Inverter AC output Current

xphysics

Hello everyone,

I am stuck about to find the ac loss of the solar plants. http://photovoltaic-software.com/DC_AC_drop_voltage_energy_losses_calculator.php
Using this formula ( in the link ) I can calculate the dc voltage loss. I have no problem about that. But I can not calculate the ac loss !

For instance, I need to find the AC current of the inveter ? How can I find that ? My one string has 19 panel one of them has 300 Wp and Vmp =35.8 volt. Also for one inverter there will be 5 string. 3 for one mppt and 2 for one mppt. The maximum ac output of the inverter is 30000 Watt.

Thanks for all answer..

Also I want to ask, what is the single phase of the ac system ? I choose there in the link 3 phase system which means there will be three wire .. but what is single phase ?

Important question is the first one

It is grid connected system.

I need really help...

westbranch

Re: Inverter AC output Current

this sounds like a GRID TIE setup, ???

xphysics

Re: Inverter AC output Current

westbranch wrote: »

this sounds like a GRID TIE setup, ???

Yes it is grid connected system.

westbranch

Re: Inverter AC output Current

AFAIK the Voltage of the GT Inverter has to/ will match the Mains Voltage, whatever that is for your location.

xphysics

Re: Inverter AC output Current

Sorry but I am so new ? What is AFAIK and GT ? I just need to learn how can I calcuate the output current of the inverter . I mean AC current.

xphysics

Re: Inverter AC output Current

westbranch wrote: »

AFAIK the Voltage of the GT Inverter has to/ will match the Mains Voltage, whatever that is for your location.

Sorry but I am so new ? What is AFAIK and GT ? I just need to learn how can I calcuate the output current of the inverter . I mean AC current.

BB.

Re: Inverter AC output Current

Afaik-as far as I know.

GT inverter is a grid tied inverter. Solar panels connected to gt inverter, then connected to utility lines. No storage batteries, no backup power if the grid fails (in general).

Off grid inverter is capable of supplying 120 vac any where, any time from DC battery bank.

Two completely different systems. Which type is yours?

-Bill

System types are actually more fuzzy/complex. Just trying to understand your question/need.

xphysics

Re: Inverter AC output Current

BB. wrote: »

Afaik-as far as I know.

GT inverter is a grid tied inverter. Solar panels connected to gt inverter, then connected to utility lines. No storage batteries, no backup power if the grid fails (in general).

Off grid inverter is capable of supplying 120 vac any where, any time from DC battery bank.

Two completely different systems. Which type is yours?

-Bill

System types are actually more fuzzy/complex. Just trying to understand your question/need.

Probably I am talking about Off grid systems. Thanks for your help...

xphysics

Re: Inverter AC output Current

xphysics wrote: »

Probably I am talking about Off grid systems. Thanks for your help...

Maybe if it is not problem, can you explain the situation for both ?

Photowhit

Re: Inverter AC output Current

xphysics wrote: »

I am stuck about to find the ac loss of the solar plants. http://photovoltaic-software.com/DC_AC_drop_voltage_energy_losses_calculator.php
Using this formula ( in the link ) I can calculate the dc voltage loss. I have no problem about that. But I can not calculate the ac loss !

I'm guessing you are trying to calculate what your system should be producing and sending back to the grid?

xphysics wrote: »

For instance, I need to find the AC current of the inveter ? How can I find that ? My one string has 19 panel one of them has 300 Wp and Vmp =35.8 volt. Also for one inverter there will be 5 string. 3 for one mppt and 2 for one mppt. The maximum ac output of the inverter is 30000 Watt.

So do you have 2 inverters? You say one mppt has 3 strings and one has 2 strings. Typically a grid tied inverter will be an mppt type, the voltage must be high enough so the inverter can convert it down to the line/grid voltage.

The statement "My one string has 19 panel one of them has 300 wp and Vmp of 35.8 volt. Doesn't appear to make sense to me. You can't feed 19 panels evenly into 3 or 2 strings, so it would have to be a single string of 19 panels and perhaps 5 of these strings? That would give pretty close to a 30kw inverter feed. Do you know the brand of inverter?

I'm not sure how you have it broken down into 3 strings and 2 strings, perhaps you have the panels installed together in 2 sets? ...both feeding the same inverter?

If you are worried about the system appearing to be not producing as much as you hoped, losses in the are likely from the DC side. A 300 watt panel likely will normally produce around 75% of it's panel rating or 225 watts. Often the panel will have a NOCT (Normal Operating Cell Temperature) value. Since they try to rate panels uniformly they 'flash' test them, this provides a wattage that is generally more than the panel can produce unless the panel is in very cold temperatures and positioned optimally. This would generally be very cold, even in cool temperature the cells become very warm and produce less current.

30,000 watt is a very large inverter.

BB.

Re: Inverter AC output Current

Can you give us some brands/model numbers?

Still not understanding your set up. Voltage / panel configuration is not common to most hardware out there in the US.

-Bill

xphysics

Re: Inverter AC output Current

Photowhit wrote: »

I'm guessing you are trying to calculate what your system should be producing and sending back to the grid?

So do you have 2 inverters? You say one mppt has 3 strings and one has 2 strings. Typically a grid tied inverter will be an mppt type, the voltage must be high enough so the inverter can convert it down to the line/grid voltage.

The statement "My one string has 19 panel one of them has 300 wp and Vmp of 35.8 volt. Doesn't appear to make sense to me. You can't feed 19 panels evenly into 3 or 2 strings, so it would have to be a single string of 19 panels and perhaps 5 of these strings? That would give pretty close to a 30kw inverter feed. Do you know the brand of inverter?

I'm not sure how you have it broken down into 3 strings and 2 strings, perhaps you have the panels installed together in 2 sets? ...both feeding the same inverter?

If you are worried about the system appearing to be not producing as much as you hoped, losses in the are likely from the DC side. A 300 watt panel likely will normally produce around 75% of it's panel rating or 225 watts. Often the panel will have a NOCT (Normal Operating Cell Temperature) value. Since they try to rate panels uniformly they 'flash' test them, this provides a wattage that is generally more than the panel can produce unless the panel is in very cold temperatures and positioned optimally. This would generally be very cold, even in cool temperature the cells become very warm and produce less current.

30,000 watt is a very large inverter.

Hey first thanks,

the panel I used http://d9no22y7yqre8.cloudfront.net/assets/uploads/products/downloads/DS_YGE72Cell-35b_40mm_EU_EN_201409_v3.pdf
İnverter -> http://www05.abb.com/global/scot/scot232.nsf/veritydisplay/915e62707dc4d58185257ce50060214a/$file/TRIO-20.0-27.6_BCD.00379_EN_Rev A.pdf

For one inverter there are 5 string. One of the string has 19 pv panel. So What is the way to calculate the ac current ?
I asked because I try to calculate ac loss of the system.

Photowhit

Re: Inverter AC output Current

I followed your link, look at the 2nd chart of Normal Cell Operating Temperature Values, You will see on normal days they will produce about 218.8 watts.

So each string will produce 218.8(watts) x 19(panels) = 4157 Watts, If their is a long wire run to the inverter you need to determine if they are combined (the 5 strings brought to gether) at the array or at the inverter. You can calculate the wire loss by using the site you found for DC wires, just find for one string the % loss and you can multiply the % x the total wattage.

If you look at the specifications for the inverter it will list a conversion or efficiency factor of 98%, multiply the total wattage. On normal days it will be 4157 watts per string x 5 strings for 20,786 watts. If you divide the wattage by the voltage that the inverter runs at(you can also apply the conversion or efficiency factor 98%) you can figure out the amount of current AC.

Now this is 3 phase, Not something I deal with! but I would assume(actually I'd find someone who knows more than I do) that the current would be split between the 2 phases so you would divide by 2.

So the figure I would get would be (20,786 total watts x .98 efficiency) ÷ 400 volts Rated AC grid voltage = 50.92 amps half or which is in each phase or about 25-26 amps(current which is what you asked for). I think Bill can give you a better idea. This is over my head, and I'm really winging it!

Also note that this is NOT what the system fuse or breaker should be, on cold days you might well produce 25-30% more current! I tried to calculate the amount on normal days.

xphysics

Re: Inverter AC output Current

Photowhit wrote: »

Also note that this is NOT what the system fuse or breaker should be, on cold days you might well produce 25-30% more current! I tried to calculate the amount on normal days.

If I calculate with maximum (mpp ) voltage and current of the panel then, I think ı do not have worry about for the cold days ?

I calculate 24.1 Amps. Also I am not sure . I follow Power = squareroot(3) *V*I .
The voltage I mean mpp => 19x5x300 =28500 Watt. = power. Then here I take the current as an amps.

To calculate the voltage loss = squareroot(3)*(R*cosQ+XsinQ)*I*L
I is found. R is resistivity of the material (cable). cosQ =1. sinQ=0

Is it true ?

xphysics

Re: Inverter AC output Current

Photowhit wrote: »

I followed your link, look at the 2nd chart of Normal Cell Operating Temperature Values, You will see on normal days they will produce about 218.8 watts.

So each string will produce 218.8(watts) x 19(panels) = 4157 Watts, If their is a long wire run to the inverter you need to determine if they are combined (the 5 strings brought to gether) at the array or at the inverter. You can calculate the wire loss by using the site you found for DC wires, just find for one string the % loss and you can multiply the % x the total wattage.

Hold the horses just a sec. You said 218.8 watts ? One pv panel is 300Wp so 19x300=5700 Watts.

xphysics

Re: Inverter AC output Current

BB. wrote: »

Can you give us some brands/model numbers?

Still not understanding your set up. Voltage / panel configuration is not common to most hardware out there in the US.

-Bill

Hey first thanks,

the panel I used http://d9no22y7yqre8.cloudfront.net/..._201409_v3.pdf
İnverter -> http://www05.abb.com/global/scot/scot232.nsf/veritydisplay/915e62707dc4d58185257ce50060214a/$file/TRIO-20.0-27.6_BCD.00379_EN_Rev A.pdf

For one inverter there are 5 string. One of the string has 19 pv panel. So What is the way to calculate the ac current ?
I asked because I try to calculate ac loss of the system.

Hey I also give you the datasheet. Please answer

Photowhit

Re: Inverter AC output Current

xphysics wrote: »

Hold the horses just a sec. You said 218.8 watts ? One pv panel is 300Wp so 19x300=5700 Watts.

Solar panels produce wattage based on their environmental conditions.

When they are rated, they are given a uniform 'flash' test. It allows panels to be compared to each other, but since the panel doesn't heat up it is not what the NOCT value will be. (NOCT = Normal Operating Cell Temperature).

So while a Panel might be rated at 300 watts, it will normally produce much less. The panel specified has a chart in the 'pdf' file specs that you provided a link to. It shows that the 300 watt panel will normally produce 218.8 watts;
Attachment not found.

In cold temperatures with direct sun, the panel CAN actually produce more wattage than the panel rating!

Since you were looking for voltage drop/loss;

xphysics wrote: »

I am stuck about to find the ac loss of the solar plants.

I suspected you were not happy with the production of you array. So I'm trying to give you some 'real world' numbers. If you are looking for Fuse/Breaker values, this involves other matters,

xphysics wrote: »

If I calculate with maximum (mpp ) voltage and current of the panel then, I think ı do not have worry about for the cold days ?

This value is different depending on what you need the calculation for.

If it's for maximum VOC, so you don't destroy your inverter, yes you just take your coldest temperature on record and calculate the maximum voltage your panel will produce.

If it's for a fuse or breaker rating you need to find out the Derating value of the breaker or fuse, if it has one, this may vary depending on temperature of it's environment.

Yes I gave you bad information about the 3 phase amperage, I was considering 2 hot lines rather than 3, my mistake!

oil pan 4

Re: Inverter AC output Current

xphysics wrote: »

I asked because I try to calculate ac loss of the system.

What were you told the system would produce?
218 watts per panel (100%) through out the entire day?