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 12/120V inverter again
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 14 2007 :  4:24:03 PM  Show Profile  Reply with Quote
The old IRF540 Mosfet has a drain to source max resistance of 0.044 ohms when it has at least 10V on its gatwe and it is cool.
Then its voltage drop is 0.44V at 10A and is 2.2V at 50A. 50A x 2.2V would make 110W of heat which would increase its resistance as shown on the graph in its datasheet.

There are hundreds of newer and better Mosfets. An IRF3711Z has an on-resistance of only 0.006 ohms. At 50A its voltage drop is only 0.3V.

Transformers have a max power rating. Do not allow the inverter and its load to exceed the max power rating then the loss is very low.
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mrenjan
Apprentece

India
19 Posts

Posted - May 14 2007 :  11:17:22 PM  Show Profile  Reply with Quote
Thank you Audioguru..

Renjan
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sunil_223
Apprentece

7 Posts

Posted - May 17 2007 :  09:30:27 AM  Show Profile  Reply with Quote
hi audioguru i have tried to make the inverter but it didnt work.
i am using 12/220v transformer.
68uf 16v capictor{tantlum}.
4007 diodes.
2n 3055 transistors.
180ohms 1 watt and 10ohms 5 watt resistor
but it didnt work.
only the transistors r heating up and no output is there.
please help me out.
can u tell me were i am wrong.
plz send me the schematic diagram of inverter if u have made any changes in it.
thanx
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 17 2007 :  11:32:31 AM  Show Profile  Reply with Quote
Hi Sunil,
The transistors in the simple inverter have avalanche breakdown if the supply voltage is more than 8V.
The capacitors are shown connected backwards.
The circuit doesn't provide enough base current for the transistors to make much power.

It has too many things wrong for me to make changes to it. It is too simple to work properly.
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sunil_223
Apprentece

7 Posts

Posted - May 18 2007 :  05:49:56 AM  Show Profile  Reply with Quote
thanx for ur reply
so audioguru have u rectified the problem?what is it can u tell me ?is it possible to make such simple inverter by making some changes in it?
waiting for reply
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sunil_223
Apprentece

7 Posts

Posted - May 18 2007 :  12:17:09 PM  Show Profile  Reply with Quote
hello audioguru
the schematic diagram for inverter on this page for 100watts is working properly?will this circuit function properly?

and what about that 500watts?shall i start making any one of them?
both r right or not?
plz reply
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 18 2007 :  4:22:48 PM  Show Profile  Reply with Quote
The 100W and 500W inverters have a square-wave output if your load doesn't mind.
I don't know if anybody has made the 100W one, but the 500W one works fine. The 100W one is the same but is smaller so it should also work fine.

Their capacitors are not connected backwards.
Their transistors do not have avalanche breakdown.
Their transistors have plenty of base current for a high power output.
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sunil_223
Apprentece

7 Posts

Posted - May 19 2007 :  01:58:49 AM  Show Profile  Reply with Quote
thanks audioguru
first i will try for 100w if it works then i will go for 500w
i want to know that what is the watts for R1,R2 and R3
and what is the volts for .1uF cap and power switch or relay?
i mean to say resistor R1 is 47k ohms but how many watts?
same for cap and relay.
relay is necessary for this circuit?
can u tell me what is 12-0-12v transformer?
i had purchased it.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 19 2007 :  1:32:35 PM  Show Profile  Reply with Quote
quote:
Originally posted by sunil_223
i want to know that what is the watts for R1,R2 and R3

Very, very low. Calculate it:
The max voltage across R1 is about 6.5V. Then its max power is only 0.9mW. The power in R2 and R3 is much lower. So any resistor power rating will be fine.

quote:
and what is the volts for .1uF cap

It gets only 6.5V across it. I would use a metalized poly 5% capacitor. Their minimum voltage rating is 50V or 63V which is fine.

quote:
and what is the volts for power switch?

It gets a max voltage of about 14V so any voltage rating will be fine.

quote:
relay is necessary for this circuit?

There is no relay in the circuit. A high current switch is shown.

quote:
can u tell me what is 12-0-12v transformer?

It is 24V with a center-tap and it is needed if a 12V car battery powers the inverter. A transformer with two 12V windings can also be used if the windings are connected together properly.

quote:
i had purchased it.

I hope it has a power rating that is high enough.
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sunil_223
Apprentece

7 Posts

Posted - May 20 2007 :  02:40:59 AM  Show Profile  Reply with Quote
thanx audioguru
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sunil_223
Apprentece

7 Posts

Posted - May 20 2007 :  03:30:55 AM  Show Profile  Reply with Quote
audioguru can u tell me that what is the effect if we use 12v but with different amps.I mean to say that if i am using 12v battery with 2.3amps/h and if i replace it with 1.2amps/h.
does it effect watts or volts or nothing will happen?

and what if i change the volt from 12v to 24v?what will be the effect?

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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 20 2007 :  9:56:34 PM  Show Profile  Reply with Quote
A 100W inverter need a battery current of 10A. A 500w inverter needs a battery current of 50A.
A car battery, not a tiny little battery like you have. A car battery is rated at 70Ah to 100Ah.
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sunil_223
Apprentece

7 Posts

Posted - May 25 2007 :  07:42:57 AM  Show Profile  Reply with Quote
hi audioguru can u tell me approximately how many solar cells i will be required to get 12v 5amps.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 25 2007 :  11:30:00 AM  Show Profile  Reply with Quote
quote:
Originally posted by sunil_223

hi audioguru can u tell me approximately how many solar cells i will be required to get 12v 5amps.



I don't know the size and the ratings for your solar cells.
I bought a 12V/150mA solar panel. I don't live on the equator so its output current at noon when it points directly at the sun outside is only 120mA. Before or after noon its output current is much less. If it is not aimed directly at the sun then its output current is also much less. Indoors with it aimed directly at the sun at noon its current is only 50mA.

Your 12V/5A solar panel will have an average current of about 2A for 8 hours per day. Not enough power for an inverter at night.

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Aaron Cake
Administrator

Canada
6710 Posts

Posted - May 27 2007 :  10:21:30 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
quote:
Originally posted by sunil_223

hi audioguru can u tell me approximately how many solar cells i will be required to get 12v 5amps.



Please keep all other topics out of this thread. This thread is for inverter discussion only. Thanks.
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