# plz help me: inveter design

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#### antoine magdi

##### New Member
first, thanks for reading my post... i'm newbie in power control and i have many problems in ac; and many other problems in electricity in general...

my friends made a wind turbine for generating electricity; they finally arrived to 2 wires each is 12V dc/40A.... they want to transfer it to 220V ac and the excess power they want to save it in a battery 12V/40A also... and i have to make the control...
i have many questions and i hope not to disturb you....

1) the 40A this: means that the maximum total power that can be drained by all the grid is 40A?!!
2) the attached 2 schematics containing ics is it normal to implement electronic devices in ac circuits with high current rating, there is no damage that have to be occured?!!!
3) if i have to choose between one from the attached schematics, what i have to choose?!! and why(what's the difference)
4)why there is many inverter each one is for an precise wattage needed, isn't it depending only on the input of the circuit of inverter
5) i can expect from the previous rating (40A/12V) that the maximum power i can deliver is 480 watt?!! and after the transformer 220V ac 480 watt also?!!! so the total current that can be drained by the grid is (approximately) 2A?!!!
(if this is the case it means that if there is only one electric device that needs over 500 watt there will be a damage?!!!)

finally, thanks for your kindness to read all this message... i will be very thankfull if you helped me.

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#### be80be

##### Well-Known Member
40 amps could charge a lot of 12 volt battery while you sleep. Like 6 of them which would let you use a bigger inverter

#### audioguru

##### Well-Known Member
The first inverter from Electronics-Lab has a square-wave output and is full of errors.
It blows up.
I fixed it but the moderator MP deleted my version and replaced it with his mess as you can see.
The grid is a sine-wave, not a simple square-wave.

The second inverter has a very low output power and its voltage drops when it is loaded.

You don't have a way to syncronize these simple inverters with the grid so the electrical utility will not allow them to feed the grid.

You also do not have a way to prevent the grid from overloading the inverter so the inverter will instantly blow up.

#### smanches

##### New Member
I think he means just the local inverter "grid", not the entire utility grid.

But yes, [email protected] is not a lot of power. You would need a battery bank to supply extra power when needed. It would also be good to increase the DC input voltage if you can, to increase efficiency at higher wattage.

#### tcmtech

##### Banned
If you have that power available fairly often I would go with the charge up some big batteries consept.
Then either run several smaller inverters independently for different loads or just go out and buy a big factory made unit to run everything. You will be time and money ahead!

Check out the online auction sites, there are loads of big units for sale real cheap. Pick up a few broken ones. 90% of them have either the input switching devices blown or the output h-bridge deviced blown from being overloaded or just having been hooked up backwards to a battery.

The cheap factory units can not be tied together on there outputs. They all have slightly differernt output voltages and the output frequencys are slightly different from one to the next.

If you looking to make a homemade grid tie to actualy feed power back to the utility supply lines, I am doing a write up on a 250 watt now. Feel free to jump in and ask questions! Since you are running a 12 volt system also just factor all of the current and power handling numbers for yours are 2 times what the 250 watt system is.

If your looking for an understanding of a basic utility grid tie system, check out the grid tie inverter schematic thread. It covers the actual theory behind how to do it on with all analog devices.

And If you do plan to charge big storage batteries watch out for the "super ultra multistage microprocessor monitored battery charger guys" They get .. Um... Well they just get carried away! lets just leave it at that!

#### be80be

##### Well-Known Member
I don't think he was wanting to sell power back he just wants 220 Ac from a inverter for his own use
and the excess power they want to save it in a battery 12V/40A also... and i have to make the control...
He just needs to charge up a bank of batterys and so he can use a bigger inverter a 1500 watt inverter. I have done a lot of checking and most homes like I live in Average use is not as much as you think for things like lights and such.

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#### tcmtech

##### Banned
how did you get 691200 watts from 12v * 40a *24h = 11520wh ???
Are you using calculus?

If your math is that bad how come I dont remember seeing you at my high school years ago?

I was not sure what he was getting at so I figured I would eleborate some.
I have been getting shot at lately for not posting every little detail.

##### Banned
Watt whats be8? Watt seconds watt hours? A watt by itself isn't a measure of energy, neither is an amp. I'm guess watt/amp hours?

#### tcmtech

##### Banned
I think he may be getting his power formulas from the overunity alternative energy nutters!

Or may be he is an overunity nutter!

#### be80be

##### Well-Known Member
Let me ask you some thing when you turn on as light and its 75 watts will it use 75 watts in min? no it uses .34amps from the time you turn it on till you turn it off. I use the dam wrong number .

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##### Banned
691200 watt seconds is 11520 watthours.
He's measuring in Joules.

#### be80be

##### Well-Known Member
A watt by itself isn't a measure of energy, neither is an amp. I'm guess watt/amp hours?
That's true what you need to know is power used over time.

##### Banned
Watt hours is typically used. Watt seconds just gives you big numbers =)

#### be80be

##### Well-Known Member
My math wasn't wrong. You can store power for 9.6 hours of power that you can use with a 1500 watt inverter .

#### tcmtech

##### Banned
To further throw gas on this fire
Average wattage consumption is just the average. Total used divided by total run time. Actual power usage is often not even close.

My monthly average is aroud 2 KWh per hour but my actual varies from less than 500 watts per hour to over 40KWh per hour. A 2.5 KW inverter may sound like it could run my place all the time but it in fact it will not!

I figured you used a joule based calculation. couldnt resist taking a cheap shot at you due to the fact most people dont even know what a joule is, let alone how to use it in electrical power equations.
If you use KWH as the base of energy referance far more people can understand it. But still even then most cant even apply it to a real life situation.

##### Banned
Joules are easy =) They're just watt seconds, nothing mysterious there.

#### tcmtech

##### Banned
I know that. But how many people could you find on the street that would know that?

I unfortunatly have to rather often work with people that cant even figure out there own electrical usage based on what they have plugged in around their homes.

I get asked several times a year how can a person cut down on there electric bill by using alternative energy sources like what this OP is working with.
I tell them turn off all that high wattage convinence crap that wastes energy. They dont understand or just dont want to believe.

They have no clue to how much power they are using in terms of trying to run off batteries.

I have one fellow that wants to convert his old 1500 watt 1920's Parris Dunn wind charger over to 240 volt to run his farm. He said it worked great when he was a kid. The whole farm could run off the batteries for a week, So it should still be able to do it now, all it needs is the voltage changed right?

his present electric bill is around $300 a month! do you think that old machine can still run his whole farm? he does! Of course he doesnt factor in that back in the 1930's his dad did not have four construction machines with 1500 watt heaters plugged in all winter just in case he needed to use them. Or that they did not have a 5000 watt electric water heater, Or a all electric stove, Or 5 big electric freezers in the basment, Or that the shop had three 32 volt electric lights back then but now has six 400 watt metal hailides along with 600 watts of floresents now, or that having three 175 watt yard lights adds up, Or that haveing 5 hp air compessor draws power, Or that running a 50 amp plasma cutter for several hours a day doing scrap iron draws some power. Or that there is a 1200 watt heater in the basement that never shuts off. He is however convinvced that by shutting off his computer when he is not using it is saving him at least$75 a month. But that other stuff isnt using that much so why bother messing with it!

So how many joules / KWH does this guy need to run for a week at his present power rate? He pays about 8 cents KWH plus a \$28 a month service fee.

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##### Banned
Every time you post tcmtech I am more amazed at the stupidity you've encountered in your life.

Figure 200watts for the computer, 300 maybe lets say he has a few peripherals and a CRT monitor instead of and LCD. Even if it was left on ALL the time
That's only about 216kwh'rs 17 bucks a month. Worst case. He needs some basic math lessons =)

#### tcmtech

##### Banned
The truth is often far dumber than any fiction I could ever come up with. Work with electrical power or alternative energy and its not hard to find these people. They will eventualy find you.
Alot of the people I know are not dumb, They just dont look at the overal big picture of what they are apart of or how everything interacts to get to that final outcome they are trying to change.

Plus I am rather social and get around alot. Most would just walk away after the first dumb question but something in me compels me to listen and try to help them out.

You can lead a person knowledge but you cant make them think!

I do my best to give them honest and useful advice or just point them in the right or just a new direction. I would rather give them new ideas to think about than just leave them sit there not knowing there may be a better solution than what they are currently trying.
Like with the grid tie info for this OP. I wasnt sure if he was refering to a homemade house grid of inverters or if he was refering to the utility grid.
If he wants to follow up on a utility grid tie inverter system its his business, not mine. If he wants to try to run everything off of batteries and inverters, factory or home built, thats for him to deside.

I just pointed out different options to think about.

#### be80be

##### Well-Known Member
. A 2.5 KW inverter may sound like it could run my place all the time but it in fact it will not!
That's where bonding comes in to play. I have worked for some real brite people they where scraping buildings for metal
had one that they used as a office. They cut out all the power line they
thought where not needed. found out later no power to the office. That's when they called me. Seeing it was going to to take MUS. 8 to 12 months to set poles and power them back up and at this time they where using 100gls fuel a day running a 125kw generator. I showed them how to run what they need with two 5.5kw and what I call bonding at 20gls fuel a day. do that math

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