# Building a 3 Phase Sine wave inverter

Discussion in 'The Projects Forum' started by Celcius1, Nov 19, 2008.

1. ### Celcius1 Thread Starter New Member

Nov 18, 2008
2
0
Hey guys i'm looking into building a pure sinewave inverter, i'm in the process of building this circuit modified of course

http://www.uoguelph.ca/~antoon/circ/555dcac.html

also the output transformer will be hand wound.

But i'm also looking at making a 3 phase version aswell by adapting this circuit into the completed unit which was posted by a forum member here

So I'll have a both a single phase and 3 phase pure sinewave inverter.

Also I spoke to a friend here who works on the power lines, and said if i wanted to get away with an allowable tied to grid inverter, as i'm in the process of using wind generators. I need to sample the grid power and use a circuit my guessing using an op amp to phase align the output to the grid.

I can get a working inverter and all but i dont know how to use an op amp to phase align an ac output, he also strongly mentioned that the current has to be aligned aswell.

So any help will be greatly appreciated

Celcius1

May 16, 2005
5,072
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3. ### Celcius1 Thread Starter New Member

Nov 18, 2008
2
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The first one is in a sense sinewave, as the amplification stage alters it to squarewave as i said i'm modifying the circuit as i know the transistor pair will amplify the sinewave output from the 555 as a 50hz oscillator to a square wave as it will cause clipping.

The first circuit is heavily modified when i get a chance to i will up the modified version

Celcius1

4. ### KL7AJ AAC Fanatic!

Nov 4, 2008
2,047
294
You're to be commended on your ambitious project. YOu area correct in that the final waveform is determined AFTER the last switching devices....since you're saturating everything before them.

If your loads are resistive, the currents will be balanced when the voltages are balanced. Probably the most crucial part of this will be the actual phase alignment...determined by the initial op-amp trio. You must carefully choose your components for stability. You get an extra gold star if you can keep them within 1% or so of absolute phase alignment.

eric

Mar 3, 2009
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Anything new on this? I am looking to do something similar.

6. ### onlyvinod56 Active Member

Oct 14, 2008
362
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Hi celcius,
I didnt catch ur point exactly. I dont know how u'll compare the samples of current to align with the grid. but u r doing something around wind power generation and u r going to connect it to the grid. Am i correct?

If u r using a DFIG, here is a link that will be useful to u. this is a 3 phase pwm inverter whose frequency can be adjustable.

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Last edited: Apr 1, 2009
7. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
718
Driving an inverter transformer with a sinewave is a waste of power.

If a true Sine output inverter is needed, The Magic Sinewave is a much better solution, which uses PWM to create a very good sinewave in either 1 or 3 phases. That link has a lot of info, as well as calculators to generate PIC code.

8. ### sriliam New Member

Sep 6, 2011
3
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Hi,
Thanks for the magic link but there's limitation : signal can not be more than 400 Hz !
What about state of art for a 12.5-16 kHz 3-phase signal range ?