inverters in June 2008? If you did both of those things, how about taking a look at that data and posting again?
NO non billing meter, the only way of recording output is the internal measurement connected to my laptop. The data would be useless as everyday output is different because of cloud cover, ambient temps, etc. The only way to compare output for the inverters is to check output at solar noon with a clear sky on any given day.

You mentioned that your two strings are identical, but why would they ever have had different inverters, and why did you end up with a SMA 3800 and a SMA 2500? I would have expected identical inverters all along, unless your arrays have different orientations. Do they?
The same orientation. The 3800 was installed because the original system was specified at 6.2KW. The installer was going to install an additional 5 panels in an eyebrow configuration above the 26, fortunately I realized that the 5 panels would have shaded the panels below in the summer.

I didn't know that the PVI 3000, which is transformerless, was certified in the USA in 2007. The SMA 3800 and 2500 are transformer type inverters. These two inverter types use very different wiring on the DC side. How did your installer deal with this? Did (do) you have two DC disconnects? How were the disconnects wired? How were the strings wired?
One DC disconnect per inverter
Wiring on the DC side not so different.The Magnatec had the ability of accepting 2 DC inputs or strings that were of different orientations or just 1 input or string, a jumper could be added and or the inverter was configured with the Magnatec software and a laptop. Check out the install & operation manual on system configuration for PVI 3000-I-OUTD- US at Power One website. www.power-one.com/resources/products/appnote/AlternativeEnergy/manual_installation_pvi-3000-i-outd-us.pdf

The SMA's have one DC input only.
13 panels wired in series to each disconnect

mradtke

Re: PVI-5000-OUTD-US 5000 watt Inverter

LucMan,

Thank you for your reply and added information.

I have come to the same conclusion as you did that the P1 was not harvesting the same amount of energy as the SMA. However, since you should have been well within the P1 specifications, I think that it bears further study to figure out what was going on. Do you still have the voltage and current readings of solar noon from 2007? What were they for the two array / inverter combinations? Did you and your installer try to figure out what was going on?

I asked about the disconnects and the DC wiring because, while the two types of inverters both require the array wiring to be floating, the transformer design requires only the positive leg to be disconnected in the DC disconnect and the transformerless design requires both legs to be disconnected. In addition, the transformer inverter internally grounds the negative through a fire protection fuse. Were the DC disconnects integrated into the inverters, or were they external? If the DC disconnect was external, was there one or two?

Where are you located? The US electrical code requires some special things be done with the array wiring for a trnsformerless inverter. Did (does) your panel wiring meet code?

Thanks,
Mike

BB.

Re: PVI-5000-OUTD-US 5000 watt Inverter

Same day, year over year, for my system--is not very predictive of output... I will look at my system, and 2,300 watts to 3,000 watts (on a "sunny" day), I cannot just look outside and say what the power output will be.

Certainly, cool windy days produce better peaks. But a bit of just the right clouds, and I will get some very nice peak outputs.

-Bill

mradtke

Re: PVI-5000-OUTD-US 5000 watt Inverter

Bill,

Thanks for your note.

I was asking LucMan for the paired P1 and SMA voltage and current readings that he took back in 2007 to determine that the P1 wasn't performing as well as the SMA. These should have been taken over just a few minutes on a clear day so should be pretty good.

My system is producing about 3700 watts in the mid day sun these days which seems correct for the dissimilar orientation of my arrays and the time of year. However, those cloud edges push it up past 5000 watts. Too bad cloud edges come with clouds.

Mike

LucMan

Re: PVI-5000-OUTD-US 5000 watt Inverter

mradtke wrote: »

LucMan,

Thank you for your reply and added information.

I have come to the same conclusion as you did that the P1 was not harvesting the same amount of energy as the SMA. However, since you should have been well within the P1 specifications, I think that it bears further study to figure out what was going on. Do you still have the voltage and current readings of solar noon from 2007? What were they for the two array / inverter combinations? Did you and your installer try to figure out what was going on?

I asked about the disconnects and the DC wiring because, while the two types of inverters both require the array wiring to be floating, the transformer design requires only the positive leg to be disconnected in the DC disconnect and the transformerless design requires both legs to be disconnected. In addition, the transformer inverter internally grounds the negative through a fire protection fuse. Were the DC disconnects integrated into the inverters, or were they external? If the DC disconnect was external, was there one or two?

Where are you located? The US electrical code requires some special things be done with the array wiring for a trnsformerless inverter. Did (does) your panel wiring meet code?

Thanks,
Mike

I have come to the same conclusion as you did that the P1 was not harvesting the same amount of energy as the SMA. However, since you should have been well within the P1 specifications, I think that it bears further study to figure out what was going on. Do you still have the voltage and current readings of solar noon from 2007? no records , only observed outputs at that time

The array is approximately at 200 degrees at 31 degree tilt when the sun was directly overhead on a full sun day the Pac output on the p1 was approximately 400-600 watts less than the SMA. Bear in mind that these reading were in June , July , August when the ambient temperatures at noon are elevated and the panels are quite hot resulting in decreased output. The SMA output was approximately 2KW more or less depending on the day. Yesterday the Pac on both inverters was approximately 2.4KW ea at solar noon . Total for the day was 24KWH.
This lower out put from the P1 was unacceptable for me. As my contract originally specified Xantrax inverters I asked that my installer replace the P1 with an SMA which was an acceptable equal to me. It did not want to go through a long drawn out ordeal with the installer trying to make what I considered an inferior product work. The Pac outputs for the 2 inverters were in black and white. The contractor verified my observations and agreed to replace the inverter.


I asked about the disconnects and the DC wiring because, while the two types of inverters both require the array wiring to be floating, the transformer design requires only the positive leg to be disconnected in the DC disconnect and the transformerless design requires both legs to be disconnected. In addition, the transformer inverter internally grounds the negative through a fire protection fuse.
What would this have to do with power output? The disconnects would be closed during operation and only opened for servicing, if one leg or both legs on a DC circuit is opened you would have no current flow.

Were the DC disconnects integrated into the inverters, or were they external? External

If the DC disconnect was external, was there one or two? Two

Where are you located? NY USA
The US electrical code requires some special things be done with the array wiring for a trnsformerless inverter.
SMA are not transformerless, they are heavy, I helped lift them onto the mounting brackets (gasp)

Did (does) your panel wiring meet code?
I hope so, it had to be inspected by the NYS underwriters and passed. The system was installed by certified solar PV installer and licensed electrical contractor. All required in NY for NYSERDA rebates.

mradtke

Re: PVI-5000-OUTD-US 5000 watt Inverter

Hello LucMan,

Thanks again for the information.

I apologize for causing some confusion. I was trying to cover 2 subjects. One was why did the P1 not, or appear not to, perform to specifications. The other was how the unit was wired to meet code since transformerless inverters are yet very rare in the USA. Of course, you are correct that the DC wiring has no effect on the AC power.

What I was hoping to get from you were voltage and current readings for the two inverters at the time that you observed the problem. I would really like to understand what was going on because if there is some design flaw in the P1, I would very much like to know about it. So, if you still have those readings, please post them. If not, then do you remember approximately what they were ... not the DC power, but the DC voltage and current.

For comparison sake, my AC output as measured on my non-billing meter was 26 kWh yesterday. My system has 28 SuntTech 180 panels, or 5040 DC watts. There was only a small amount of high cloudiness yesterday.

By the way, how do you know the AC power output for yesterday? Earlier, you mentioned that you do not have a non-billing meter. Others have pointed out that the inverter internal readings are not very accurate.

I apologize for being so anal about this. I respect your decision to quickly reject the P1 and move on. I should have done that with my Fronius. However, I disagree that you should call the P1 inferior without knowing what the problem was. I see at least the following possibilities:

1) Your P1 had a defect.

2) The P1 model has a design defect.

3) The measurements that you based your decision on were faulty.

4) Your panels are not rated for a transformerless system.

5) The installation / inverter setup was faulty.

Item #4 brings up why I keep asking about the DC wiring. I have pointed out that the use of the P1 inverter requires unique electrical code considerations. I am not an expert on this, but in 2007, I believe that the inter panel wiring and the panel feeds all needed to be in conduit. The building inspector may not have realized that the P1 was transformerless since this inverter type was very rare in 2007. Are your panels wired with conduit? (The 2008 electrical code changes some of this and is not relevant to this discussion.)

Or putting it another way, if your contractor chose the unique P1 inverter and then did not follow through with wiring it correctly, why should it be a surprise that it didn't (or appear to) meet expectations?

Again, I apologize for being so persistent and you if don't want to spend any more of your time on this, I'll understand. Perhaps another reader of this chain will join us and can help explain just what was going on.

Thanks again,
Mike

LucMan

Re: PVI-5000-OUTD-US 5000 watt Inverter

After checking my notebook here is what I found:
10/16/07 daily output SMA 9.47 KWH
Mag 7.624 KWH

10/17 SMA 6.03 KWH
Mag 4.81 KWH

10/21/07 1 pm 75F SMA 285 vDC 2020 W total for day 6.24 KWH
Mag 248 vDC 1670 W 4.859 KWH

mradtke

Re: PVI-5000-OUTD-US 5000 watt Inverter

LucMan,

Thanks again for the response.

I think that you are tired of this conversation since you didn't address several of my questions. I don't blame you. Thank you for taking the time to post your experience and taking the time to follow up yet again.

The only measurements that you supplied that are complete enough to draw any conclusion are those for 10/21/07. There are only two conclusions possible for these results. Either your two strings were not identical at the time (shade?), or your measurements are wrong. No inverter malfunction can account for your measurements. Here is my reasoning.

Below are your 10/21/07 1 pm measurements again with the currents computed using your watts figures:

SMA 285 vDC 7.09 amps (2020 W)
Mag 248 vDC 6.73 amps (1670 W)

Please assume:
The measurements that you supplied are relatively accurate, and
Your two strings are similar in every way, including illumination and temperature.

While your system is in operation, the arrays act as energy sources. From any PV panel manufacturer's product graph, it can be observed that the slope of the current / voltage curve of an illuminated panel is negative. In other words the more current that is drawn from the panel, the lower the voltage. Since the panels are placed in series for an array, the array acts the same way as an individual panel.

An inverter acts as a load on the array. It has the complicated job of determining exactly what current to draw from the array to harvest the maximum energy, but that is not relevant to this discussion. What is relevant is that for the PV array, higher currents draw MUST result in lower voltages. Your measurements show a lower voltage with a lower current. Therefore, one of the starting assumptions must be wrong. There is no evidence of an inverter problem.

A "red flag" to me was your installer's use of dissimilar inverters on a symmetrical system to begin with. If your installer fixed your system when he replaced the inverter, he may have actually done something else that was the real fix and perhaps he "forgot" to mention it to you.

Thanks again,
Mike

mradtke

Re: PVI-5000-OUTD-US 5000 watt Inverter

Hello,

The PVI-5000-OUTD-US inverter continues to work as expected. I am still watching it very carefully after my bad experience with my original Fronius inverter.

One thing has come to light that may be a concern for some people. I mentioned before that I liked the Power One's quiet operation since it is convection cooled as compared to the fan cooled Fronius that it replaced. However, my son who is in his 20's has complained about the noise it makes. Younger folks have good hearing in the higher frequencies. He can hear the high frequency inverter stages squealing something like the sound of the horizontal sweep that can be heard on CRT type television sets. I can only hear a low level 60 Hz hum and a regular quiet tick just like a clock.

Thanks,
Mike