# How to best simply invert a 110v ac current w/minimum change to the voltage

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#### David Kimbley

Jun 3, 2015
16
Hi Electronics Gurus,
I am working on a project which needs to have a 110v ac current simply inverted with as little effect to the current as possible. (and keep it a 110v ac wave. (just inverted). Any ideas?

David K

#### Minder

Apr 24, 2015
3,482
Invert the AC? it already inverts 50/60 x/sec ?
M.

#### Alec_t

Jul 7, 2015
3,653
If you're looking for phase inversion, just use a 1:1 ratio transformer.of appropriate rating.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Aren't the two 110v phases inverted with respect to the other?

#### AnalogKid

Jun 10, 2015
2,925
I am working on a project which needs to have a 110v ac current simply inverted with as little effect to the current as possible. (and keep it a 110v ac wave. (just inverted). Any ideas?

This might be a simple as one small transformer, but your question doesn't have nearly enough information to work with. "simply inverted" is not a good description of anything. Traditionally, an inverter is a DC-input, AC-output power supply, and there is nothing simple about them. Please post a schematic or block diagram sketch of the input you have, the output you want, and any important details like timing or phase relationships, the power level, etc.

ak

#### Minder

Apr 24, 2015
3,482
IOW inverted WRT to what??
1ph phase shifted 180° is an inversion.
M.

#### David Kimbley

Jun 3, 2015
16
Hey All,
Thanks for all the replies... Yes, I was vague. It's for a project very similar to the "Balanced signals" which eliminates the noise from a signal by (as I understand it) 1) inverting the signal, 2) transfering the original signal along with the inverted signal, 3) re-inverting the inverted signal back, and adding them together to get rid of the noise aquired during transmission (for those who dont know about balanced signals). So, my question is:
Can you invert a signal such that it is an exact opposite of the original, or does the inversion distort the original signal so that if it were re-inverted it would have lost something? It seems invertion would have to have some affect on the signal, and if so, can the original signal be changed to match it (so it would be the mirror image of the inverted signal? Yes, the signal happens to be 110v ac single phase current (house current). I'm not interested in a DC to AC inverter,... just ac 110 to ac 110. (but inverted). And Yes, Steve, the two 110 legs in a house ARE inverted with respect to each other. And getting back to my question, IF you were to invert the one leg, would it be just like the other leg, or would the inverted also change something else, like it had gone through a resistor perhaps? Thanks for all your replies, David K

#### Minder

Apr 24, 2015
3,482
And Yes, Steve, the two 110 legs in a house ARE inverted with respect to each other.
That doesn't make sense, unless you constantly change the reference point from one to the other, they are two legs of a single phase supply.
As mentioned, you can do it with a 1:1 transformer.
M.

#### BobK

Jan 5, 2010
7,682
I still have no clue what you are trying to do, and you questions are nonsense. Please describe what you are trying to achieve rather that ask up about a part of what you think the solution is.

Bob

#### Alec_t

Jul 7, 2015
3,653
Since the signal has to pass through some device to do the inversion, and since no device is perfect, there will inevitably be some distortion.

#### David Kimbley

Jun 3, 2015
16
Sorry, I will try to be more descriptive about what I'm wanting to do. What I need is to invert 1 leg of 110v house current (60 hz) so that it will match exactly the other side of the 110v house current. How is this done? And if it is done, how closely will it match the other leg? I'm considering the 2 legs to be a "balanced signal" (since they are inverted from each other). Now when you add the two together, you get the 220 v. If you invert one and then add them together, what I want to see is .. How closely do they cancel each other out? That is the essence of the project I'm working on. If the inverter was 100% efficient, they would be pretty close to zero.. right? How efficient can an AC inverter be? Hope this helps.
Thanks again, David

#### AnalogKid

Jun 10, 2015
2,925
I also have no clue what he is trying to do, but I understand the question.

Yes. If you do a very good job of inverting a non-DC signal, you can sum the two signals to get zero, the definition of perfect invert-and-add. In the real world there is no such thing as *perfect* inversion, but in the pro audio world you can achieve -130dB of common mode cancellation, one way of measuring the perfectness of the inversion. Doing this with power line voltages is risky and expensive. You could use a three-winding transformer to get two out-of-phase signals with the same phase delay from the input, but even that probably will not get you 40 dB common-mode rejection.

Why?

ak

#### David Kimbley

Jun 3, 2015
16
Normally, the idea of the "balanced signal" is to keep the signal, and elimiate the noise. I was hoping to do the opposite,.. keep the noise, and eliminate the signal (110v ac signal). So it would essentially be a way to measure the "noise" on an ac line.
You said, "Risky and expensive". Granted risky yes, thanks for the admonition... but expensive?? That is what I thought at first, but,... if they actually do canceled each other out,... I think it would not register as a voltage at all (or actually very little). Don't you agree?

David

#### AnalogKid

Jun 10, 2015
2,925
For noise already on your input powerline signal, invert and add will cancel the noise voltage as well as the power line voltage. Balanced noise suppression techniques work only when the noise is added *after* the balanced signals are created. To measure the noise on a single powerline phase, highpass filter it off of the input. That will get you all noise components down to the filter cutoff frequency. What are you looking for?

ak

#### David Kimbley

Jun 3, 2015
16
Hey again AK,
As I understand it, the 110 is inverted at the transformer, so the invert and add will give you the noise acquired from the transformer to the house receptical, ... and the noise is all I am looking for. (I know, it seems strange to just look for noise on an ac line). So, wouldn't this give what I'm looking for? (and I dont think the power company will even see the voltage---right?).

David

#### Martaine2005

May 12, 2015
4,967
David, nobody understands what you are talking about. Inverting AC? Turn your scope upside down. Job done!
Sorry to say this, you are talking nonsense. Noise on the Ac will duplicate as it goes through 0 to the opposite side of AC
AC goes up then through 0 to AC down. It's a sinusoidal (sine) wave.
You cannot invert an AC to show one half either. You can change it or 'convert it'.

I think you are after something else and not explaining yourself properly!
Do you want to elaborate?

Martin

#### duke37

Jan 9, 2011
5,364
As I understand it, you have 110V 60Hz power coming into your house which is contaminated with noise and you wish to measure this. The way to do this would be to use a high pass filter with a notch at 60Hz so that most of the 60Hz is eliminated and the higher frequency noise components are passed through the filter.

#### Martaine2005

May 12, 2015
4,967
As I understand it, you have 110V 60Hz power coming into your house which is contaminated with noise and you wish to measure this. The way to do this would be to use a high pass filter with a notch at 60Hz so that most of the 60Hz is eliminated and the higher frequency noise components are passed through the filter.
Sorry Duke. He wants to keep the noise. And invert AC siganal.

Martin

#### duke37

Jan 9, 2011
5,364
The noise will pass through the filter and can be measured.

Any broadband circuit will affect the noise in the same way as the 60Hz, it is necessary to separate one from the other.

#### davenn

Moderator
Sep 5, 2009
14,301
Im closing this thread its going around in circles

@david Kimberly
Duke37 in posts # 17,19 gave the closest answer to what could be understood from your comments/request

if this isn't enough ... then feel free to start a new thread and explain VERY EXACTLY AND CLEARLY
what you are trying to achieve

cheers
Dave

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