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vivek_pv

DC to AC

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The way I read it is that the %duty at Q and Q_bar will be 50% and that the signal at the oscillator output is not guaranteed to be 50%

AN920: It says a 50% duty cycle is not guaranteed. Period. It does not say that you get a "perfect 50% duty cycle" anywhere....which is what audioguru says the datasheet says.


Dear MP....

What is the technique to generate a set of sinewaves (of opp phase)?

Is it the regular oscillator?

vivek: to get a sinewave inverter, you would use a different technology. You cannot use a sinewave and amplify it like a squarewave. Too much heat loss. Many manufacturers use a microprocessor to digitally simulate a sinewave in a switch mode.

MP

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Ok...MP.

Then can you briefly explain what is the design technology of a simple 500VA-1kVA lighting purpose inverter?

I have heard about using a microcontroller in inverters. But I suppose the above one doesn't use it.

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vivek,
we do not have a project on this site for such a large consumption. Here is a website that fully documents a 2KVA that has a modified sine wave:
http://www.technology.niagarac.on.ca/people/mcsele/i2k.htm

This project uses the microcontroller as I had described above, but don't worry if you have never programmed a PIC. Everything is on this website, including the code for the micro. I think you can even contact the author with questions.

MP

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I have gone through that; mp.

I must say that was a good model ofcourse.

But to be more specific, I have raised this question only to know construct an inverter (DC to AC) with a cheap and best technique. Also, at the times, I wanted to know about different techniques employed in the said project.

Can you people please tell me about a best 50Hz, 12VDC to 220VAC inverter design technique.

By the way, is the square wave AC suitable for home appliances' (tube light, incandescent light, induction motors, etc.) usage?

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But to be more specific, I have raised this question only to know construct an inverter (DC to AC) with a cheap and best technique.
Can you people please tell me about a best 50Hz, 12VDC to 220VAC inverter design technique.
By the way, is the square wave AC suitable for home appliances' (tube light, incandescent light, induction motors, etc.) usage?

Our 500W square-wave inverter project was fixed and used in The Philippines to power incandescent and fluorescent lights, and multi-voltage TVs. It uses cheap 2N3055 transistors because power Mosfets were not available.

I think the square-wave would cause trouble with transformers and electronic items that rectify then use the peak voltage of a sine-wave. The web says that light dimmers and motor speed controls have trouble with modified-sine-wave inverters. Then a square-wave inverter would be worse.

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vivek,
we do not have a project on this site for such a large consumption. Here is a website that fully documents a 2KVA that has a modified sine wave:
http://www.technology.niagarac.on.ca/people/mcsele/i2k.htm

This project uses the microcontroller as I had described above, but don't worry if you have never programmed a PIC. Everything is on this website, including the code for the micro. I think you can even contact the author with questions.

MP



"This inverter is of a traditional ferroresonant design using large step-up transformer"

This type of transformer to obtain a sine output is hardly used anymore because of high cost, bulk and is also not very efficient.

http://www.allaboutcircuits.com/vol_2/chpt_9/6.html

"Ferroresonance" is a phenomenon associated with the behavior of iron cores while operating near a point of magnetic saturation (where the core is so strongly magnetized that further increases in winding current results in little or no increase in magnetic flux).

Normally, core saturation in a transformer results in distortion of the sinewave shape, and the ferroresonant transformer is no exception. To combat this side effect, ferroresonant transformers have an auxiliary secondary winding paralleled with one or more capacitors, forming a resonant circuit tuned to the power supply frequency. This "tank circuit" serves as a filter to reject harmonics created by the core saturation, and provides the added benefit of storing energy in the form of AC oscillations, which is available for sustaining output winding voltage for brief periods of input voltage loss (milliseconds' worth of time, but certainly better than nothing).


Unfortunately, these devices have equally noteworthy disadvantages: they waste a lot of energy (due to hysteresis losses in the saturated core), generating significant heat in the process, and are intolerant of frequency variations, which means they don't work very well when powered by small engine-driven generators having poor speed regulation. Voltages produced in the resonant winding/capacitor circuit tend to be very high, necessitating expensive capacitors and presenting the service technician with very dangerous working voltages. Some applications, though, may prioritize the ferroresonant transformer's advantages over its disadvantages. Semiconductor circuits exist to "condition" AC power as an alternative to ferroresonant devices, but none can compete with this transformer in terms of sheer simplicity.




"In general, ferroresonant UPSs that use transformers are often larger in size and produce heat which can impact sensitive components in a computer and batteries in the UPS".

http://www.natpow.com/power101/ferro%20ups.htm


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Our 500W square-wave inverter project was fixed and used in The Philippines to power incandescent and fluorescent lights, and multi-voltage TVs. It uses cheap 2N3055 transistors because power Mosfets were not available.


Ok....

Well; Do these fluorescent lights are normal fluorescent (220VAC with a choke coil) lamps? are some special creatures?

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