# Half sine wave inverter

1. Nov 29, 2013

### abdo799

I know that normal DC can be inverted to square wave , modified sine wave or pure sine wave , what about half sine wave dc , like the one resulted from ac current passing through a simple diode rectifier, can this be inverted?

2. Nov 29, 2013

### Drakkith

Staff Emeritus
Practically any type of waveform can be created given the right setup, incluing the half sine wave.

3. Nov 29, 2013

### abdo799

I am talking about the input....the input is half sine wave

4. Nov 29, 2013

### sophiecentaur

IF the source resistance is low enough and a big enough capacitor is used then you can use a half sine wave as input. What did you want for output?
You need to define the requirement better if you want a proper answer, I think. Are you after a change of frequency, perhaps?

5. Nov 29, 2013

### abdo799

I have an ac source.... i used a rectifier, it gave me a half sine wave dc current, how can i change it back to ac?

6. Nov 29, 2013

### CWatters

I think what Sophiecentaur meant was.. You can convert the half sine to DC using a capacitor. Then convert the DC to AC

7. Nov 29, 2013

### Okefenokee

It would be pretty easy to convert a half-wave sine back into something close to AC. All you need is a band-pass filter targetted for the frequency of the original AC signal. The output may be weak and it won't be a perfect sine wave. It's probably not easy to make a high enough quality filter for the job either.

Usually in a situation like this you would want to convert the rectified output to a steady DC voltage using a capacitor like the others suggested. After that, the sky is the limit on what kind of outputs you can create.

8. Nov 29, 2013

### Okefenokee

Scratch the band-pass filter. You could do it with a low-pass filter which has a cut-off somewhere between the original AC frequency and twice that frequency.

This is all justified by the fact that the fourrier transform says that the majority of the signal's energy is going to go be in its fundamental frequency. All you have to do is filter out the higher order components.

9. Nov 29, 2013

### sophiecentaur

But that would give you a massive DC component - not much use if you wanted to follow it with a transformer. A bandpass filter would remove the DC through a transformer primary.

I am still not sure what the context of the original question is. It could be about a thought experiment and an 'is it possible?' or it could be a serious application. Yes, it 'could' be done but it's not a viable engineering scheme. What would be the point in doing what the original post seems to be proposing? You don't need an 'inverter' when you have AC; all you need is a transformer, unless you require (as I suggested earlier) a different output AC frequency from the input AC frequency. If that's what you want then you need to produce an intermediate 'smoothed DC' supply or you will get beats between the two AC frequencies.

I do wish people would declare their real objectives when they suggest novel schemes. The devil is always in the detail.