Author Topic: One way AC  (Read 867 times)

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george65

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One way AC
« on: February 19, 2017, 07:07:22 AM »

Don't want to go into specifics because I'll get advise on that rather than what I want to know....

Is there a way to make AC power only travel one way?
 If I had DC I could put in a Diode and I could have power coming out of a supply but not going back in.
 Is there a way to do the same with AC power?
I want to be able to bring power in from 2sources but not have it back feed from one to the other.

Any simple ways of doing this?


joestue

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Re: One way AC
« Reply #1 on: February 19, 2017, 12:18:20 PM »
Short answer is no.

DamonHD

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Re: One way AC
« Reply #2 on: February 19, 2017, 12:27:24 PM »
You could imagine some fancy electronics where you measure both voltage and current instantaneously to determine direction of power flow, and disconnect somehow if the flow in the wrong direction, but it would be complex and might well have nasty side-effects.

Rgds

Damon

george65

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Re: One way AC
« Reply #3 on: February 19, 2017, 03:10:29 PM »

Ah well, at least I didn't miss anything obvious.

Back to the drawing board.  :P

joestue

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Re: One way AC
« Reply #4 on: February 19, 2017, 04:59:26 PM »
one way roller clutch between two synchronous ac generators. but that is just messy.

another way to do it, but will probably only work with two three phase systems, is a three phase rotary transformer connected to a dc servo motor.
they actually make these things in 1 gigawatt sizes.. there are several that are used to connect the american and canadian ac grid.


george65

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Re: One way AC
« Reply #5 on: February 19, 2017, 05:07:33 PM »

Yes, way too messy, expensive, bulky, heavy and everything else for my application.

A switch is probably the easiest option if not the most efficient one to just break the connection when I am generating and don't want the power to go the wrong way.
Maybe there is a way to sense that and do it electronically as it would be all I need. Power would be in the lin all the time, just have to sense which way it was going.
Otherwise a manual switch would be better than nothing.

joestue

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Re: One way AC
« Reply #6 on: February 19, 2017, 06:08:31 PM »
if you have a 120/240v inverter, you can utilize a current transformer and spdt switch for each breaker.

next you need a computer with simple algorithm to try and find a combination of loads that equals the incoming power supplied to your inverter. this is harder than you think. I believe it is np hard, meaning you might need something more than an arduino--you literally have to try adding up every combination of loads to see which one best matches the power available. and there's a lot of combinations.

also the inverter has to be large enough to handle the largest load. it also needs to remain in synchronization with the grid so that when you switch a motor or transformer load from the grid to the inverter and back, it doesn't have a huge current spike during the process.

a smart UPs such as APC's line of them, will maintain grid synchronization but remain on the battery if the input voltage is below 90 volts. this is simple to construct, but the problem is the 24v system in apc's smart ups sine wave inverter consumes about 20 watts no load for their 1KW inverters. but this is probably the cheapest way to build such a system.