Design and construction of 3kVA inverter incorporating a 200Ah battery

[alabimusty]

Hi to everybody,

I need your assistance in the design and construction of a 3kVA inverter incorporating a 200Ah battery. Please, I need the circuit diagram and the necessary components calculation and explanation in achieving this.

I have seen and study the 500W inverter circuits designed by Seyd Ashad Mustufa Younus but I need your urgent attention.


Musty

[Guest Alun]

Please provide more information.

Input/output Voltage?
Frequency?
Sine/square wave?

[audioguru]

Hi Musty,
Welcome to our forum. ;D
The biggest problem with building a 3kW inverter will be obtaining a large, very expensive transformer. It will probably need to be custom-made for you.

For the design, you need to determine its battery voltage. The inverter will probably be 80% efficient because it will heat-up, so the power from the battery will be 3750W. If you use a 12V truck battery then its current will be 313A and it will boil then blow-up!
If you use six 12V batteries in series (72V) then their current will be a reasonable 52A and if they are monster 200A/hr ones then will last about 3.5 hrs per charge.

The most efficient circuit would use power Mosfets for its output transistors.
A simple circuit would produce a square-wave output.
A more complicated circuit would produce a modified sine-wave output which has voltage steps in it.
A very complicated circuit would produce a pure sine-wave output using pulse-width-modulation.

Are you wealthy?
Do you have lotsa batteries to put in series?
Are you also going to design and build a monster charger for all those batteries?
Do you want the inverter to have square, stepped or sine waves output?
It ain't simple. ;D ;D

[alabimusty]

Thanks for the response.

The frequency is 50Hz
Input is expected to be 12v dc
The output is 230v ac (sinusoidal wave)

I am a student, so, I need a circuit cheap to construct and reliable performance.
Please, help me with the schematics and neccessary components calculation and explanation. I know it aint easy.

Musty

[ante]

Hi Musty,

There are a few things which do not add up here, first “I need a circuit cheap” is not possible at this power and to make things even worse you need sinusoidal wave = very expensive stuff! Second you want to run it from a 12V battery, ok but the battery should be at least a 1200Ah one to survive repeated use = very expensive!

Please ask yourself:
You might not need sinusoidal wave?
You might not need 3kW available at all times?
You can perhaps use 4 smaller (500W square wave like the one on this site = cheap) inverters whit separate batterys (car size = cheap)?

;D

[Guest Alun]

Not meaning to be discouraging but this idea is impracticle, this power level is impossible without very big bulky and expensive batteries and at 12V the efficiency  will be very low as there'd be huge I²R losses in the cables and battery due to the large current.

[alabimusty]

Actually, I know it is going to be very expensive, even, from the battery level but I really want it to help me understand the principle better and moreso, get a much lower mode for myself after understanding it!! 

[audioguru]

There isn't much to understand about an inverter. It is a power oscillator driving a step-up transformer. The input power is more than its output power. Power equals Volts times Amps, so to get a high power from a low voltage battery you are going to need many Amps. ;D

[alabimusty]

Hi Audioguru,

Thanks a lot, but I really want to understand the principle behind it as well as the sinusoidal output, oscillators and the calculation involved in the output frequency, power and ampere.

Thanks in anticipation.

Musty

[audioguru]

Hi Musty,
You need to learn Ohm's Law and the Power Law about Volts times Amps before studying circuits like an inverter, an oscillator and using sine waves.

Then you will learn about many oscillator types, and calculating their frequency is simple.

Then you will learn that amplifying a sine wave in a simple amplifier produces an awful lot of heat which is wasted power that must be provided by the battery of an inverter.

Then you will learn about Pulse-Width-Modulation which can be used to reduce the wasted heat of a sine wave inverter.

Then you will learn why sine waves from an inverter usually aren't necessary anyway. ;D

[ante]

I am a student, so, I need a circuit cheap to construct and reliable performance.

How about this? ;)

[alabimusty]

Thanks and regards to Audioguru and Ante. I know these principles, all I need to know now is to apply it to the circuit operations.

I will get across to you, if I hanged along the line.

Once again, thanks.

Musty