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General Category => General Discussion => Topic started by: cheerio on January 14, 2013, 11:24:24 AM

Title: AC current direction?
Post by: cheerio on January 14, 2013, 11:24:24 AM
Hey guys,
i recently watched an AC Energy meter showing the direction of the current flow. Or i other words, on which side the load was. Do you guys have any idea how this works? The first guess would be a shunt. The voltage on the supply side would be higher than the voltage on the load side. Are there other ways?
Title: Re: AC current direction?
Post by: kam on January 14, 2013, 13:42:01 PM
I suppose that this meter is in series with the load, right? And probably parallel to the source as well.
First of all there is indeed some sort of a series resistor inside in the magnitude of ohms or milliohms, so it is possible to find out where the load is as you said.

But... Why?????  ??? ??? ??? ??? ??? ???
Title: Re: AC current direction?
Post by: cheerio on January 14, 2013, 15:47:02 PM
Yes it is in series with the load. The reason i am interested in this is that we have some ridiculous laws in Germany. I am thinking about producing electricity and use it parallel to the mains. If i don't use all the electricity i can sell the unused electricity to the power company in theory. But there is a shitload of regulations and paperwork attached to this. So i want to cut the mains off when i produce more electricity than i consume. That way i can dodge the regulations and paperwork.
In case of a blackout i need to cut the mains off too because the guys that will repair the system might be fried if i don't.
The easiest way to prevent all of this is to detect if the load is on my side of the energy meter and cut the mains off if the load is not on my side.
 Do you have a better idea?
Title: Re: AC current direction?
Post by: kam on January 14, 2013, 15:54:36 PM
I see. Well, the series resistor - comparator method is the most reliable (IMO) and since reliability is your #1 "must" (you don't want to have a fried electrical guy in front of your door) this is how you should go.  Of course, the resistor will not be a resistor. It will be a wire wound resistor of some sort.