[SOLVED] Inverter design for 230V,500W

Hi!
I am thinking of designing an inverter to produce 230V,500W.The battery voltage i can use is 12V.I must be able to provide the required output for 5hrs continuously.The battery size and cost should be minimum and the battery used should be a lead-acid battery.

The following are my doubts regarding the design.

1)What should be the ampere-hour rating of the battery i should use to provide the current required for the given power and how to calculate it?
Is it possible to use 12v 4.5AH or 12V 12AH(bike battery) or an computer UPS battery,if so how long will these provide the required power.
2)PWM or square wave inverter,trapezoidal wave inverter,sine wave wave inverter.What is the advantage of using one over the other?
3)Can the household appliances work safely with a PWM or trapezoidal wave outputs?

Also please suggest me a good book or a site for efficient design of inverters.
Thanks in advance!!

Dear sriblue7
Hi
You need 2.5 amperes ( approximately ) at your out put , so if your battery is about 12 volts , your input current will be (with neglect from dissipation ) about : 47.9 amperes . if we add dissipations , you'll need 50 amperes ( estimated ) . so if you use 50 A/hour battery , it will be empty after one hour , so you have to use 5*50 = 250 A/hour , battery .
Best Wishes
Goldsmith

Thanks Mr.Goldsmith!!I have some more questions regarding the design please help me with these too.
Is it difficult to design a sine wave inverter compared to PWM inverters?if so why?
Can i use 12V 120 or 135Ah battery along with 2 or 3 stages of darlington pairs in the input side to achieve the above requirements(50A and 5hrs supply)?Or is there any other techniques to achieve this?(because the inverter which i have in my house provides 600VA with 12V 135Ah battery for 5hrs continuously)
If i use resistors in the input side(for making oscillator)with 50A current wont this damage the resistors and also the power dissipation will be more.What is the solution for this?

sriblue7 said:

Hi!
I am thinking of designing an inverter to produce 230V,500W.The battery voltage i can use is 12V.I must be able to provide the required output for 5hrs continuously.The battery size and cost should be minimum and the battery used should be a lead-acid battery.

The following are my doubts regarding the design.

1)What should be the ampere-hour rating of the battery i should use to provide the current required for the given power and how to calculate it?
Is it possible to use 12v 4.5AH or 12V 12AH(bike battery) or an computer UPS battery,if so how long will these provide the required power.
2)PWM or square wave inverter,trapezoidal wave inverter,sine wave wave inverter.What is the advantage of using one over the other?
3)Can the household appliances work safely with a PWM or trapezoidal wave outputs?

Also please suggest me a good book or a site for efficient design of inverters.
Thanks in advance!!

Click to expand...

2) It would be best if the output was sine wave. But for home inverters, usually, 230W is only used for running lamps and fans. For this, generating sine wave may not be feasible (economically). You can make do with PWM based modified square wave inverter. If you're going to use sensitive equipment, then, it's best you use sine wave inverter.
3) Fan and light can. PC can. Fridge, AC should not be run with square wave. You should use sine wave. In fact, sine wave is best for everything, but it may or may not be economically and/or technically feasible.

Hope this helps.
Tahmid.

---------- Post added at 23:37 ---------- Previous post was at 23:31 ----------

sriblue7 said:

Thanks Mr.Goldsmith!!I have some more questions regarding the design please help me with these too.
Is it difficult to design a sine wave inverter compared to PWM inverters?if so why?
Can i use 12V 120 or 135Ah battery along with 2 or 3 stages of darlington pairs in the input side to achieve the above requirements(50A and 5hrs supply)?Or is there any other techniques to achieve this?(because the inverter which i have in my house provides 600VA with 12V 135Ah battery for 5hrs continuously)
If i use resistors in the input side(for making oscillator)with 50A current wont this damage the resistors and also the power dissipation will be more.What is the solution for this?

Click to expand...

Designing a sine wave inverter is difficult, compared to designing a square wave (or modified square wave) inverter. This is due to the complexity of generating the sine wave with a high enough efficiency. If you are a beginner and plan to design the inverter yourself, you should not embark on designing a sine wave inverter just now. First, get the modified square wave inverter done and move on to sine wave next. Sine wave inverters also, usually rely on microcontrollers as using a combination of analogue or digital ICs may become too complex.

For switching, you should use MOSFETs to keep conduction losses low. Parallel a number of MOSFETs as required to achieve the required current rating. BJTs would be too inefficient. Some common MOSFETs you should take a look at are:
IRFZ44N, IRF3205, STP55NF06, IRF540, IRFP054, IRFP064

For the oscillator section, use a PWM chip. You can use SG3525. Then you can drive MOSFET directly. There will be no hassle of pulse-generation and not much to worry about in terms of pulse mismatch and flux-walking as far as the oscillator is concerned. And, you have feedback system for maintaining a fixed output voltage.

You should aim to make your inverter as efficient as possible. The more power you waste/dissipate in the inverter, the less available for driving load, and the lower the back-up time.

Hope this helps.
Tahmid.

Thank you Tahmid...