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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 16 2008 :  1:05:52 PM  Show Profile  Reply with Quote
quote:
Originally posted by JUAN DELA CRUZ
Regarding about the Xformer....If I'll make a 8v -0v- 8v primary winding(w/ 220V secondary) I'll turn the magnetic wire "8 times" in the iron core????

The turns ratio of the primary to the secondary determines the voltage. It probably will not be 8 times.

quote:
Do you have an short & overvoltage protection circuit that I can use w/ my Modified Sine Inverter to protect the Load...cause I'll using it to power a modified sine compatible COMPUTER.????

We talked about an over-voltage circuit in these forums recently. It was a window caomparator to turn off the Mosfets if the battery voltage is too high or too low.
You need to design a simple over-current detector circuit yourself.

quote:
What will be the value of ZENER diode to Protect the Power mosfet from "Voltage Spike" when the Battery clip is suddenly disconnected????[/b]

I don't know. Maybe a 16V/1W zener diode will work.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 17 2008 :  11:13:39 AM  Show Profile  Reply with Quote
You found a very old under-voltage and over-voltage circuit. A simpler modern circuit is made with two opamps or comparators performing as a window comparator. Dennis recently posted the schematic for his window comparator.

What will cause the 12V input voltage of your inverter to be too high?
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kivdenn
Nobel Prize Winner

Uganda
535 Posts

Posted - May 17 2008 :  11:39:00 AM  Show Profile  Reply with Quote
Please can any one help me change this charger circuit http://www.aaroncake.net/circuits/charger2.asp to a 24V and also 48V charger circuit. Show me how to change the necessary parts especialy resistor values. Thanks
Dennis
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - May 18 2008 :  12:25:48 AM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

You found a very old under-voltage and over-voltage circuit. A simpler modern circuit is made with two opamps or comparators performing as a window comparator. Dennis recently posted the schematic for his window comparator.

What will cause the 12V input voltage of your inverter to be too high?



Thank you again Mr. audioguru,

The 12V input voltage of my modified sine inverter is O.K.

........but my problem lies at the output of the Xformer(secondary side).The voltage in the output of my inverter varies.
(due to battery voltage variation, i.e. approx. 13.8V when full & 9V
when nearly discharge).

....do you think a Zener diode can regulate the output before coming to the primary side of the Xformer????

...the down side will be less power output because less RMS voltage will go to the primary winding right...???

.......but the output will be more stable.


OR....do think an "automatic voltage control" w/ SCR will be the answer????
quote:




P.S...........Do you think this charger(Aaron designed) can lenghten the charge of the battery of my Modified sine inverter if I'll power it in the output of my inverter & then automatically charge the battery (i.e. disconnect when fully charge & then charge it again when the charge is low)??????
Download Attachment: charger2-1.gif
4.32 KB






Thank you.....


juan dela cruz
Penniless INVENTOR

Edited by - JUAN DELA CRUZ on May 18 2008 01:47:24 AM
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 18 2008 :  10:56:57 AM  Show Profile  Reply with Quote
You should not regulate the output voltage of your simple inverter by using a huge zener diode to short its input with about 700W of wasted power. The inverter circuit is too simple for voltage regulation.

The inverter cannot charge itself because that is impossible perpetual motion. The input power to a charger is more than its output power so power is wasted and the battery will run down instead of charging.
The charger must be powered from the mains.
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - May 19 2008 :  12:15:31 AM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

You should not regulate the output voltage of your simple inverter by using a huge zener diode to short its input with about 700W of wasted power. The inverter circuit is too simple for voltage regulation. [quote]


Thank you Mr. Audioguru....

What should I do so that the output voltage of my modified sine inverter will be more stable.

...you said that using a Zener to regulate the output will wasted a lot of power.

...what if the output of the individual power mosfet is regulated so that the voltage coming to the primary winding of the xformer is stable likewise the output will be stable right???


Thank you.

juan dela cruz
Penniless INVENTOR

Edited by - JUAN DELA CRUZ on May 19 2008 12:16:18 AM
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 19 2008 :  12:45:15 AM  Show Profile  Reply with Quote
If you adjust the input to the Mosfets so that they regulate the voltage to the transformer then the Mosfets will melt.
If the Mosfets must reduce the voltage by 2V then at 80A their power wasted is 160W in addition to their power loss.

Modern inverters use Pulse-Width-Modulation to have a regulated average current in the load. The Mosfets turn on completely and turn off completely to stay fairly cool.
Your simple inverter is not designed for Pulse-Width-Modulation. It is old and CHEAP!
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kivdenn
Nobel Prize Winner

Uganda
535 Posts

Posted - May 19 2008 :  02:46:59 AM  Show Profile  Reply with Quote
quote:
Originally posted by JUAN DELA CRUZ

quote:
Originally posted by audioguru

You found a very old under-voltage and over-voltage circuit. A simpler modern circuit is made with two opamps or comparators performing as a window comparator. Dennis recently posted the schematic for his window comparator.

What will cause the 12V input voltage of your inverter to be too high?



Thank you again Mr. audioguru,

The 12V input voltage of my modified sine inverter is O.K.

........but my problem lies at the output of the Xformer(secondary side).The voltage in the output of my inverter varies.
(due to battery voltage variation, i.e. approx. 13.8V when full & 9V
when nearly discharge).

....do you think a Zener diode can regulate the output before coming to the primary side of the Xformer????

...the down side will be less power output because less RMS voltage will go to the primary winding right...???

.......but the output will be more stable.


OR....do think an "automatic voltage control" w/ SCR will be the answer????
quote:




P.S...........Do you think this charger(Aaron designed) can lenghten the charge of the battery of my Modified sine inverter if I'll power it in the output of my inverter & then automatically charge the battery (i.e. disconnect when fully charge & then charge it again when the charge is low)??????
Download Attachment: charger2-1.gif
4.32 KB






Thank you.....




Hey all,
I would like to modify this circuit to a 24V battery charger circuit. How do i do that I mean what parts should I change to what?.Thanks
Dennis
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 19 2008 :  1:50:01 PM  Show Profile  Reply with Quote
I have never made a PWM circuit for an inverter. I made one to control the speed of a DC electric motor.

The LM393 and LM339 are not opamps. They are comparators. Their outputs are the collector of an NPN transistor not the complete output circuit that opamps have. The low battery cut-off circuit will need to be changed a little to use them.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 20 2008 :  12:00:48 PM  Show Profile  Reply with Quote
The comparator has only the collector of a single NPN transistor at its output. It needs a resistor connected to the positive supply to pull the output high. Opamps have multiple transistors and PNP pullup transistors at their outputs.
But the LM393 and LM339 comparators are low power so their minimum output current is low, only 6ma. Opamps have a minimum output current of 20mA.

Why use a low power dual comparator or quad comparator to replace a single more powerful opamp? What will you do with the extra comparators?
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 21 2008 :  12:26:02 AM  Show Profile  Reply with Quote
Look at the datasheet for an LM1458 dual opamp. The MC1458 is the same. Their spec's are the same as a 741 opamp.

Why will the battery voltage be too high??
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 21 2008 :  11:41:41 AM  Show Profile  Reply with Quote
The high and low cutoff circuit STOPS the inverter when the battery voltage is too high or is too low. I think Dennis uses it to stop the inverter from working when somebody connects a 24V battery to it.
The circuit with the two opamps as a window comparator does not regulate and does not sense the output voltage so it does not regulate the output voltage.
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rauf
New Member

Pakistan
2 Posts

Posted - May 21 2008 :  12:44:09 PM  Show Profile  Send rauf an AOL message  Click to see rauf's MSN Messenger address  Reply with Quote
quote:
Originally posted by audioguru

quote:
Originally posted by mrenjan

One Question to AudioGuru.. Is there any advantage of using 2N3055 instead of Mosfet's like IRF540 directly tied to CD 4047. We dont even need the OP-amps since Mosfet requires only less Drive current. Probably the only other change required is in the Transformer side (9-0-9 instead of 12-0-12). I thought the efficiancy of Mosfet is much higher than Transistor since leakage current is less. Not sure whether i am wrong.


2N3055 transistors were used in the 100W and 500W inverter because the circuit is very old and 2N3055 transistors atre available in countries that don't have Mosfets. Mosfets are much better.

The IRF540 Mosfet is also getting pretty old since much better Mosfets are available now.

The CD4047 can directly drive two Mosfets in an inverter and the output power depends on their current rating and the size of the heatsink. Cheap Chinese inverters use Mosfets.

Efficiency is determined by how much power is wasted as heat in the transistors when they conduct, not leakage current.
A 2N3055 transistor has a max saturation voltage of 3V at a collector current of 10A and a huge base current of 3.3A. That is 35W of heat for a 100W inverter.
An IRF540 Mosfet has a max saturation voltage of 0.44V at 10A so wastes only 4.4W in a 100W inverter. Better Mosfets would operate cooler and therefore the efficiency would be higher.

If you use a 9-0-9 transformer with Mosfets then with a fully charged battery at 13.8v the output voltage will be 170VAC instead of 115VAC or will be 341VAC instead of 230VAC.

If you use a 12-0-12 transformer with Mosfets and a fully charged battery then the output will be 128VAC instead of 115VAC and will be 256VAC instead of 230VAC.

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rauf
New Member

Pakistan
2 Posts

Posted - May 21 2008 :  12:45:04 PM  Show Profile  Send rauf an AOL message  Click to see rauf's MSN Messenger address  Reply with Quote
quote:
Originally posted by audioguru

quote:
Originally posted by mrenjan

One Question to AudioGuru.. Is there any advantage of using 2N3055 instead of Mosfet's like IRF540 directly tied to CD 4047. We dont even need the OP-amps since Mosfet requires only less Drive current. Probably the only other change required is in the Transformer side (9-0-9 instead of 12-0-12). I thought the efficiancy of Mosfet is much higher than Transistor since leakage current is less. Not sure whether i am wrong.


2N3055 transistors were used in the 100W and 500W inverter because the circuit is very old and 2N3055 transistors atre available in countries that don't have Mosfets. Mosfets are much better.

The IRF540 Mosfet is also getting pretty old since much better Mosfets are available now.

The CD4047 can directly drive two Mosfets in an inverter and the output power depends on their current rating and the size of the heatsink. Cheap Chinese inverters use Mosfets.

Efficiency is determined by how much power is wasted as heat in the transistors when they conduct, not leakage current.
A 2N3055 transistor has a max saturation voltage of 3V at a collector current of 10A and a huge base current of 3.3A. That is 35W of heat for a 100W inverter.
An IRF540 Mosfet has a max saturation voltage of 0.44V at 10A so wastes only 4.4W in a 100W inverter. Better Mosfets would operate cooler and therefore the efficiency would be higher.

If you use a 9-0-9 transformer with Mosfets then with a fully charged battery at 13.8v the output voltage will be 170VAC instead of 115VAC or will be 341VAC instead of 230VAC.

If you use a 12-0-12 transformer with Mosfets and a fully charged battery then the output will be 128VAC instead of 115VAC and will be 256VAC instead of 230VAC.

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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - May 22 2008 :  12:29:13 AM  Show Profile  Reply with Quote
A lead-acid battery is not fully charged when its voltage reaches a certain voltage. It is fully charged when its current drops to a certain low amount.

Go to the Battery University and read about it. http://www.batteryuniversity.com/partone-13.htm

Download Attachment: lead-acid battery charging.PNG
19.96 KB

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