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king
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« on: June 29, 2010, 03:55:01 15:55 »

Hi!
I am working on the project of making UPS with Microcontroller and using PIC16F86A with PWM Freq=20Khz
the problem which i am facing now is that when i have used 12V Battery then i will get maximum voltage of 9VAC and at 24V Battery i will get Max 17.94VAC but i need 12vAc from 12VDc Battery and vice versa for 24VDc Battery to feed Ac Voltage to Transformer (12V to 220V stepup Transformer) but at 9Vac i will get just 168VAC please suggest me the solution regarding this problem.

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King
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titi
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« Reply #1 on: June 29, 2010, 06:10:06 18:10 »

Hi,

To have 220v, you need produce RMS Voltage.
So if you have 12v DC (like 12v peak to peak), you will produce 12/square root(2)=8.48v AC RMS.
This without lossless.
So in this case you need use a transformer 220v/8v and not 220v/12v.
A transformer as a constant ratio beetween Primary and Secondary Voltage and U sec*Ratio=U Prim or U Sec=U Prim/Ration (Usec and UPrim expressed in RMS voltage)

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king
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« Reply #2 on: June 30, 2010, 12:25:57 12:25 »

But if you consider Local UPS(square Wave Output) then in there design they have used 12V to 220V Transormer and battery is of 12Vdc so how they can produce more than 12Vac from it because i have checked on my local made ups that battery voltage is 11.61Vdc but at transformer input i have measure 19.16Vac(RMS) how this is possible?Please help in solving this query

If anybody made true sinewave UPS using PIC16F876A controller then kindly confirm me that at 12Vdc or 24vDc do we get 12Vac(RMS)/24Vac(RMS) or we will get just the peak voltage of 8.5/17 Vpk-pk

Any kind of Help will be highly appreciated
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ravenfeather
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« Reply #3 on: June 30, 2010, 10:14:38 22:14 »

May be  a stupid question , but is your voltmeter true RMS? They are 2 or 3 times more expensive than ordinary.For different forms RMS is calculated differently .
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king
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« Reply #4 on: July 03, 2010, 07:33:49 07:33 »

Can anybody provide me the Documnet or link on Transformer based UPS with true sinewave output
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titi
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« Reply #5 on: July 03, 2010, 11:43:02 11:43 »

Hi,

May this help you: Pic 16f876a Pure Sinewave inverter http://www.edaboard.com/ftopic249177.html

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king
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« Reply #6 on: July 05, 2010, 02:45:56 14:45 »

Hi!
If anybody has the schematic of "True sine wave UPS" with 24V Dc battery then please upload it or provide the relavant document.
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borberk
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« Reply #7 on: July 05, 2010, 03:53:52 15:53 »

From battery you can get by means of PWM max. Vbat/3 sine AC RMS voltage. That is from 12V you can get max 4V RMS sine. From 24V it is two times more. Usual inverters are using push-pull transformer which virtually doubles AC voltage on primary side. To drive such transformer you need two signals which are out of phase.
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titi
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« Reply #8 on: July 05, 2010, 07:40:19 19:40 »

Hi,

Here is a small project with PIC12F509 to drive an inverter 12v/220v.

To have good sinus, it is necessary to filter output.

http://www.sm0vpo.com/power/pic_dc-ac_01.htm

Source is available on web site.



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king
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« Reply #9 on: July 06, 2010, 05:53:51 17:53 »

Hi!
Thanks for your answers actually i have already generated 18V Pure AC(Using H-Bridge Circuit) with the help of PWM by using 24V battery but i need 220Vac output at 24Vac input so for that i have to use transformer in push pull way and in this method the battery positive end is connected at the center tape of the transformer while the other two ends of winding ON and OFF 24V so in this way we will get exactly 24Vac at Transformer input and 220Vac at Output so for this i need 24V UPS Schematic.If any body has it then please upload it.
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king
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« Reply #10 on: July 07, 2010, 06:41:52 18:41 »

Hi!
I have search a lot the circuit of 24V UPS (Transformer Based) on Google but till now i haven't found any circuit for 24V UPS which is Micro-controller based or should work at 20Khz PWM Frequency if you guys has any idea related to 24V UPS then please share it or have Schematic of 24V UPS then please Upload it.

Regards

King
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